By Dr J Floor Anthoni (2003)
|An introduction to the problems and why this section was created. An explanation of top-down control and the ecologyy of urchin barrens. The myth of unproductivity of barrens and the productivity of kelp.|
|Our own research into the extent of the kelpbed death of 1993, followed by observations of its recovery gives us the strength to contest the findings and conclusions of scientific research done on this subject.|
|Our version of the urchin barrens story is based on continual observation of the marine reserve and nearby areas starting in 1976, but intensified since establishing Seafriends in 1990, when we attained a boat. It allowed us to study the kelpbed death in 1992/1993. We observed how the area recovered, how urchins died and how isolated reefs did not recover until 1998. We followed these observations up till today.|
|Discusses recurring mistakes made by scientists, like not comparing apples with apples, using flawed fish counting techniques and so on.|
|Summary of conclusions|
|The extent of die-back of the kelp Ecklonia radiata in the Cape Rodney to Okakari Pt Marine Reserve. Russell C Babcock & Russ G Cole. Jan-May 1993.|
|Changes in community structure in temperate marine reserves. Babcock et al, 1998-99|
|Marine reserves demonstrate top-down control of community structure on temperate reefs Nick T Shears. Russell C Babcock, March-June 1998.|
|Protection of exploited fish in temperate regions: high density and biomass of snapper Pagrus auratus (Sparidae) in northern New Zealand marine reserves. Trevor J Willis, Russel B Millar, Russ C Babcock. October 1997 to April 1999.|
|Effects of marine reserve protection on benthic reef communities: northeastern New Zealand. Nick T Shears, Russell C Babcock. 2001|
|Indirect effects of marine reserve protection on New Zealand's rocky coastal marine communities. Shears N T, Babcock R C (2004)|
|From time to time we will report changes to the environment as they occur and any updates to this chapter.|
on this web site
barrens of NZ: urchin barren zones are created by storms rather
than by urchins. Most storm barrens are not populated by urchins.
The snapper-urchin-kelp myth: an explanation of the snapper 'trophic cascade' for the general public. Your starting point.
The Dark Decay Assay: a new plankton tool overturns our knowledge of the sea while quantifying degradation and eutrophication. Important reading.
Survey93: a survey of the inner and outer Hauraki Gulf after the mass kelp die-off of 1993. Floor Anthoni.
Bloom92: The algal bloom and climate anomalies of 1992. Dr Bill Ballantine.
Science needs skeptics: why skeptics are an integral and necessary part of science
Science, technology and human nature: the three culprits that caused all problems. Why do we think they can save us?
The Goat Island marine reserve: a virtual visit with history, ecology, biogeography, dive spots, monitoring and more.
Introduction to marine habitats: what it is like to live in the sea.
The ecology of Niue: cyclones create very deep barrens on one side of Niue Island and many grazers maintain these.
Floor Anthoni, June 2003.
When the search for truth is confused with
the pursuit of knowledge is reduced to the quest for power. - Alston Chase
For comments, suggestions and improvements, please e-mail
the author, Dr Floor Anthoni.
For best printed results, read instructions for printing.
-- seafriends home -- conservation index -- Rev 20030731,20031211,20050803,20051219,20060926,20070315,20090521,
Marine research is difficult and arduous because of limited access to the sea. As a result, the sea and its environments are some of the least understood on this planet. Whereas ecological research has been hampered by not being able to take the experiment into the laboratory, the sea is worse still because it can also easily destroy experiments.
The following summary describes some of these concerns
The main issue we contend is the finding that the sea urchin habitat zone is unnatural and that it disappears in marine reserves which have had sufficient time to acquire stocks of large predators, particularly predatory fish (like snapper) and crayfish (rocklobster). We contend that this is not true and that scientists have taken insufficient precaution in their experiments. They have also taken insufficient precaution in attaching far-reaching conclusions to failed experiments. As counter arguments, we dissect the very research done by these scientists, supplemented by work done by ourselves and by extensive observations. Since first publication (2003), a number of overseas scientific publications have supported us.
|the ecology of barrens
In the study of ecology, the way species interact while depending on one another, has been a subject of intense speculation. One often encounters the idea that all species are interconnected by an invisible 'web' where each is as important as any other ('all things are connected'). However, this idea or model as scientists call it, is entirely wrong.
Since there exists a discernable food chain with producers (plants) at the bottom, grazers above it and predators above grazers, and many more grazers than predators, there must be a mechanism that regulates it. The question is how?
The sea in its weirdness adds another dimension to this problem. On land habitat zones (desert, savannah, forest) are so large that those who live from it are also living on it. In addition, the offspring of all terrestrial species are born near their parents. And the number of offspring is limited to a few. Although this is never mentioned in books about ecology, these points are of major importance to understand the sea, where it is often not the case as the habitat forming organisms spawn profusely (millions of offspring) and their offspring is born somewhere else. It implies that the genes of survivors are not expressed where the survivors live. Evolution and adaptation in the sea are thus necessarily weak. In the sea the narrow habitat zones of the rocky shore are frequented by predators who do not live there, like snapper. The very narrow intertidal zone is even visited by grazers who do not live there.
The rocky shore where the urchins live, is but a narrow fringe of the wide open sea with its vast expanse of sea bottom and water above it. The sea bream snapper (Sparus auratus) lives mainly over the sandy and muddy sea bottom, and only very few take residence on the rocky reefs. It has been shown that most fish specialise in a certain diet during their lives, and snapper being quite versatile, can be found as predator, scavenger, crab-and-worm eater and mollusc eater, yet seldom all of the above. The point I wish to make here is that there are high numbers of snapper that could arrive from the open sea to wreak havoc on coastal populations, but very few actually do. And those who could do harm, are not constrained by a marine reserve. The situation is different for rocklobsters who live on the rocky shore, but they scavenge more than predate.
The trophic cascades model (or paradigm as the authors called it) became popular after a publication (1974) by Estes & Duggins [1,2,3 and many more] who saw a correlation between sea otters (who eat urchins) and the giant kelp (which can be eaten by sea urchins). Thus catching sea otters for the fur trade can have a decisive influence on the algal assemblages it was thought. This uncritically became established knowledge and some of the most cited articles in marine ecology. But although a correlation was seen, a causation was never established (see below)! So much for trusting marine science, its practitioners, its peer reviewers and its prestigious journals!
Finally in April 2006 (22 years later!) the trophic cascades paradigm
was tested by Carter, VanBlaricom and Allen , showing
that there is no significant increase in algal growth when sea urchins
are removed manually inside the San Juan Marine Reserve, not even over
a longer time period of 2 years. One would
have thought that this experiment would settle the matter, but please note
that their study happened in a sheltered place (San Juan Channel, Washington
State) where storm barren zones cannot occur, while urchin densities were
very low (1 per square metre). This means that the available sea urchins
had no influence on their environment, and removing them of course had
no influence either. The study is thus too weak to disprove the trophic
Monterey Bay National Marine Sanctuary has been closely monitored for many
years. The graph shows how sea otter numbers (red curve) increased from
near-zero in 1900 to over 2000 in 2000, proof that they had been hunted
to near extinction. However, recently their numbers have been declining
but why is not known. The kelp harvested here is mainly the giant kelp
pyrifera (and Nereocystis luetkeana) which prefers sheltered
waters, but even so is erratic in its year to year densities. They are
also easily removed by waves. The blue curve shows total kelp harvest in
all of California, climbing as otter numbers increase, suggesting that
there is a linkage between the two. But there are inconvenient exceptions.
Remember that the influences of market demand and price, regulation, nutrient
supplies and degradation can be decisive. The green curve shows kelp harvested
inside the sanctuary, declining as otter numbers are increasing. Kelp is
harvested by cutting the floating fronds off their stipes. The seaweeds
are used to cultivate abalone, and they are exported to Asian countries.
Monterey Bay was famous for its sardine fisheries wich crashed in 1940-1960, presumably due to overfishing and pollution.
|tethering urchins to confirm predation
Predation on urchins is usually studied separately by tethering urchins to the substrate. In the laboratory a string is threaded through the urchin, which causes it to bleed, as well as internal damage. But the urchin is first kept to recover, before transplanting. The experiment then shows that urchins inside protected areas disappear faster than outside, proof that predators remove them. But is this true?
We discovered that urchin barren zones are created by large storms and that urchins and other grazers just maintain these. Urchin barrens are thus a normal and healthy habitat, not in any way caused by humans. We propose to rename them storm barrens, for this is what they are. Such barrens are defined and restricted by wave propagation laws, which explain where they are found, where they cannot occur, and how deep they extend. One of the deepest storm barrens is found on the northern side of Niue Island where due to extreme water clarity (40-80m viz), the photic zone extends far beyond diving depth. Poorly occupied by day but grazed by numerous fish species, the night brings out a true city of sea urchins in perhaps two dozen different species. Read our account of Storm barrens in New Zealand, and underwater images from Niue, its ecology, index1 and index2 (for large picures, our CD is required).
 Estes, J A & J F Palmisano (1974): Sea otters:
their role in structuring near shore communities. Science 185: 10858-1060.
 Estes JA, N S Smith & J F Palmisano (1978): Sea otter predation and community organization in the western Aleutian Islands, Alaska. Ecology 59: 822-833.
 Estes, J A & D O Duggins (1995): Sea otters and kep forest in Alaska: generality and variation in a community ecological paradigm. Ecol. Monog. 65: 75-100.
 Carter, Sarah K & Glenn R VanBlaricom, Brian L Allen (2006): Testing the generality of the trophic cascade paradigm for sea otters: a case study with kelp forests in northern Washington, USA. Hydrobiologia (2007) 579:233-249 (freely available on the Web)
|Urchin barren productivity
(the myth of urchin barren unproductivity)
Over 200 scientific publications and over 1000 news and opinion articles, refer to the extremely low productivity of sea urchin barrens cited by Chapman . Here are some statements:
 Chapman, A.R.O. 1981. Stability of sea urchin dominated
barren grounds following destructive grazing of kelp in St. Margaret's
Bay, eastern Canada. Mar. Biol 62:307-31 1.
Our driticism of marine studies done here in NZ and elsewhere has not been left unnoticed, and we publish it here for you to judge. Please understand that the criticisms expressed on this chapter are not personal. They are directed at the research done, the methods and conclusions. More correspondence in opinion.
I was amused, but not altogether happy, to see what you have to say in your recent posting to the NZMSS list. The style of writing and the naivety of some of the ecological interpretations you have made are reminiscent of some of the most outlandish writings of "creation science" advocates. Do you not care that your musings have made you an object of ridicule among the scientific community (and increasingly among the general public)? You should, because they only serve to discredit the cause of marine conservation and play into the hands of those who wish to ignore the consequences of continued environmental degradation. The fact that you continue to do this suggests that notoriety, rather than real concern for the environment, is the real motivation for your actions.
Such speculation aside, I challenge you to scientifically refute any of the work you have chosen to highlight in your web pages. To do this, you will have to take Sam McClatchie's advice, and enroll in some basic ecology papers at University. You will find that the topics that concern you have been the subjects of intensive research for some time. Actually collect some data, display and analyse it, and test some of your ideas; you might begin to get somewhere. Write up your results in a coherent form and submit them to review by your peers. If the work passes scrutiny it might even get published. All of the papers you have placed (often illegally) on your site have been thru this process, which is not something that can yet be said about your ideas. Your claim that "scientific data is missing" smacks more than a little of hypocrisy. If you devoted half as much energy to constructive enquiry as you do to your current style of sensational and ill founded exposition I am sure you would achieve much more positive outcomes for the marine environment about which you claim to care so deeply.
Yours etc Dr. Russ Babcock
10 Oct 2003
I knew you would be unhappy with the marine research criticised by me on the Seafriends web site, because much of it relates to the work done by you. I have taken your own work and refuted it on your own findings, with my observations added, which are there for all to see and to refute if possible. You must be aware that as long as you are speculating that the environmental changes you are observing in marine reserves are related to their long-term 'benefit', you lay yourself open to this kind of rebuttal. In your letter you mention environmental degradation, but you don't seem to recognise it in your work.
You (and other scientists) must start by taking each of the points you disagree with and refute them one by one. I will publish this on the net to let people make up their minds. In the end, science does thrive from discussion. I will change what I have written if you are right and I am wrong. It is as simple as that. Every page on this web site asks for scientific input and correction. But don't forget that I too have done my homework and done a lot of studying and research of published scientific fact. Study the references and 'further reading' to satisfy yourself. Also don't underestimate my knowledge of New Zealand's seas.
To say that I have made myself the ridicule among the scientific community, is true particularly with those who profess to be scientists but are not in their way of thinking. What you fail to recognise is that I have also gained a lot of respect from those scientists who care to be challenged. I write about new ideas and pass these on for scientists to investigate. I have many letters of appreciation from overseas scientist.
Your statement that I don't care for the environment but am out to gain notoriety, is hurting. Just look at what I have been through so far in the past 13 years. Can you mention anyone with this amount of commitment for no pay? It is not easy to be the one noting the emperor has no clothes, and having the courage to say so. But I carry on because in the end, we must do the right things for the right reasons at the right time. We owe it to our children.
So, take a positive step and take some time to comment or criticise each of the points on the Seafriends web site that you find is wrong; provide proof; send it to me and I will correct my mistakes. For if you don't, you have said nothing at all. Invite others to do so too.
Regards, Floor Anthoni.
Specialisation in science has led to small groups or cliques sharing their experiences, visiting the same conferences while refereeing one another's papers. In such a close côterie robust criticism is not delivered for fear of alienating oneself. Whatever the reasons, it is deplorable that the scientific literature on marine reserves contains so much opinion, speculation and flawed research with many citations of the same.
Immediately after the mass die-off of the kelp forest inside the Goat Island marine reserve, we undertook a survey of the extent of the damage. We were there when dense plankton blooms covered the area between October and December 1992. We warned the scientists that the kelp would not be able to survive. Before Christmas 1992 we observed that all the kelp had already died, and again we warned the scientists of this. In the first week of 1993 cyclone Oli just finished it off. Not a trace was found of the entire kelp forest's canopy deeper than 15m. Only the stalks stood as evidence that a forest was once there. Again the scientists were informed, but nobody could take a look because of the summer holidays. Only after these holidays, did scientists discover that the kelp forest had indeed disappeared.
Scientists were confused finding kelp death both in the shallows and deeper than 15m but not in between. They could not conceive that the one had been caused by wave damage whereas the other was caused by lack of light. As a result they went about their investigations in a less than thorough way. They did not recognise the importance of such a major experiment conducted by nature and the possible lessons that could be learnt from it, and its possible ramifications. This spurred us to do an extensive survey to establish the precise areas affected and what other lessons could be learnt. It taught us much about the ecology of the sea coast, particularly that of kelp and urchins. You can find this report in www.seafriends.org.nz/enviro/habitat/survey93.htm.
Our main findings relating to urchin barrens:
In the period that the kelp forest disappeared, we were fortunate that we were able to make many dives around Leigh and further out. Because of our school programmes during which we guide students snorkelling the Goat Island Channel, we were frequently in the sea from September to May every year. Dense plankton blooms are not welcome because it hampers the programme and reduces the 'wow' experience of the school visit.
the plankton blooms between October and December 1992 were exceptionally
dense, a few exploratory dives were made to observe plant life in the dark.
At the peak of plankton blooms, visibility was less than 2m at the surface
and the light at 20m depth was so poor that the sandy bottom could hardly
be distinguished from the dark rock. It was darker than a moon-lit night.
In November the kelp turned dark brown and started to look like wet kraft
paper on woody stalks. By mid December, their crowns fell apart when touched
but in shallower water the kelp appeared entirely unaffected. It was clear
that a major event had happened, and we informed the Marine Laboratory
accordingly. The photo shows what the dead kelp forest looked like.
In the first week of January 1993 tropical cyclone Oli struck, and when diving became possible again, we saw that the whole kelp forest below 15m had disappeared. In the months following, the kelp died back further to effectively disappear where once the forest stood. Some shallow water dieback was also evident but this was caused by the waves of cyclone Oli. The second photo shows what an extensive sea urchin barren looked like (June 1995, Waterfall Reef), with a cluster of sea urchins in the foreground and a leatherjacket (Parika scaber) above. Note that the kelp had not yet invaded the barrens.
In March 1993 we did an exploratory study in order to prepare a more
extensive one, which we did in the winter of 1993 (Aug-Sep). The results
of this study you can find on this web site in /enviro/habitat/survey93.htm.
The above two maps are important to understand why the urchin barrens
theory is a myth. The first shows where the 91/92 kelp deaths occurred,
but more importantly, the second shows where the 92/93 kelpbed death occurred
and to what extent. The areas marked 4 and 5 lost 80-100% kelp cover, and
all these areas recovered the way of Goat Island, with loss of urchin habitats.
Yet these are not marine reserves. Here is what happened to their kelp
and urchin habitats:
diagram depicts our observations in the years preceding and following
the kelpbed death events. On the left the situation where the kelp bed
was removed twice, first partially in 1992, then fully in 1993 (Little
Barrier, Simpsons Rock, Arid Island). On right the situation where the
kelp was removed once, but completely.
In 1991 both areas had a mixed age kelp forest. In 1992 part of the kelp forest disappeared in some areas, followed by rapid recruitment and full regrowth because grazers had plenty of food in the remaining stands of kelp. The urchins stayed in their barrens. By late 1992 the kelp forest had almost complete coverage.
In Dec 1992/ Jan 1993 the kelp died, again because of dense plankton blooms. Recruitment was immediate and intensive in the areas where the kelp once stood but not outside these. However, all regrowth was eaten by the remaining grazers, which included fish. The urchins strayed from their barrens into the deep, leaving their barrens insufficiently grazed.
Successive waves of recruitment but much less intensive followed. Kelp settled slowly into the urchin barrens and the areas where the kelp once stood. This time it was successful and it took over the urchin barrens. The full takeover took several years until the kelp reached maximal growth rates. Isolated reefs like Floors Reef and Leigh Reef took until 1998 before they were recovered fully. These have no urchin barrens, yet grazing there was very intensive.
We also noticed massive urchin deaths and poor recruitment, which affected the process.
From the scientific research dissected on this page, it can be seen
that scientists were not aware of the above, even though they were in possession
of our Hauraki Gulf Marine Survey 1993 report.
The changes in community structure by top-down control (the urchin barrens theory) was a reverberation of the 1993 kelpbed death. It was caused not by the beneficial effect of no-take protection but by degradation! The urchin barrens theory is a myth.
The map above is a composite of three maps drawn by Land Information
(LINZ), which was the Department of Lands and Survey. The data for this
map was obtained by a team of divers under leadership of Dr Tony Ayling
in 1977. Click on the map for a page-sized one. The depth of the rocky
shore ranges from 15m in the west to 23m in the east with a sandy bay about
one quarter from west ending in a shelly beach.
The habitat zoning can clearly be seen. The shallow dark brown zone consists of tough bladder weeds (Carpophyllum spp). The grey/blue zone corresponds to the urchin barren zone. Notice the large area of submerged rocky shore around Goat Island, which is unique. Because of its gentle slope, most of the barren zone is also found here. Also unique are Goat Island's areas of shelter preferred by fish, its extensive crayfish habitat and shellfish beds, caves and broken rock (large boulders). To the west of Goat Island the substrate consists of layered mudstone; to the east of (broken) hard greywacke. Note how the shores to the west and east become more representative of the coast in this region, having a narrow rocky substrate. Further west extends the 25km long Pakiri Beach, which makes Goat Island the first rocky outcrop with shelter and currents, like an oasis at the end of a long stretch of desert. There is no place like Goat Island in a vast region around.
Scientists also do not take sufficient care in comparing apples with apples on the choice of their transects and areas of study. They believe too much in the impartiality of dice. Yet transects and areas of study must be chosen carefully to match exposure, aspect (orientation), depth and isolation (sand, crevices, walls). Otherwise too much spurious data will spoil the experiment.
Scientists view snapper (Pagrus auratus) and crayfish (Jasus edwardsii) too much as predators rather than scavengers. These animals are strongly attracted by stressed organisms such as damaged sea urchins (Evechinus chloroticus), shellfish and other. Likewise the common urchin (Evechinus chloroticus) is strongly attracted to stressed kelp.
Scientists make no mention of major oceanographic events happening during their experiments (or just before), events that could have influenced the outcomes of these experiments. Chronology, mentioning the precise start and end of the experimental period is therefore important. In their papers they fail to report the time of study relative to large events like cyclones, kelpbed deaths, large urchin mortalities and the disappearance of crayfish.
Scientists are so keen to show overwhelming benefits arising from marine reserves that they lose objectivity. It has led to nonsensical conclusions as the reader may see for himself. The fact that much research was funded by the Department of Conservation who manages reserves and whose task it is to create more, did not help - one does not bite the hand that feeds. As a result, politics have entered science. Read also our extensive myths and fallacies section.
The baited underwater video camera (BUV)
is a highly questionable measuring device since it aims to influence the
quantity measured rather than minimising its influence as is required for
any other scientific measuring device. Not only does it bait the camera,
but it also offers an additional pilchard as food! Such a method grossly
overestimates the quantity measured and should never have been attempted
as a scientifically acceptable measuring device. But it can be used qualitatively
to say that at some place there are more or less fish than at some other
place. Scientists have never proved its linearity (as in a voltmeter) for
quantitative measurements. [in a linear instrument, there is a one-to-one
correspondence between the measured and actual quantities]. For a description
of the BUV method, see further on this page and in our
Asked Questions about marine reserves.
By exposing a number of scientific experiments on this page, we have shown that marine ecological research in New Zealand has not matured. Marine scientists have drawn major conclusions from failed experiments while not taking sufficient care in comparing apples with apples. Rather than following the traumatic events of 1992/93 with an interest in learning from them, scientists have been only too keen to explain ecological changes in terms of the success of marine reserves rather than due to their failure (degradation, kelp death, mass mortalities, poisonous slime).
Our own research adds a refreshing turn to the issue, filling in the missing bits while providing new insight into the rocky shore ecology. Although it is not our task to do marine research, it is nonetheless the task of the public to expose faults and fallacies where scientific self-policing fails. We are waiting for the scientific community in Leigh to correct its mistakes, by looking at the bloom-affected areas around the outer Hauraki Gulf, in order to arrive at the inescapable conlusions:
the snapper-urchin-kelp hypothesis is a
marine reserves do not cause sudden ecological changes after a long period of stability.
urchin barrens are created mainly by storms.
to prove that coastal marine reserves are working is wasting time and money.
marine research should focus on studying the causes and effects of land-based pollution and degradation.
in the Cape Rodney to Okakari Pt Marine Reserve
Advice to the Department of Conservation, June 1993
R C Babcock and R G Cole
University of Auckland Leigh Marine Laboratory
[our comments in blue]
In our own study we excluded the areas north of Whangarei after a preliminary survey in March 1993. It allowed us to concentrate more on the areas surrounding the outer Hauraki Gulf. Because of our extensive spatial data, we can say that the bloom and its mortality did not centre on the Goat Island marine reserve. See our map on right. The area around Port Fitzroy on Gt Barrier I is rather patchy, possibly because this harbour has its own plankton ecosystem and may have been spared some of the bloom's ravages. Also unaffected water flows north and out of the Hauraki Gulf past these areas.Mortality is patchier in other areas such as Great Barrier Island. Recovery of affected populations is already underway with high levels of recruitment having taken place at the marine reserve between January and May 1993. Full re-establishment of kelp populations should proceed over the next year, unless recruiting kelp become susceptible to mortality in the post-juvenile phase. The causes of the mortality are not yet known but all hypotheses put forward to date have related to natural environmental processes and human impacts are not implicated.
It is always surprising how the human factor is reasoned out of the equation so quickly. If something is unique or cyclical, then humans are not at fault, it is reasoned. But what caused the concentrations of nutrients necessary for this plankton bloom build-up? When is a unique event just the first of many to come? When is a deteriorating trend from moderate kelp die-off in 1982 to a large one in 1992, recognised? When are such events admitted to be degradation of the environment?
These two data points are accidentally the only ones showing the situation before and after. The top two curves of the before situation, show that the kelp forest is found deeper than 9-12m. After the plankton blooms the deep kelp disappeared, leaving the shallow kelp unaffected. Note how kelp diminishes with depth in the bottom diagrams.
Local mortality patterns
The proportion of kelp populations damaged or intact varied considerably among sites within the marine reserve (Fig 4), though all sites had low densities of intact plants. The proportion of intact plants was relatively high (over 50%) at Marimo and Point, but was much lower elsewhere. For example Waterfall and 'D' the mortality process appeared to be still active. The proportion of the populations contributed by recruits was also variable with North Reef and Lookout having the highest levels. Despite the overall variability, highest levels of damage were consistently seen in the deepest levels at each site.
Fig 4. Local variation in relative kelp mortality, May 1993. Data presented are proportions in each damage category based on video transects and they represent all depth categories.
The authors made a major error of judgement by including recruitment, which happened after the kelpbed death, in their results, rather than dealing with this separately. The pie diagrams should also have included barren areas without kelp. In this map a shallow shore like Marimo seems to have sustained little kelpbed damage whereas in reality it does not go deep enough to have a substantial kelp bed. The map cannot be interpreted without much local knowledge. Had the authors displayed the amount of kelp canopy left as part of the natural kelpbed zone, it would have been very clear that the kelpbed death is very consistent along the shore. The method also becomes useless in areas or zones which have been hit by a kelpbed death in two successive years, see below.
A survey of sites between Cape Karikari in the north and Kawau Island in the south, and offshore to western Great Barrier Island, revealed that in this region kelp mortality was restricted to the outer Hauraki Gulf area. Sites at Whangarei Heads, Okakari Pt to Cape Rodney Marine Reserve, Little Barrier Island and Great Barrier Island were all affected by recent large-scale mortality of Ecklonia. However, other sites at Gt Barrier I were unaffected, as were sites at Takatu Peninsula and Okakari Pt.
This observation agrees with our findings. What confused the authors is that their method could not distinguish between sites that had been devastated twice, such as some of the Gt Barrier sites. The authors have not taken due caution excluding sites with shallow sand bottoms such as at Okakari Point and some at Takatu. The authors did not make a distinction between shallow and deep kelp death.Thus within the region where mortality is evident there was variation in the level of mortality between sites as well as at local scale within sites. This local scale variability was evident over short distances with the first two sites for Gt Barrier Island, being separated by only 100m. See notes before.
In our surveys we identified the seemingly contradictory site at Gt Barrier I as a marginal case where the kelp jaundiced but recovered. It was then destroyed in shallow water by the force of Cyclone Oli. The author's method is not suitable for sites with complete loss of kelp and no recruitment, yet many such places could be found. Although the Gt Barrier I site seems inconsistent, it is consistent with nearby sites. See also notes below.
Very few recruits of Ecklonia were detected in surveys of the marine reserve during January. During March numerous recruits were noticed in parts of the reserve and by May high levels of recruitment were evident at most sites. . .
The recruits should have been dealt with separately since they did not exist before the plankton blooms.
Possible causes of mortality
Several scenarios have been proposed in attempts to explain the mass mortality of Ecklonia radiata in the region under consideration. There are three basic hypotheses:
. . The patchy nature of the mortality at other locations such as Gt Barrier I is consistent with this hypothesis, rather than a broad-scale physical phenomenon. . . [viral tests] . . The possibility of viral involvement is still being actively pursued but the presence of agar in algal tissues has hampered progress since it interferes with techniques used as assays for viral activity. . .
Every marine organism with reduced health runs the risk of attack by decomposing organisms like viruses and bacteria. To find these pathogens on dead and dying kelp is akin to finding fungi on rotting apples. What is pathetic is that the authors have been warned before December 1992 that the kelp forest stood dying and their fronds drooping like wet kraft paper. It is notable that after Cyclone Oli not a trace was found of the masses of dead canopies. They seemed to have vaporised. They did not have any food value left in them. Pathogens cannot achieve a kelpbed disappearance within several hours or even days.
. . . The first general hypothesis is that mortality is simply and directly related to low temperatures, an idea consistent with the gradual onset of the mortality during 91-93, but at odds with the observation that plants in shallow water were unaffected, and also with the lack of mortality at points further north.
Ecklonia is found all around the North and South Islands, tolerating temperatures between 6 and 23 degrees, and mortality was abrupt, rather than having a gradual onset.Phytoplankton blooms have also been suggested as a possible causative agent since they would reduce light available to the kelp for photosynthesis. The mortality of deep water kelp first in the reserve is consistent with this hypothesis, as is the regional distribution of the mortality, since the plankton bloom of late 1992 was most intense in the Hauraki Gulf between Whangarei Heads and Great Barrier Island. The mortality of shallow-water kelp in some locations, as well as the continued progress of mortality long after phytoplankton blooms had dispersed, contradict this hypothesis, unless the energy debt is so great that plants cannot catch up despite improved conditions.
The deep kelp death was without any doubt caused by lack of light. Not only have we seen it happen, we have also predicted that it would happen! What the authors don't realise is that the shallow kelp death was caused by wave action. The authors are rather naive about the nature of life and survival after being exposed to a gradient of a lethal agent. The Hiroshima and Nagasaki atom bombs caused immediate deaths but also some forty years later. Even on the way to recovery, an organism remains susceptible to other attacks.Demographic cycles
Although the above reasoning is valid, the authors and many before them have never looked at the age composition of a natural kelp forest. There is talk about the number of plants per square metre or the amount of cover but the age composition is nevere mentioned. Thus the transition from a multiple-aged forest in 1991 to a single aged forest in 1994 has been left unnoticed.
Kelp mortality is limited in extent and is seemingly most severe in the outer Hauraki Gulf region. Within the affected area mortality is patchy, but is most common below 10m. Populations have been recruiting rapidly and should recover over the next one to two years unless the cause of mortality (which has not yet been identified) persists.
The effects of the kelp mortality on other organisms on the reef are not readily predictable, but appear to be of considerable potential importance to energy flows, growth rates and behaviour of grazers, and the population characteristics of fishes. Insufficient long-term information exists to judge the magnitude of the effects which may derive from this event, or the significance of the mortality to the reef environment.
The authors give themselves advanced warning that after a major event, major changes could follow. Yet they have not taken heed as some of the following papers show how they interpreted the disappearance of urchin barrens as a beneficial effect of aged marine reserves (due to the presence of large predators), rather than being related to the 1993 kelpbed death (degradation).
Russell C Babcock, Shane Kelly, Nick T Shears, Jarrod W Walker, Trevor J Willis
Mar Ecol Prog Ser 189:125-134 (1999)
Leigh Marine Laboratory, University of Auckland
P O BOX 349, Warkworth, New Zealand.
[blue text is ours]
The authors studied two 'old' marine reserves in northeastern New Zealand, at Goat Island (established in 1975) and Tawharanui (established in 1982), in order to detect whether changes in protected predator populations had resulted in other indirect changes to grazers and consequently to algal abundance. They conclude that this is indeed the case and that they found more urchin barrens in the protected areas.
The 1977 date is misleading because the situation stayed stable until the large kelp dieback. Not a word about the large-scale kelp forest die-off in 1993. The 1994 date is wrong since kelp recruitment failed that year due to hungry grazers of all kind. The conclusion is not at all substantiated by the research done (see below). Large-scale disappearance of urchin barrens was caused by the 1993 disaster. This aerial photo taken in April 1999, shows the main barren area of the Goat Island marine reserve. Notice how the kelp is beginning to invade, but most of the invasion happened suddenly a year later. Scientists maintain that it was a gradual process that began before 1980, which is proved false by this photo.
|This location map shows in dashed lines the countours of the Goat Island marine reserve in the north and the Tawharanui marine park in the middle. The numbered areas are the places where measurements were taken. The shaded circles are the places where lobster abundance was measured.|
The study areas were the two oldest marine reserves in New Zealand, the Cape Rodney to Okakari Point Marine Reserve (hereafter the Leigh marine reserve, 518ha, established in 1975) and Tawharanui Marine Park 15 km to the south (350ha, established 1982). Non-reserve reference sites were located on similar areas of coast adjacent to the reserves.
It is misleading to call these the two oldest
marine reserves, even though they are. Why are the Poor Knights (1981)
not included? Why is this not explained? Our objection is that north facing
coasts (exposed) cannot be compared with south-east facing coasts (sheltered).
The outcome of the results of this study could be interpreted as 'north
facing slopes have lost their barrens' rather than 'marine reserves did'.
Another problem of the choice of study site is the choice of areas 1, 2, 3, 13, 14 and 15. These shores are too shallow to have urchin habitat zones. They are bound to cause unnecessary noise in the data.
Sampling effort was spread evenly across both reserve and non-reserve areas by dividing them into a number of sites and then sampling haphazardly within them. This was done to avoid biases that might be associated with human activities in the Leigh marine reserve, (e.g. fish feeding, c.f. Cole et al 1990) . . . .
Estimates of predatory fish abundance and size were made during October and November 1997 using remotely-deployed baited video stations. A vertically oriented video camera was mounted over an enclosed bait consisting of four whole pilchards (Sardinops neopilchardus) with one additional pilchard tied externally to the food container. . . . .
The baited video camera method exaggerates. See comments about the BUV in recurring mistakes.Spiny lobster abundance
The timing of these surveys is at odds with the time of the experiment (1998), since the lobsters were counted in 1995 when all sites were still having urchin zones. During the time of the main experiment, this was no longer so. Furthermore, between June and October 1998, 85% of all crayfish walked out of the marine reserve due to a prolonged period of heavy rains and sediments (personal observation). Not a word about this in this paper. Note also that the Little Barrier Island survey was not part of the 1998 study area, although the areas surveyed are more similar to the marine reserves they are compared with. The graphs below must therefore be interpreted with care, also because the results of each reserve are not shown separately. Leigh may for instance swamp the data from Tawharanui. Why was it done this way? Our suspicion is that Tawharanui has a very low crayfish density.
The diagrams show the densities of snapper (left), as counted with the baited camera and that of crayfish (right) counted visually.Algal abundance
As mentioned before, the SE facing coast cannot be compared with the north facing reserves, since it is more sheltered and more shallow. The sites near large beaches are similarly incomparable. More caution should have been exercised in choosing the survey sites.
Temporal changes in the density of kelp and urchins in the Leigh Marine Reserve.
Measurements of the abundance and size of kelp and urchins made in prescribed areas of the Leigh reserve in 1977-78 ("permanent quadrats" Ayling 1978) provided a direct basis for assessing temporal change. These data were obtained in a range of habitat types using haphazard 1m2 quadrats within 26 defined 100m2 areas. The same measurements were repeated as close as possible to nine of these areas in 1994 and fourteen of them in 1996, using the detailed maps provided by Ayling (1978). All of these areas were classified by Ayling (1978) as either kelp forest or rock-flats. Samples from 1994 and 1996 were estimated to be within 20m radius of the original 1978 areas, and were in the same depth range as Ayling's areas, as indicated on his habitat maps (Ayling 1978) . . . .
It is a blessing to have permanent quadrats for monitoring how the environment changes with time. However, Ayling's maps were used and these have proved to be less accurate. It would have been more helpful to establish new 'permanent quadrat' sites with accurate GPS co-ordinates. The dates of these surveys are again not concurrent with the 1998 date of the main survey, and particularly 1994 is questonable in relation to the 1993 kelp death. However, the data reflects what can be seen with the untrained eye.
(The analysis is waiting for a copy of Littler & Arnold's and Novacek's publications). It would have been more helpful to have measured the productivity in-situ, since using other people's data from other places in the world, and from so long ago, is highly questionable. It is not clear precisely what productivity has been measured. Is it the production of algal biomass? That certainly does not follow ecological concepts of productivity. It is often better to estimate the biomass of the grazers because kelp makes much indigestible biomass. Kelp has very few grazers, which includes fish. Its fronds are often found rotting back for lack of grazers. Broken fronds are caught and eaten by sea urchins. One cannot compare the 1997 kelp forest, consisting essentially of one year class, with that of 1978 which consisted of many year classes (personal obs).In the discussion we find many nonsense statements:
The most disturbing aspect of this part of the research is that it is at odds with ecological principles. The productivity of micro algae growing on the crustose coralline is much higher than that of macro algae because of their much smaller size and much higher growth rate. Furthermore, urchin barrens experience more light and the light colour of the CCA reflect light back, thus enhancing productivity further. Even measuring the biomass of grazers is fraught with problems since urchins spend most of their energy producing spawn.
Reader please note that CCA (Pink paint) is like living stone, hard and inedible while growing only very slowly. No surprise then that its 'productivity' is very low. However, the barrens' productivity comes from fast growing green hairy algae growing on top of the ink paint. Yet this was not measured. This is akin to claiming that the productivity of grassland equals that of bare land.
Note that other research has been done on the predation of 'tethered' urchins, see further on this page. The authors do not mention mass urchin mortality in the 1994-1997 period even though they studied this as well. But the most worrisome aspect of this research is the absence of a time study of the populations of the major players, snapper, crayfish, kelp and urchins. Had they done so, they would have seen that the 1993 kelp die-off event was the cause of all instability observed later, including urchin deaths.
Our results also suggest how no-take marine reserves can change benchmarks for environmental and fisheries management. This statement is for the benefit of DoC.
The recovery of kelp populations subsequent to protection indicates that fishing activities on New Zealand's northeastern coast have had ecological impacts far beyond the target species. These effects, though indirect, are just as striking as those caused by fishing practices such as trawling, that remove or destroy conspicuous components of fished habitats (Rothschild et al. 1994, Dayton et al. 1995, Watling & Norse 1998). Perhaps more importantly in the case of kelp forests, these conspicuous components are also major primary producers (Mann 1973), whose contribution to detrital food webs is central to ecosystem function and diversity (Duggins 1980). . . . (sigh)
. . . The corollary of this (higher productivity) is that benthic primary productivity in areas outside of reserves is much lower than it was prior to intensive fishing. . . . Kelp forests in northeastern New Zealand are known to have far higher rates of secondary production than do rock-flats habitats (Taylor 1998), supporting the suggestion that these effects are likely to be broadly felt throughout the ecosystem. (awaiting arrival of Taylor's publication)
These observations indicate that the efficient management of coastal fisheries can no longer ignore the consequences of fishing on the wider ecosystem and attempts are now being made to understand the benthic ecosystems in terms of multi-species fisheries models (McClanahan & Sala 1997). No-take marine reserves represent a large scale ecological tool that can play an important part in the development of such models. Unfished areas provide a way of assessing ecosystem function and avoiding the 'sliding baseline' phenomenon, in which expectations of what is natural are reduced because may of the original components of the system are reduced or absent (Dayton et al. 1998). . .
Far-reaching conclusions for what is in essence an experiment that measured the sliding baseline effect of degradation, triggered by the kelpbed death in 1993, and did not provide significant results! (Sigh again)
Although the author identifies surprise: p30: "Research within reserves continues to generate surprises about how marine ecosystems function (Babcock et al 1999)", he asserts on p24:
"One of the most dramatic reserve effects occurs when habitat protecion leads to a wholesale ecosystem shift. On the coast of New Zealand, where fishing for spiny lobster (Jasus edwardsii) has been severe, urchin populations have exploded and kelp almost disappeared. Halting the exploitation of lobsters in New Zealand marine reserves brought the kelp back, along with the fish that inhabit kelp forests, reconstituting a whole ecosystem (Babcock et al. 1999). In this case, lobster exploitation cost the marine ecosystem much more than this one species, and protection restored the ecosystem by limiting biological habitat destruction caused by overabundant urchins. This is a simple case because only one pivotal species, the spiny lobster, is present, and it could be argued that single-species management would do the job as wel. . . " [sigh]
National Research Council, 18 authors. Marine Protected Areas: tools for sustaining ocean ecosystems. p129:
In New Zealand such trophic interactions impacted even more of the food chain. Because fish are the major predators regulating the population of sea urchins, closing areas to fishing converted them from urchin-dominated algal 'barrens' to kelp forest (Babcock et al, 1999) . . . . Studies in the Leigh Marine Reserve in New Zealand indicated that target fish species can act as keystone predators whose removal causes strong shifts from sea urchin barrens to kelp-dominated ecosystems (Babcock et al 1999).
Nick T Shears. Russell C Babcock
Springer Verlag May 2002
Replicated ecological studies in marine reserves and associated unprotected areas are valuable in examining top-down impacts on communities and the ecosystem-level effects of fishing. We carried out experimental studies in two temperate marine reserves to examine these top-down influences on shallow subtidal reef communities in northeastern New Zealand. Both reserves examined are known to support high densities of predators and tethering experiments showed that the chance of predation on the dominant sea urchin, Evechinus chloroticus, within both reserves was approximately 7 times higher relative to outside. Predation was most intense on the smallest size class (30-40mm) of thethered urchins, the size at which urchins cease to exhibit cryptic behaviour. A high proportion of predation on large urchins could be attributed to the spiny lobster Jasus edwardsii.
Top-down regulation of biological communities has been a focal point in ecological theory (Hairston et al 1960). This is ironic, given the efficiency with which humans have themselves harvested the large-bodied animals which may be responsible for the top-down control of ecosystems, in many cases to extinction (MacPhee 1999).
The authors seem to have missed the point that predation by Homo sapiens has not led to extinctions in the continent where humans evolved. However, whenever humans migrated to new continents and islands, they were able to extirpate large animals that had not evolved either fear of or defences to humans. The same happened with the introduction of alien predators like rats, cats and stoats to remote islands.The authors continue with a list of examples of trophic cascades and research done on this.
Top-down regulation is a myth since populations interact on the basis of economy or effort. See our explanation of the economics of exploitation in the Resource Management chapter.
Trophic cascades are defined as predatory interactions involving three
or more trophic levels, whereby primary carnivores indirectly increase
plant abundance by suppressing herbivores (Menge 1995). . . (more references)
. . However, good empirical examples supporting the existence of such trophic
effects are generally lacking (Scheibling 1996). . . . (The authors mention
the Californian sea otter - urchin - kelp story. Which
may well be flawed like the research done here in NZ) . . In some
areas where sea otters do not occur, fish and lobsters have been implicated
as important predators of urchins. (more doubt) While
the destruction of kelp beds by sea urchins in these areas has been linked
to overfishing of both lobsters and fish, the existence of a direct causal
linkage has received much debate (Scheibling 1996).
. . . . . (more references) . . However there has not yet been any decline in the extent of urchin barrens in these protected areas (Mediterranean Sea). Other factors such as recruitment, pollution, disease, large-scale oceanographic events, urchin harvesting, food subsidies and availability of shelters may also be important in controlling algal assemblage structures (Sala et al 1998).
This paper deliberatley fails to discuss the most important effects on urchins and kelp, those of recruitment failure, massive kills, pollution and storms, all of which have had a major influence during and before the experiments. Note how other studies could not replicate the decline of urchin barrens in protected areas.The aim of this study was to demonstrate the indirect effects of fishing on lower trophic levels by experimentally examining the top-down role of predators in explaining the habitat change documented in marine reserves in northeastern New Zealand. This was done by:
It is deplorable that this study was motivated politically, to show that marine reserves work, rather than searching for more understanding of urchin and kelp populations. The authors chose the only two marine reserves in New Zealand (out of 15 others) where urchin habitat disappeared!! Is this by chance?
|Materials and methods
Study area: see map.
Daily monitoring enabled detection and replacement of urchins that appeared to be dying as a result of tethering. In each experiment only four out of a total of 180 tethered urchins died as a result of tethering. . . .
Fig 1. Location of study sites in the Cape Rodney to Okakari Point Marine Reserve (CROP) and Tawharanui Marine Park. Circles indicate sites where the predation experiment was carried out. Inset shows general location of study area in New Zealand's North island.
This is a well thought-out experiment with adequate precautions in the laboratory. When urchins bleed (coelomic fluid leakage) they attract scavengers of which there are many, and it cannot be guaranteed that the urchins had indeed healed completely. To do an experiment where this does not play a role, requires careful execution. However, the two coasts selected are incomparable. Both reserves are facing north, being much more exposed than the SE facing coast. Three locations to the west of both reserves are located in shallow water where urchin barren zones normally don't occur. Results could be interpreted as "north-facing coasts favour survival of tethered urchins". coscinasterias being the main predator in the non-reserve group, bears this out. Worse still, was the north facing slope of Kawau (SE of Tawharanui) ignored as control site because it produced inconsistent data in other experiments?
|Predation on urchins was significantly
higher at reserve sites than at non-reserve sites (F=9.44, P=0.0133), with
the relative odds of predation being 6.9 times higher at reserve sites
(Fig.2, Table 1).
The fate of all small urchins preyed upon at reserve sites was unknown as the tests were completely removed from their tethers (Table 2). This could have been due either to predation by fish, which completely engulf the urchin, or by lobsters breaking up or removing small urchins. (or by wave action?) At reserve sites approximately 45% of preyed individuals in the larger size classes showed patterns of damage characteristic of spiny lobster predation. No urchins showed signs of spiny lobster predation at non-reserve sites. In most cases mortality at non-reserve sites could be attributed to starfish (Coscinasterias muricata) or the gastropod Charonia lampax, both of which are slow-moving predators. (but which remain on-site, having an acute sense of smell for stressed animals)
Reader please note that a sleight
of hand is presented here, where the researchers talk about odds of predation,
which is the inverse of survival. The curves on right show survival
rates, with non-reserve sites doing between 30-90% of reserve sites. Leigh
approx 30,50,70% and Tawharanui 40, 80, 80%. Note also that mortality is
critical in the first few days, after which it becomes negligible.
The authors do not attempt to explain this effect.
Fig 2. Survival of tethered urchins at reserve (black circles) and non-reserve (open circles) areas. The mean number of tethered urchins surviving in each of the three size classes is given for Leigh and Tawharanui.
We wonder why this experiment was not continued for days 15, 20 and 30, which would have revealed more interesting information. Reader please not that the difference between 98% and 96% survival rate is negligible while this corresponds to mortality rates of 2% and 4%, representing a major difference. Note how survival rates eventually level off.
Urchin density and size structure
Densities of Evechinus in the urchin-grazed habitat varied widely between sites but were generally lower at reserve sites for both areas (Fig 3). the density of exposed urchins (Fig 3A) was significantly lower at marine reserve sites (Tables 1,3 [left out]). Exposed urchins were 1.7 times more abundant overall at non-reserve sites (Table 1 [left out]). There was no difference in urchin density between Leigh and Tawharanui areas but there was a significan interaction between Area and Status (parameters of the statistical mixer).
This graph shows fewer large urchins in reserves but a comparable number of recruits. Also those inside reserves are larger, although not so for Tawharanui. The difference is more pronounced for Goat Island and almost negligible for Tawharanui. when expressed in grazing capacity, the difference is likely to become even less significant. This difference comes to expression in the bimodal size distribution of urchins inside the Leigh reserve.
|Comparisons of urchin populations
Populations were more bimodal (having two peaks) at reserve sites, with very low numbers of urchins between 30 and 50mm and they generally remained cryptic (hidden in cracks and under boulders) to a greater size. This pattern was stronger in the Leigh marine reserve.
The authors make no effort explaining the bi-modality, which could well be a symptom of stress, degradation, mortality or recruitment failure, all three symptoms have been observed in the reserve areas. The fact that urchins remained cryptic to a greater size may well be related to the difference in wave exposure between the reserve and non-reserve sites. It urges caution in interpreting the tethered urchin experiments where the small urchins (35mm) and arguably also the 55mm ones were indeed still cryptic for the north facing coasts. If these are omitted from the experiment, only very little difference in survival rate remains to explain the disappearance of the barren zones.
Fig 4. Size frequency distribution of all Evechinus measured during quadrat sampling at each area. Shaded bars indicate poportion of cryptic urchins.
At the commencement of the experiment in January 1998 Evechinus densities did not vary between treatments. Densities of urchins ranged from 1.2 to 2.4 per 0.25m2. Crustose coralline algae (Lithothamnion and Lithophyllum spp.) were dominant, covering 63-99% of the substratum. Articulated coralline turf was the other dominant encrusting form with cover ranging between 0 and 35%. There was no significant difference between either crustose coralline algae or coralline turf between treatments or between plots within treatments. Macroalgae were rare at the start of the eperiment, with Carpophyllum flexuosum which is relatively resilient to urchin grazing (Cole and Haggit 2001), being the only conspicuous large seaweed. . . .
After 1 year the control plots remained as urchin barrens dominated by crustose coralline algae, while the urchin-removal plots had become dominated by coralline turf, with a mixture of large and small brown algae. . .
This experiment was conducted in the SE facing
shore near Mathesons Bay, which is characterised by medium exposure and
rock fissures creating ideal isolation for experimental plots. Although
the experiment removed the urchin as grazer, other grazers such as Cookia
sulcata and many fish species still had access.
Fig 7 A-D. Response of macroalgae to urchin removal. The mean abundance of A Carpophyllum flexuosum, B Ecklonia radiata, C Halopteris virgata and D small brown algae in both control (open circles) and urchin-removal plots (full circles) following the commencement of the experiment in January 1998.
Distribution of urchins habitat
The general distribution of habitats (Fig. 8) at non-reserve sites is typical of northeastern New Zealand with shallow fucoid (bladder weed) assemblages, deep kelp forests (Ecklonia radiata) and intermediate depths dominated by urchin barrens (Choat & Schiel 1982). However, at marine reserve sites all depth ranges were dominated by macroalgal habitats. The proportion of urchin barrens habitat was significantly lower than at non-reserve sites (Tables 1,7) [7 left out]). The relative odds ratio for the proportion of urchin barrens at reserve vs non-reserve sites was 0.2 to 1 (Table 1) or inversly, 5.9 times higher at non-reserve sites. This pattern was consistent between both areas but varied significantly with depth (Table 7). Differences . . were greatest in the shallow depth strata (0-3m and 4-6m) where urchin barrens covered approximately 54% of available reef at non-reserve sites and only about 20% of the reef at reserve sites. The deeper strata (7-9m and 10-12m) at both reserve and non-reserve sites were dominated by macroalgal habitat, predominantly Ecklonia forest.
Fig 8. Mean percent cover of major habitat types (shallow fucoids, urchin barrens, turfing algae
and kelp forest), within each depth range for reserve and non-reserve sites at Leigh and Tawharanui.
The top two bar charts show that the fucoid zone in Leigh is deeper than elsewhere, wich demonstrates what we alluded to earlier, that the Goat Island coast is more exposed. Note how the urchin barrens have been invaded by the kelp forest, which is easy to see under water. Had Kawau and/or Little Barrier Island been included, they too would have shown a kelp takeover. Sadly, this has not been done.Discussion
Their study was carried out after only 4 years of marine reserve protection. If it were to be repeated now after 25 years of protection and recovery of predator populations, a larger effect may be expected. This myth lies at the heart of so much research done in recent years, blinding researchers from seeing the obvious. Where is the proof?
This study demonstrates the value of marine reserves as experimental tools to test ecosystem-level hypotheses at ecologically relevant scales, previously unfeasible using traditional caging and manipulation experiments. (Andrew & MacDiarmid 1991). Marine reserves have enabled us to measure the top-down role of predators in structuring subtidal reef communities in northeastern New Zealand, as well as the indirect effects of fishing on the trophic structure of reef communities.
This study does not give enough evidence for the above statement. When other areas are taken into account (Kawau, Little Barrier, Great Barrier, Rakitu, Mokohinau) it can be proved that this study is a failed experiment.The map shows how the authors have observed kelp invasions inside two marine reserves (red areas), but failed to observe similar effects elsewhere, particularly in the yellow areas nearby the study area (yellow areas). All areas where we observed kelp invasion of the urchin barrens were located where previously kelpbed death has been observed. This can still be confirmed today (2006).It is unclear whether, or to what extent, these findings can be extrapolated to other regions where urchin barrens are less common and interactions between trophic levels are weaker. They CANNOT.
high density and biomass of snapper Pagrus auratus (Sparidae)
in northern New Zealand marine reserves.
Trevor J Willis, Russel B Millar, Russ C Babcock.
Journal of Applied Ecology (2003) 40,
It has been widely suggested that marine reserves (areas of sea permanently closed to all forms of fishing or disturbance),
in addition to performing a conservation function, might be of long-term benefit to fished stocks. The potential benefits are many [oops, see marine conservation and FAQs] and have been described extensively (Roberts & Polunin 1991; Allison, Lubchenco & Carr 1998; Bohnsack 1998; Jennings 2000).
In essence, the ideal is protection of a portion of an exploited stock,
with the expectation that the biomass of targeted species within protected
areas will rebuild to approach unfished densities. Density-dependent processes
might then cause emigration of adults from the ‘source’ (reserve) population
to fished areas, either by passive diffusion (Beverton & Holt 1957)
or by displacement of individuals caused by space limitation (Kramer &
Chapman 1999). Additionally, spawning activity within the reserve by greater
numbers of large individuals should result in greater production of gametes
than in similar, unprotected areas.
. . . (the authors discuss computer models in studies) . . . While these effects are generally positive, on a case-by-case basis evidence for substantial recovery in populations is often limited (Jones, Cole & Battershill 1993; Rowley 1994; but see Russ & Alcala 1996a; Wantiez, Thollot & Kulbicki 1997; Edgar & Barrett 1999). There are three main reasons.
The three reserves were the Cape Rodney to Okakari Point (Leigh) Marine Reserve, Tawharanui Marine Park and Te Whanganui a Hei (Hahei) Marine Reserve ( Table 1 and Fig. 1a). All three are complete no-take areas administered under different legislation and by separate government departments (the ‘reserves’ are controlled by the Marine Reserves Act 1971 and administered by the Department of Conservation, whereas the ‘park’ is controlled by the Fisheries Act 1983 and administered by regional authorities). The management of the Tawharanui Marine Park has no nearby local community that can provide day-to-day surveillance to assist enforcement because the adjacent land is a regional park.
Incorrect. Local communities have not been involved in managing any of the three reserves. This is done centrally by government departments.
Fig. 1. (a) Map of the Hauraki Gulf and environs, showing the location of the three reserves surveyed in this study. Depth contours are in metres (?). The inset shows the location of the area in the North Island of New Zealand. (b) Details of the three reserves surveyed, showing reserve boundaries (dashed lines) and survey areas. Top: Leigh (1977); centre, Tawharanui (1982); bottom, Hahei (1992).
|At each sampling site, observations of snapper relative density were made using a baited underwater video (BUV) system (Willis & Babcock 2000). This system was developed in response to difficulties in accurately sampling a species whose behavioural reactions to divers vary markedly between sites (Cole 1994; Willis, Millar & Babcock 2000). Fish feeding by visitors to the Leigh marine reserve has resulted in snapper exhibiting diver-positive behaviour at some sites, whereas elsewhere they are wary of divers, and outside the reserve they actively avoid divers. Use of a remotely deployed sampling method eliminates this source of bias.|
We have serious doubt about the accuracy of the BUV system as explained in Recurring Mistakes. Just the way snapper develop diver-positive behaviour, they also develop BUV-positive behaviour with pilchards as reward.The BUV system consisted of a Sony XC-999P high-resolution colour camera mounted on a stainless steel stand 115 cm above the substratum and faced straight down. A bait holder (containing c. 200 g of pilchard Sardinops neopilchardus Steindachner) was attached to the triangular base of the stand so that it lay in the centre of the camera’s field of view. The base was marked with cable ties, and the distance between them was measured to allow spatial calibration of digitized images. This allowed accurate estimation of the lengths of fish responding to the bait (Willis & Babcock 2000; Willis, Millar & Babcock 2000).
The entire method is aimed at attaining the maximum result.. . . (the authors explain how biomass and egg production were estimated, and explain the statistical analyses applied)
The formula for daily batch fecundity (F) of Zeldis & Francis 1998 is F = 73.9 x W -7793 where W = snapper biomass or weight. For ease of reference, it approximates to F= (W - 105) x 74, where snapper need to weigh over 105g to produce 74 wet-weighted eggs per gram of body weight in each spawning batch. The formula was derived from snappers weighing between 200g and 5kg (65cm).
EFFECTS OF MARINE RESERVE PROTECTION ON P. AURATUS DENSITY, BIOMASS AND EGG PRODUCTION
Biomass per BUV deployment and density of legal-size snapper (LEGsna) were higher in the reserve than adjacent non-reserve areas at all three locations and for all four surveys (Figs 2 and 3). In particular, the Leigh reserve recorded the highest value of LEGsna on all four survey occasions, and the highest density of snapper of all sizes (MAXsna) on all but the April 1999 survey, when the Hahei reserve MAXsna was boosted by large numbers of sublegal fish.
The graphs show the number of snapper (above)
and their relative biomass (below) for the two years of observation. It
shows that the number of snapper in each reserve were comparable but that
the ones in Leigh were much larger. It also shows that the numbers and
sizes of snapper outside the reserves were similar for all areas. The main
conclusion could be either that Leigh is a special area attracting large
fish, or that Leigh has larger fish because it is older. For each possibility,
proof is still lacking.
. . . (the authors continue explaining statistical niceties) . . .
Fig. 2. Mean reserve (filled symbols) and non-reserve (open symbols) snapper Pagrus auratus relative density at Leigh, Hahei and Tawharanui from November 1997 to April 1999. (a) Total numerical relative density, all size classes (MAXsna); (b) relative biomass.
Fig. 3. Mean reserve (filled symbols) and non-reserve (open symbols) snapper Pagrus auratus numerical relative density at Leigh, Hahei and Tawharanui from November 1997 to April 1999. (a) Fish > minimum legal size (LEGsna); (b) fish < minimum legal size (JUVsna).
The above graph (Fig3) shows that legal-sized snapper are more abundant inside reserves during the end of summer, but Leigh has more legal sized-snapper all year round. Juveniles do not make a distinction between reserve or non-reserve.
Fig 4 and 5 show how adult and juvenile snapper are distributed along the reserve's coast. As expected, juveniles are not affected by marine reserves but adults do. Only in Leigh does the density increase towards its centre. It again demonstrates that Goat Island is a special place which cannot be compared to others. It is remarkable that the number of juveniles increases in areas 9-13 outside the Leigh reserve. But this coast is also more sheltered and influenced by currents.
It is important to note that the differences between a reserve of 7 years old (Hahei, 1992) and one of 17 years (Tawharanui, 1982) is negligible. Only Leigh (1977, 22 years old) stands out, but it is an oasis with an island, next to a long beach.
Surveys of three marine reserves in northern New Zealand, repeated biannually for 2 years, have allowed estimation of the effects of protection on snapper populations, as well as location and seasonal effects. The design of the study reduced the risk of location-specific biases that may have been present due to the lack of ‘before’ data, which in marine reserve studies are often unobtainable. The data presented here demonstrate large differences in relative density of the heavily exploited sparid fish P. auratus between marine reserves and adjacent fished areas in northern New Zealand. Log-linear modelling indicated a common status (reserve or non-reserve) effect corresponding to a 14-fold increase of legal-size snapper in the reserve compared with the adjacent non-reserve areas, despite significant between-location and between-survey variability in densities.
Repeatedly, all studies where the Leigh reserve is included, show that Leigh is an exception to the rule. When do scientists become honest by excluding Leigh from their data, certainly when such data is obtained by BUV. Fig 2b shows clearly that there are no large differences (about 2 times by BUV standards) between reserves that are typical of our coast and non-reserve sites. This is also more in line with studies done overseas. Also in winter/spring, the differences disappear.
It is regrettable that the experiment does not show four sample points for each year. Yet the need for this could have been foreseen.The large seasonal fluctuations in snapper density have implications for marine reserve monitoring and the prediction of potential reserve benefits to fisheries. First, there is need for standardization of the timing of surveys to determine reserve effects. If different reserves are surveyed at different times of year, the results will not be comparable, and will give misleading impressions of the relative effectiveness of the different reserves.
This has indeed happened in several surveys.This may apply to species other than snapper. Theoretical reviews have predicted that migratory species, or species with moderate mobility, will not benefit significantly from marine reserve protection (Kramer & Chapman 1999). In this case, however, the density of a migratory species is much higher within reserves than in fished areas. It appears that most snapper are seasonally mobile, but some individuals have shown a marked degree of site fidelity (Willis, Parsons & Babcock 2001). Thus, generalizations about the entire species are inappropriate, and theoretical predictions made from such generalizations are likely to lead to incorrect conclusions.
Goat Island is a special place with a mix of desirable habitats, exposure and shelter, extensive shellfish feeding grounds and sleeping habitat, all of which are important to snapper, particularly large ones. The outside of Goat Island, in the centre also has the clearest water.. . . . . . There are two potential direct benefits of marine reserves to fisheries: (i) enhancement of spawning stock biomass and (ii) ‘spillover’ of adults to enhance local fisheries (Roberts & Polunin 1991; Rowley 1994; Allison, Lubchenco & Carr 1998; Bohnsack 1998; Horwood, Nichols & Milligan 1998). Seasonal peaks in inshore snapper density coincide with the spawning season and post-spawning period (Crossland 1977; Scott & Pankhurst 1992), implying that marine reserves protect both resident fish and some proportion of migratory fish during spawning, assuming that they spawn within reserves. However, greater output of eggs need not necessarily translate into production (Francis 1993).
This is not borne out by this experiment. The claim of 14 times is caused by the Leigh data set swamping the two other data sets. By all scientific standards, it should have been removed as a spurious dataset biasing the experiment unduly. The remaining bias comes from the BUV counting method, whose linearity has not been proved. It is a method that exaggerates.The term ‘spillover’ implies that density-dependence (whether via resource limitation or territoriality) actively displaces fish across reserve boundaries, where they become available to the fishery (Kramer & Chapman 1999). In this study, the survey areas adjacent to the reserve boundaries generally contained the lowest overall density of P. auratus of non-reserve areas. This was most likely because of concentrated recreational fishing effort at those locations (especially area 9 at Leigh; authors’ personal observation) caused by perceptions that catch rates next to the reserve are likely to be high. If emigration from the reserve has been occurring, numbers were too low to be detected with the current methodology. In this regard, the importance of knowing the distribution of fishing effort outside reserves cannot be understated.
The outside areas are all different habitats. To the west under influence of the Pakiri Beach and to the SE they offer more shelter. They cannot really be compared with Goat Island.
This research was conducted with a measuring device (BUV) which fails the scientific requirements for measuring devices and cannot be used for quantitive values. The data obtained from Leigh completely swamps all other data such that the conclusions in their generality are not substantiated. But it is clear that marine reserves do have more snapper and crayfish.
northeastern New Zealand
Nick T Shears, Russell C Babcock, 2001
Report to the Department of Conservation. 31p.
[even after repeated requests, DoC refused to give us a copy of this report,
so here is the authors' executive summary obtained from the Internet]
The same ecological theory demands that such changes happen as gradually as large predators establish themselves. The observed disappearance of urchin barrens however, happened rather quickly between 1995 and 1998, in one reserve of 24 years of age (Leigh, 1977) and at the same time also in a younger but nearby one of 19 years (Tawharanui, 1982).To test the generality of this prediction, subtidal reef communities were compared between six northeastern New Zealand marine reserves and adjacent unprotected areas. The marine reserves studied included the Cape Rodney to Okakari Point (Leigh), Long Bay - Okura, Poor Knights Islands, Tuhua (Mayor) Island and Whanganui A Hei (Hahei) marine reserves and the Tawharanui Marine Park. These areas are located across a large geographic and environmental gradient and varied in size and age of protection. All were completely no-take and included extensive subtidal reef systems. It has previously been shown in the reserves at Leigh and Tawharanui that increases in predator densities, following the cessation of fishing, has resulted in declines of urchin populations and a subsequent increase in macroalgal habitats.
A cause and effect relationship has never been demonstrated. See also the research exposed above. But the decline of urchin populations could readily be observed, as it happened in 1994/95. After the 1993 kelpbed death, the new kelp invaded the urchin habitat because (i) urchins wandered into the wide kelp zone, (ii) urchins died from mass mortalities, (iii) the kelp plants reached maximal growth all at the same time and (iv) there were no storms to re-create the urchin barrens.Our findings support this with the extent of urchin barrens habitat and the overall density of urchins being significantly lower in these reserves than on adjacent coasts.
However, the other reserves refute these findings, as do a number of other places around the outer Hauraki Gulf. The use of the word 'significant' is suspect, since it usually means 'just detectable'. Why not quantify the difference such as 10%, 2-3 times or so?These patterns were not consistent for the other marine reserves examined. While urchin densities were generally lower at marine reserve sites, the relative importance of the habitat forming sea urchin, Evechinus chloroticus and subsequently the extent of urchin barrens habitat, varied considerably both within and among areas. There were also differences in algal assemblages among areas and between reserve and non-reserve sites. Only at Long Bay and Tuhua Island were no differences detected between reserve and non-reserve sites. This is not surprising for Long Bay, which is very sheltered [and very dirty and very shallow] and Evechinus does not play an important structuring role on the reefs. For Tuhua Island the lack of differences between reserve and non-reserve sites may be due to the reserve only being 7 years old at the time of sampling.
Tuhua is located in the Bay of Plenty where the dense plankton blooms of 1991/92 did not happen. However, in 2002 they suffered mass urchin mortality.The importance of environmental variables (wave exposure, turbidity and sediment) in explaining the difference in algal communities observed between reserve and non-reserve sites was tested using multiple regression. The differences in algal assemblages at Leigh and Tawharanui, between reserve and non-reserve sites, could not be explained by environmental variables, thus supporting a significant reserve effect. However, similar differences observed at Hahei between reserve and non-reserve sites, were confounded by differences in wave exposure and turbidity between the reserve and unprotected reference sites.
The control sites chosen around Tawharanui and Leigh are facing southeast rather than north, or they are located in shallow water. These places are unsuitable control sites. The Hahei effect also applies to the control sites around Leigh and Tawharanui. The use of the 'statistical mixer' method hides whether the Leigh marine reserve data swamps that of Tawharaunui.For the Poor Knights Islands, when compared to the Mokohinau Islands as the reference location, reserve status remained significant even though there was a significant effect of wave exposure. Given that this reserve had only been completely no-take for approximately one year, trophic level effects due to an increase in predators are not likely and the observed differences were probably due to other environmental differences between these island groups.
After becoming a fully protected marine reserve in 1999, the number of snapper suddenly increased spectacularly, including large snapper but the islands have only a small rocklobster population, even though these have been protected since 1981. The Mokohinau Islands have experienced extensive kelpbed death and disappearance of their urchin barren zones, thus confounding the picture.While reserve-related differences in benthic communities can only be detected for the two oldest reserves at this stage, we may expect continued monitoring to demonstrate similar patterns at other reserves after longer periods of protection. This study demonstrates the importance of how benthic communities vary over environmental gradients in order to detect marine reserve effects. The implementation of pre-reserves sampling programs will help avoid confounding environmental and spatial effect when assessing the effects of marine reserve protection.
The main point is that this study does not prove anything at all. By any standard, it is a failed experiment from which no conclusions can be drawn. If it takes so much effort to demonstrate the effects of marine reserves, they are perhaps too small to be of any practical value. More monitoring and pre-and post-reserve sampling will not change this.
Shears NT, Babcock R C (2004):
DOC Science Internal Series DSIS192. (available on the DOC web site)
In a recent study, marine scientists quantified coastal marine communities in 13 marine reserves spanning the length of New Zealand. They looked at algal communities and their grazers, particularly the green sea urchin Evechinus chloroticus. They also noted environmental variables such as slope of the substrate (rock) and made an estimate of the fetch (distance over open water) as a measure of wave exposure. To their credit, they also included degradation variables of Secchi disc visibility (the opposite of turbidity) and the percentage sediment cover. They also included the maximum transect depth even though they did not dive deeper than 12m. Unfortunately they did not include maximum sand depth which is a direct indication of maximum storm damage and where barrens should occur.
|Their most important result is the proof that degradation (=turbidity + sediment) is by far the most decisive factor on what grows where. In other words, the seascape cannot be understood without understanding degradation. Yet it took us over 15 years of prodding to get them interested in this very important phenomenon (and they are still not interested)! Note how the presence of sea urchins also plays a role (of course) but that marine reserves have practically no effect at all (not measurable), proof that they do not have an effect on urchin barrens and also that they do not save the environment against degradation. Why did the report not mention these points? These results also refute the urchin barrens or top-down trophic cascades theory as espoused by Babcock et al.||
As we keep monitoring the environment over as large an area as possible, we observe changes and document these photographically. This chapter intends to bring you uptodate with the latest observations. Also overseas studies are appearing that refute the trophic cascades theory and resulting urchin barrens.
Destructive grazing, epiphytism, and disease: the dynamics of sea urchin - kelp interactions in Nova Scotia
Robert E. Scheibling, Allan W. Hennigar, and Toby Balch
Can. J. Fish. Aquat. Sci. 56(12): 2300–2314 (1999) | doi:10.1139/cjfas-56-12-2300 | © 1999 NRC Canada
We measured the rate of advance of urchin (Strongylocentrotus droebachiensis) feeding aggregations (fronts) as they destructively grazed kelp beds (Laminaria longicruris) at both a wave-exposed site and a sheltered site in Nova Scotia over 3.5 years. The grazing fronts were composed of high densities of large adults (up to 98 and 70 per 0.25 m2 at the exposed and sheltered sites, respectively). Urchins in the recently formed barrens, or in adjacent kelp beds, occurred at much lower densities and consisted mainly of juveniles. The fronts moved onshore into shallower water at each site, but their rate of advance varied markedly between sites and over time at each site, ranging from 0 to 4 m·month-1. The rate of advance of a front was related to the biomass of urchins; fronts did not advance below a threshold biomass of ~2 kg·m-2. Infestations of kelp by an epiphytic bryozoan (Membranipora membranacea) caused marked reductions in kelp canopy cover and biomass during winter, but the canopy regenerated through recruitment of juvenile sporophytes in spring. A localized outbreak of disease (Ostreopsis?) decimated S. droebachiensis at the exposed site in 1993, which enabled kelp to recolonize the barrens. Surviving urchins gradually reaggregated and resumed destructive grazing after ~1.5 years. A recurrence of disease in 1995 eliminated urchins at both sites and terminated the transition from kelp beds to barrens on a coastal scale. Our findings have important implications for the management of the urchin fishery, which targets grazing fronts for harvesting.
It is quite amazing that they had similar ecological problems to the ones experienced in NZ, and also in the same years! The kelp afterwards destructively re-invaded the urchin barrens.
In a CSIRO marine and atmospheric research seminar at the University of Tasmania, Dr Russ Babcock reports that there is no difference between fished and non-fished areas: "Studies from north-eastern New Zealand provide some of the best evidence, so far available, that kelp forest can be converted to coralline algal dominated barrens as an indirect effect of fishing for lobsters and fish." None of your or anyone else's studies has proved this.
"A reversion from urchin barrens to kelp forest has been shown in areas of north-east NZ where lobster densities were 1.6-4.0 times higher than in fished areas". This statement has been refuted and rebutted extensively by us. Why not mention all the failed experiments?
"While such barrens are present in many parts of Australasia and around the world, their distribution is far from uniform." When you consider them as storm barrens, their distribution is entirely consistent.
"For example, at Rottnest Island in Western Australia, habitats are relatively uniform across fished and unfished areas, despite a 6.5 fold difference in lobster density. Such inconsistencies present real difficulties for predicting marine ecosystem responses to fishing and consequently to the implementation of ecosystem based fisheries management. Differences between the two systems are likely to be the result of different ecosystem dynamics rather than differences in levels of fishing pressure." Why not stop believing in the myth and spreading it, Russ? Read about storm barrens.
|September 2004, July 2005
We visited Niue to study the devastating effect of Tropical Cyclone Heta (Jan 2004) and found perhaps the deepest storm barrens in the world, as Niue does not have a continental shelf to diminish the destructive power of storm waves, and its clear waters support an exceptionally deep photic zone. A major storm happens here about once in a decade. Calcareous crustose algae and filamentous algae proved very productive, sustaining schools of grazing fish by day and huge numbers of sea urchins of many species by night. We then realised that major storms may also be decisive on the ecology of the Kermadec Islands, visited by us in May 2002.
Ecological Role of Purple Sea Urchins
John S. Pearse
Science 10 November 2006: Vol. 314. no. 5801, pp. 940 - 941
Sea urchins are major grazers in shallow seas worldwide. Purple sea urchins (S. purpuratus) and other strongylocentrotid sea urchins of the Northern Hemisphere are particularly important and are the most intensively studied. A delicate balance between sea urchin grazing and kelp forest productivity leads to stable states that alternate between luxuriant kelp forests and relatively species-depauperate sea urchin "barrens". Curiously, the densities of sea urchins are often similar within kelp forests and sea urchin barrens. Within kelp forests, sea urchins are nearly stationary, feeding on captured pieces of kelp litter ("drift kelp") that are produced and shed in high quantities from the kelp plants. However, when the kelps are removed by storms or El Niño events, the remaining sea urchins actively forage on young kelp recruits and on drift kelp brought in from elsewhere, preventing the reestablishment of the kelp forest. The sea urchins can be decimated by storms or diseases, allowing the kelp forest to return to the area. Wow, finally someone who has the right perspective. From here it is but a small step to storm barrens.
Having visited the east coast of New Zealand from the very north to the Bay of Plenty, the situation is now that urchin barrens have been overrun by the kelp forest everywhere, whether marine reserve or not. It has happened in the near-shore environment as well as on remote islands: Cavalli Is, Poor Knights, Mokohinau, Cuvier, Merury Is, Mayor I.
In all cases we observed an equal presence of dinoflagellate slime (Ostreopsis) and absence of major grazers such as Cooks turban Cookia sulcata, sea urchin Evechinus chloroticus and others. These observations establish firmly the correlation between slime and the absence of sea urchins, and also that marine protection has no influence whatsoever. The evidence is there for all to see and it won't go away!