Ecologically Sustainable Yield - Report

[John_Brandt]

Ecologically Sustainable Yield


Marine conservation requires a new ecosystem-based concept for fisheries management that looks beyond sustainable yield for individual fish species


Richard W. Zabel, Chris J. Harvey, Steven L. Katz, Thomas P. Good, Phillip S. Levin


Excerpt: "The goal of long-term sustainable harvest has been a mainstay of fisheries science for the past half century. This concept was crystallized with the development of a model in 1954 by Milner Schaefer of the Scripps Institution of Oceanography that incorporates both fish-population dynamics and harvest. An important feature of this and other early models was the recognition that a population's size determines its growth rate. Thus the growth rate (overall numbers of new organisms produced per year) is low when a population is small. It is also low when a population nears its carrying capacity, because of density-dependent processes such as food availability. Intermediate-sized populations have the greatest growth capacity and ability to produce the most harvestable fish per year. The key realization of these early models was that fisheries could optimize harvest of a particular species by keeping the population at an intermediate level and harvesting the species at a rate equal to the annual growth rate. This strategy was called the maximum sustainable yield.

Although models are now able to capture more of the complexity of the dynamics of fish populations, two concepts remain integral parts of most management plans. The first, as noted above, is that average harvest rates should equal growth rates. The second is that harvests are sustainable even when fish populations fall well below unfished levels. The widely used term "surplus production" implies that populations produce biomass beyond that required to sustain them—and therefore that this surplus can be harvested without impacts. There is a growing sentiment, however, that we need to go beyond considering only target species in fisheries management. For example, the U.S. Congress, as part of the Sustainable Fisheries Act of 1996, directed the National Marine Fisheries Service to establish an Ecosystem Principles Advisory Board. An emerging question is: Do levels of exploitation consistent with sustaining marine fish populations have long-term, detrimental effects on ecosystems? "

Report continued here:
http://www.americanscientist.org/template/AssetDetail/assetid/17216/page/1

 

[Kalkbreath]

They really think the fishermen collected all the algae blennies and blue tangs, emerald crabs? Sea urchins dont even eat that type of algae and algae dont grow unless excess nutrient is added......... :roll: Next they will be blaming cyanide and George Bush......for the demise of those reefs as well..........

 

[mkirda]

Sea urchins dont even eat that type of algae and algae dont grow unless excess nutrient is added.........

This is probably the most ill-considered post I think I have seen you make so far, Kalk.

It betrays a horrendously flawed understanding of ecosystems, algae growth and grazing pressure.

Go back and look at pictures of the Florida reefs pre-1983, then post-1983. Compare the reefs after the great urchin die-off. See all the excess algae? See the enormous decline in coral cover? Urchins don't eat algae? Really?
Literally everywhere in the Caribbean is evidence to the contrary.

If you need more scientific proof, go to the local college library, start pulling the journals and read about the experiments where they used enclosures to keep out the urchins and fish. In other words, they eliminated the grazing pressure. No nutrient increase was necessary to make the algae grow like crazy- it was the grazing pressure that kept it down. There are dozens of papers that show this- something that could be figured out by common sense, really...

Seriously, Kalk, you really oughta get out more. Go read Birkeland or Dubinsky or even Sorokin. They all have written books about coral reef ecology. You might learn something and actually stop churning out these ridiculous posts.

Regards.
Mike Kirda

 

[Kalkbreath]

"fleshy algae, such as Sargassum"........Can you Name one species that eats the species which this story claims to have smothered the live coral?{did you even read the link?} I see plenty of urchins in Fla........in fact I saw some last week!{and I caught groupers using reef fish for live bait!Blue hula} Despite the presence of lots of algae, the current population of urchins remains the same..........Its the runoff and sewage which causes the Algae to overtake the reefs .........And the Urchin disease.....If I remove the urchins in my ref tank .that does not mean my tank will become overgrown with algae!....Another fine example of placing the Blame on the wrong shoulders........food fish collectors in Jamaica dont collect algae blennies or blue tangs {which do eat macro algae} So how did fishing for snappers and groupers make all the other non target reef fish disappear? It didn't....... its the feces of tourists which increased the sewage and killed of the reefs .........not snapper fishing.....next please

 

[mkirda]

I see plenty of urchins in Fla........in fact I saw some last week!

Kalk,

Why do you persist in touting your ignorance as fact?

Name one site in the Caribbean where the Diadema sp. populations are anywhere near the pre-1983 levels? I'll give you a hint: It ain't Florida.

By not addressing the core issues, nor understanding the dynamics of algae and grazing pressure, you've failed miserably in answering my last post.
Next please, indeed.

Regards.
Mike Kirda

 

[Kalkbreath]

I see plenty of urchins in Fla........in fact I saw some last week!

Kalk,

Why do you persist in touting your ignorance as fact?

Name one site in the Caribbean where the Diadema sp. populations are anywhere near the pre-1983 levels? I'll give you a hint: It ain't Florida.

By not addressing the core issues, nor understanding the dynamics of algae and grazing pressure, you've failed miserably in answering my last post.
Next please, indeed.

Regards.
Mike Kirda

Thats right !, Your making my point! Its not because of over fishing like this artical would suggest......it pollution......if not , Then tell me why the populations are not returning............There is plenty of algea and plenty of male and female urchins to make babies.......But the pollution is acting like a spermacide and an anti-Viagra and not allowing larva to mature.........charter boats and tunna collectors have nothing to do with the Algea or the urchinS.....in Fla or Jaimaca.....or the price of tea in China :roll:

 

[mkirda]

Omigod... Puleeze...

I'm addressing one of your flawed underlying assumptions.

You said "algae dont grow unless excess nutrient is added", which is patently and demonstrably false.

The issue(s) you raised after this have *absolutely nothing* to what I said, or even what you said here, frankly.

Regards.
Mike Kirda

 

[Kalkbreath]

Do you even own a reef tank? How many urchins do you stock per gallon? :roll: If you remove your fish from your tank , does the Algae overtake your aquarium? And lastly Explain how over collection of food fish causes urchin populations to decline and sargassum to proliferate? Then explain how untreated sewage does not!

 

[mkirda]

Do you even own a reef tank? How many urchins do you stock per gallon? :roll: If you remove your fish from your tank , does the Algae overtake your aquarium? And lastly Explain how over collection of food fish causes urchin populations to decline and sargassum to proliferate? Then explain how untreated sewage does not!

Have you seen pictures of the reef in Florida before 1983?

I rest my case.

Next!

Mike

 

[Kalkbreath]

Do you even own a reef tank? How many urchins do you stock per gallon? :roll: If you remove your fish from your tank , does the Algae overtake your aquarium? And lastly Explain how over collection of food fish causes urchin populations to decline and sargassum to proliferate? Then explain how untreated sewage does not!

Have you seen pictures of the reef in Florida before 1983?

I rest my case.

Next!

Mike

Yes, I lived in Fla from 1972 to 1988 ......I remember when the water hydra choked the rivers .......the water plants reached epic proportions ......the rivers were totally covered with plants in 1975......WHY ? It was not over fishing, there were plenty of fish underneath the blankets of green .......There was obviously too much nutrient in the water......this was back before Phosphate was outlawed and removed from household detergents and I would watch turds float out of the pipe discharge at the treatment plant.....{Just like algae on the reefs}..The waterplants responded and tried to soak up all the excess nutrient in the water.......It was not because there were less ducks around to eat the duckweed!......... And the plant most likely would have succeeded in cleaning up the water if the government had let them.........but the plants were "effecting the boating traffic" ........so what did they do ? they spayed and killed off the plants with Paraquat......Within a few months the plants were gone......and so were the fish .........There were plenty of fish before the plants ......and no one could fish during the blanketing of waterplants ...........so the fish were not over collected? We used to swim in the rivers before the waterplant event .......but after the plants were gone we would develop rashes with contact in the water......The change in the clarity of the water was also night and day.......before I could see all the way to the bottom.......after not two feet down .........even thirty years later......the river is nothing like what it was........The abundance of water plant has nothing to do with the number of herbivores.,..... even in the most intense herbivore collection sites in Hawaii {yellow tangs along the Kona coast} there is no evidence of increased algae growth....... Just like in our reef tanks, {well maybe not m.kirda's urchin tank}......excess nutrients is the only event that leads to continued increase in Algea growth .........the argument that Jamaican fishermen collected all the natural consumers of Sargassum weed is silly ......because those fish and inverts that eat algea are not collected as food items in that country anyway!.......

 

[mkirda]

Yes, I lived in Fla from 1972 to 1988 ......I remember when the water hydra choked the rivers .......the water plants reached epic proportions ......the rivers were totally covered with plants in 1975......WHY ? It was not over fishing, there were plenty of fish underneath the blankets of green .......There was obviously too much nutrient in the water......this was back before Phosphate was outlawed and removed from household detergents and I would watch turds float out of the pipe discharge at the treatment plant.....{Just like algae on the reefs}..The waterplants responded and tried to soak up all the excess nutrient in the water.......It was not because there were less ducks around to eat the duckweed!......... And the plant most likely would have succeeded in cleaning up the water if the government had let them.........but the plants were "effecting the boating traffic" ........so what did they do ? they spayed and killed off the plants with Paraquat......Within a few months the plants were gone......and so were the fish .........There were plenty of fish before the plants ......and no one could fish during the blanketing of waterplants ...........so the fish were not over collected? We used to swim in the rivers before the waterplant event .......but after the plants were gone we would develop rashes with contact in the water......The change in the clarity of the water was also night and day.......before I could see all the way to the bottom.......after not two feet down .........even thirty years later......the river is nothing like what it was........The abundance of water plant has nothing to do with the number of herbivores.,..... even in the most intense herbivore collection sites in Hawaii {yellow tangs along the Kona coast} there is no evidence of increased algae growth....... Just like in our reef tanks, {well maybe not m.kirda's urchin tank}......excess nutrients is the only event that leads to continued increase in Algea growth .........the argument that Jamaican fishermen collected all the natural consumers of Sargassum weed is silly ......because those fish and inverts that eat algea are not collected as food items in that country anyway!.......

Kalk,

Seriously, were you ever diagnosed with ADD?

Let me lay it out for you: You claimed A and B leads to C.
I came back and said that B is not true, A is not exactly true, and that A and B do not lead to C anyway.

Instead of addressing the either A or B, you started throwing in Points D, E, F, G, H, I and G. None of these have anything to do with A or B.
Many were not even about the same ecosystem, unless you abstracted it to the level of "Earth". Urchins do not live in rivers, nor do coral, nor do reef fish.

I've finally figured out the tactic that you use- Say something, and when challenged on it, never return to address the point ever again. Instead throw in as much other tangential points as possible. When these are addressed, repeat. When these are addressed, repeat. Repeat until the person who started questioning you finally tires of running in circles.

Then start another thread and try to start it all over again.

The only point that you have made that makes any sense is the fact that humans have an impact on the reefs. You understand this, but you seeming lack the background in coral reef ecology to understand the impacts and their effects. I recommended you three books before and I would recommend them again.

I swear off circle running permanently.

Regards.
Mike Kirda

 

[PeterIMA]

Response to American Scientist article,
The article in American Scientist posted is very important. It is too bad that Kalk lacks the education to appreciate most of it. As a fisheries scientist, who has done stock assessments for the Canadian Dept of Fisheries and Oceans, I recognize its importance. One of the main points is that we are fishing down the food chain (by eliminating the apex predators). In the process we may be disrupting communities in unknown ways. The authors call for development of new methods to assess Ecologically Sustainable Yield. This is a multispecies approach that might replace single species approaches to stock assessment, in which management is based on production models that determine Maximum Sustainable Yield (MSY).

I have participated in workshops run by Dr. Carl Walters (of the University of British Columbia in association with Dr. Dan Pauly, Dr. Villy Christensen and Dr. Tony Pitcher) who conducted simulations concerning the fish community on the West Florida Shelf. The fisheries scientists from the Florida Marine Research Institute helped to parameterize the models mentioned in American Scientist. The models in question were Ecopath and EcoSim. These are food-web based models. It is possible to simultaneously model as many as 50 species, and play God by adding parameters to simulate the food web, to then predict growth and production for each species and the total community. In the case of Florida, we did not have detailed data on what fish species eats what, so we (the fisheries scientists) were asked for our expert opinions. As a scientist, I found this rather unsettling. However, the results were of great interest and enhanced our understanding of the fundtioning of the marine ecosystem.

In the case of the Baltic and the North Sea more work has been done to determine what eats what by massive programs to sample stomach contents of all of the marine fish species. These data were used in an ecosystem based model called MultiSpecies Virtual Population Analyses (MSVPA). I assume that similar datasets were used as input to the Ecopath and Ecosim analyses referred to for the Baltic (in the article for American Scientist). In any event, the main idea is that much more study is needed of marine food chains and food webs, and that we need to not only try to maximize fisheries production, but also develop models to ensure that we do not disrupt the ecosystem by destroying the building blocks in the food chain etc.

There is a need for new fisheries models to determine "Ecologically Sustainable Yeild". Hopefully, this will not be like the concept of "Optimum Sustainable Yeild" which Congress mandated should simultaneously maximize biological yeild and economic benefits to the fishery. The models should be science-based rather than politically-based. Ecosystem-based models need to take into account not only the food chain, but also changes in oceanographic conditions, habitats, and climate in addition to elucidating the effects of fishing (fishing mortality, natural mortality for each species and for the whole community etc). So far, nobody has developed such a model that I know of. Anyway, with computers and more funding the modelers will be happy to try to solve these problems.

In the mean time, the precautionary approach (also called adaptive management) should be applied. This means reducing fishing effort, creating Marine Protected Areas (MPAs) to protect habitats and create refugia for spawing stocks, and putting more money into research to develop better models. I could go on, but think this is enough for now.

Right now, the scientific community does not know enough to precisely model and manage marine communities and ecosystems. In other words, there is a lot that we don't know. So, Kalk you have lots of company.

Peter Rubec

 

[Kalkbreath]

By the 1990s, Jamaica's reefs were depleted of both carnivorous and herbivorous fish and smothered with fleshy algae, such as Sargassum. Sea urchins were uncommon, and the vast diversity of the reefs was reduced. Because the algae had taken over the real estate, there was little space for renewal by larval corals. Back in the late 1970s, surveys off the northern coastline had found corals over half the reefs' surface, with fleshy algae covering only 4 percent. By the early 1990s, Terry Hughes from James Cook University demonstrated that those figures were more than reversed: 3 percent of the space occupied by corals, 92 percent by algae. Thus reefs that had existed for thousands of years as one of the most diverse habitats on earth had changed into algal mats in a few decades.{END} ...................................................................Its called runoff and sewage.......Fecal counts and bacteria killing the coral are not from over fishing........There is a big difference between stating a coincidence and demonstrating a direct link .........Just because disco music was popular in the 1970s the same time that the reefs were declining does not make it a contributor to reef decline........At the same time Jamaica's reefs were experiencing decline so were reefs all over the Caribbean, even in remote and uninhabited regions........even the Fla Keys suffered the same coral decline and algae blooms .....and very few herbivore fish or urchins have ever been collected in US waters ..........Do the authors of this piece real y think fish removal has a more direct link to urchin health then water quality? There are no urchins in the majority of reef tanks in this hobby .....in fact many have no herbivores at all .......Why is it that these tanks dont have the same problems with algae overtaking the aquariums that the reefs do? Why is it that there are huge areas of algae covered reefs in the keys and yet very few tangs or urchins around chewing down? Would it not make sense that if there are fewer and fewer groupers and game fish feeding on the herbivores {removed by sportfishing}......that this would translate into more herbivores around? It seems undeniable that there is something in the water effecting the urchins .......and it aint charter captains fly fishing for tarpon? Why do researchers waste time and resources on studying minor impact activities? Because the real causes of reef decline were determined years ago ...Just like new music artists need new material ...new scientists need new material and angles on to draw interest and attention to themselves.......they know that millions of humans crapping in the water is not going to end any time soon .....so why waste your government grant money studying something that the public has become dumb and indifferent to ......like raw sewage emptying into the ocean?............. Peter, if researchers have never been able to discover the link between food fishing and algae growth? Why would they not look elsewhere? Like water chemistry? And why would the same results {algea growth and urchin demise........here in the USA happen even though the reefs in Florida have never been fished for herbivores ?Without explanations as to why rules would apply to one set of Caribbean reefs and not to another.......does this not place serious concerns on the reasonability of conclusions made by these researchers?

 

[blue hula]

By the 1990s, Jamaica's reefs were depleted of both carnivorous and herbivorous fish and smothered with fleshy algae, such as Sargassum. Sea urchins were uncommon, and the vast diversity of the reefs was reduced. Because the algae had taken over the real estate, there was little space for renewal by larval corals. Back in the late 1970s, surveys off the northern coastline had found corals over half the reefs' surface, with fleshy algae covering only 4 percent. By the early 1990s, Terry Hughes from James Cook University demonstrated that those figures were more than reversed: 3 percent of the space occupied by corals, 92 percent by algae. Thus reefs that had existed for thousands of years as one of the most diverse habitats on earth had changed into algal mats in a few decades.{END} ...................................................................Its called runoff and sewage.......

The decline in Jamaican (and other Caribbean) reefs can be attributed to a lot of factors. Runoff, sewage, sedimentation, hurricanes, the sea urchin (Diadema antillarum) die off throughout the region, and yes overfishing.

In Barbados, the combination of nutrient loading, seaurchin loss and overfishing contributed to declines in reef health. Coastal development provided the nutrients to increase algal growth on the reef. This was kept reasonably in check by urchins but not by herbivorous fish which were at low levels due to overfishing. However, when what is now considered to be a virus swepth through the urchins and knocked them all off, the algae went nuts ... overgrowing many surfaces and preventing coral recruitment (still no herbivorous fish to keep them down). Then the urchins started to recover and in the absence of fish that ate urchins (triggers for example - which had been knocked off by overfishing), the urchins went nuts. They mowed down the algae and also scraped over what ever coral was trying to recover (small recruits).

This is all well documented in the scientific literature. Similar work by McClanahan in Kenya also shows the importance of urchins in reef health and the outbreak of urchins on Danajon Bank is again a sign of reef decline.

The point is that there is no one single factor that has led to declines in reef health. They work together synergistically to screw the reefs which, stressed by one factor, have less resilience to others. So, overfishing is iimportant in terms of how it changes fish community structure and consequently reef community structure and health. And that is the point of an ecosystem approach to fisheries management. We should be trying to get it right on as many fronts as possible.

Cheers, Blue hula

 

[mkirda]

Why do researchers waste time and resources on studying minor impact activities? Because the real causes of reef decline were determined years ago .new scientists need new material and angles on to draw interest and attention to themselves.......they know that millions of humans crapping in the water is not going to end any time soon .....so why waste your government grant money studying something that the public has become dumb and indifferent to ......like raw sewage emptying into the ocean?............. Peter, if researchers have never been able to discover the link between food fishing and algae growth? Why would they not look elsewhere? Like water chemistry? And why would the same results {algea growth and urchin demise........here in the USA happen even though the reefs in Florida have never been fished for herbivores ?Without explanations as to why rules would apply to one set of Caribbean reefs and not to another.......does this not place serious concerns on the reasonability of conclusions made by these researchers?

Kalk, yet another tap into the id? Jeez...

Let's make a simple model of a coral reef ecosystem.

A + B + C = D

A = nutrient runoff.
B represents fishing effort
C represents grazing pressure on algae
D = Growth of algae.

Scientists have used it for years. They have found it mostly works, but ignores some things, making it over-simplistic. So they study it, then apply some changes to it...

aA + bB + cC = D

Where a, b, and c become weightings across the equation, adjusting the factors relative importance. This is what they have done to refine the models, to understand the relative impacts. This is why they continue to study the problem.

The models now used are far more complex than this, looking more like the linkages of the world airlines flying to every airport in the world.

You asked why, this is why. The need to really, truly understand the problem, then be able to attack the most important core problem.

Read any of the books I have suggested previously, this will become far clearer to you.

Point being that nutrient enrichment does stress the reefs, but with enough grazing pressure, the algal biomass does not increase at all. But you can eliminate just one species from within all the grazing pressure and the equilibrium can vanish overnight.

Regards.
Mike Kirda

 

[PeterIMA]

Blue Hula stated "We should be trying to get it right on as many fronts as possible". I agree. However, the models that I mentioned (Ecopath, Ecosim, MSVPA) do not take into account a number of factors that both you and Kalk have mentioned. These include, nutrient inputs, changes in climate and oceanographic conditions (such as salinity, temperature), and habitat parameters (these can be both water-column and benthic habitats according to the EFH definition), coastal pollutants etc.

I attended an international conference in Sarasota (at the Mote Marine Laboratory) last year. The purpose of the conference was ecosytem modeling to support ecosystem-based management. I was disappointed that the ecosystem-based models discussed were Ecopath, Ecosim and MSVPA. These models basically are related to traditional single-species fisheries models (like Virtual Population Analysis-VPA). For example, MSVPA is just many VPAs liked together using the stomach contents data (what eats what). Ecosim can take into account spatial patterns of fishing mortality, MPAs, and food webs to make spatial predictions about the impacts of various fishing strategies.

My point (and Kalk's) is that these models do not take into account the nutrient pollution (like nutrients from septic tanks in the Florida Keys) or other anthropogenic influences. Basically, the fisheries scientists leave pollution problems to other agencies (like USEPA). Hence, the fisheries models are not comprehensive ecosystem models (they do not model the whole ecosystem, just the part that pertains to fishing).

There are other models that are used to support estuarine and coastal management (nutrient loading models, hydological models, pollutant models, energy flow models, circulation models etc) used by other disciplines other than fisheries science. I agree with Blue Hula that true ecosystem management must be interdisciplinary. There is a need to manage marine ecosystems (like coral reefs) in a more holistic manner. Coastal zone managers are trying to do this. So are scientists associated with the National Estuary Program (NEPs) funded by USEPA. Quite a lot of what is being done to manage marine ecosystems (like estuaries or coral reefs) is not related to mathematical models; but still can be effective (like creating Marine Managed Areas-MMAs).

As a scientist working within the GIS group at the Florida Marine Research Institute, I see the need to develop better GIS-based spatial models that can incorporate habitat and other factor (like oceanographic conditions) into spatial models. My present research relates to the development of Habitat Suitability Models (HSM) in Florida estuaries. For example, I am presently completing HSM analyses that relate changes in freshwater inflow(changes in salinity patterns) to changes in the spatial distributions and abundance of 11 species of estuarine fish and invertebrates (shrimp) in Rookery Bay, Florida.

Enough for now.
Peter Rubec

 

[Kalkbreath]

By the 1990s, Jamaica's reefs were depleted of both carnivorous and herbivorous fish and smothered with fleshy algae, such as Sargassum. Sea urchins were uncommon, and the vast diversity of the reefs was reduced. Because the algae had taken over the real estate, there was little space for renewal by larval corals. Back in the late 1970s, surveys off the northern coastline had found corals over half the reefs' surface, with fleshy algae covering only 4 percent. By the early 1990s, Terry Hughes from James Cook University demonstrated that those figures were more than reversed: 3 percent of the space occupied by corals, 92 percent by algae. Thus reefs that had existed for thousands of years as one of the most diverse habitats on earth had changed into algal mats in a few decades.{END} ...................................................................Its called runoff and sewage.......

The decline in Jamaican (and other Caribbean) reefs can be attributed to a lot of factors. Runoff, sewage, sedimentation, hurricanes, the sea urchin (Diadema antillarum) die off throughout the region, and yes overfishing.

In Barbados, the combination of nutrient loading, seaurchin loss and overfishing contributed to declines in reef health. Coastal development provided the nutrients to increase algal growth on the reef. This was kept reasonably in check by urchins but not by herbivorous fish which were at low levels due to overfishing. However, when what is now considered to be a virus swepth through the urchins and knocked them all off, the algae went nuts ... overgrowing many surfaces and preventing coral recruitment (still no herbivorous fish to keep them down). Then the urchins started to recover and in the absence of fish that ate urchins (triggers for example - which had been knocked off by overfishing), the urchins went nuts. They mowed down the algae and also scraped over what ever coral was trying to recover (small recruits).

This is all well documented in the scientific literature. Similar work by McClanahan in Kenya also shows the importance of urchins in reef health and the outbreak of urchins on Danajon Bank is again a sign of reef decline.

The point is that there is no one single factor that has led to declines in reef health. They work together synergistically to screw the reefs which, stressed by one factor, have less resilience to others. So, overfishing is iimportant in terms of how it changes fish community structure and consequently reef community structure and health. And that is the point of an ecosystem approach to fisheries management. We should be trying to get it right on as many fronts as possible.

Cheers, Blue hula

My point is that the reason the Urchins and herbivores cant rebound is the water quality......Use the Fla Keys as the , example, the scenario does not fit there because neither urchins or herbivores have ever been collected......Your blaming the overfishing of food fish ...........but all the fish disappeared, even tiny blennies and gobies ! no one over fished these guys......there is little connection between the two........do you think the urchin virus is from over fishing?

 

[Kalkbreath]

Blue Hula stated "We should be trying to get it right on as many fronts as possible". I agree. However, the models that I mentioned (Ecopath, Ecosim, MSVPA) do not take into account a number of factors that both you and Kalk have mentioned. These include, nutrient inputs, changes in climate and oceanographic conditions (such as salinity, temperature), and habitat parameters (these can be both water-column and benthic habitats according to the EFH definition), coastal pollutants etc.

I attended an international conference in Sarasota (at the Mote Marine Laboratory) last year. The purpose of the conference was ecosytem modeling to support ecosystem-based management. I was disappointed that the ecosystem-based models discussed were Ecopath, Ecosim and MSVPA. These models basically are related to traditional single-species fisheries models (like Virtual Population Analysis-VPA). For example, MSVPA is just many VPAs liked together using the stomach contents data (what eats what). Ecosim can take into account spatial patterns of fishing mortality, MPAs, and food webs to make spatial predictions about the impacts of various fishing strategies.

My point (and Kalk's) is that these models do not take into account the nutrient pollution (like nutrients from septic tanks in the Florida Keys) or other anthropogenic influences. Basically, the fisheries scientists leave pollution problems to other agencies (like USEPA). Hence, the fisheries models are not comprehensive ecosystem models (they do not model the whole ecosystem, just the part that pertains to fishing).

There are other models that are used to support estuarine and coastal management (nutrient loading models, hydological models, pollutant models, energy flow models, circulation models etc) used by other disciplines other than fisheries science. I agree with Blue Hula that true ecosystem management must be interdisciplinary. There is a need to manage marine ecosystems (like coral reefs) in a more holistic manner. Coastal zone managers are trying to do this. So are scientists associated with the National Estuary Program (NEPs) funded by USEPA. Quite a lot of what is being done to manage marine ecosystems (like estuaries or coral reefs) is not related to mathematical models; but still can be effective (like creating Marine Managed Areas-MMAs).

As a scientist working within the GIS group at the Florida Marine Research Institute, I see the need to develop better GIS-based spatial models that can incorporate habitat and other factor (like oceanographic conditions) into spatial models. My present research relates to the development of Habitat Suitability Models (HSM) in Florida estuaries. For example, I am presently completing HSM analyses that relate changes in freshwater inflow(changes in salinity patterns) to changes in the spatial distributions and abundance of 11 species of estuarine fish and invertebrates (shrimp) in Rookery Bay, Florida.

Enough for now.
Peter Rubec

Holly sh** Peter!, That is the first Post by you in which not only was I unable to find anything silly ......I think you might get my gist?...on this one !.... Without fixing the greater problem {water quality} and attempts to understand sustainability and what effects stresses like fishing and pet collection have on wild ecosystems is impossible......because a reef that has raw sewage dumping into it or cyanide fishing is not really a natural environment .......Stop excepting tokens of good faith and demand action on the real reef killing activities..

 

[mkirda]

Use the Fla Keys as the , example, the scenario does not fit there because neither urchins or herbivores have ever been collected.

Another absolutist statement that has no basis in reality.

Of course urchins and herbivores have been collected!
You can get urchins and tangs from several Florida collectors, and they are all located in the Keys! Argh. Be that as it may...

Regarding your theory about water quality having an effect on the urchin's relative lack of comeback, you are both right and wrong. The problem is that urchins have two issues: First, the relatively small number that survived means that they are spread further apart, so reproduction is far less likely. Sperm and egg bundles have to meet. If they don't, it doesn't matter how fecund the urchins are- there will be no reproduction at all. Second, from what is known about the settlement cues for urchin larvae, they require a rather specific habitat in order to settle. If they don't find it, they just die. The papers I have read all indicated specific coralline algaes as I recall, though it has been a few years since I have read them. So it would make sense that fleshy algaes would decrease coral cover and decrease coralline algae cover. Urchins wouldn't settle directly onto fleshy algaes.

So you can see a reasonable explanation exists that does not require a major nutrient input increase in order to explain what happened to the reefs post-1983. Nutrient levels stay the same, grazing pressure decreases, fleshy algae growth proliferates. Fleshy algae growth comes at the expense of coral/coralline algae cover, which thereby limits areas where new urchins can recruit. This thereby explains why they haven't rebounded in numbers over the past 20 years. This explanation does not require nutrient levels to increase in order to work, but it should be obvious that if they did, the problem would only become worse.

I'll leave it to others to work out why herbivorous fish have not recovered or peaked in the past 20 years.

Regards.
Mike Kirda

 

[blue hula]

My point is that the reason the Urchins and herbivores cant rebound is the water quality......Use the Fla Keys as the , example, the scenario does not fit there because neither urchins or herbivores have ever been collected......Your blaming the overfishing of food fish ...........but all the fish disappeared, even tiny blennies and gobies ! no one over fished these guys......there is little connection between the two........do you think the urchin virus is from over fishing?

What baloney Kalk. Urchins do unbelievably well in poor water quality which you'd know if you'd been to the Philippines. Danajon bank - turbid, full of algae is an urchin haven (for some species).

In the Caribbean, they got wiped out with a DISEASE that came up from S America some where. Since then, urchins, in the absence of heavy predation by fish that eat them have been doing just find.

Who knows what triggered the virus. Maybe overfishing in S America released urchins from predation, allowing them to increase and when they got to really high densities, disease kicked in. Often happens in areas that are "mono crops'

The point is that no one is saying "overfishing is the only issue on reefs". But similarly, I won't accept that overfishing is irrelevant in the face of larger problems. It's just not true.

Why don't you check out the work on Florida fish populations by Jerry Ault at Rosenstiel ...

Blue hula