SEAFOOD.COM NEWS by John Sackton Feb 27, 2013 — In the current February 21st issue of Nature, there is a debate between Daniel Pauly vs Ray Hilborn and Trevor Branch, that gets to the heart of the entire issue of fisheries sustainability.
Pauly, who famously developed the analysis that was used to claim that all fisheries would be collapsed by 2048, basis his arguments on his view that catch data reflects the abundance of fisheries, and that declines in catches can be used to estimate declines in stock abundance. He then goes on to say that catch data is notoriously under reported, and therefore actual historical abundance was orders of magnitude higher than today.
Although he has backed off the 2048 extrapolation, this is very much still his main argument.
Hilborn, and Trevor Branch at the University of Washington, have disproved this hypothesis by conducting studies of fisheries stocks that have survey and abundance data as well as catch data, and that are under some type of management.
What Hilborn and Branch have found is that the survey and assessment data paint a very different picture from the catch data, and that survey data is a far more reliable indicator of biomass than extrapolation from catch data alone.
The reason is many factors impact catches beyond simple abundance. They include regulatory limits, bycatch limits, economic incentives, ecological changes and long term stock movements.
Why does this scientific argument matter? Because in a nutshell it frames the debate between environmentalists who believe the only way to preserve fish stocks is to shut down fishing vs scientists like Hilborn, who have shown conclusively that effective fisheries management – including stock assessments and controls on landings – is a key component in stock recovery and sustainability.
Far from a doom and gloom approach that says only by cutting catches drastically can we save fisheries, Hilborn’s position is that the data show that it is scientific management that saves fisheries, and that where these controls are in place, stocks recover and maintain themselves.
Pauly says that actual fishery landings are underreported by 30-50% in developed countries, and by 100% to 500% in developing ones. Such a claim makes it seem fisheries are in an uncontrollable crisis.
Hilborn on the other hand, says that fishermen are already catching 80–96% of the potential global yield.
Unfortunately, the wild assumptions made by Pauly are driving the environmental view of fisheries, which can potentially lead to a very destructive limitations for food output from the oceans.
Here are a few excerpts from the point counterpoint articles in Nature:
Pauly:
In 2006, a group of researchers from various institutions used a stock status plot to project, among other things, that all stocks would be collapsed by 2048. Unsurprisingly, this projection, although a small part of the study, triggered an avalanche of alarmist headlines: “Seafood may be gone by 2048,” wrote the National Geographic; “The end of fish, in one chart,” said The Washington Post.
The weirdly precise 2048 date, with echoes of George Orwell's Nineteen Eighty-Four, was widely derided within the fisheries community. Given the myriad factors that can affect fishing — shifts in policy, rising fuel costs, market crashes and natural disasters — it is impossible to predict where fisheries will be even ten years from now. But, of the various lines of attack that fisheries scientists have used to discredit the 2006 paper, one charge has since gained momentum and stands to do much more damage to fisheries science and management than the original paper. This is the idea that catch data are not useful for determining the health of fish stocks. This is wrong. Dangerously so.
As part of the Sea Around Us initiative – a collaboration between the University of British Columbia in Vancouver, Canada, and the Pew Charitable Trusts, which aims to monitor the impact of fisheries on marine ecosystems – I am leading a project to evaluate the entire body of FAO catch data collected since 1950. So far, my team has gathered information on fish consumption and the tonnage of fish imported and exported, for instance, to verify the catch data of 180 countries and island territories. Our findings suggest that catches, with the notable exception of domestic catches by China, are underreported by about 100–500% in many developing countries, and by 30–50% in developed ones.
Hilborn and Branch:
The major database on all the fisheries of the world is the FAO Yearbook Fishery and Aquaculture Statistics. This collates the amount (in weight) of haddock, bream, cod and more than 1,000 other species hauled in each year by fishermen, whether from commercial trawlers or canoes, using estimates sent in by officials from individual countries.
For the past few years, researchers have been conducting analyses to use these data to assess the health of the world's fish stocks. And high-impact journals, including this one, have published them. Such assessments consistently overlook the fact that the amount of fish caught does not necessarily reflect the number of fish in the sea.
Attempts to use catch data as an indication of fish abundance have spread alarm and confusion in policy circles, and fuelled the perception among the public and conservation organizations that fisheries management is failing. A much better approach is to deduce the health of stocks region by region and fishery by fishery using scientific stock assessments, which collate all sorts of data – from the results of surveys conducted from research vessels to the catch per fishing effort, and the age and size distributions of the fish caught. This can reveal which management strategies are actually effective.
In 2006, researchers projected that all the fisheries in the world would collapse by 2048. The group classed a stock as 'collapsed' if less than 10% of the highest catches ever recorded were being harvested each year, using an approach developed by others. For many of us in the fisheries community, the 2048 projection was hard to believe; Alaskan salmon fisheries, for instance, were in better shape than they had been in the history of industrial fishing.
The 2048 projection and the controversy it sparked within the fisheries community undermined conservationists' confidence in the ability of governments to prevent overfishing. Even more misleading, in our view, is the most recent attempt to assess all the fish stocks in the world using catch data.
The Ocean Health Index, published in Nature last year, aggregates various measures, such as biodiversity, into a single score that is meant to indicate how healthy the seas are. To calculate the capacity of the oceans to generate food, the researchers estimated the maximum sustainable catches of 100 well-studied stocks using the results of stock assessments. They then used a previously devised equation relating these maximum sustainable catches to the highest catches ever recorded from these same fisheries to estimate the maximum sustainable catches for all the fisheries in the FAO database.
Hugely unreliable predictions result. For instance, the maximum sustainable yield for Antarctic krill assigned by the Ocean Health Index is 174 times lower than the estimate derived from detailed stock assessments conducted by the International Commission for the Conservation of Antarctic Marine Living Resources. Overall, the health-index study implies that fishermen could theoretically catch several times more marine fish if fisheries were better managed. This wildly contradicts the findings of several other studies – that fishermen are already catching 80–96% of the potential global yield.
Analyses based largely on catch data are fuelling a view held by numerous non-governmental organizations and environmentalists that the only solution to marine conservation is a ban on fishing in large areas. Between 2007 and 2009, for instance, several non-governmental organizations and US foundations spent $58 million each year on efforts to create 'marine protected areas'. This campaign has been spectacularly successful in Australia, where 3.1 million square kilometres of ocean are now closed to fishing.
This approach overlooks the enormous successes of many management strategies. For example, on the east coast of the United States the total abundance of bottom fish, such as redfish and haddock, increased more than fivefold from 1995 to 2007 after fishing restrictions were strengthened from the mid-1990s.
Various data collected by national fisheries agencies, fishing companies and marine scientists are also available for the rest of the world. Currently, there is no global database for this information. We (the authors) have recently begun working with more than 20 countries, the FAO and the World Bank to try to assemble a database for a good sample of the world's fisheries. We estimate that obtaining the kind of data needed for 40 countries (focusing on 6–8 fisheries in each country) will take 10 years and require US$20 million.
Meanwhile, we urge researchers to use all the available data in addition to the FAO database, and to validate their results by consulting local experts or other data sources.
Catch data are a crucial part of any fisheries assessment – it is impossible to calculate the maximum weight of fish that could be harvested sustainably without knowing what is being caught each year. But on their own, catch data cannot answer the question at the heart of fisheries science: how many fish are in the sea?
The Citation for the Nature article is Fisheries: Does catch reflect abundance? by Daniel Pauly, Ray Hilborn and Trevor Branch Nature 494, 303–306 (21 February 2013)
This article is from Seafood.com, a subscription site. The article is reprinted with permission.