Saving Seafood

Authors of Recent Research on Forage Fish Respond to Criticism from Lenfest Task Force

WASHINGTON – September 20, 2017 – In April, a team of respected fisheries scientists led by Dr. Ray Hilborn published a study that found fishing of forage species likely has a lower impact on predators than previously thought. This conclusion challenged previous forage fish research, most notably the 2012 Lenfest Oceans Program report “Little Fish, Big Impact,” which recommended leaving more forage fish in the water to be eaten by predators.

The Lenfest task force responded to this new research with a Letter to the Editor of Fisheries Research, where the Hilborn et al. study was published. In response to this letter, Hilborn et al. wrote their own letter, which was published August 5 in Fisheries Research and is reproduced below:

Our paper highlighted that key biological relationships between forage fish and their predators were not included in the models used in the LENFEST report. These missing elements were (1) the high level of natural variability of forage fish, (2) the weak relationship between forage fish spawning stock size and recruitment and the role of environmental productivity regimes, (3) the size distribution of forage fish, their predators and subsequent size selective predation and (4) the changes in spatial distribution of the forage fish as it influences the reproductive success of predators. We demonstrate that each of these elements can have a major impact on how one evaluates the impact of fishing forage species on their predators. The LENFEST report used EwE models without these factors to determine the very specific recommendations they made about how to manage forage fish.

We certainly agree that in some cases fishing forage fish will affect their predators, but in other cases there may be little if any impact – it all depends on the biology that was not included in the models used.

This critique of our paper suggests that we are offering alternative evaluation of the impact of fishing forage fish that are, like the LENFEST recommendations, broadly applicable. We make no such claim and much of their critique is against the straw man they have constructed. We are not arguing that fishing forage fish does not affect predators. Rather we show how, in specific cases, there may be little if any impact of fishing forage fish and that general conclusions simply are not possible.

We suggest that the very specific quantitative measures proposed in the LENFEST report result from models that do not have these components and that if these elements were included in the models the conclusions would likely be different. While the authors of the letter argue that they conducted a comprehensive literature review, the specific recommendations came from their modelling, and it is the modelling we criticize and their critique makes few attempts to defend.

We stated “Pikitch et al. (2012) argued forcefully that their analysis provided general conclusions that should be broadly applied. However, relevant factors are missing from the analysis contained in their work…” Their response is that their recommendations were “tailored to the level of uncertainty and data availability of each system.” What we refer as “general conclusions” contain a set of recommendations for three uncertainty tiers, but our point is that the biology of each system is different, not the availability of data or uncertainty, and the differences in biology should be considered when evaluating management options for forage fisheries.

The specificity of their recommendations is clear – for high information situations (which would include the California Current, Humboldt Current, NE Atlantic sand eel and herring) their recommendation is “In any case, lower biomass limits should not be less than 0.3 B0, an MAX F should not exceed 0.75 FMSY or 0.75 M.” These numbers are not the result of their case studies or literature review but the result of their models that did not include a number of important elements.

Finally, we agree that situations where detailed information is lacking are challenging for management, and that is why it is important to identify species and system attributes that make systems less resilient to fishing. Low trophic level species constitute the largest potential sources of increased fish production in the world and much of the recent suggestions for “balanced harvesting” relies on significant increases in exploitation rates on trophic levels associated with forage fish. Since almost all of these potential low trophic level species would be considered in the “low information tier” the LENFEST recommendation is that new fisheries not be allowed until sufficient data are collected. Given that few countries will devote resources to research on fisheries that do not exist, the LENFEST recommendation essentially says no new fisheries on these species, and thus in effect precludes development of what may be significant food resources.

We believe the authors of our paper and the LENFEST report all accept that in some cases predators may be highly dependent on forage fish, but in other cases there may be little dependence. Management should be based upon what is known about the dependence of the predators on forage fish and the relative importance the local agencies place on maintaining high predator abundance verses the benefits of full exploitation of the forage fish. The major forage fisheries of the world are very valuable and currently intensively studied. What is needed for each of these fisheries is a new set of models that incorporate the elements that were missing from the LENFEST analysis.

Ray Hilborn, Ricardo O. Amoroso, Eugenia Bogazzi, Olaf P. Jensen, Ana M. Parma, Cody Szuwalski, Carl J. Walters

Authors of New Research on Forage Fish Respond to Critiques from Lenfest Task Force

June 5, 2017 — The following was written by authors of a new paper on forage fish that found that previous research likely overestimated the impact of forage fishing. The piece addresses criticisms made by the Lenfest Forage Fish Task Force. The authors are Dr. Ray Hilborn, Dr. Ricardo O. Amoroso, Dr. Eugenia Bogazzi, Dr. Ana M. Parma, Dr. Cody Szuwalski, and Dr. Carl J. Walters:

First we note that the press releases and video related to our paper (Hilborn et al. 2017) were not products of the authors or their Universities or agencies. Some of the authors were interviewed for the video, and each of us must be prepared to defend what was said on the video. The LENFEST Task Force authors criticize our statement in the video that:

“What we found is there was essentially no relationship between how many forage fish there are in the ocean and how well predators do in terms of whether the populations increase or decrease.”

Our paper was specifically about U.S. forage fish, where we found very few relationships that were stronger than one might expect by chance. It is certainly likely that there are places where there is a significant relationship, but we noted that the LENFEST report did not include any analysis of the empirical data and relied only on models. Our point is that the models used by the LENFEST Task Force assume there will always be such a relationship, whereas in many, and perhaps most cases there may be little if any impact of fishing forage fish on the abundance of their predators. The scientific literature suggests that central place foragers, such as seabirds and pinnipeds at their breeding colonies, may be exceptions, and we acknowledge as much in our paper (p. 2 of corrected proofs, paragraph starting at the bottom of first column).

Specific response to the “shortcomings” of our study listed in the LENFEST Task Force response

  1. We included species not considered by the LENFEST Task Force to be “forage fish.” We simply looked for harvested fish and invertebrate populations that were an important part (> 20%) of the diet of the predators, and thus we would argue that our analysis is appropriate and relevant to the key question: “Does fishing the major prey species of marine predators affect their abundance?”
  2. The LENFEST Task Force authors criticize our use of estimates of abundance of forage fish provided by stock assessment models, and then suggest that because these models were not designed to identify correlations between predators and prey we were committing the same error that the LENFEST Task Force did, using models for a purpose they were not designed for. This is wrong: the stock assessment models are designed to estimate the abundance of fish stocks and the estimates of forage species we used to examine correlations with predators were considered the best available estimates at the time of the analysis. Similarly, the stock assessment models used for the predatory fish species represent the best available estimate of the abundance, and rate of change in abundance, of these predators. We did not claim the stock assessment models told us anything directly about the relationship between forage abundance and predator rates of change. We simply asked “Is there any empirical relationship between forage species abundance and either the abundance or rate of change in abundance of their predators?” The answer, with very few exceptions, was “no.”
  3. The LENFEST Task Force authors criticize our use of U.S. fisheries because they are better managed than the global average. Most of the key criticisms we made of the LENFEST study were unrelated to how fisheries are managed, but to the basic biological issues: recruitment variation, weak relationship between spawning biomass and recruitment, relative size of fish taken by predators and the fishery and the importance of local density of forage fish to predators rather than total abundance of the stock. U.S. fisheries are not only better managed, but also often better researched, so U.S. fisheries are a good place to start examining the biological assumptions of the models used by the LENFEST Task Force.
  4. We did not argue that fisheries management does not need to change – instead we argued that general rules such as the LENFEST Task Force’s recommendation to cut fishing mortality rates to half of the levels associated with maximum sustainable yield for “most forage fisheries now considered well managed” (LENFEST Summary of New Scientific Analysis) are not supported by sound science. Our analysis suggests that there’s little empirical evidence that such a policy will increase predatory fish abundance. Instead, every case needs to be examined individually and management decisions should weigh the costs (economic, social, and ecological) of restricting forage fisheries to levels below MSY against the predicted benefits, while accounting for uncertainty in both. Our abstract concludes “We suggest that any evaluation of harvest policies for forage fish needs to include these issues, and that models tailored for individual species and ecosystems are needed to guide fisheries management policy.”
  5. Essington and Plagányi feel we incorrectly characterized their paper. We simply rely on the words from the abstract of their paper. “We find that the depth and breadth with which predator species are represented are commonly insufficient for evaluating sensitivities of predator populations to forage fish depletion. We demonstrate that aggregating predator species into functional groups creates bias in foodweb metrics such as connectance.” Carl Walters, one of our co-authors and the person who conceived and built the EcoSim model certainly agrees that the models the LENFEST Task Force used were insufficient for the task they attempted.

Moving forward

We agree that the next steps are to move beyond U.S. fisheries and we are doing so. We have current projects doing a global analysis of relationships between forage fish abundance and the population dynamics of their predators. We have an almost complete review of recruitment patterns in forage fish stocks. We are doing specific case studies of other regions with models explicitly designed to evaluate the impact on predators of fishing forage fish. Finally, we are exploring alternative management strategies for forage fish, considering alternative recruitment patterns, across a range of case studies. We hope that many of the authors of the LENFEST report will collaborate with us in these efforts.

Predators may be less affected by catch of small fish than previously thought, new study says

WASHINGTON (NCFC) – April 3, 2017 – New research published today in the journal Fisheries Research finds that fishing of forage species likely has a lower impact on predators than previously thought, challenging previous studies that argued forage fish are more valuable left in the ocean.

A team of seven respected fisheries scientists, led by Prof. Ray Hilborn, Ph.D., of the University of Washington, found that predator populations are less dependent on specific forage fish species than assumed in previous studies, most prominently in a 2012 study commissioned by the Lenfest Ocean Program, which is managed by The Pew Charitable Trusts. The Lenfest Forage Fish Task Force argued that forage fish are twice as valuable when left in the water to be eaten by predators, and recommended slashing forage fish catch rates by 50 to 80 percent.

For fisheries management, such a precautionary approach would have a large impact on the productivity of forage fisheries. As groups such as IFFO (The Marine Ingredients Organisation) have noted, these stocks contribute strongly to global food security, as well as local and regional social and economic sustainability.

However, the new research found multiple omissions in the methodology of the Lenfest study. “When you review the actual models that were used [by Lenfest], there are a few key elements on the biology of these animals that were not represented,” said Dr. Ricardo Amoroso, one of the study’s co-authors. He added that one of the authors’ approaches was to “look for empirical evidence of what is actually happening in the field.” Previous studies relied on models which took for granted that there should be a strong link between predators and prey.

Specifically, the Lenfest study and another study using ecosystem models ignored the natural variability of forage fish, which often fluctuate greatly in abundance from year to year. It also failed to account for the fact that predators tend to eat smaller forage fish that are largely untouched by fishermen. Because of these oversights, the new study concluded that the Lenfest recommendations were overly broad, and that fisheries managers should consider forage species on a case-by-case basis to ensure sound management.

“It is vital that we manage our fisheries to balance the needs of the ecosystem, human nutrition and coastal communities,” said Andrew Mallison, IFFO Director General. “These findings give fishery managers guidance based on science, and update some of the inaccurate conclusions of previous reports.”

The Lenfest findings were largely based on a model called EcoSim, developed by Dr. Carl J. Walters, one of the co-authors of the new paper. Dr. Walters found that the EcoSim models used in earlier studies had omitted important factors, including natural variability, recruitment limitations and efficient foraging of predators.

Dr. Walters noted that there were “very specific” issues with previous uses of the EcoSim model. “It was predicting much higher sensitivity of creatures at the top of the food webs to fishing down at the bottom than we could see in historical data,” he said.

This is not the first time ecosystem models used in earlier studies have been questioned. One year after the Lenfest study was completed, two of its authors, Dr. Tim Essington and Dr. Éva Plagányi, published a paper in the ICES Journal of Marine Science where they said, “We find that the depth and breadth with which predator species are represented are commonly insufficient for evaluating sensitivities of predator populations to forage fish depletion.” The new study reaffirmed this finding, noting “several reasons to concur with the conclusion that the models used in previous analysis were insufficient.”

In addition to its critiques of previous research, the researchers found further evidence of the lack of fishing impact on forage fish. Their research indicated that environmental factors are often much more important drivers of forage fish abundance. They also found that the distribution of forage fish has a greater impact on predators than simply the raw abundance of forage fish.

The authors concluded by noting the importance of forage fish as a part of human food supply chains, praising their high nutritional value, both through direct human consumption and as food in aquaculture, as well as the low environmental impact of forage fishing. Cutting forage fishing, as recommended by the Lenfest group, would force people to look elsewhere for the healthy protein and micronutrients provided by forage fish – likely at much greater environmental cost, the authors wrote.

“Forage fish provide some of the lowest environmental cost food in the world – low carbon footprint, no water use,” Dr. Hilborn said. “[There are] lots of reasons that forage fish are a really environmentally friendly form of food.”

It is also well-established that forage fisheries provide substantial health benefits to human populations through the supply of long chain omega-3 fatty acids, both directly through consumption in the form of fish oil capsules, and indirectly through animal feed for farmed fish and land animals.

The paper was authored by Dr. Ray Hilborn, Dr. Ricardo O. Amoroso, and Dr. Eugenia Bogazzi from the University of Washington; Dr. Olaf P. Jensen from Rutgers University; Dr. Ana M. Parma from Center for the Study of Marine Systems -CONICET, Argentina; Dr. Cody Szuwalski from the University of California Santa Barbara; and Dr. Carl J. Walters from the University of British Columbia.

Read the full study here

Watch a video about the study here

Read an infographic about the study here

Predators may be less affected by catch of small fish than previously thought, new study says

April 3, 2017 — WASHINGTON — The following was released by the National Coalition for Fishing Communities and IFFO: 

New research published today in the journal Fisheries Research finds that fishing of forage species likely has a lower impact on predators than previously thought, challenging previous studies that argued forage fish are more valuable left in the ocean.

A team of seven respected fisheries scientists, led by Prof. Ray Hilborn, Ph.D., of the University of Washington, found that predator populations are less dependent on specific forage fish species than assumed in previous studies, most prominently in a 2012 study commissioned by the Lenfest Ocean Program, which is managed by The Pew Charitable Trusts. The Lenfest Forage Fish Task Force argued that forage fish are twice as valuable when left in the water to be eaten by predators, and recommended slashing forage fish catch rates by 50 to 80 percent.

 For fisheries management, such a precautionary approach would have a large impact on the productivity of forage fisheries. As groups such as IFFO (The Marine Ingredients Organisation) have noted, these stocks contribute strongly to global food security, as well as local and regional social and economic sustainability.

 However, the new research found multiple omissions in the methodology of the Lenfest study. “When you review the actual models that were used [by Lenfest], there are a few key elements on the biology of these animals that were not represented,” said Dr. Ricardo Amoroso, one of the study’s co-authors. He added that one of the authors’ approaches was to “look for empirical evidence of what is actually happening in the field.” Previous studies relied on models which took for granted that there should be a strong link between predators and prey.

 Specifically, the Lenfest study and another study using ecosystem models ignored the natural variability of forage fish, which often fluctuate greatly in abundance from year to year. It also failed to account for the fact that predators tend to eat smaller forage fish that are largely untouched by fishermen. Because of these oversights, the new study concluded that the Lenfest recommendations were overly broad, and that fisheries managers should consider forage species on a case-by-case basis to ensure sound management.

 “It is vital that we manage our fisheries to balance the needs of the ecosystem, human nutrition and coastal communities,” said Andrew Mallison, IFFO Director General. “These findings give fishery managers guidance based on science, and update some of the inaccurate conclusions of previous reports.”

 The Lenfest findings were largely based on a model called EcoSim, developed by Dr. Carl J. Walters, one of the co-authors of the new paper. Dr. Walters found that the EcoSim models used in earlier studies had omitted important factors, including natural variability, recruitment limitations and efficient foraging of predators.

Dr. Walters noted that there were “very specific” issues with previous uses of the EcoSim model. “It was predicting much higher sensitivity of creatures at the top of the food webs to fishing down at the bottom than we could see in historical data,” he said.

This is not the first time ecosystem models used in earlier studies have been questioned. One year after the Lenfest study was completed, two of its authors, Dr. Tim Essington and Dr. Éva Plagányi, published a paper in the ICES Journal of Marine Science where they said, “We find that the depth and breadth with which predator species are represented are commonly insufficient for evaluating sensitivities of predator populations to forage fish depletion.” The new study reaffirmed this finding, noting “several reasons to concur with the conclusion that the models used in previous analysis were insufficient.”

In addition to its critiques of previous research, the researchers found further evidence of the lack of fishing impact on forage fish. Their research indicated that environmental factors are often much more important drivers of forage fish abundance. They also found that the distribution of forage fish has a greater impact on predators than simply the raw abundance of forage fish. 

The authors concluded by noting the importance of forage fish as a part of human food supply chains, praising their high nutritional value, both through direct human consumption and as food in aquaculture, as well as the low environmental impact of forage fishing. Cutting forage fishing, as recommended by the Lenfest group, would force people to look elsewhere for the healthy protein and micronutrients provided by forage fish – likely at much greater environmental cost, the authors wrote.

“Forage fish provide some of the lowest environmental cost food in the world – low carbon footprint, no water use,” Dr. Hilborn said. “[There are] lots of reasons that forage fish are a really environmentally friendly form of food.”

It is also well-established that forage fisheries provide substantial health benefits to human populations through the supply of long chain omega-3 fatty acids, both directly through consumption in the form of fish oil capsules, and indirectly through animal feed for farmed fish and land animals. 

The paper was authored by Dr. Ray Hilborn, Dr. Ricardo O. Amoroso, and Dr. Eugenia Bogazzi from the University of Washington; Dr. Olaf P. Jensen from Rutgers University; Dr. Ana M. Parma from Center for the Study of Marine Systems -CONICET, Argentina; Dr. Cody Szuwalski from the University of California Santa Barbara; and Dr. Carl J. Walters from the University of British Columbia.

Read the full study here

Watch a video about the study here

Read an infographic about the study here

About the NCFC

The National Coalition for Fishing Communities provides a national voice and a consistent, reliable presence for fisheries in the nation’s capital and in national media. Comprised of fishing organizations, associations, and businesses from around the country, the NCFC helps ensure sound fisheries policies by integrating community needs with conservation values, leading with the best science, and connecting coalition members to issues and events of importance. For more, visit www.fisheriescoalition.org.

About IFFO

IFFO represents the marine ingredients industry worldwide. IFFO’s members reside in more than 50 countries, account for over 50% of world production and 75% of the fishmeal and fish oil traded worldwide. Approximately 5 million tonnes of fishmeal are produced each year globally, together with 1 million tonnes of fish oil. IFFO’s headquarters are located in London in the United Kingdom and it also has offices in Lima, Peru, and in Beijing, China. IFFO is an accredited Observer to the UN Food and Agriculture Organisation (FAO). To find out more, visit www.iffo.net.

PRESS CONTACT

Robert Vanasse

National Coalition for Fishing Communities

Washington

+1 (202) 333-2628

bob@savingseafood.org

Georgie Harris

IFFO, The Marine Ingredients Organisation

London

+44 (0) 2030 539 195

gharris@iffo.net