Coastal Researchers, Fishermen Worried About More Frequent Low Oxygen Zones

Olympic Coast National Marine Sanctuary research team members, Kathy Hough and LTJG Alisha Friel, recover sensors deployed seasonally off the coast of Washington from the research vessel Tatoosh in July 2017. — S. Maenner / NOAA

Scientists in Oregon and Washington are noticing a disruptive ocean phenomenon is becoming more frequent and extreme. It involves a suffocating ribbon of low oxygen seawater over our continental shelf.

The technical term is hypoxia, sometimes called “dead zones,” It’s an unwelcome variation on normal upwelling of cold, nutrient rich water from the deep ocean. When the dissolved oxygen drops too low, it drives away fish and can suffocate bottom dwellers such as crabs and sea worms who can’t scurry away fast enough.

It seemed to marine ecologist Francis Chan like this is happening most every summer lately. So the Oregon State University researcher looked back as far as coastal oxygen readings go—to about 1950—to see if it’s always been this way.

“The ocean starting in 2000 really looked different from the ocean we had between the 1950s and 1990s,” Chan said.

Chan said climate change could affect oxygen levels via disrupted circulation and ocean warming. 
 A September storm flushed away this year’s low oxygen zone by churning Northwest coastal waters. But Chan described the severity of the low oxygen readings recorded this summer as among the worst ever observed locally.

“It’s very much a patchy ribbon,” he said from his post in Newport, Oregon. Marine surveys and fixed instruments recorded notably low oxygen values from south of Yachats up past Newport.

Ten oceanographic moorings deployed by the Olympic Coast National Marine Sanctuary also found very low (hypoxic) oxygen values between Cape Elizabeth and Cape Flattery, Washington, this summer.

“This is not a happy year for organisms out on the coast,” said Jenny Waddell, the marine sanctuary’s research coordinator.

Waddell added that at least one sensor dipped into anoxic conditions, “where there’s literally no oxygen.”

“We had indications of a relatively persistent hypoxia event along the Quinault Reservation coastline,” wrote marine scientist Joe Schumacker of the Quinault Department of Fisheries in an email Friday. “Dead fish and shellfish at various locations and times beginning near the end of July and extending through most of August.”

More frequent and severe near-shore hypoxia concerns fishermen and crabbers. Commercial harvesters face reduced catches and economic losses when crabs suffocate and fish and prawns flee the oxygen-starved waters.

One of the tip-offs to OSU researchers of the onset of low oxygen conditions this summer was when Oregon Department of Fish and Wildlife biologists monitoring crab populations noticed crabs dying from lack of oxygen in a research trap. Other observers noted crabs leaving the ocean to seek more oxygenated waters in coastal estuaries and bays.

Earlier this year, researchers and fishery advocates found a receptive ear at the Oregon Legislature when they presented their concerns about silent changes in the ocean. Legislators approved the creation of a new council to be co-chaired by the state Fish and Wildlife director and an OSU leader.

The council is tasked with recommending and coordinating a long-term strategy to address hypoxia as well as ocean acidification.

Originally published: http://nwnewsnetwork.org/

What scientists are learning about the impact of an acidifying ocean

The effects of ocean acidification on marine life have only become widely recognized in the past decade. Now researchers are rapidly expanding the scope of investigations into what falling pH means for ocean ecosystems.

The ocean is becoming increasingly acidic as climate change accelerates and scientists are ramping up investigations into the impact on marine life and ecosystems. In just a few years, the young field of ocean acidification research has expanded rapidly – progressing from short-term experiments on single species to complex, long-term studies that encompass interactions across interdependent species.

“Like any discipline, it takes it time to mature, and now we’re seeing that maturing process,” said Shallin Busch, who studies ocean acidification at the National Oceanic and Atmospheric Administration’s (NOAA) Northwest Fisheries Science Center in Seattle.

As the ocean absorbs carbon dioxide from the burning of fossil fuels, the pH of seawater falls. The resulting increase in acidity hinders the ability of coral, crabs, oysters, clams and other marine animals to form shells and skeletons made of calcium carbonate. While the greenhouse gas effect from pumping carbon dioxide into the atmosphere has been known for decades, it wasn’t until the mid-2000s that the impacts of ocean acidification became widely recognized. In fact, there is no mention of acidification in the first three reports from the United Nations Intergovernmental Panel on Climate Change, issued in 1990, 1995 and 2001. Ocean acidification did receive a brief mention in the 2007 report summarizing the then-current state of climate science, and finally was discussed at length in the latest edition released in 2014.

But about halfway through that brief dozen years of acidification research, a shift started taking place.

“The early studies were just a first step and often quite simple,” said Busch of ocean acidification research. “But you can’t jump into the deep end before you learn how to swim.”

That started to change about five or six years ago, according to Philip Munday, who researches acidification effects on coral reefs at Australia’s James Cook University. “The first studies were often single species tested against ocean acidification conditions, often quite extreme conditions over short periods of time,” he said. “Now people are working on co-occurring stresses in longer-term experiments.”

That includes studying how acidification could change how organisms across a community or ecosystem interact – in other words, how the impacts on one species affect those it eats, competes with or that eat it. It also means looking at how impacts could change over time, due to species migrating or adapting, either in the short term or across a number of generations and how such effects may vary within the same species or even with the same population.

Nine examples of this new generation of acidification research are included in the latest issue of the journal Biology Letters. One study, for example, found that the ability to adapt to pH changes differed in members of the same species of sea urchins based on location. Another discovered that a predatory cone snail was more active in waters with elevated carbon dioxide levels but was less successful at capturing prey, reducing predation on a conch species. Another highlights that an individual organism’s sex can affect its response to acidification.

Munday, who edited the series of papers, said one of the major takeaways is that researchers are increasingly studying the potential for species to adapt to ocean acidification and finding those adaptations can be quite complex.

He pointed to a study on oysters. Previous work had shown that oysters whose parents were exposed to acidification conditions do better in those conditions than those whose parents weren’t. But in a new study, researchers found that when they exposed the offspring to additional stressors – such as hotter water temperatures and higher salinity – those adaptive advantages decreased.

All the studies call for including often-overlooked factors such as sex, location or changes in predation rate in future studies. Otherwise, researchers warn, impacts will be increasingly difficult to predict as the ocean continues to acidify.

“It’s far too early to make any sort of generalities,” Munday said.

The latest paper from NOAA’s Busch also cautions against generalities. By building a database of species in Puget Sound and their sensitivity to changes in dissolved calcium carbonate, she found that summarizing species’ sensitivity by class or order rather than the specific family can result in overestimating their sensitivity.

She compared it to similarities between people in the same immediate family versus people who are distant cousins. “There would be a lot more variation among those people because they’re not super closely related,” she said. “But when people started summarizing data really early in the field, there wasn’t much data to pull from. So it was done at a class level.

“Now that we have many more studies and information to pull from, how we draw summaries of species response should be nuanced,” she added.

Acidification research is likely to get only more nuanced in the years ahead. From the broad initial projections of average, ocean-wide surface acidity, for instance, researchers have started to pinpoint local pH projections, local impacts and local adaptations.

“We know the ocean is changing in a number of ways,” said Busch. “So just studying one of those factors without looking at the other changes in what’s going on in the ocean is not going to yield useful results.”

Matthew O. Berger, NewsDeeply, 2 October 2017. Article.

Originally published: https://news-oceanacidification-icc.org/

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

Study negates concerns regarding radioactivity in migratory seafood

Assistant professor Kevin Weng of the Virginia Institute of Marine Science with a dolphinfish or mahi-mahi (Coryphaena hippurus) collected as part of the study of Fukushima-derived radioactivity in large Pacific Ocean predators. Credit: A. Gray aboard FV Aoshibi IV.

When the Fukushima power plant released large quantities of radioactive materials into nearby coastal waters following Japan’s massive 2011 earthquake and tsunami, it raised concerns as to whether eating contaminated seafood might impair human health—not just locally but across the Pacific.

A new study by an international research team shows that those concerns can now be laid to rest, at least for consumption of meat from migratory marine predators such as tuna, swordfish, and sharks.

The team focused on cesium, a silvery metal with a large number of radioactive isotopes. Two of these, 134Cs and 137Cs, form when uranium fuel breaks down in nuclear reactors. The cesium isotopes are of particular concern because they were discharged in large quantities following the disaster, exhibit relatively long half-lives (2.1 and 30 years respectively), and tend to accumulate in the muscle tissues that people like to eat.

However, the team’s sampling of tissues from predatory fishes and other large vertebrates collected across the northern Pacific between 2012 and 2015 revealed no detectable levels of 134Cs, and 137Cs concentrations that were generally consistent with background levels from aboveground nuclear testing during the 1940s and 50s. They collected the animals from waters near Japan, Hawaii, and California.

Lead author Daniel Madigan of Harvard University says, “Our measurements and associated calculations of how much radioactive cesium a person would ingest by eating this seafood shows that impacts to human health are likely to be negligible. For marketed fish to be restricted from trade, the cesium levels would have to be more than 1,600 times higher than in any samples we measured.”

Co-author Kevin Weng, an assistant professor at William & Mary’s Virginia Institute of Marine Science, participated in the study by collecting fish samples in waters around Oahu and a remote seamount. He says, “Go ahead and eat some sushi! Our work shows that radioactivity from the Fukushima disaster is very low in open-ocean vertebrates.”

Assistant professor Kevin Weng of the Virginia Institute of Marine Science with a bigeye tuna (Thunnus obesus) collected as part of the study of Fukushima-derived radioactivity in large Pacific Ocean predators. Credit: A. Gray aboard FV Aoshibi IV.

Also contributing to the study were Zofia Baumann and Nicholas Fisher of Stony Brook University; Owyn Snodgrass, Heidi Dewar, and Peter Dutton of NOAA’s Southwest Fisheries Science Center; Michelle Berman-Kowalewski of the Channel Islands Cetacean Research Unit; and Jun Nishikawa of Tokai University.

The researchers undertook their analysis partly in response to earlier studies by Madigan and colleagues showing elevated levels of radioactive cesium in bluefin and albacore tuna caught off the California coast shortly after the Fukushima disaster—evidence that these fishes had swum almost 6,000 miles in less than two months. (It took ocean currents more than two years to deliver much-diluted cesium from Fukushima to those same waters.)

Although this early work focused on the utility of cesium isotopes as a happenchance tool that could help scientists characterize migratory patterns among a group of heavily exploited commercial fishes, public attention focused on perceived risks to human health.

“The earlier studies showed extremely low risks from cesium to anyone eating these migratory species, but public concern persisted,” says Weng. That concern also expanded to include not only the species of tuna in which cesium had been measured, but to other fishes, marine mammals, and sharks.

“People were very concerned about North Pacific salmon, halibut and scallops off British Columbia, and sea lions in Southern California,” says Madigan. “There was even information on the Internet that ‘the Pacific is dead’.”

“One goal of our study,” he says, “was to put these perceived risks in context by surveying a broad range of vertebrate species across the entire North Pacific for the presence or absence of Fukushima-derived radiocesium. Our results, which show very low or undetectable levels in these animals, are important both for public perception of seafood safety and for scientific understanding of radionuclide transfer.”

The authors suggest that scientists and funding agencies should look for at least one silver lining in any future nuclear or industrial accidents. “We can and should use future point sources of contamination, radioactive or otherwise, to shed new light on migratory dynamics of pelagic species that are poorly understood, heavily exploited, or of high conservation concern,” says Madigan. “But we would need to act quickly, within that narrow opportunistic timespan.”

Originally posted: https://phys.org/news/2017-08-negates-radioactivity-migratory-seafood.html

Fishermen See ‘Science in Action’ Aboard NOAA Survey Ship

Each spring and early summer, scientists set out along the West Coast aboard NOAA vessel Reuben Lasker to survey coastal pelagic species, or CPS, which includes small schooling fish such as northern anchovy, Pacific sardine, and jack and Pacific mackerels.

This year, with the help of West Coast fishermen, the scientists tested a new approach to extend their reach into nearshore waters to improve the accuracy of the survey results. The collaboration involved the fishing vessel Lisa Marie, of Gig Harbor, Washington, and brought two commercial fishermen aboard Lasker for an inside look at NOAA Fisheries surveys that inform stock assessments and guide decisions on how many fish can be caught by West Coast fishermen.

The idea emerged years before when the then-Director of NOAA’s Southwest Fisheries Science Center in La Jolla, California,  Cisco Werner, along with Deputy Director Kristen Koch and Fisheries Resources Division Director Gerard DiNardo, discussed the potential collaboration with Mike Okoniewski of Pacific Seafood and Diane Pleschner-Steele of the California Wetfish Producers Association.

Werner has since been named Chief Scientist of NOAA Fisheries.

The Magnuson-Stevens Fishery Conservation and Management Act requires NOAA Fisheries to use the best available science to help managers set catch limits and prevent overfishing. Annual surveys, using echosounders to detect and measure the abundances of CPS populations off the coasts of California, Oregon, Washington, and Canada’s Vancouver Island help fulfill this mandate. NOAA Fisheries also uses trawl catches, and fish-egg samples to help gauge fish reproduction and population trends.

“Acoustic-trawl surveys are our principal tool for monitoring the various species and determining how their abundances, distributions, and sizes are changing,” said David Demer, the Chief Scientist of the survey and leader of the Advanced Survey Technologies Group at Southwest Fisheries Science Center in La Jolla. “The surveys are very rigorous because they’re very important to our mission.”

To quantify any CPS in the shallow, nearshore waters off Oregon and Washington where Lasker cannot survey, Demer’s group equipped Lisa Marie, calibrated the instrumentation, and sailed with the fishermen to collect and analyze echosounder and sonar data along coastal transects.

Meanwhile Andy Blair, fisherman and owner of Lisa Marie, and Greg Shaughnessy, Chief Operating Officer of Ocean Gold Seafoods in Westport, Washington, spent five days aboard Lasker, learning how NOAA Fisheries scientists collect information that informs NOAA Fisheries stock assessments and leads to CPS harvest decisions by the Pacific Fishery Management Council.

“I learned a lot, even though I’ve been out fishing for years,” said Shaughnessy. “Now that I’ve been out there and seen how the work is done, I have a much better understanding of the logistics involved and how thorough and rigorous the work really is.”

A spotter pilot flew overhead during parts of the survey looking for and photographing schools of fish from above. The digital images will augment the measurements made aboard Lasker and Lisa Marie.

The vessels and aircraft confirmed each other’s findings when concurrently surveying the same areas.

Okoniewski praised NOAA Fisheries for welcoming commercial fishermen aboard Lasker and explaining the survey methods and science.

“We’ve really opened some new doors with this collaboration,” said Okoniewski, who with Shaughnessy and Blair are members of West Coast Pelagic Conservation Group, a non-profit advocacy and conservation group that represents commercial fishermen and processors. “There’s now a much greater understanding of what we each do and how we do it. It’s kind of a new age in terms of how we see each other.”

Sardine fishing is currently closed off the West Coast because sardine numbers, which are known for boom-bust cycles, have fallen below a protective threshold in a rule that governs harvest. Surveys are essential in determining when the cycle reverses, the population rebounds and, in turn, when fishing for sardines can resume.

“It was a wonderful chance to see science in action,” Shaughnessy wrote in a letter to SWFSC leadership. “From a fisherman’s perspective, the array of acoustic and scientific equipment itself is stunning. However, it was the dedicated men and women that made the real difference. Every crew member was very professional in every sense and yet made us feel included, safe, and at home.”

NOAA Fisheries Vessel Reuben Lasker uses echosounders, sonars, and a trawl net to survey populations of sardine, anchovy, and mackerels. (Photo credit: NOAA Fisheries) 

Fishing Vessel Lisa Marie, based out of Westport, Washington, uses a purse-seine net to fish for sardine and other small fish. (Captain: Ricky Blair; owner: Andy Blair; photo credit: NOAA Fisheries/Scott Mau)

CPS schools (dark patches) in shallow, nearshore water off Washington, and a ship, imaged from an aircraft. (Photo credit: Frank Foode)

Echogram of fish schools (red patches), one near the sea-surface (top of the image), and multiple others deeper. Also visible are plankton (blue layers), individual fish (discrete blue spots), the seabed (jagged red line), and 50- and 100-m depth markers (dotted lines). (Image credit: NOAA Fisheries/Scott Mau)

Read the original post: https://swfsc.noaa.gov/news.aspx?ParentMenuId=39&id=22667

Oceanographic influences on the distribution and relative abundance of market squid paralarvae (Doryteuthis opalescens) off the Southern and Central California coast

Americans Need to Know U.S. Fisheries are Sustainable: Former Senior NOAA Official

July 24, 2017 — Earlier this month, Saving Seafood unveiled our campaign to tell the public that American Seafood is Sustainable Seafood™. A recent paper by Mark Helvey, former NOAA Assistant Regional Administrator for Sustainable Fisheries for the Pacific Region, confirms that purchasing U.S.-caught seafood is one of the most sustainable choices consumers can make, and notes that, “Most Americans remain unaware of the high environmental standards by which U.S. federal marine fisheries – and many state fisheries – are managed, in compliance with multiple state and federal laws.”

According to the paper, the standards under which U.S. fishermen operate “conform to or exceed internationally accepted guidelines for sustainable fisheries adopted by the Food and Agriculture Organization of the United Nations.”

The first recommendation made in the peer-reviewed paper is to “increase awareness…of the high environmental standards by which U.S. federal marine fisheries – and many state fisheries – are managed.”

The paper makes the case that, “Sea Grant Extension Programs in U.S. coastal states and territories have conducted education and out-reach, with NOAA Fishwatch and a number of nongovernmental organizations also helping to bridge this gap. However, further efforts to address this lack of understanding are needed.”

This is precisely the goal of our American Seafood is Sustainable Seafood™ campaign.

Mr. Helvey provided the following summary of his paper to Saving Seafood:

• The United States is recognized for its robust seafood appetite and strong commitment to environmental conservation. However, efforts to close or restrict its own domestic fisheries in pursuit of environmental protection are often not considered within the context of seafood consumption.
• Restricting U.S. fisheries comes at the cost of displaced negative environmental impacts associated with the fishing activities of less-regulated, foreign fisheries.
• The authors provide six solutions for addressing this issue beginning with the need for U.S. consumers becoming more aware of the exceedingly high environmental standards by which U.S. marine fisheries are managed relative to many foreign ones.
• While efforts by NOAA’s Sea Grant Extension Program, FishWatch, and a number of nongovernmental organizations are bridging the information gap, the authors stress that more is required for increasing awareness that U.S fisheries are sustainable fisheries.

The paper, “Can the United States have its fish and eat it too?,” was published in the January 2017 volume of Marine Policy and is co-authored by Caroline Pomeroy, Naresh C. Pradhan, Dale Squires, and Stephen Stohs.

What factors play a role in analyzing forage fish fishing regulation?

The interaction of predators, fishing and forage fish is more complicated than previously thought and that several factors must be considered, says researcher.

The group of researchers was evaluating the interaction after results from an earlier report found that fishing of forage species had a large effect on predator population, said the Marine Ingredients Organization (IFFO). Those harvested fish are used in several areas including as feed ingredients.

The new study was initiated because there were some questions regarding the methods used in the initial project, said Ray Hilborn, with the school of aquatic and fishery sciences at the University of Washington and corresponding author.

“When the original Lenfest [Forage Fish Task Force] report came out, a few of us said it seemed that the methods they were using were not up to the questions they were asking,” he told FeedNavigator. The report also offered several policy recommendations, he added.

“It was on our radar screen,” he said. “And one of the things I’ve been interested in looking at is the intensity of natural fluctuation in populations, and forage fish are notable for how much they vary naturally.”

The interaction between forage fish populations and predators is more complicated than may have been suggested by earlier studies tracking that relationship, and several factors need to be considered when analyzing the role that fishing plays on that relationship, he said. “The key point isn’t that there isn’t an impact, but that you have to argue case-by-case,” he added.

Several factors need to be considered when assessing the interaction among predators, forage species, and fishing of those forage species, the researchers said in their study. “We show that taking account of these factors generally tends to make the impact of fishing forage fish on their predators less than estimated from trophic models,” they added.

Study response

The results from Hilborn’s group have seen responses from groups including IFFO.

Previous research based on models suggested that forage fish were more valuable when left in the ocean and recommended reducing forage fish collection rates by 50% to 80%, said IFFO. However, the new paper presents an argument for a more case-by-case basis for management.

“For fisheries management, such a precautionary approach would have a large impact on the productivity of forage fisheries,” the organization said. “As groups such as IFFO have noted, these stocks contribute strongly to global food security, as well as local and regional social and economic sustainability.”

It is important that fisheries are managed with an effort to balance requirements from the ecosystem, coastal communities and human nutrition, IFFO said. The new results provide additional guidance and update conclusions from past reports.

“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 organization said.

Study specifics

Fishing of low trophic or forage fish has generated interest in recent years, the researchers said. These fish include small pelagic fish, squid and juveniles of many species.

The evidence and theory suggest that fishing can limit the abundance of some fish stocks and can affect predators’ reproductive success by the density of their prey, they said.

“Although it would therefore seem obvious that fishing forage fish would have a negative effect on the abundance of their predators, the empirical relationships between forage fish abundance and predator abundance, or population rates of change, have not been examined in a systematic way,” they said.

In the study, the group examined 11 species of forage fish in the US, including what animals eat them and the role the species play in their predators’ diets, they said.

Species’ predators were identified, estimated fish abundance was analyzed and several models were fit to the data being assessed, they said. A simulation model also used information from fisheries regarding six different species of forage fish to evaluate the potential reduction in food for predators given a 5,000-year timespan.

“The question that they were asking is an important question, but to ask it properly you need to have analysis that includes the important biology,” said Hilborn of earlier evaluations. “We’re just doing a more detailed look at the biology, which you need to do to understand fishing forage fish and what happens to their predators.”

Research findings

The goal of the study was to identify the key factors that should be considered by analyzing the effect of fishing on forge fish, said the researchers. The group found, overall, that the models previously used were “frequently inadequate” for determining the role the fishing of forage fish plays on their predators.

“The most important feature that needs to be considered is the natural variability in forage fish population size,” they said. “Their abundance is highly variable even in the absence of fishing, and creditable analysis of the fishing impacts must consider how the extent of fishing-induced depletion compares with that of the natural variability.”

The research results did offer some unexpected results, said Hilborn.

“I was really surprised that we didn’t see any empirical data showing the relationship between predators and prey,” he said. “We only looked at American fisheries, but didn’t find at any correlation with fish and the predators.”

The majority of cases did not offer an obvious relationship between prey and predator abundance, the researchers said. The size of the fish eaten by predators may play a role.

“While some predators selectively eat small fish (usually not selected by the fishery), others prey on a large range of forage fish sizes,” they said. “The degree of overlap between fisheries and predators is highly variable.”

However, work on the subject is not complete, said Hilborn. Several groups of researchers interested in the area are addressing different elements of the analysis.

“We’re doing more detailed analysis of several of the components,” he said. “A more detailed model of specific places.”

The work includes looking more closely at the interaction of key predators and some of the larger forage fisheries around the world, he said. “I expect in some of these that we’re going to find some impact – overlap between what the fishery takes and the predator takes,” he added.

Read the original post: http://mobile.feednavigator.com/

RAY HILBORN: WORLD FISH STOCKS STABLE

June 12, 2017 — Speaking at the SeaWeb Seafood Summit on Wednesday, 7 June in Seattle, Washington, U.S.A., University of Washington fisheries researcher Ray Hilborn said the perception that the world’s fish stocks are declining is incorrect, and that fishing could sustainably be stepped up in areas with good management.

Hilborn pointed to figures from the RAM Legacy Stock Assessment Database that indicate that fish stocks dipped through the last part of the 20th century, but have since recovered in many fisheries.

“There is a very broad perception that fish stocks around the world are declining. Many news coverages in the media will always begin with ‘fish stocks in the world are declining.’ And this simply isn’t true. They are increasing in many places and in fact, globally, the best assessments are that fish stocks are actually stable and probably increasing on average now,” Hilborn said.

The RAM Legacy Database collects information on all the stocks in the world that have been scientifically assessed, which is a little more than half of the world’s catch.

“What we don’t really know about is the big fisheries in Asia, in the sense that we don’t have scientific assessments of the trends in abundance,” Hilborn said.

He added that the general consensus is that the status of those stocks is poor, a result of, among other things, poor fisheries management, reinforcing surveys that have shown a direct correlation between high stock abundance and high intensity of management.

“For most of the developed world fisheries’ management is quite intense, and South and Southeast Asia stand out as really not having much in the way of fisheries’ management systems, particularly any form a enforcement of regulations, if regulations exists,” he said.

But in much of the developed world, Hilborn said fish stocks are robust, even when they sometimes get labeled as overfished.

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:

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.

Originally posted by: Saving Seafood