Archive for the Research Category

Dec 10 2021

Retraction of Flawed MPA Study Implicates Larger Problems in MPA Science

Source: University of Washington, Sustainable Fisheries
By Max Mossler, UW Sustainable Fisheries Managing Editor
December 9, 2021

Editor’s note: This article was originally published on, a University of Washington project to better communicate fishery science.

After months of public criticism and findings of a conflict of interest, a prominent scientific paper (Cabral et al. 2020, A global network of marine protected areas for food) was recently retracted by The Proceedings of the National Academy of Sciences (PNAS).

A retraction is a Big Deal in science, especially from a prominent journal. What’s strange in this story is how the conflict of interest intersects with the science. The conflict of interest was apparent immediately upon publication, but it wasn’t until major problems in the underlying science were revealed that an investigation was launched, and the paper eventually retracted.

Cabral et al. 2020 claimed that closing an additional 5% of the ocean to fishing would increase fish catches by 20%. That snappy statistic made for a great headline—the paper was immediately covered by The Economist, Forbes, Anthropocene Magazine, and The Conversation when it was published in October 2020. It made its way through the popular press (the New York Times, Axios, National Geographic, and The Hill have all cited the paper)—and eventually into the U.S. congressional record: It was submitted as supporting evidence for a bill by then-Representative Deb Haaland, now the Secretary of the Interior. Cabral et al. 2020’s Altmetric Attention Score, a measure of how widely a scientific paper is shared, is in the top 5% all-time.

But with increased press comes increased scrutiny. Several close collaborators of the Cabral et al. group wrote scientific critiques that PNAS published earlier this year. The critiques pointed out errors and impossible assumptions that strongly suggested the paper was inadequately peer reviewed.

PNAS later determined that the person responsible for assigning Cabral et al.’s peer reviewers, Dr. Jane Lubchenco, had a conflict of interest. She collaborated with the Cabral et al. group and was the senior author on a follow-up paper published in Nature in March 2021. That follow-up paper, Sala et al. 2021, included the authors of Cabral et al. and depended on the same MPA model meant to be reviewed in PNAS.

Shortly after the Nature paper was published, Dr. Magnus Johnson (of the University of Hull in the U.K.) wrote a letter to the editor-in-chief of PNAS reporting the conflict of interest; an investigation was launched, and PNAS decided to retract Cabral et al. 2020 on October 6th, 2021—nearly a year from its original publication.

According to the editor-in-chief of PNAS, the frequent collaboration relationship Lubchenco had with the authors constituted a conflict of interest, as did the personal relationship with one of the authors, Dr. Steve Gaines—her brother-in-law. She should not have accepted the task of editing the paper. These conflicts of interest were clear and apparent from the time Cabral et al. 2020 was first submitted, but it wasn’t until the follow-up paper, Sala et al. 2021, received more press than any other ocean science paper in recent memory that eyebrows were raised.

Now the Sala et al. follow-up paper is being questioned—more potential inaccuracies have been found.

A highly flawed computer model with poor assumptions

Cabral et al. 2020 assembled a computer model out of several kinds of fishery data to predict where marine protected areas (MPAs) should be placed to maximize global sustainable seafood production. The model produced the map below, where the areas in green are high priority for MPAs and the orange areas are low priority.

Figure 2a from the now retracted Cabral et al. 2020, A global network of marine protected areas for food.

MPAs meant to increase food production do so by reducing fishing pressure in places where it is too high (overfishing). Asia and Southeast Asia have some of the highest overfishing rates in the world—reducing fishing pressure there is a no-brainer, but the model determined many of those areas to be low priority for protection.

The map above (Figure 2a from the retracted paper) should have been a big red flag for the peer reviewers of Cabral et al. 2020. Why were MPAs prioritized all around the U.S., where overfishing has been practically eliminated, but not prioritized around India, Thailand, Indonesia, Malaysia, Vietnam, and China?

Clearly, something was wrong with the model.

Several researchers with a long history of collaboration with the Cabral et al. authors noticed the oddity in the MPA prioritization and pointed out a fundamental issue: the model contained biologically impossible assumptions. It assumed that unassessed fish populations were globally linked—in the model, their geographic ranges could stretch across multiple oceans and their growth rates were based on global data rather than more-precise local data.

An “unassessed” fish population means there is no consistent scientific assessment of its status. Data on those fisheries is sparce. They comprise about half of the world’s catch with the other half monitored and assessed. In monitored or assessed fisheries, all kinds of data are consistently collected and stored in the RAM Legacy Database.

With little data, uncertainty about the future of unassessed fish stocks requires assumptions to be made. But the need for assumptions doesn’t excuse impossible ones. The model in Cabral et al. assumed unassessed fish populations could travel and mate across the species’ entire range rather than just within the population. This is akin to assuming North Sea Atlantic cod could interact with Gulf of Maine Atlantic cod who live over 3,000 miles away. There were cases in the model that assumed MPAs in the Atlantic would benefit fish in the Pacific.

Cabral et al. also assumed density dependence was global rather than local or regional, meaning recruitment of new fish to a population (basically a birthrate) depended on its global abundance rather than local abundance. In reality, density dependent effects are only relevant to the specific population of a particular species, e.g. North Sea cod versus all Atlantic cod; the abundance of North Sea cod has no relation to the abundance of Gulf of Maine cod despite being the same species.

The first critique pointing out issues with the model was published in April by Ray Hilborn (founder of this site). Another critique by Dan Ovando, Owen Liu, Renato Molino, and Cody Szuwalski (all of whom did their Ph.D.’s or a postdoc with members of the Cabral et al. group) expanded on Hilborn’s critique by digging into the math. They found that, due to the assumption that species were connected globally, Cabral et al.’s model overestimated the geographic range of unassessed fish by a factor of seventeen, compared to the scientifically assessed stocks.

Perhaps because it is biologically impossible, there is little precedent for modeling the dynamics of a species as one globally connected population. However, there is precedent for modeling unassessed fish populations at regional scales. Hilborn, Ovando, Szuwalski, Cabral, and many other authors of Cabral et al. 2020 were all authors on Costello et al. 2016Global fishery prospects under contrasting management regimes, a seminal paper that modeled the range of unassessed fisheries on a regional scale. The authors of Cabral et al. 2020 had a path to follow from Costello et al. 2016, but changed assumptions.

Data errors
Since the authors of the Ovando et al. critique had been intimately involved in the Costello et al. 2016 paper, they were uniquely capable of looking at and interpreting the code for Cabral et al. They found two major errors:

1. Cabral et al. inadvertently created and used incorrect estimates of fishing mortality for the world’s assessed fisheries. This resulted in an overestimation of the amount of food benefits that MPAs could produce, and the size of MPAs that would produce those benefits. This error also contributed to the map that incorrectly prioritized areas with good fisheries management for MPA implementation; and

2. They mistakenly included a large (~3 million metric tons) and nonexistent stock from an outdated version of the RAM legacy database. They also placed this stock in the wrong ocean for their analysis.
Ovando et al. corrected the coding errors and reran the analysis. They found that the proposed benefits of MPAs for food decreased by 50% but still produced strange results.

Ovando et al. note (emphasis added):

“Using the corrected [model], Cabral et al.’s food-maximizing MPA network would close 22% of the United States’ exclusive economic zone (EEZ) to fishing, yet places only 2.5% of India’s, 10% of Indonesia’s, and 12% of China’s EEZs in MPAs… the median F/FMSY (fishing mortality rate F relative to the fishing mortality rate producing maximum sustainable yield FMSY) of fisheries in India, Indonesia, and China is nearly twice that of the United States, creating almost 5 times as much potential food upside from fishery reforms in those regions relative to the United States.”

In their response to Ovando et al., the authors of Cabral et al. acknowledge the model is not particularly realistic:

“The key assumption we made—that populations are well mixed throughout their geographic range—is indeed a heroic one.”

However, in their retraction note, the authors maintain that their conclusions are valid and intend to resubmit the paper.

Connection to Sala et al. 2021
Their persistence may be tied to Sala et al. 2021, Protecting the global ocean for biodiversity, food, and climate, the prominent follow-up paper published this past March in Nature. It presents several computer models that predict that an increase in MPAs to reduce fishing has benefits for biodiversity, food production, and carbon emissions. The food provisioning MPA model used by Sala et al. 2021 is the same one as Cabral et al. 2020 and was justified based on the results of the now-retracted paper.

Indeed, all the Cabral et al. 2020 authors were authors on the Sala et al. paper, including the first four authors of the Sala paper (authors are generally ordered in order of contribution, except for the “senior author,” who is the last listed). The Sala et al. paper was the most prominent ocean science paper of the year with an Altmetric score 4x higher than Cabral et al. 2020—it was covered in nearly every major newspaper in North America and Europe.

The acknowledged outright errors from Cabral et al. 2020 were corrected in the Sala et al. paper, but the biologically impossible assumptions that unassessed fish can travel across oceans, and that density dependence is global rather than local, remain.

The same authors from the Ovando et al. critique of the Cabral paper have responded to the Sala et al. paper, demonstrating that Sala et al.’s estimates of the effects of a global MPA network on food production were unreliable.

In the original Cabral et al. critique, the Ovando et al. authors argue that “omitting distance from MPA models produces results that are not credible.” Before it was retracted, the Cabral et al. authors responded saying their results were “a useful starting point.”

However the Ovando et al. critique of Sala et al. shows why that isn’t true:

Instead of just arguing the assumptions were poorly chosen, the recent Ovando et al. re-ran Sala et al.’s analysis with the assumption that fish stay in their region (defined by the U.N. FAO) and are dependent on local factors (the same, more realistic assumptions from Costello et al. 2016 that they all worked on together and that both Cabral et al. 2020 and Sala et al. 2021 were based on).

“By changing only two assumptions made by Sala et al. 2021 to different and equally if not more plausible assumptions, we produced a starkly different picture of the magnitude of potential food benefits from MPAs, and the location of priority areas for MPAs designed around food security.”

Costello et al. 2016 set a reasonable standard for evaluating unassessed fish stocks. That paper assumed fish live in their FAO region and are dependent on local abundance for population growth rates—about the best assumptions you can make about unmonitored fish populations given available data.

Sala et al. and Cabral et al. modified those assumptions to say that unassessed fish stocks are interconnected around the world and depend on global ecology for population growth rates. Why do this when more realistic assumptions are available and had been previously used by the authors? Both the Cabral and Sala papers used values from the Costello et al. paper as the basis for the model then changed the assumptions to less plausible ones.

Peer review was flawed – how much was due to the conflict of interest?
Cabral et al. clearly suffered from an inadequate peer review. An appropriately thorough reviewer would have seen the map of proposed MPAs, wondered why MPAs were prioritized in the U.S. but not overfished regions in Asia, and pushed the authors to explain why the map seemed “off.” Catching the coding errors would be a difficult task; perhaps only those who contributed to the original code on the earlier Costello et al. paper could have found them, but scrutinizing the map and clarifying the assumptions should have been primary, first principle peer-reviewing steps that should have led to the discovery of errors.

So how did Cabral et al. end up in PNAS, one of the most prestigious journals in the field, then get reproduced in Nature in the most covered paper of the year? The first decision was made by the editors at PNAS who read the paper, thought it was worthy of consideration, then assigned an individual PNAS editor to dive deeper and find peer-reviewers for it. In this case, the editor assigned to Cabral et al. was Dr. Jane Lubchenco, the former NOAA administrator and notable MPA scientist and advocate. She would make perfect sense as a choice to edit and find reviewers for MPA models, but she had a conflict of interest:

Cabral et al. was submitted to PNAS on January 6th, 2020. Notably, the Sala et al. paper was submitted to Nature two weeks prior, on December 19th, 2019. The senior author on the Sala et al. paper was Jane Lubchenco. She should not have been allowed to submit the Sala paper alongside other authors and then assign reviewers for a fundamental part of the paper two weeks later. Her brother-in-law, Dr. Steve Gaines, was also an author on both papers—familial relationships are another conflict of interest.

The editor in chief of PNAS told Retraction Watch both conflicts of interest would have been enough for retraction, even “absent the data errors.”

It will be interesting to see where the Cabral paper is resubmitted and how it is reviewed.

More scrutiny of the other models presented in Sala et al. 2021
You probably saw a headline covering Sala et al. 2021. Most of the press focused on its carbon model that concluded, Bottom Trawling Releases As Much Carbon as Air Travel. Most of the headlines were almost certainly not true.

The carbon model was the first attempt to quantify the global climate change impact of bottom trawling, a type of fishing in which nets are dragged along the seafloor. Bottom trawling kicks up sediment; the researchers tried to figure out how much carbon stored in sediment is redissolved into seawater due to trawling disturbances. More carbon dissolved in seawater means less atmospheric carbon can be absorbed by the ocean, contributing to climate change. Carbon dissolved in seawater also causes ocean acidification.

Sala et al. claimed their carbon model is a “best estimate,” but other scientists disagree and are have pointed out issues in the model that echo the same problems with the Cabral et al. model: impossible assumptions.

A response from Hiddink et al. noted one of the carbon model’s untrue assumptions: that sediment is inert until disturbed by trawling. According to Hiddink et al., this ignores “decades of geochemical research on natural processing of [carbon] in marine sediments.” There are many sea creatures that burrow in the seafloor—nearly all of them cycle carbon back into seawater (most organisms, like humans, respirate carbon).

Hiddink et al. also claim that the Sala et al. model greatly overestimated the amount of sediment that is disturbed: The model assumed all the sediment in the penetration depth is resuspended in the water column, whereas “field observations show that trawling resuspends only [~10%].”

Hiddink et al. say the Sala et al. model overestimates carbon impacts by an order of magnitude or more.

Was this another case of inadequate peer-review? An order of magnitude or more is a substantial error.

The carbon and food models weren’t the only ones with questionable assumptions. The biodiversity model in Sala et al. claimed that with increased MPAs, ocean biodiversity would increase. This is undoubtedly true inside an MPA, but the model assumed fishing rates remain constant outside the proposed MPAs, meaning effort that was inside the MPA disappears, rather than moving elsewhere. This is in direct conflict with the assumptions of the food provision model presented in their primary results which assumed the effort from inside the MPA moved elsewhere.

Not only is this picking and choosing MPA assumptions to present; in real life, this is rarely what happens. When fishermen are told they can’t fish in a particular area, they generally fish harder in other areas. Assuming fishing rates remain the same outside of MPAs probably exaggerates the practical benefits of MPAs for biodiversity.

The picking and choosing of model assumptions in Sala et al. has drawn yet another critique by Hilborn and Kaiser (not yet published on a preprint server). Sala et al. 2021 did report consistent fishing pressure assumptions in secondary results and supplementary materials, however those were not part of the main paper.

When asked about the status of the three known responses to Sala et al. (Ovando et al., Hiddink et al., and Hilborn & Kaiser), Nature had no comment as the review process is confidential.

Predictions need more scrutiny and less press
Regardless of any conflict of interest, the science in both Cabral et al. and Sala et al. is critically flawed, but being used to advocate for public policy. Both follow a recent trend of publishing predictions that use a limited set of assumptions (in a very uncertain world) to produce global maps that get published in high-profile journals and garner considerable media and political attention.

Computer models are essential tools for science and management, but the accuracy of their predictions depends on both the quality of the data and the assumptions they are based on. Often, a problem is so complex that several assumptions may be equally plausible; readers need to be made aware when different assumptions lead to vastly different outcomes.

The Cabral et al. and Sala et al. papers disregard uncertainty in favor of set values for their model parameters. They don’t account for the enormous uncertainty in these parameters and don’t provide strong evidence that their choice of values was correct. The assumptions and parameters produce big headlines, but are fundamentally unhelpful for the future of ocean governance and sustainability. We expect policy-makers and resource managers to make decisions based on the best available science. Inconsistent and unrealistic assumptions are not that.

Original post:

Posted with permission.

Jul 22 2021

California Current Fish Surveys Resume with 3-Month Assessment of Sardine, Anchovy, and Mackerel

NOAA Ship Reuben Lasker, a fisheries survey vessel, departed San DIego in early July to assess coastal pelagic species such as sardine and anchovy. Credit: Paul Hillman/NOAA Fisheries


NOAA Fisheries has begun an ambitious assessment of small pelagic fish reaching from the Canadian border to the southern tip of the Baja Peninsula, in cooperation with Mexico, which will help determine how many fish can be caught off the West Coast.

The COVID-19 pandemic had idled surveys for sardine, anchovy, and other species of small coastal pelagic species (CPS) off the West Coast since 2019. Small pelagic species are important ecologically and provide food for larger fish, such as tunas. The new assessment resumes regular CPS  surveys by collecting data from NOAA Ship Reuben Lasker, commercial fishing vessels equipped with acoustic technology, and autonomous Saildrones.

The Lasker left San Diego on July 6, becoming the centerpiece of the 3-month survey. It will cover thousands of miles in U.S., and Mexican waters. NOAA Fisheries scientists are coordinating efforts with federal fisheries agencies in Mexico and Canada, providing a science foundation for future decisions on fishing levels and seasons.

“Organizing and coordinating this survey was a tremendous feat of collaboration,” said Kristen Koch, Director of the Southwest Fisheries Science Center in La Jolla, which is leading the survey. “Collecting data across all three countries will provide a valuable foundation for management of these important transboundary species.”

The Lasker will survey coastal pelagic fish along transects in the California Current, quantifying the fish with echosounders. These instruments include an advanced new model that can for the first time also measure the velocities of fish as they swim relative to the ship. The measurements will help to understand whether and how fish respond to survey vessels and if those reactions affect the quality of data on the numbers and distributions of fish.

Combined Vessels Extend Reach

The fishing industry vessels Lisa Marie and Long Beach Carnage will join the survey effort in waters closer to shore and shallower than Lasker can sample. This collaboration with the fishing industry expands sampling nearer the shore, more fully capturing the fish present in shallower waters. Meanwhile, autonomous Saildrones will improve the survey precision and accuracy by increasing sampling in areas with higher fish abundance and allow Lasker to cover a larger area.

“We’re making use of a combination of resources in ways that should yield complementary data and increase the information about seven populations of five fish species,” said David Demer, Advanced Survey Technology Program Lead at the Southwest Fisheries Science Center and Chief Scientist of the survey.

Anchovy are among the pelagic fish species the survey is assessing off the West Coast. Credit: Shutterstock

After surveying U.S. waters, Lasker for the first time will continue south to cover waters around the Baja California Peninsula in Mexico. Where Lasker concludes sampling, the Mexican research vessel Dr. Jorge Carranza Fraser will sample the Pacific and Gulf of California coasts of the Baja Peninsula. The two ships will use the same protocols so their data can be combined into more comprehensive analyses. Scientists from Mexico’s national fishery agency, the National Institute of Fisheries and Aquaculture, or INAPESCA, will join Lasker to foster cross-training and collaborations.

Dr. Pablo Roberto Arenas Fuentes, General Director of INAPESCA, highlighted that not since the late 1980s has such a combined international effort been assembled. He said this joint survey, using the same methodologies and data analysis between nations, truly represents something never done before on the scale of the California Current.

“The historic collaboration between INAPESCA and NOAA Fisheries represents the first time we will combine research methods to focus acoustic evaluation on the biomass of small pelagic fish,” he said. “This will generate continuous biological and environmental data along one of the most important coastal ecosystems of the North American continent.”

The survey will examine the abundance and distribution of the three subpopulations of Pacific sardine in the California Current, two of which are potentially fished by the United States and Mexico. The northern subpopulation historically occurred largely in Canadian and U.S. waters but declined to such low levels in recent years that the fisheries have been closed since 2015.

Less is known about another subpopulation that principally occupies waters off Mexico and Southern California. U.S. fishermen have shown interest in recent reports of increases in the proportion of the subpopulation in U.S. waters. The survey’s new reach into Mexico and the advanced acoustic technology aboard the vessels should provide more complete information on the distribution of the subpopulation, Koch said.

“The joint analysis will improve our knowledge of the distribution and abundance of these species at the regional level, which will support important fisheries,” said Dr. Pablo Arenas.

Survey Also Includes Anchovy and Mackerel

Additional information will also serve to assess the total abundance and extent of northern anchovy, and the jack and Pacific mackerel populations in the survey area. Anchovy have been extremely abundant in the California Current in recent years. Pelagic fish are known for boom-bust fluctuations in their populations.

A map outlines the survey transects for the vessels surveying small coastal pelagic species. Some of the northernmost transects were canceled but otherwise the solid lines show the course of the survey, with the magenta lines showing nearshore transects and blue lines showing the course of Saildrones. Credit: NOAA Fisheries

“Integrated surveys, such as this one, are essential in helping us understand how these populations change and shift over time so we can ensure that fisheries are sustainable,” said Josh Lindsay, fisheries biologist with NOAA Fisheries West Coast Region.

The Lasker, the Fraser, Saildrones, and the industry vessels all use advanced echosounders emitting sound waves to detect and map fish schools. Each of the crewed vessels then deploy either trawl or purse-seine nets to catch samples of the fish. The net catches identify the species of fish that reflect sound in each area, and their lengths, ages, and reproductive status.

In 2020, NOAA Fisheries’ Saltonstall-Kennedy Competitive Grants Program awarded funding to Ocean Gold Seafoods to help pay for the Lisa Marie to participate in the survey and provide more complete data. “The Coastal Pelagic Species industry feels strongly that it has a stake in robust fisheries management of this complex and dynamic assemblage, which can only be achieved with extensive data collection efforts,” industry supporters wrote in their application for the funding.

The cooperative research that combines NOAA Fisheries science and insight from fishermen provides long-term benefits for both. It is an area of increasing focus for NOAA Fisheries.

“The immense scale and scope of the survey is really significant,” said Joel Van Noord, a biologist with the California Wetfish Producers Association who will join the survey aboard Long Beach Carnage. He said the fishing fleet benefits from high-quality data on fish populations that help ensure they are managed sustainably, providing continuing benefits to fishing communities and the marine ecosystem.

Original post:

Jul 7 2021

New Study: Precautionary Catch Limits on Forage Fish Unlikely to Benefit Predators


July 6, 2021 — The following was released by the Science Center for Marine Fisheries:

A newly released study finds that, for many predator species, extra-precautionary management of forage fish is unlikely to bring additional benefits. How to manage forage fish sustainably, both by themselves and for the rest of the ecosystem, has become a much-discussed topic in fisheries management, with regulators of several forage fisheries beginning to adopt precautionary strategies on the premise that they will better provide for the needs of predator species including seabirds, marine mammals, and fish.

The study, from Drs. Chris Free of the University of California-Santa Barbara, Olaf Jensen of the University of Wisconsin-Madison, and Ray Hilborn of the University of Washington, examines decades of historical abundance data of both forage species and their predators, and uses mathematical models to determine to what extent predator populations benefited from increasing abundance of their forage fish prey. Of the 45 predator populations examined, only 6, or 13 percent, were positively influenced by extra forage.

“Our work suggests that the sustainable limits that we already employ are sufficient for maintaining forage fish abundance above the thresholds that are necessary for their predators,” said Dr. Free. “Predators are highly mobile, they have high diet flexibility, and they can go and look for forage fish in places where they’re doing well, switch species for species that are doing well, and have often evolved to breed in places where there’s high and stable forage fish abundance.”

The results have important implications for how strictly to manage forage fisheries. The study finds that, at least in forage fisheries that are already being well managed and are closely monitored, adopting additional precautionary measures will “rarely” provide any additional benefits to predator population growth. However, fishery managers who deal with less well-monitored fisheries may consider more precautionary strategies.

“In places of the world where we already have really strong, very effective fisheries management, additional limitations on forage fish catch are not likely to benefit their predators,” said Dr. Free.

“Management of forage fish populations should be based on data that are specific to that forage fish, and to their predators,” said Dr. Jensen. “When there aren’t sufficient data to conduct a population-specific analysis, it’s reasonable to manage forage fish populations for maximum sustainable yield, as we would other fish populations under the Magnuson-Stevens Act.”

According to the models used in the study, other environmental factors, such as water temperature, are more likely to influence predator populations. These results are consistent with previous efforts to examine the relationship between predator and prey populations.

“What we’ve done here that’s different from previous analyses is try to control for some of the other factors that influence predator population dynamics,” said Dr. Jensen. “In this case, we included in the models a covariate representing ocean temperature.”

SCEMFIS produced a video of the authors and independent experts discussing the results of the paper. Watch it here.

SCEMFIS utilizes academic and fisheries resources to address urgent scientific problems limiting sustainable fisheries. SCEMFIS develops methods, analytical and survey tools, datasets, and analytical approaches to improve sustainability of fisheries and reduce uncertainty in biomass estimates. SCEMFIS university partners, University of Southern Mississippi (lead institution), and Virginia Institute of Marine Science, College of William and Mary, are the academic sites. Collaborating scientists who provide specific expertise in finfish, shellfish, and marine mammal research, come from a wide range of academic institutions including Old Dominion University, Rutgers University, University of Massachusetts-Dartmouth, University of Maryland, and University of Rhode Island.

The need for the diverse services that SCEMFIS can provide to industry continues to grow, which has prompted a steady increase in the number of fishing industry partners. These services include immediate access to science expertise for stock assessment issues, rapid response to research priorities, and representation on stock assessment working groups. Targeted research leads to improvements in data collection, survey design, analytical tools, assessment models, and other needs to reduce uncertainty in stock status and improve reference point goals.

Original post: Saving Seafood | Sign up for our Daily News Updates from Saving Seafood.

Jun 1 2021

Ray Hilborn: MPAs aren’t the answer to ocean biodiversity, sustainability efforts

A global movement to create additional marine protected areas (MPAs) has been steadily gaining traction in recent years, with the initiative picking up milestone victories in the past few months.

In January, newly inaugurated U.S. President Joe Biden signed an executive order committing to a “30 by 30” goal, whereby the United States would designated 30 percent of its land and territorial waters to conservation by the year 2030. The move heightened the potential that MPAs will be used as a tool to tackle climate change.

A recent study supports the hypothesis that MPAs could be beneficial for climate change, maintaining biodiversity, and boosting the yield of fisheries. According to the study, strongly protecting at least 30 percent of the ocean – primarily in the 200-mile exclusive economic zones of coastal nations – would result in substantial environmental and commercial benefits.

But University of Washington Professor of Aquatic and Fishery Sciences Ray Hilborn told SeafoodSource that the study – and the concept of MPAs – are both flawed. The study, he said, made some assumptions and contains inconsistencies that effectively invalidate the conclusions it reached.

“It’s a classic example of where the peer-review process totally failed to identify inconsistencies, bizarre assumptions, and improper conclusions,” Hilborn said.

The study, he said, made different assumptions on different types of fishing effort.

“It happens that each of the assumptions they made about fishing effort is the one that makes MPAs look better,” he said.

A key example, Hilborn said, is how the study approaches trawling. The study made biodiversity calculations based on fishing effort shifting in geography as MPAs are put in place – which itself poses problems, he said. However, the study assumed that an MPA ban on trawling wouldn’t result in increased fishing effort in other areas.

“When it comes to the impact of trawling and the impacts on biodiversity, they assume when you close an area, the effort disappears,” Hilborn said.

The study found a ban on trawling in designated MPAs would have a carbon benefit – but that is true only if that trawling effort doesn’t move holds, Hilborn said.

“If you move the effort, the carbon benefit disappears,” Hilborn said.

Hilborn said the study also assumes an “instantaneous connection” between different species around the world – when in reality, species in separate oceans aren’t going to interact. And the analysis wasn’t actually global, as South Asia and Southeast Asia were not accounted for in the study.

“This isn’t a global analysis, because they don’t have trawl effort in Southeast Asia,” Hilborn said.

Protecting biodiversity is a key issue that needs to be tackled, and the core motivation behind MPAs and Biden’s 30 by 30 plan are sound, Hilborn said.

“[The] 30 by 30 [movement] is not ambitious enough,” Hilborn said. “We need to protect the biodiversity of 100 percent of our [exclusive economic zone].”

Protecting biodiversity in the oceans is not best accomplished via MPAs, especially in light of climate change, Hilborn said. In fact, while advocates have touted MPAs as a means to fight climate change, in reality, they do little to help, he said.

“They want to see 30 percent of the oceans permanently closed,” Hilborn said. “That’s absolutely the wrong thing to do. With climate change, things are shifting.”

Hilborn used the interactions between fisheries and the critically endangered North Atlantic right whale as an example of how a proposed MPA might not work as intended. In recent years, the species has been the center of an ongoing push for increased protections, and recently NOAA outlined new regulations to protect the species.

Climate change has forced the 400 or so remaining North Atlantic right whales to chase food sources that are now located in parts of the ocean with more fishing effort, primarily in the Gulf of Saint Lawrence. That movement highlights how MPAs would struggle to protect species in the ocean, Hilborn said.

“If you had closed areas to protect northern right whales 20 years ago, they’d be in all the wrong areas,” he said.

Protected areas on land, he added, make sense because of the nature of human interaction with the land.

“The reason you want parks on land is that human use is transformative. If you put a city on it, or you farm it, it’s gone,” Hilborn said. “In the ocean, fishing doesn’t really change the structure of the ecosystem. We don’t kill the plants which is what farming does, we don’t harvest the second trophic level, we just harvest the top of the food chain.”

Plus, many of the actual threats to the ocean aren’t coming from the ocean itself, or from fishing.

“If you look at what the threats to the oceans are, they’re ocean acidification, climate change, invasive species, various kinds of pollution, land runoff, and none of those are impacted by MPAs,” Hilborn said.

A great example is the large dead zone that forms in the Gulf of Mexico every year.  The dead zone is created by excess nutrient pollution from agricultural areas – mainly related to fertilizers washed into the gulf through the Mississippi River and other inland waterways. NOAA makes annual predictions for how large the dead zone will be, based on things like rainfall. An MPA in the area to protect that environment, Hilborn pointed out, would have no effect on the biodiversity of the ocean in the region.

“You could make it an MPA and ban everything, you could ban shipping, you could ban mining, you could ban fishing, and you’d have no effect on the dead zone,” he said.

Protecting biodiversity is possible, but MPAs are the wrong tool for the job, Hilborn said.

“You don’t need no-take in order to protect the biodiversity. Again, high profile things, marine birds, marine mammals, turtles, sharks, those are things where there’s very specific – gear specific – things that impact them,” he said. “Closed areas aren’t going to help, because they’re all so mobile.”

The solution for those species, he said, is simple.

“Take sharks or turtles – all you have to do is stop killing them,” he said.

Current fisheries management agencies already serve as a tool for protecting biodiversity, and Hilborn said additional effort can be made using those existing agencies.

“What I would like to see is very explicit targets in what are we trying to achieve in biodiversity, and for each one of those targets, what’s the best tool to achieve it,” Hilborn said. “In almost every case, you’re going to be modifying fishing gear, and how fishing takes place, rather than closing areas to all fishing gears.”

MPAs, he said, are essentially just regulating a few activities in an area, without addressing wider issues.

“Fundamentally, all MPAs are doing is regulating fishing, and maybe oil exploration and mining,” he said. “It’s just the wrong tool. The illusion that you’re protecting the ocean by putting in MPAs, it’s a big lie.”

Original post:

Jan 18 2021

West Coast Fisheries Impacts from COVID-19

In April 2020, NOAA Fisheries prepared its first national report on the regional impacts of COVID-19 on the commercial, recreational and aquaculture sectors.

This report updates that initial assessment, capturing economic changes experienced by the fishing industry as the country began its phased reopening along with infusion of Federal funding through the CARES Act. NOAA
Fisheries will continue to use this information to identify economic hardship where it exists and identify pathways for enhancing the resilience of the U.S. seafood and fisheries industries.



Dec 22 2020

An Open Letter to the 116th Congress from U.S. Marine Fishery Scientists


Marine Protected Areas – Title II of the Ocean-Based Climate Solutions Act (H.R.8632)


December 10, 2020

Dear Senators and Representatives:


As scientists engaged in the provision of information to support federally managed fisheries, we are concerned that Title II of the proposed Ocean-Based Climate Solutions Act (H.R.8632), which would require the establishment of marine protected areas that ban all commercial fishing activity in 30% of U.S. ocean waters by 2030, is not based on the best scientific information available and would not be the most effective way to protect marine biodiversity. Conservation of marine ecosystems in the U.S. waters is challenged by a rapidly changing climate, but the proposed marine protected areas will not solve climate-related impacts on biodiversity, instead they will decrease flexibility of the fishery management system to adapt to climate change. The most significant impact of marine protected areas is a spatial shift in fishing, which is effectively a fisheries management action. Marine biodiversity is protected by the mandates of the Magnuson-Stevens Fishery Conservation and Management Act, the Endangered Species Act, the Marine Mammal Protection Act, and other legislation. The implementation of those requirements with respect to fisheries impacts is through the regional Fisheries Management Council system to protect target species, bycatch species, protected species, ecosystem components, essential fish habitat and other sensitive habitats.

Although several U.S. fish stocks have been overfished, the fisheries are highly regulated to avoid overfishing and rebuild stocks with a precautionary approach. A large portion of U.S. waters are currently closed to fishing, either seasonally or year-round. A prevalent impact of climate change in the U.S. has been shifting spatial distributions, generally northerly and to deeper habitats. Many fisheries are flexible enough to adapt to such shifts, but the proposed extension of permanent marine protected areas would prohibit many adaptive responses to climate change. Based on our experiences and case studies, marine protected areas that are not based on the best scientific information available, such as the uninformed target of restricting commercial fishing in 30% of U.S. waters, will have unanticipated consequences such as increased bycatch and habitat destruction by shifting the location of fishing effort.

As an example, after over a decade of scientific analysis, the New England Fishery Management Council recently re-designated essential fish habitat for all 28 Council managed species, designated new habitat areas of particular concern, revised habitat and groundfish management areas, and designated deep-sea coral management zones and fishing gear restrictions. We affirm that these management areas are based on the best scientific information available, as required in the Magnuson-Stevens Fishery Conservation and Management Act. By contrast, we are concerned that establishing new marine protected areas to meet the arbitrary 30% objective stated in Title II of the Ocean-Based Climate Solutions Act will not be based on the best scientific information available, will have negative unanticipated consequences, and will decrease the ability of U.S. fisheries to adapt to a changing climate.

Title II of the Ocean-Based Climate Solutions Act is predicated on a view that marine biodiversity in the U.S. EEZ is decreasing but provides no evidence that this is true. It is well established that targeted U.S. fish stocks are rebuilding and on average above target levels. A high proportion of benthic habitat and benthic ecosystems are already protected throughout the U.S. EEZ, and the non-target species of conservation concern are governed by other legislation, including the Endangered Species Act. Title II provides no evidence that biodiversity will be increased by more MPAs and provides no metrics for how the impact of additional MPAs would be evaluated.

Yours sincerely,

The undersigned are all marine scientists who have been involved in providing advice to the Federal or State governments on management of marine biodiversity. These scientists include former NOAA employees, former members of Science and Statistics Committees of Fisheries Management Councils including two chairs of those committees, a director of a NMFS regional center, the Editor in Chief of a major marine science journal and members of government advisory panels including the Ocean Studies Board of the National Research Council.


Judith R. Amesbury Micronesian Archaeological Research Services, Guam

David Bethoney, Commercial Fisheries Research Foundation

Debra T. Cabrera, University of Guam

Steven X. Cadrin, University of Massachusetts

Paul Callaghan, University of Guam

Yong Chen, University of Maine

Charles Daxboeck, Biodax Consulting

David Fluharty, University of Washington

Daniel Georgianna, University of Massachusetts Dartmouth

David Itano, Opah Consulting

Brad Harris, Alaska Pacific University

Ray Hilborn, University of Washington

Pierre Kleiber, NOAA retired

Olaf Jensen, University of Wisconsin

Bill Karp, NOAA retired

Kai Lorenzen, University of Florida

Franz Mueter, University of Alaska

Robert D. Murphy, Alaska Pacific University

Catherine E. O’Keefe, Fishery Applications Consulting Team

Richard Parrish, NOAA retired

Eric N. Powell, University of Southern Mississippi

Craig Severance, University of Hawaii Hilo

John Sibert, University of Hawaii (retired)

Robert Skillman, NOAA retired

Kevin Stokesbury, University of Massachusetts Dartmouth

 Robert Trumble, MRAG America (retired)

Vidar G. Wespestad, NOAA retired

Michael Wilberg, University of Maryland Center for Environmental Science

Affiliations are listed for identification purposes only and do not imply institutional support for the views expressed.

Original post:

Mar 12 2020

West Coast Waters Shift Toward Productive Conditions, But Lingering Heat May “Tilt” Marine Ecosystem

Burgeoning populations of anchovy and a healthy crop of California sea lion pups reflected improved productivity off parts of the West Coast in 2019. However, lingering offshore heat worked against recovery of salmon stocks and reduced fishing success, a new analysis reports.

The California Current Ecosystem Status Report explains that ocean conditions off the West Coast remain unusually variable. This has been the case since the arrival of a major marine heatwave in 2014 known as “The Blob.” NOAA Fisheries’ two West Coast laboratories, the Northwest Fisheries Science Center and Southwest Fisheries Science Center, issue the report each year to the Pacific Fishery Management Council.

“There is not a real clear picture here,” said Chris Harvey, co-editor of the report developed by the two laboratories’ Integrated Ecosystem Assessment approach. The approach integrates physical, biological, economic, and importantly social conditions of the California Current marine ecosystem into the decision-making process. “On the one hand, we have a lot of anchovy out there. On the other hand, we also have a lot of warm water. That is not usually a sign of improved productivity.”

Lingering Warm Waters

A marine heatwave rivaling “The Blob” emerged in the Pacific in the second half of 2019 but waned by the beginning of 2020. The repeated warm events have left a remnant reservoir of heat deep in offshore waters. That could help “tilt” the system in a way that favors future heatwaves.

“Since a similar buildup and then recession occurred during 2013-2014, and we continue to observe anomalously warm water far offshore and retention of heat by deeper waters, it is unclear if we may see a resurgence of another heatwave in the summer of 2020,” the report says.

Warm conditions off the West Coast are generally associated with less productive conditions. Colder water from the north injects more energy-rich plankton into the marine ecosystem. Young salmon entering the ocean in cooler conditions, for example, grow bigger faster and support stronger adult salmon returns to the rivers where they spawn.

Ecological and Economic Indicators

The annual analysis hinges on a series of ecological and economic indicators. They range from the size of krill—small crustaceans that form the base of the food chain—to trends in fishery landings in port communities. Krill density was very low off much of the West Coast in 2019, and commercial fishery landings dropped 8 percent in 2018 compared to the year before.

Highlights of trends for several economic and ecological indicators outlined in the California Current Ecosystem Status Report.

The 2020 State of the California Current report introduces a new ecological indicator known as the “habitat compression index.” It reflects how warm offshore waters run up against cold, deeper waters that well up near the coast. The result is a narrow, “compressed” band of coastal ocean with cool, productive waters that draw fish and their predators together.

Other recent research found that during the Blob years, the compressed habitat brought humpback whales closer to shore to feed on booming numbers of anchovy. That put many whales in the same waters where Dungeness crab fishermen set their traps, and record numbers of whales became entangled in the fishing lines.

The habitat compression index will provide a running barometer of how offshore heat is affecting nearshore waters and the species that depend on them. “We will continue to study this metric in relation to other indicators in hopes of understanding why coastal impacts in recent years have been so severe,” the report says.

Fisheries landings on the West Coast have seen big ups and downs in recent years. There have been large catches of hake but fewer landings of salmon and coastal pelagic species such as sardines. Commercial landings in 2018, the last year with data available, fell 8 percent, with declines in shrimp, market squid, and many groundfish species. Dungeness crab, however, is a bright spot, with increased landings in recent years.

“Through presenting ecosystem trends, our goal is to provide the Council and the public with a snapshot of the health of the California Current ecosystem,” said Toby Garfield, the co-editor of the report. “Understanding these changes is critical to preserving the productivity and sustainability of West Coast fisheries.”

Original post:

Feb 4 2020

Fisheries Management Is Actually Working, Global Analysis Shows

Increasing fish stocks around the world give credibility to strong management and the importance of fisheries data

Story modified from the original press release issued by the University of Washington 

Nearly half of the fish caught worldwide are from stocks that are scientifically monitored and, on average, these stocks are increasing in abundance. According to a new global analysis, effective management appears to be the main reason these stocks are at sustainable levels or rebuilding successfully.

The analysis, which incorporated fisheries data from around the world, was conducted by an international research team supported by the Science for Nature and People Partnership. Their results were published January 13th in the Proceedings of the National Academy of Sciences.

The results show that fisheries management works when applied, and the solution for sustaining fisheries around the world is implementing effective fisheries management, the authors explained.

“There is a narrative that fish stocks are declining around the world, that fisheries management is failing and we need new solutions — and it’s totally wrong,” said lead author Ray Hilborn, a professor in the University of Washington School of Aquatic and Fishery Sciences. “Fish stocks are increasing in many places, and we already know how to solve problems through effective fisheries management.”

The project builds on a decade-long international collaboration to assemble estimates of the status of fish stocks — or distinct populations of fish — around the world, from Peru to the Mediterranean, and to Japan. This information helps scientists and managers know where overfishing is occurring or where some areas could support even more fishing.

The team’s database includes information on nearly half of the world’s fish catch, or about 880 fish stocks, providing perhaps the most comprehensive picture worldwide of the health and status of fish populations.

“The key is we want to know how well we are doing, where we need to improve, and what the problems are,” Hilborn said.

By pairing information about fish stocks with recently published data on fisheries management activities in about 30 countries, the researchers found that more intense management led to healthy or improving fish stocks, while little to no management led to overfishing and poor stock status.

“With these data, we could test whether fisheries management allows stocks to recover. We found that, emphatically, the answer is yes,” said co-author Christopher Costello, a professor of environmental and resource economics at University of California, Santa Barbara, and a board member with Environmental Defense Fund. “This gives credibility to the fishery managers and governments around the world that are willing to take strong actions.”

To be successful, management should be tailored to fit the characteristics of the different fisheries and the needs of specific countries and regions. The main goal should be to reduce the total fishing pressure when it is too high, and find ways to incentivize fishing fleets to value healthy fish stocks.

“There isn’t really a one-size-fits-all management approach,” Costello said. “We need to design the way we manage fisheries so that fishermen around the world have a long-term stake in the health of the ocean.”

Still, there are data-deficient areas of the world. Scientific estimates of the status of most fish stocks in South Asia and Southeast Asia are not available, and fisheries in India, Indonesia and China alone represent 30% to 40% of the world’s fish catch that is essentially unassessed.

“There are still big gaps in the data and these gaps are more difficult to fill,” said co-author Ana Parma, a principal scientist at Argentina’s National Scientific and Technical Research Council and a member of The Nature Conservancy global board. “This is because the available information on smaller fisheries is more scattered, has not been standardized and is harder to collate, or because fisheries in many regions are not regularly monitored.”

Hilborn and collaborators recently presented this work at the Food and Agriculture Organization of the United Nations’ International Symposium on Fisheries Sustainability in Rome.

Other co-authors are from University of Victoria, University of Cape Town, National Institute of Fisheries Research (Morocco), Rutgers University, Seikai National Fisheries Research Institute Japan, CSIRO Oceans and Atmosphere, Fisheries New Zealand, Wildlife Conservation Society, Marine and Freshwater Research Center (Argentina), European Commission, Galway-Mayo Institute of Technology, Center for the Study of Marine Systems, Sustainable Fisheries Partnership, The Nature Conservancy, and the Food and Agriculture Organization of the United Nations.

The research was funded by the Science for Nature and People Partnership (SNAPP), a collaboration between the National Center for Ecological Analysis and Synthesis at UC Santa Barbara, The Nature Conservancy, and Wildlife Conservation Society. Individual authors received funding from The Nature Conservancy, The Wildlife Conservation Society, the Walton Family Foundation, Environmental Defense Fund, the Richard C. and Lois M. Worthington Endowed Professorship in Fisheries Management and donations from 12 fishing companies.

Original post:

Jan 29 2020

‘Blob’ research shows ecological effects that halted fishing and hiked whale entanglements

Unprecedented environmental changes inspire new online tools to better spot them next time

NOAA Fisheries West Coast Region

An ecological pileup of unprecedented changes in the ocean off the West Coast beginning about 2014 led to record entanglements of humpback and other whales, putting the region’s most valuable commercial fishery at risk, new research shows.

The findings reflect a new management challenge brought about by a changing climate, recovering whale populations, and fishing pressure, according to the new research published in Nature Communications. The situation calls for new measures to alert fishermen to the risk of entanglements and help managers adjust to more rapid and frequent changes in the marine environment.

“We need to put information in the hands of those who can use it, at a time when it can make a difference,” said Jarrod Santora, a research scientist at NOAA Fisheries’ Southwest Fisheries Science Center (SWFSC) in Santa Cruz, California, and lead author of the research. “We are seeing changes coming at us in ways they never have before.”

Santora and his colleagues are developing a website that will use oceanographic data to forecast the areas where whales are most likely to be feeding off the West Coast. Crab fishermen could then use the information to help decide where–and where not–to set their traps. It may also help managers decide where and when to open–or close–fishing.

The new research teases out the ecological causes and effects that contributed to the spike in reported whale entanglements. Many involved traps set for Dungeness crab, said Nathan Mantua, a research scientist at the SWFSC and coauthor of the research. Reported entanglements have since dropped off but remain higher than before the increase.

“We had all these things that weren’t part of anyone’s experience come together in this remarkable three-year period,” he said.

Conflict Prompts Improved Communication

The entanglements have also prompted environmental lawsuits that threaten to restrict crab fishing. At the same time, though, the focus on entanglements has led to better communication and conversation between fishermen, environmental groups, and managers. Collaborative working groups have also developed tools to better anticipate and avoid entanglement risk.

“If the working group knew then what we know now, it wouldn’t have happened,” said John Mellor, a crab fisherman from San Francisco, referencing the increased entanglements. “The more we understand the whole picture, the better chance we have to mitigate the impacts.”

The driver behind many of the environmental changes was an unprecedented marine heatwave that took hold in 2014. It became known as “the warm Blob,” because of the large expanse of unusually high temperatures that dominated waters off the West Coast. The warm temperatures attracted subtropical species rarely seen in the region. The krill that humpback whales typically feed on grew scarce.

The whales switched to feed instead on high concentrations of anchovy that the warm, less productive waters had squeezed into a narrow band near the coast.

At the same time, the higher temperatures fueled a record bloom of toxic algae. It shut down crabbing on the West Coast from November 2015 through March 2016. When toxin levels eased and the Dungeness season finally opened, fishermen set multitudes of crab traps in that same narrow band where many whales were feeding.

NOAA Fisheries’ West Coast Region confirmed a then-record 53 whale entanglements in 2015 and 55 in 2016.

The scientists developed a new measure for ocean conditions called the Habitat Compression Index. It tracks the width of the productive band and how tightly species are coalescing there.

Whale Numbers Reflect Unprecedented Change

Research Biologist Karin Forney, also from the SWFSC and a coauthor of the research, lives in Moss Landing, California. She has a view of Monterey Bay and has long seen occasional humpback whales feeding just offshore. During the “the Blob” years, she would regularly see 30 to 40 whales from her front windows. Local whale watch boats made two to three trips a day to keep up with the demand.

Some 300 whales were counted at once in Monterey Bay.

“In our lifetimes living here, that was unprecedented,” she said. “We knew something dramatically different was pulling these whales closer to shore.”

She is also part of a NOAA team trained to free entangled whales.

“We were on call every day for weeks, with simultaneous reports of two or three entangled whales, so we could respond if they were sighted again,” she said. The team disentangled a few, while others were never seen again.

The lesson of the research, Forney said, is that scientists and fishermen must share information. They can help each other understand how complex environmental connections affect marine species and fisheries. Communication may be one of their most important tools as environmental changes come ever faster.

“Things are dynamic, and things are changing,” she said. “That is not going away.”

Humpback whales feed on anchovy off the Coast of California. New research shows that warm ocean temperatures pushed whales into the same water as crab fishermen, and whale entanglements increased. CREDIT: John Calambokidis/Cascadia Research Collective


Original post:

Jan 25 2020

Dungeness crab larvae already showing effects of coastal acidification

This infographic shows the location of larval Dungeness crab sampling in 2016, examples of impacts from ocean acidification, as well as photos of a larval (left) and adult (right) crab. Credit: Nina Bednarsek, SSCWRP.


A new NOAA-funded study has documented for the first time that ocean acidification along the US Pacific Northwest coast is impacting the shells and sensory organs of some young Dungeness crab, a prized crustacean that supports the most valuable fishery on the West Coast.

Analysis of samples collected during a 2016 NOAA research cruise identified examples of damage to the carapace, or upper shell, of numerous larval Dungeness crabs, as well as the loss of hair-like sensory structures crabs use to orient themselves to their surroundings.

The study was published in the journal Science of the Total Environment.

Impacts to wild crab mirror results of laboratory study

Prior to this study, scientists thought that Dungeness crab were not vulnerable to current levels of ocean acidification, although a laboratory study conducted on Dungeness crab larvae by NOAA’s Northwest Fisheries Science Center in 2016 found that their development and survival suffered under pH levels expected in the future.

“This is the first study that demonstrates that larval crabs are already affected by ocean acidification in the natural environment, and builds on previous understanding of ocean acidification impacts on pteropods,” said lead author Nina Bednarsek, senior scientist with the Southern California Coastal Water Research Project. “If the crabs are affected already, we really need to make sure we start to pay much more attention to various components of the food chain before it is too late.”

What is ocean acidification?
Ocean acidification refers to a reduction in the pH of ocean water, primarily caused by the uptake of carbon dioxide from the atmosphere over long time spans. When CO2 is absorbed by seawater, a series of chemical reactions occur resulting in the increased concentration of hydrogen ions. This increase causes the seawater to increase its acidity and causes carbonate ions to be less abundant.

Carbonate ions are an important building block of structures such as sea shells and coral skeletons that rely on using calcium carbonate for structural growth. Decreases in carbonate ions can make building and maintaining shells and other calcium carbonate structures difficult for calcifying organisms such as oysters, clams, sea urchins, crabs, corals, and some kinds of shelled plankton, such as pteropods.

Close examination reveals patterns of damage
In this study, examination under a high-magnification, scanning electron microscope revealed that the corrosive conditions of coastal waters had affected portions of the fragile, still-developing external shell and legs of the tiny, almost translucent post-larval Dungeness crabs, leaving tell-tale features, such as abnormal ridging structures and scarred surfaces. This could, in turn, impair larval survival by altering swimming behaviors and competence, including the ability to regulate buoyancy, maintain vertical position, and avoid predators.

One of the more important findings of this study was that crabs showing signs of carapace dissolution were smaller than other larvae. This was disconcerting, scientists said, because the damage during the crab’s larval stages could cause potential developmental delays that could increase energy demands and interfere with maturation.

Sensory organ damage seen for the first time
In a surprising discovery, the team found that the low pH water in some coastal areas damaged the canals where hair-like bristles called mechanoreceptors stick out from the shell. These receptors transmit important chemical and mechanical sensations to the crab, and may help crabs navigate their environment. Examination showed that carapace dissolution destabilizes the attachment of the mechanoreceptor anchor, resulting in them falling out in some individuals.

This is a new aspect of crustacean sensitivity to ocean acidification that has not been previously reported. The team hypothesize that the absence or damage of mechanoreceptors within their neuritic canals may in part explain potential aberrant behavioral patterns, such as slower movement, less tactile recognition, and prolonged searching time, as well as impaired swimming, that have been observed in various crustacean species exposed to low pH conditions in laboratory settings.

“We found dissolution impacts to the crab larvae that were not expected to occur until much later in this century,” said Richard Feely, Senior Scientist with NOAA’s Pacific Marine Environmental Laboratory and one of the co-authors of the study.

Combining observations and modelling work, the research team, which included scientists from JISAO, NOAA’s cooperative institute at the University of Washington, from the University of Connecticut, and from Quebec, Britain and Slovenia, demonstrated that the impacts of dissolution were the most severe in the coastal habitats, where crabs grow and mature.

Previous research has indicated that Dungeness crab may also be vulnerable to future declines due to lack of availability of prey – including bivalves such as clams and other bottom-dwelling invertebrate species.

More research needed
Bednarsek emphasized that more research will be needed to determine whether the external dissolution seen in crabs at this early life stage could carry over into later life stages, including the reproductively active adult stage, and what the potential consequences may be for the population dynamics.

“If these larval crab need to divert energy to repair their exoskeletons, and are smaller as a result, the percentage that make it to adulthood will be at best variable, and likely go down in the long-term,” she said.

Ocean acidification is a major concern for West Coast fishery managers, said Rich Childers, Washington Department of Fish and Wildlife’s ocean acidification policy lead. “These data and results give state and tribal fishery managers and policy makers information that’s vital for harvest and conservation planning.”

The research was supported by the NOAA’s Ocean Acidification Program and NOAA’s Pacific Marine Environmental Laboratory.

NOAA Research News, 23 January 2020. Article.

Original post: