Climate Change Impact on Fisheries Studied

By YERETH ROSEN
Alaska Beacon
    In the marine waters off Alaska’s coast, climate change is triggering disruptions that can be dramatic and sudden. For fishery officials, that presents a quandary: How can that be suitably addressed by a fishery management system that is legally required to be cautious and deliberate and for which policy changes can take several years to carry out?
    That was the question presented at a two-day climate scenarios workshop held last Wednesday and Thursday in Kodiak by the North Pacific Fishery Management Council. The workshop was in conjunction with the council’s June meeting.
    There were repeated calls among workshop participants — fishers, fishery managers, scientists and others involved in the Alaska seafood industry — for more extensive and frequent federal data collection. But there were also calls for the way data is collected to change.
    Surveys used to set seafood harvests in the federal waters of the Bering Sea, around the Aleutians and in the Gulf of Alaska are conducted by the Alaska Fisheries Science Center, a branch of the National Oceanic and Atmospheric Administration’s Fisheries service.
    While those surveys represent “world-class” and “robust” data gathering, they will be increasingly difficult to do, said Bob Foy, the center’s science and research director.
    “Climate change is going to push the boundary of our ability to do that. It is pushing the boundaries of our ability to do that,” he said during a workshop session on Thursday. Tools may need to change, and the thinking may as well, he said. “Those underlying assumptions right now are being challenged by climate change.”
    Long-term changes in the Alaska marine system are causing what may be permanent alterations in fish populations and shocks to fish-dependent communities, numerous studies have found. Just Thursday, a new study led by scientists at Japan’s Hokkaido University that was published in the journal PLOS ONE described forecasts for dramatic shifts of Bering Sea fish stocks northward and westward through the rest of the century. Those are expected to have dramatic economic effects as well, the study said.
    But what is most difficult for fisheries and those who manage or depend on them, said the scientists at the workshop, are the extreme events like marine heatwaves that cause sudden disruptions.
    “The last two heat waves are why we’re here talking about it. Climate change, slow, has been going on a long time,” Foy said. “It’s the extreme nature of climate change, it’s the next heat wave, which is coming, that we have to be prepared for.”
    Extreme marine heat waves were triggers to two recent fishery collapses that were among the climate case studies presented at the workshop on Wednesday.
    Elizabeth Siddon, a fisheries biologist with the Alaska Fisheries Science Center, described a cascade of effects resulting from a record-breaking marine heatwave in the Bering Sea that erased even winter sea ice in 2018 and 2019.
    “Climate change is here. Our fisheries are already challenged by the climate extremes that we’re experiencing. The black swan events like 2018 and ‘19 are always going to be difficult to predict, but I think what we learned in hindsight is we should expect large ecosystem impacts of these big climate extremes,” said Sidden, who regularly briefs the North Pacific Fishery Management Council on the Bering Sea ecosystem status.
    “We shouldn’t expect to be able to be able to predict exactly what the ecosystem will do, but we should expect that the ecosystem will respond. And I think that’s the uncomfortable part.”
    An example of the damage wreaked by extreme events was the wipeout of Gulf of Alaska Pacific cod, said Mike Litzow, director of the Alaska Fisheries Science Center’s Kodiak laboratory.
    “The simplest explanation is it just got warmer in the Gulf of Alaska between 2014 and 2019 than we’d ever seen before – like, considerably warmer,” Litzow said.
    He and his colleagues analyzed the collapse and determined that the level of warmth that caused the cod crash would almost certainly not have happened in the pre-industrial ocean.
    “It’s clear evidence that this is a human caused event that’s affecting our fisheries. And that unprecedented warming had really rapid and fairly catastrophic consequences to the ecosystem that are fairly familiar to the people in the room,” he said. He listed seabird die-offs – including the biggest Alaska bird die-off ever recorded, which was among murres – and die-offs of large whales as some of the effects of the heatwave that became known as “The Blob.”
    For Bering Sea snow crab, the crash was sudden and dramatic, and it caught fishery managers off guard, said Erin Fedewa, a Kodiak-based biologist with the Alaska Fisheries Science Center.
    In 2018, she said, surveys of the Bering Sea snow crab population found record-high recruitment, which in fishery science is an indicator of population health. But the 2019 survey turned up significantly lower-than-expected numbers of those young crab — what Fedowa said might have been a “really big red flag.” The 2020 survey that might have provided critical follow-up information was canceled because of the COVID-19 pandemic.
    That left managers, fishers and fish-dependent communities in bad shape in 2021, when low snow crab numbers led to a deep cut in the allowable harvest. Things got only worse from there; the 2022-23 season harvest was closed entirely for the first time, and the closure was extended for a second year.
    Research so far shows that heat in the Bering Sea pushed the crab into smaller areas while increasing their need for food, resulting in mass starvation deaths, Fedowa said. “This was essentially a large-scale mortality event that was driven by climate,” she said.
    The long-term outlook appears dim. Snow crab are dependent on cold conditions and the presence of sea ice, she noted. “So the assumption or the expectation is that as we continue to lose these Arctic conditions in the eastern Bering Sea, that snow crab productivity will also decline. So as the sea ice declines, so do snow crab,” she said.
    And the snow crab crash provides important lessons for other vulnerable species, she said.  “Snow crab is a prime example for how quickly the outlook of a population can change,” she said.
    A changing climate can have the opposite effect on some species, as was seen with a boom in the population of sablefish, another case study that was presented on Wednesday.
    Sablefish, also called black cod, are a deepwater species known for their long lifespans – some have lived as long as 90 years – and their wide-ranging movements. They are considered premium fish and are particularly prized in Japan.
    After a decade of decline, sablefish numbers in the waters off Alaska started to rocket up in 2014, said Dana Hanselman, director of the NMFS Auke Bay Laboratory, who presented results of team research into that species. But because of uncertainties, catch limits set by managers did not increase in a corresponding way until several years later, Hanselman said. The market response was also problematic, with the normal disparity between high-priced big sablefish and lower-priced small sablefish widening as total numbers swelled, he said.
    The lag in response shows a weakness in the way catch limits are set, said Hanselman, who is also a member of the North Pacific Fishery Management Council’s Scientific and Statistical Committee. “For this stock, I think, short-term climate and ocean projections would be really useful,” he said.
    The sablefish example, though it is one of unexpected abundance rather than a sudden crash, fits with the others, he said. “I think the lessons from all these are that really big population changes are going to require adaptive management,” he said.
    Workshop participants made repeated pleas for more frequent and detailed fish surveys and more data-gathering, something that would require additional funding.
    The Alaska Fisheries Science Center is already starting to change the way it surveys Alaska marine waters. A new system is being developed that managers hope will be more suited to climate change.
    Climate change responses should go beyond fisheries science and harvest management, participants said. They recommended more focus on the social and economic effects in fishing communities. Several called for more diversification of the industry. One way to do that would be better marketing and education, they suggested.
    Another way to achieve diversification is through more flexibility to switch their fishing efforts between species and locations – though that might be more difficult to do under the rigid individual quota systems put in place through the process known as “rationalization,” some panelists said.
    Future fishing in a changing climate might also require better coordination with other activities in marine areas, such as shipping that is increasing as Arctic ice diminishes or production of offshore renewable energy that is seen as an alternative to carbon-emitting fossil fuels. And diversification and flexibility could mean that fishers and fishing communities branch out themselves, into non-fishing but ocean-related activities themselves, some said.
    No decisions were made at the workshop, but the ideas generated are intended to be considered in future North Pacific Fishery Management Council and agency actions.
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