Wednesday, September 25, 2019

Study Estimates Vulnerability of Eastern Bering Sea Fisheries

A climate vulnerability assessment released on Sept. 19 by NOAA scientists and partners has determined that six stocks in the Eastern Bering Sea, including Tanner crab, are the most vulnerable to climate change.

Also included among the most vulnerable were Pacific ocean perch, rougheye rockfish, shortraker rockfish, shortspine thoryhead and flathead sole.

Snow crab and Bristol Bay red king crab were among species determined to be less vulnerable. The study looked at potential impacts of changing climate, ocean temperatures and other environmental conditions on 36 groundfish, crab and salmon stocks in the Eastern Bering Sea.

Several other fish stocks were determined to be potentially more resilient because they may be able to move to areas with more favorable environmental conditions, such as more food and optimum water temperatures or growth and survival.

“Alaska fisheries are really important,” said Bob Foy, director of the Alaska Fisheries Science Center. “They contributed 58 percent of US landings and 29 percent of US ex-vessel value in 2016, with the majority of Alaska landings and value obtained from the Eastern Bering Sea shelf. In the past few years water temperatures have been much warmer than average, making the need for studies like this all the more imperative.

“Our science both in the field and in the lab is critical to monitor ecosystem changes and provide short-term and long-term forecasts to help commercial, recreational and subsistence communities anticipate and respond to changes that impact their way of life.”

The 34 scientists who assisted in this stock analysis considered the likelihood of exposure to climate change for all stocks studied, and the sensitivity and adaptability if exposed. They used existing information on climate and ocean conditions, species distributions and species growth and development, then estimated each stock’s overall vulnerability to climate related changes in that region.

“Our models projected more variability in salinity and water temperatures in the offshore ocean habitats where all of these species tend to be found, making them more vulnerable than other species which inhabit different areas,” said Paul Spencer, a fisheries biologist and lead author of the study.

Participating scientists classified nine flatfish stocks, crab, forage fish, rockfish, sablefish, Giant Pacific octopus, sculpin, Pacific cod and walleye Alaska pollock as having lower vulnerability due to their mobility. Still additional research conducted by the Alaska Fisheries Science Center suggests that the story for Alaska pollock, Pacific cod and possibly other species is more nuanced, the report said.

Field and laboratory studies of Pacific cod have shown that warmer water and lower pH levels can affect prey availability, as well as Pacific cod egg, larvae and juvenile development, which ultimately affects Pacific cod survival. Fewer young fish mean fewer adult fish, so there could be delayed impacts of changing climate and ocean conditions on this species, the report said.

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