Regional models being developed by NOAA Fisheries indicate that some fish and crab may shift further north in Alaskan waters than previously predicted due to climate change.
A new report issued by NOAA Fisheries on Dec. 17 says scientists have developed new models that predict more extreme changes in the ecosystem of the eastern Bering Sea by the end of the century, with larger summer northward shifts and changes in areas occupied by important commercial crab and fish species.
Specifically, the majority of models estimate changes in the center of distribution for several commercially important species. They predict that most species’ summer distributions will shift north by between 50 and 200 kilometers by 2080-2089.
Scientists also project large declines in the amount of area occupied by red king crab and snow crab and potentially northern rock sole in summer months, a substantial increase in area occupied by arrowtooth flounder who are a key predator of walleye pollock and declines in probability of occurrence of most species in areas with low pH and oxygen concentration.
Such changes are more extreme than previous species distribution model projections, which accounted for fewer climate effects.
The eastern Bering Sea is warming faster than much of the global ocean, resulting in rapid redistribution of key fishery and subsistence resources, said Maurice Goodman, lead author and NOAA Affiliate, at the University of Alaska Cooperative Institute for Climate, Oceans and Ecosystems Studies.
“We need to provide resource managers, fishermen, and coastal communities information so they can make informed decisions about how to adapt to these changing conditions,” Goodman said.
Scientists involved in this study built species distribution models for eight common and/or commercially important species of groundfish and crabs in the eastern Bering Sea (adults and juveniles) – including walleye pollock, Pacific halibut, Pacific cod, arrowtooth flounder, northern rock sole, yellowfin sole, snow crab, and red king crab.
To date, most studies projecting marine species distributions rely principally on temperature and static habitat characteristics such as depth. This can potentially lead to significant underestimation of species vulnerability to climate change, the study said.
For this study, ecologists combined 40 years of scientific surveys with a high-resolution oceanographic model. The model was adapted to the eastern Bering Sea by scientists at NOAA’s Alaska Fisheries Science Center as part of the Alaska Climate Integrated Modeling project.
“A big challenge for this modelling effort was to determine how likely certain outcomes are if some aspects of the system are not exactly known,” said Jonathan Ream, co-author and fisheries biologist at AFSC. “We compared projections among different types of models to quantify the sources of uncertainty when including these novel factors (pH, oxygen, and the cold pool) in species range projections.”
The study notes that the dynamics of the Bering Sea ecosystem are coupled with the annual extent of sea ice and the cold pool that forms beneath it. The colder water impacts primary production in the Bering Sea as well as the spatial distribution of groundfish and their prey, including krill and forage fish.
The cold pool may also act as a barrier to moving of groundfish along the shelf.
With the projected loss of the cold pool under some future carbon dioxide emission scenarios, a much larger portion of the shelf could become accessible to flounder.
Oceans absorb about 30% of global carbon dioxide emissions, and warmer water holds less oxygen. Climate change is also leading to the acidification of deoxygenation of much of the global ocean. All animals need oxygen to survive, and many species are expected to shift toward deeper, cooler waters to keep up with climate change, the report concluded.
