Study Finds Increased Genetically Distinct Alaska Crab Populations
New genetic research on Alaska red king crab indicates there are at least six, and possibly seven, genetically distinct populations, making the species more resilient to climate and ocean condition changes.
The report released Jan. 2 by NOAA Fisheries identifies the genetically distinct populations being in Southeast Alaska, Gulf of Alaska, Aleutian Islands, Bristol Bay, Pribilof Islands, Norton Sound and the Chukchi Sea.
Researchers found previously unrecognized differences between crab in the Gulf of Alaska and East Bering Sea regions, plus the Eastern Bering Sea region split into separate Bristol Bay and Pribilof Islands populations.
They also found that the Aleutian Islands and Norton Sound/Chukchi Sea regions are unique. Data suggests that Norton Sound and Chukchi Sea populations may be distinct as well, although further research is required to determine if this is the case.
NOAA Fisheries attributes this genetic diversity to a combination of factors including populations deriving from different glacial refugia, areas that remained ice-free during the Ice Age. Refugia is an area in which a population of organisms can survive through a period of unfavorable conditions, especially glaciation.
They determined that natural selection — genetic changes driven by adaptation — and genetic drift likely contributed to this diversity. Evidence of local adaptation in most populations was documented as well, by sequencing the whole genome of red king crabs.
The research also confirmed that these fisheries are being managed effectively by region.
Crab stocks in the Gulf of Alaska, Aleutian Islands, Bristol Bay and the Pribilof Islands are each managed separately. Before this research began the Bristol Bay and Pribilof Islands were not found to be genetically distinct.
Understanding population structure and the newly learned genetic signals of local adaptation is also important for preventing overfishing on genetically unique populations, and critical to provide information on how local adaptations influence responses to different climate conditions.
Some populations have the potential to do better in future conditions that will occur as climate changes, the study showed.
Some shifts may already be underway in the Bering Sea as the North Pacific Ocean warms.
Researchers also said that with the Gulf of Alaska red king crab population being depressed, they expect a higher potential for inbreeding and lower genetic diversity, but they found no evidence of reduced diversity, meaning genetic health has not suffered as the population declined.
This foundation of genetic diversity means that genetic factors should not limit recovery, they said.
Data collected during the study can be used to inform broodstock selection for red king crab enhancement program, used to raise young crabs in hatcheries and release them into the wild to enhance populations.
Researchers said it will be vital to prioritize local broodstock for enhancement before sourcing from elsewhere, to keep genetic diversity intact and ensure that the genetic integrity of locally adapted populations is not jeopardized.
Source: https://fishermensnews.com/study-finds-increased-genetically-distinct-alaska-crab-populations/
