New technical reports released Jan. 12 by NOAA Fisheries’ Alaska Fisheries Science Center provide an update on sources of Chinook salmon caught incidentally in Bering Sea and Gulf of Alaska trawl fisheries.
Dave Witherell, deputy director of the North Pacific Fishery Management Council, notes that Jeff Guyon, supervisory research geneticist at the Auke Bay Laboratories, reports to the council every year at its April meeting on the most recent results of salmon bycatch composition, which the council monitors closely. Witherell said it does not appear that the composition of fish changes dramatically from year to year.
The latest genetic analysis of samples from the Chinook salmon bycatch of the 2014 Bering Sea/Aleutian Island trawl fishery for pollock used a systematic random sampling protocol where one of every 10 Chinook salmon was sampled.
The analysis of 1,385 Chinook salmon bycatch samples showed that coastal Western Alaska stocks comprised 49 percent of the sample set. Chinook salmon from the North Alaska Peninsula made up 18 percent, British Columbia 14 percent and West Coast (California, Oregon and Washington) 7 percent.
Analysis of temporal groupings within the pollock “A” and “B” seasons showed changes in stock composition during the course of the year, with lower contributions of coastal Western Alaska, North Alaska Peninsula and Yukon stocks and higher contributions of West Coast US, British Columbia, Northwest Gulf of Alaska and coastal Southeast Alaska stocks during the “B” season.
In the Gulf of Alaska, NMFS similarly analyzed Chinook salmon bycatch in the 2014 Gulf trawl fishery for pollock, rockfish and arrowtooth flounder, with 10.7 percent of the salmon bycatch successfully genotyped.
Based on the analysis of 1,163 Chinook salmon bycatch samples, 43 percent of the samples were determined to be from British Columbia, 35 percent from the West Coast of the US, 16 percent from coastal Southeast Alaska and 5 percent from northwest Gulf of Alaska stocks.
Weighting the available sample sets to the total bycatch by season and statistical area did not appreciably change the overall stock composition, NMFS said.
Genetic samples from the bycatch of the rockfish catcher vessel fishery in the central Gulf were collected by the fishing industry, using a census sampling protocol where every Chinook salmon encountered was sampled.
A total of 398 Chinook salmon bycatch samples collected in NMFS Statistical areas 620 and 630. Analysis of those samples showed that 72 percent came from West Coast US stocks, 17 percent from British Columbia, 7 percent from coastal Southeast Alaska and 3 percent from the northeast Gulf.
Another 404 Chinook salmon bycatch samples genotyped from the 2014 Gulf arrowtooth flounder trawl fishery from the catcher-processors F/V Vaerdal and F/V US Intrepid showed that 51 percent of those kinds came from West Coast US stocks, 36 percent from British Columbia, 10 percent from coastal Southwest Alaska, 2 percent from the Northeast Gulf and 2 percent from the Northwest Gulf.