Abundance of Salmonids

by Wyatt Fournier from the Northwest Explorer

Fish samples for this survey are collected using a mid-water rope trawl that has been modified to fish at the surface by stringing buoys along the head rope. This allows us to catch juvenile and larval fish of our focal species that utilize the upper portion of the water column. In the Gulf of Alaska, this also means we catch a lot of Pacific salmon. During this leg, we have caught all five species of Pacific salmon: Chinook, sockeye, coho, chum and pink. The dominant species is the pink salmon, also known as the “humpy” due to its morphology during maturation. This short-lived species has been forecasted to be abundant this year, partially due to successful hatcheries in Prince William Sound.

Today we were reminded why the Gulf of Alaska has such an abundance of salmonids, as our trawl intercepted a school of adult coho salmon with stomachs that were bursting with prey. Note the size of the removed stomach relative to the body length of the adult Coho (left pic). After dissecting the stomachs, the prey items were identified as capelin, an energy-rich forage fish. Our very next tow caught a large school of capelin (right pic) from which we sampled individuals that will be brought back to the laboratory for caloric content analysis.