AFSC/ABL: Deep-Water Longline Survey for Giant Grenadier and Sablefish in the Western Gulf of Alaska

An experimental bottom longline survey was conducted at depths >1,000 m in the western Gulf of Alaska in August 2008. The objective was to investigate the abundance and biological characteristics of giant grenadier (Albatrossia pectoralis) and sablefish (Anoplopoma fimbria) in deep waters of the Gulf of Alaska that have not been previously sampled in fishery surveys. Several difficulties were encountered during the fishing operations which indicate special problems may occur when fishing longlines at these depths, including substantial gear drift after setting and hang-ups on the bottom that caused the longline to part. Although results were not conclusive because only stations in the western Gulf of Alaska were sampled, there was consistency in the results which provides an indication of fish abundance and distribution in depths >1,000 m. Catch rates of giant grenadier were relatively high, although not as large as those in nearby longline survey stations in depths <1,000 m. Female giant grenadier were much larger in size at the deep-water stations, and their weight averaged 69% greater than females at depths <1,000 m. Males, which comprise a low percentage of the catch in shallower water, were caught in much higher numbers at the deep-water stations. Catch rates for sablefish at the deep-water stations were extremely low, and it appears abundance of sablefish is negligible in the western Gulf of Alaska at depths >1,000 m. Besides giant grenadier, Pacific grenadier (Coryphaenoides acrolepis) was the only other species caught in substantial numbers. At one deep-water station, Pacific grenadier were extremely abundant and were caught on 56% of the longlines hooks.