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NOAA Technical Memorandum NMFS-AFSC-247

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Deep-water longline experimental survey for giant grenadier, Pacific grenadier, and sablefish in the western Gulf of Alaska

Abstract

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 fishing operations highlighting the unique challenges that 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 break. 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 make up 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 that the abundance of sablefish is negligible in the western Gulf of Alaska at depths > 1,000 m. Pacific grenadier (Coryphaenoides acrolepis) were caught in substantial numbers at depths > 1,000 m, but were not caught at depths < 1,000 m.


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