Assessment of Gulf of Alaska sablefish and other groundfish species based on the 1988 National Marine Fisheries Service longline survey

Abstract

The Alaska Fisheries Science Center conducted the second annual National Marine Fisheries Service (NMFS) longline survey to study the abundance and biological condition of sablefish (Anoplopoma fimbria) and other groundfish along the upper continental slope of the Gulf of Alaska during the summer of 1988. This survey replicated the 1987 survey, with some modifications to the sampling gear and a change in the bait from Pacific herring (Clupea pallasi) to Atlantic squid (Illex spp.). Sampled stations were the same as those used during the Japan-U.S. cooperative longline survey which has been conducted in the Gulf of Alaska from 1979 to 1988. In addition, 11 stations were sampled in gullies. The most notable change in abundance during the second NMFS survey was the decrease in sablefish and the increase in giant grenadiers (Albatrossia pectoralis) in the western Gulf of Alaska. Sablefish relative abundance was the highest of any species, followed by grenadiers. Sablefish abundance indices were highest in the 401-600 m depth interval and grenadiers were most abundant in 801-1,000 m. Those two species accounted for 83.1% of the total relative population number (RPN) and 93.9% of the relative population weight (RPW). Rockfish (Sebastes aleutianus and S. borealis), Pacific cod (Gadus macrocephalus), and arrowtooth flounder (Atheresthes stomias) together comprised 10.8% and 5.5% of the total RPN and total RPW.


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