Standardizing sablefish (Anoplopoma fimbria) long-line survey abundance indices by modeling the log-ratio of paired comparative fishing cpues

From 1979 to 1994, the US National Marine Fisheries Service (NMFS) and the Fisheries Agency of Japan (FAJ, 1979-1988), and later the North Pacific Cooperative Fisheries Company (NPCFC, 1989-1994), have performed joint long-line surveys on chartered Japanese commercial fishing vessels in the Gulf of Alaska. These surveys were designed primarily to monitor the relative abundance of sablefish (Anoplopoma fimbria). To prepare for the future termination of these joint surveys, between 1988 and 1994 NMFS performed similar long-line surveys aboard US vessels in the Gulf of Alaska. These paired (i.e. duplicated) surveys from 1988 to 1994, provide a basis for comparing future NMFS survey results with the past time series of joint US and Japanese surveys (i.e. the joint 1979-1994 surveys). This paper describes how modeling the log-ratio of paired cpue results (i.e. the log((NMFS cpue)/(joint cpue))), from a standardized survey design, was used to provide a basis for converting the joint survey cpue values to values directly comparable to those from the NMFS surveys. This was necessary because sablefish long-line surveys will be carried out solely by NMFS in the future.