Survey Protocol for the Alaska Sablefish Longline Survey
November 20, 2016
Sablefish (Anoplopoma fimbria) are a commercially important fish species in the northeast Pacific Ocean. Found along the upper continental slope, in Alaska they are caught primarily by longlines. Catches in the Alaskan EEZ have averaged 15,000 mt in recent years with an annual value of about $100 million. The fishery has been managed by an Individual Fisheries Quota system since 1995. Fishery-independent longline surveys have been conducted annually since 1978 to assess the relative abundance of this valuable resource. The survey abundance indices are combined with age, length, and fishery data to estimate absolute abundance and recommend catch quotas with age-structured models.
Since 1978, the U. S. National Marine Fisheries Service (NMFS), Alaska Fisheries Science Center (AFSC) has conducted annual longline surveys with Japan (Japan-U.S. cooperative longline survey, 1978-94) and alone (1987-present, domestic longline survey). The survey has covered the upper continental slope (1978-present) and selected gullies (1987present) of the Gulf of Alaska and the upper continental slope of the eastern Bering Sea (198294, biennially since 1997) and Aleutian Islands region (1980-94, biennially since 1996). A unique aspect of this survey is that the charter vessel retains most of the catch after the scientific data are recorded. The survey lasts three months. The survey is conducted jointly by two components of the AFSC: the Auke Bay Laboratory and the Resource Assessment and Conservation Engineering Division.
Sablefish have been exploited since the end of the 19th century by U.S. and Canadian fishermen. The North American fishery on sablefish developed as a secondary activity of the halibut fishery of the United States and Canada. Initial fishing grounds were off Washington and British Columbia and from there spread to Oregon, California, and Alaska during the 1920's. Since then, and up to 1957, the sablefish fishery was exclusively a U.S. and Canadian fishery, ranging from off northern California northward to Kodiak Island in the Gulf of Alaska. Japanese longliners began operations in the eastern Bering Sea in 1958. As the fishing grounds in the eastern Bering Sea were preempted by expanding Japanese trawl fisheries, the Japanese longline fleet expanded to the Aleutian Islands region and the Gulf of Alaska. Heavy fishing by foreign vessels during the 1970's led to a substantial population decline and fishery regulations in Alaska which sharply reduced catches. Data collection from sablefish fisheries in Alaska began in 1963. Catch, effort, age and length data have been collected to compute relative abundance indices (catch/hook), age and length compositions.