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Shortraker rockfish (''Sebastes borealis'') is an offshore, demersal species distributed from the southeastern Kamchatka Peninsula, Russia, to Fort Bragg, California. It attains lengths greater than one metre (>39 inches) and weighs up to 20 kg (44 pounds). In the Gulf of Alaska, shortraker rockfish are sampled annually during longline surveys and are most abundant between depths of . Commercial harvesting in the Gulf of Alaska began in the early 1960s when foreign trawl fleets were targeting more abundant.〔Sebastes spp〕 In recent years, high catch rates indicate that the domestic trawl fleet targets this species; shortraker rockfish comprised 14.9% of the species composition of slope rockfish harvested in 1990, although trawl survey data indicates they comprised only 2.5% of the biomass.〔Heifetz and Clausen, 1991〕 In 1991, catch limits were established for shortraker rockfish to prevent overharvesting of this species in the Gulf of Alaska. Catch limits are based on biomass estimates derived from bottom trawl catch rates. These biomass estimates are questionable, however, because the catch efficiency of bottom trawls on shortrakers is unknown. Fishermen report that shortrakers school off-bottom and above rugged habitat in steep-slope areas where bottom trawls cannot sample effectively.〔(Encyclopedia.com )〕 ==Old specimens== In 2007, fishermen caught a specimen that was estimated to be between 90 and 115 years old. The fish weighed in at and was measured at . It was caught south of the Pribilof Islands at an estimated depth of .〔(Century-old fish found off Alaska ) BBC News, 2007-04-06. Retrieved 2007-04-07.〕〔(Photo in the News: Century-Old Fish Caught in Alaska ) National Geographic, 2007-04-06. Retrieved 2007-04-07〕 In 2013, a sport fisherman from Seattle caught a specimen from below the surface and 10 miles offshore near Sitka, Alaska. At , experts believe the 42-inch shortraker is the oldest ever caught, with an estimated age of 200 years.〔〔 Update: Fish was found to be 64 years old. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Shortraker rockfish」の詳細全文を読む スポンサード リンク
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