Численность, распространение восточноберинговоморского минтая и промысел в начале 2000-х гг.

• Main Authors: Степаненко, М., Николаев, А., Грицай, Е.
• Format: Text
• Language: unknown
• Published: Федеральное государственное унитарное предприятие «Тихоокеанский научно-исследовательский рыбохозяйственный центр» 2007
• Subjects: Atka; Bering Sea; Gulf of Alaska; Берингов*; Alaska
• Online Access: http://cyberleninka.ru/article/n/chislennost-rasprostranenie-vostochnoberingovomorskogo-mintaya-i-promysel-v-nachale-2000-h-gg; http://cyberleninka.ru/article_covers/11372030.png

В 20002006 гг. отмечена значительная межгодовая изменчивость численности, биомассы и пространственной дифференциации восточноберинговоморского минтая. В этот период численность и биомасса снизились, и в 2006 г. они находились на самом низком уровне за последний пятнадцатилетний период. В 2006 г. в популяции минтая преобладали по численности примерно в равном соотношении поколения 19982002 гг. Численность младшевозрастного пополнения 2005 г. находилась на среднем уровне. Очевидны две основные причины значительного уменьшения численности и биомассы восточноберинговоморского минтая к 2006 г. отсутствие многочисленных поколений в 20022004 гг. и высокий уровень промысловой эксплуатации единственного с начала 2000-х гг. многочисленного поколения 2000 г. как в восточной, так и в северо-западной частях Берингова моря. Масштаб распространения минтая в северо-западную часть Берингова моря в нагульный (летне-осенний) период в 20022006 гг. увеличился и был наиболее значительным в 2006 г. High interannual variation of abundance and distribution of the eastern Bering Sea pollock was observed in 20002006. Its abundance and biomass declined significantly in 2006 to the lowest level for the last 15 years. The 19982002-year classes dominated in the population, abundance of the 2000-year class was comparable with the most numerous generations of the 1989 and 1992. The 20022003-year classes were low, and the 2005-year class had average level. As a result, the pollock recruits abundance at age 14 reduced almost twice during the period 20022004, from 10.48 x 109 to 5.85 x 109 specimens. Besides the low abundance of the 20022004-year classes, extremely high fishing exploitation of the single abundant 2000-year class both in the eastern and northwestern Bering Sea was the reason of the pollock population declining. High fishery exploitation of strong year classes is usual for pollock. As a rule, immature fish of strong year classes composes a significant part of bycatch because it is wide distributed over the Bering Sea shelf. The 2000-year class of the eastern Bering Sea pollock was exploited actively in 20022006. Its biomass was estimated as 1.44 mln t in 2004, but just 0.86 mln t in 2006. There is no special regulation of the eastern Bering Sea pollock fishery for reducing bycatch of immature fish belonget strong year classes. Scale of the eastern Bering Sea pollock feeding migration into the northwestern Bering Sea in summer and autumn increased in 20022006 because of zoo-plankton production increasing. Interannual variation of its spatial distribution in summer-autumn period depended on feeding conditions: in late 1990s the main part of postspawning and immature pollock migrated from the southeastern Bering Sea northwestward, but in 20002003 a lot of the pollock stayed in summer-autumn period in the southeastern Bering Sea. The biomass of postspawning pollock at the southeastern shelf at Unimak Island and Alaska Peninsula in early summer was estimated from 365 th. t to 710800 th. t. In 20042006, the most of postspawning and immature pollock began to migrate again to the northwestern area. The main reason of the active migration was low zooplankton production in the southeastern Bering Sea in this period. In the northwestern Bering Sea, distribution of the pollock is limited by low water temperature. In spite of extremely high abundance of zooplankton (euphausiids) in shallow areas water (90100 m) of the northwestern Bering Sea in summer of 2004 and 2006, the abundance of pollock there was very low. Some cases of unusual behavior of pollock and other fish species observed in 20032007 are discussed, as well. For example, in February 2003, mature pollock migrated from the Gulf of Alaska to the southeastern Bering Sea shelf through the Unimak Pass, and atka mackerel concentrated off the eastern Aleutians.