北太平洋狭鳕资源声学评估调查研究

STOCK ASSESSMENT OF WALLEYE POLLOCK IN THE NORTH PACIFIC OCEAN BY ACOUSTIC SURVEY

１９９３年夏季使用“北斗”号渔业调查船对北太平洋的狭鳕进行资源声学评估和渔场环境调查，调查覆盖面积达７６万平方公里。调查结果表明：夏季白令海阿留申海盆区５０—２００ｍ为冷水团占据，水温为１．３—４．９Ｃ。狭鳕成鱼主要分布于海盆区东南部及公海区，主要栖息在１７５－２２５ｍ层。在公海区东北部与陆架之间，首次发现大量狭鳕当年生幼鱼，主要栖息在８０—１００ｍ层。成鱼和幼鱼均有明显昼夜垂直移动。海盆区狭鳕平均叉长５２．６ｃｍ，平均体重１０９５ｇ，个体较往年偏大，公海区狭鳕资源评估结果为５．２万吨，预计１９９５年公海狭鳍资源将逐渐恢复。夏季鄂霍次克海公海区５０—１５０ｍ为较强冷水团占据，水温为－１．２－０．２℃。狭鳕密集分布区在北纬５５°以北的５００ｍ等深线以浅海区，主要分布水层在冷水团下方的１５０—３００ｍ处。该海区狭鳕平均叉长３８．３ｃｍ，平均体重３５８．７ｇ，优势年龄组成为５—６龄，资源状况良好。

An acoustic/midwater trawl survey of the resource of walleye pollockTheragra chalcogramma (Pallas) in the Aleutian Basin and the high seas of the Sea ofOkhotsk was carried out by the R/V 'Bel Don)' during the period of June 10 - August 24,1993 with a coverage of 760 × 103 km2. The survey results indicate that: (1) during summer,the water from surface to 25 m depth vertically mixed well in the Aleutian Basin with thetemperature of 5. 4- 9. 6℃, salinity of 32. 4-33. 2, dissolved oxygen of 9. 7- 10. 6 mg/L,while the water layer 50-200 m was occupied by the cold water mass with the temperatureof 1. 3- 4. gb. Adult walleye pollock were mainly distributed in the southern part of theBasin and the Bering High Seas at 175- 225 in depth water layer. A large concentration ofage-0 pollock was first discovered in the waters between the northeastern part of the BeringHigh Seas and the shelf of the eastern Bering Sea, and inhabited mainly the water layer 80-100 m. The adult and age-0 pollock both showed distinct diurnal vertical migration pattern.The mean fork length of pollock from the Basin was 52. 6 cm, and mean body weight 1095 g.There were different spawning stocks in the Aleutian Basin. The pollock from the wateraround Bogoslof Island were aged at 4- 20 years with a dominant age group of 11 - 15 years.The 1978 and 1977 year classes were relatively strong. However, the pollock from thesoutheastern part of the Basin were young, and dominated by the age group of 3- 4 years.The biomass of pollock in the Bering High Seas was estimated about 52 × 103t. It is predictedthat the stock will be gradually recovered after 1995. (2) the water temperature at surface inthe high seas of the Sea of Okhotsk ranged from 11. 9- 13. 0 ℃, salinity from 32. 7- 32. 9 1dissolved oxygen from 8. 9- 9. 5 mg/L, while the water layer 50- 150 m was controlled bythe relatively strong cold water mass, at the temperature of -1. 2-0.2℃. Pollock inhabitedmainly the water below the cold water mass at 150 - 300 m depth, and the densestconcentration was observed in the area north 55°N. The mean fork length in this area was38. 3 cm, mean body weight 358. 7 g, and the dominant age group was 5- 6 years. The stockwas in a good condition.