狭鳕（Theragra　chalcogramma　Palas）目标强度的现场测定

IN SITU TARGET STRENGTH MEASUREMENTS ON WALLEYE POLLOCK (THERAGRA CHALCOGRAMMA PALLAS)

１９９３年夏季“北斗”号调查船白令海狭鳕（ＴｈｅｒａｇｒａｃｈａｌｃｏｇｒａｍｍａＰａｌａｓ）资源声学调查期间，利用计数—积分法对狭鳕的目标强度进行了现场测定。结果表明，平均叉长５１６ｃｍ的狭鳕的平均目标强度为－３４３ｄＢ；以常规的２０Ｌｏｇｌ形式表示，其目标强度与叉长的关系式为ＴＳ＝２０Ｌｏｇｌ－６８．６ｄＢ。该测定结果较目前采用的关系式：ＴＳ＝２０Ｌｏｇｌ－６６．０ｄＢ低２６ｄＢ；应用于资源量计算，其估算值将比现估算值高８２％。

Target strength of walleye pollock (Theragra chalcogramma Pallas) was measured in situ using the Counting Integration method during the “Bei Dou' acoustic survey in the Bering Sea in summer 1993. The average target strength of walleye pollock with the mean fork length of 51.6cm was estimated to be -34.3 dB, resulted in a Target Strength Fork Length relation of TS=20Logl-68.6 dB, which is 2.6 dB lower than the currently applied relation TS=20Logl-66.0 dB (Foote and Traynor, 1988), meaning that when it is employed in abundance estimation, the results will be 82% higher than the current estimates.