底拖网资源调查的昼夜误差分析

ANALYSIS OF B0TTOM TRAWL SURVEY BETWEEN DAY AND NIGHT

利用1985和1986年秋季底拖网资源调查数据,分析了昼夜平均渔获量的差异,采用Bray－Curtis系数测量其不相似性。结果表明,除底层鱼类外,总平均和中上层鱼类平均渔获量昼夜差异显著,白天平均渔获量远高于晚上,特别是中上层鱼类相差10余倍,主要种类的差异亦较大。底层鱼类昼夜调查差别较小,基本能够代表资源的分布状况和资源量指标,而中上层鱼类则不适合于用底拖网进行调查。用底拖网和声学调查相结合可以同时进行底层和中上层鱼类资源评估。

An analysis of the difference between day and night average catch wasmade from bottom trawl surveys in autumn 1985 and in 1986. The Bray-Curtis index wasused to measure the dissAnilarity between day and night average catch. The results indicatedsignificant difference between day and night average catch, and in total, pelagic and mainspecies. lt concludes that bottom trawl survey for abundance index can be used for bottomfish during day and night,but not for pelagic fish. A better strategy is to combine bottomtrawl with acoustic surveys.