南海北部拖网30·3mm方形网目网囊的渔获选择性分析

Analysis on catch selectivity of 30.3 mm square mesh codend oftrawl in Northern South China Sea

根据1997年10月和2000年11月在南海北部珠江口以外传统拖网渔场进行的网目选择性试验资料,分析了网目内径为30·3mm的方形网目网囊对南海北部多种渔获的选择性能。结果表明,这种规格的方目网囊平均尾数逃逸率为29·76%,平均重量逃逸率为8·46%;出现在套网中的经济种类少、数量少,条尾绯鲤、金线鱼、多齿蛇鲻、大头狗母鱼4种鱼的尾数和重量分别占套网抽样渔获的95·4%和86·0%;网囊中带鱼、长尾大眼鲷、黄鳍马面鲀、白姑鱼、深水金线鱼等鱼种的体长小于可捕标准的个体尾数比例均超过或接近50%,枪乌贼、乌贼、乌鲳等幼鱼尾数比例达90%以上,多齿蛇鲻和金线鱼50%选择体长均未达到最低可捕标准,表明该种规格网囊对多数经济种类幼体的损害比较严重。总体来说,使用该规格的方目网囊作业不利于南海北部多数种类资源的繁殖、恢复及其可持续利用,不利于海洋生物多样性保护。

Based on mesh selectivity data of trawl eodend tested in the offshore waters of Northern South China Sea in October 1997 and in November 2000, catch selectivity of 30. 3 mm square mesh codend was analysed. The results indicated that the average escape rates of 30. 3 mm square mesh codend for catch were 29. 76% in number and 8.46% in weight. There were lesser and fewer in commercial species and its numbers in the cover net, and the sum of Nemipterus virgatus, Saurida tumbil, Upeneus bensasi, Trachinocephalus myops comprised 95.4% in number and 86.0% in weight of sample catch in the cover net, respectively. The high percentage of juvenile commercial species that were undersized in the codend showed 30. 3 mm square mesh codend had more serious damage to most juvenile commercial species, approaching or exceeding 50% in percentage of juvenile species which body length is smaller than fishable size--Trichiarus haumela , Priacanthus tayenus , Navodon tessellatus , Argyrosomus argentatus , Nemipterus bathybius and so on, even exceeding 90% in percentage of juvenile Sepia spp, Loligo spp and Parastromateus niger. In particular, 50% selection lengths （L0.5 ） caught Saurida tumbil and Nemipterus virgatus were smaller than their minimum fishable size. To sum up, the use of 30. 3 mm square mesh codend will make against sustainable utilization to most fishery resource and biodiversity protection in Northern South China Sea.