南海北部主要捕捞种类最适开捕规格研究

根据南海水产研究所使用elefan技术基于体长数据求得的南海北部50种主要捕捞种类的von Bertalanffy生长参数，以Beverton-Holt模型计算最适开捕年龄后用von Bertalanffy生长方程计算其相应开捕体长，再参考实际调查最小性成熟体长、临界体长、拐点体长和Froese-Binohlan经验公式计算的初次性成熟体长范围等数据确定最适开捕规格；部份分海区研究的种类先确定同一种类于各海区的最适开捕规格，再考虑不同海区的适用性确定其在南海北部的最适开捕规格。本文研究了南海北部50种主要捕捞种类的最适开捕规格，结果表明，所求得的最适开捕规格比原广东、广西、福建“水产资源繁殖保护实施细则暂行规定”的开捕规格都大；建议选择19种在以往的生产中和历次调查研究中出现频率较高、产量较高的主要捕捞种类作为南海北部实行开捕规格保护幼鱼幼虾措施的指标种，并提出开捕规格的随机抽样检查方法。

Optimum first capture standards of major capture species of the northern South China Sea

The fish stock of Northern South China Sea is being confronted with exhaustion situation at the present time. The measures to protect juvenile fish and juvenile prawn of first capture standards of northern South China Sea strictly will become one of the effective measures to restore the fish stock and to utilize the fish stock continuously. The elefan technique was adopted to calculate the von Bertalanffy growth parameters of some species, based on their body length data of northern South China Sea that surveyed by South China Sea Fisheries Research Institute before. In this paper, the von Bertalanffy growth parameters of 50 major capture species of northern South China Sea were used. The Beverton-Holt model was adopted to calculate the catch per recruitment of each species based on its capture mortality rate (F) equaled its natural mortality rate (M). The curve of equal catch of each species was drawn out and the first capture age of each species was determined. The yon Bertalanffy growth equation was adopted to calculate the first capture length of each species. And the optimum first capture standard of each species was determined, based on its minimum length at maturity by survey, based on its critical length, based on its length of point of inflection, and based on its range of length at maturity that calculated by Froese-Binohlan experienced equation. The optimum first capture standards of some species had been determined to different sea areas firstly and then their optimum first capture standards of Northern South China Sea had been determined, based on their adaptability of different sea areas. This paper studied the optimum first capture standards of 50 major capture species of northern South China Sea, the result showed that, the optimum first capture standards had been calculated in this paper were larger than that in the regulations drawn up by Guangdong, Fujian and Guangxi before. The species of fish stock of northern South China Sea are numerous, and the composition is complicated, and they often mix in same habitat, so 19 major capture species have been selected as index species to execute the measures of protecting juvenile fish and juvenile prawn of first capture standards of Northern South China Sea in this paper, because their catch frequency is higher and their catch yield is higher when fished and surveyed before. The 19 index species are: Sardinella aurita, llisha elongata, Decapterus maruadsi , Trachurus japonicus , Pneumatophorus japonicus , Pampus argenteus , Saurida undosquamis , Muraenesox cinereus , Priacanthus macracanthus , Argyrosomus argentatus , Parargyrops edita , Nemipterus virgatus , Upeneus rnoluccensis, Trichiurus haumela, Psenopsis anomala, Navodon xanthopterus, Penaeus japonicus, Metapenaeus ensis, and Loligo chinensis. This paper put forward the check method of the optimum first capture standards : total weight of juvenile fish and juvenile prawn that do not reach their optimum first capture standards should not exceed 20% of total catch yield. Random sampling some catch of total catch, when proportion of juvenile fish and juvenile prawn of index species exceeds 20 % sampled catch, the fishing ship should be removed out of the fishery because the habitat of adult fish and adult prawn differs from the habitat of juvenile fish and juvenile prawn.