瓯江口海域夏秋季蟹类数量分布与环境的关系

Relationship of crab density distribution with environment in the Oujiang Estuary during summer and autumn

利用2007年6月和9月瓯江口海域渔业资源调查资料,分析瓯江口蟹类资源密度的分布,及蟹类优势种、水团、水深和水文因子对蟹类数量分布的影响。结果表明,6月和9月蟹类重量密度分别为112.99 kg/km2和73.48 kg/km2,尾数密度为16.84×103ind/km2和3.80×103ind/km2,资源总量为50 845.5 kg和33 066.0 kg。蟹类密度分布,在6月,调查海域东部高于西部,南部高于北部。高密度区出现在瓯江口洞头群岛外侧,尤其是受台湾暖流影响明显的海域;在9月仅是南部明显高于北部,其他海域分布比较均匀。瓯江径流从瓯江北口下泄,在口外形成冲淡水水团,使瓯江口北侧蟹类密度较低。瓯江口底层温度与蟹类重量密度呈显著的负相关关系,与其它温盐因子正相关,但是水文因子与尾数密度相关关系不显著。日本蟳(Charybdis japonica)是瓯江口蟹类最重要的优势种,三疣梭子蟹(Portunus trituberculatus)是最重要的经济品种。

A study was conducted to define summer and autumn distribution patterns of crabs in the Oujiang Estuary and to relate these patterns to environmental variation. The result indicated that the weight densities in June and September were 112.99 and 73.48 kg/km^2, respectively. Yet, the number densities were 16.84 × 10^3 ind/km^2 and 3.80 × 10^3 ind/km^2 , respectively. In June, both of weight and number densities in the south-east studied area were higher than those in the west, and that of the south area was higher than that of the north area, in September, however, those in the east area was lower than the west. The crabs continually stayed at outer waters of investigated areas in June, especially in south-east where the water is affected by the Taiwan Warm Current, but higher density in south coastal waters in September. The low crab density in north waters of the Oujiang Estuary was ascribed to the existence of the Oujiang dilute water. Numerically Charybdis japonica was the most important crab species, but Portunus trituberculatus was a critic economical species. The hydrological factors were significantly related with weight density but not significantly with individual density. The total standing stock of crabs decreased from 50 845.5 kg in June to 33 066.0 kg in September in the whole fishing ground.