春夏季闽江口和兴化湾虾类数量特征

本文利用2008年4月和9月闽江口和兴化湾海域渔业资源调查资料,研究这两个不同类型海域虾类密度的时空分布,优势种特征、地形地貌、海流和水文等因素对分布的影响。结果表明,4月闽江口虾类生物量(22.05kg/km₂)低于兴化湾生物量(23.33kg/km₂), 而尾数密度(12.34?10₃ ind./ km₂)高于兴化湾尾数密度(8.42?103 ind./ km₂),9月也是如此,闽江口虾类生物量(205.54kg/km₂)低于同期兴化湾生物量(329.60kg/km₂),但尾数密度(131.25?10₃ ind./ km₂)大于兴化湾尾数密度(95.79?10₃ ind./ km₂)。这一现象的产生,与闽江口和兴化湾虾类资源种类规格特征有一定的关系：依据优势性分析,在兴化湾,优势种以广盐性大规格的哈氏仿对虾为主,其它主要优势种优势性不明显,对总生物量变化的贡献不大。反观闽江口的优势种,除了广盐性的哈氏仿对虾,还有个体数量巨大的半咸水小规格中国毛虾,其中,中国毛虾尾数密度的百分比占了虾类的大部分。不同盐度环境,种类对不同盐度环境盐度适应是形成闽江口和兴化湾优势种不同格局的主要原因。在闽江口,南部渔场是当地的主要渔场,9月是主要的渔汛,与闽江径流量的季节变化和闽江口地形地貌特征有关。在兴化湾,湾口是虾类的主要产卵场和索饵场,湾外则是虾类越冬场,与构成资源主要种类哈氏仿对虾暖水性和兴化湾水团特征有关。不同季节比较,在9月,兴化湾和闽江口虾类资源品种呈现多样化的趋势,兴化湾和闽江口比较,闽江口虾类资源品种呈现更加多样化的特征。

Comparison of shrimp density between the Minjiang estuary and Xinhua bay during spring and summer

Based on the data from four oceanographic censuses in the Minjiang estuary and Xinghua bay during April and September 2008, this paper compared the spatial-temporal distribution of shrimp density between the two kinds of waters, involved in some impact factors such as dominant species, background of topography and geomorphy, as well as hydrological features. Results showed that total weight density (22.05kg/km2) at the Minjiang estuary was lower than that (23.33kg/km2) at the Xinghua bay, while total individual density (12.34?103 ind./ km2) at the Minjiang estuary was higher than that 8.42?103 ind./ km2) at the Xinghua bay during April. Same as in April, the total weight density (205.54kg/km2) at the Minjiang estuary was lower than that (329.60kg/km2) at the Xinghua bay, while total individual density (131.25?103 ind./ km2) at the Minjiang estuary was higher than that 95.79?103 ind./ km2) at the Xinghua bay in September. The phenomenon was related with the individual size of shrimp species from the two different waters. In the Xinghua bay, the most dominant species was a euryhaline large size species, Parapenaeopsis hardwickii, with high dominance and great contribution to total weight density, while other dominant species with low dominance and small contribution. But in the Minjiang estuary, brackish species, a very small size shrimp, Acetes chinensis were the important dominant species with the most percent in individual densities and the greatest contribution to the total individual density. The different body size of dominant species between the two waters formed because of large size Parapenaeopsis hardwickii as the main dominant species at the Xinghua bay while small size Acetes chinensis, adapted to low salinity, as the important dominant specie at the Minjiang estuary. At the Minjiang estuary, the most shrimp resource aggregated in the south area which was thought as the main fishing ground, and, September was thought as the main fishing season because both weight density and individual density in September were far higher than those in April at the Minjiang estuary. The seasonal runoff of the Minjiang River and topography of the estuary were main environmental reasons which produced the variation in the estuary. At the Xinghua bay, spawning and feeding ground of shrimps lay in waters near the mouth of the bay in September, and the wintering ground located in the deeper outside waters of the bay in winter, related with distribution of shrimp weight density. The main dominant species Parapenaeopsis hardwickii, a warm-water species occupied 89.43% of total shrimp weight density determined the distribution pattern in April. The mixture of different water masses in waters near the mouth of the bay was another reason determined the distribution pattern. The shrimp dominant species in September showed a more diversify trend than that in April both in the Xinghua bay and the Minjiang estuary, while the dominant species at the Minjiang estuary is more diversify than that at the Xinghua bay compared with the two different kind of waters.