Biological characteristics, density and its spatial distribution of Portunus trituberculatus in Laizhou Bay, together with the impact of environmental factors, were analyzed based on the bottom trawl data of 9 surveys from May 2011 to April 2012, in order to provide scientific basis for utilizing and protecting the resource of P. trituberculatus. The monthly variation of biomass density could be described as September > October > July > August > June > November > March > May > April. The average values were highest in August 2011 and lowest in April 2012, for body mass, width and length, respectively. The individual fatness coefficient was highest in August 2011 both for the female (1.030) and the male (1.023), lowest in July both for the female (1.007) and the male (1.007). The difference of fatness coefficient was not significant (P>0.05) between the female and the male. The sex ratio (female/male) was less than 1.0 in most of all months except June, July and August. P. trituberculatus was mainly distributed in the Yellow River estuary and the offshore off Longkou in May-July, in offshore off Weifang and Longkou in August-September, and in deep-water area of the Laizhou Bay mouth from October to next April. Pearson correlation analysis indicated that environmental factors that best matched the density of P. trituberculatus were sea surface temperature (SST), dissolved oxygen (DO) and water depth (Dep), followed by salinity (Sal) and zooplankton density, the last were phytoplankton density and the number of other demersal fisheries species. The body length of P. trituberculatus in 2011 was significantly smaller (P<0.01) compared with that in 1981. To sustainably utilize the resource of P. trituberculatus in Laizhou Bay, we suggested that the fishing effort should be reduced, the catchable size should be raised, the research of enhancement basements should be promoted and more reasonable releasing quantity should be proposed.
根据2011年5月—2012年4月进行的9个航次(月份)的底拖网调查,研究了莱州湾水域三疣梭子蟹的生物学特征、数量分布以及环境因子的影响.结果表明: 莱州湾三疣梭子蟹生物量密度的月间排序为9月>10月>7月>8月>6月>11月>3月>5月>4月.其中1龄以下个体占绝对优势,2011年7—10月4个航次所占比例平均值为86.1%.9个航次中,三疣梭子蟹的体质量、头胸甲宽及头胸甲长的平均值均以8月最高、4月最低.7—11月,雌、雄个体肥满度均以8月最高,分别为1.030和1.023,7月最低,雌雄均为1.007;雌雄个体肥满度的性别差异不显著.除6—8月外,其他月份性比(雌/雄)均小于1.0.莱州湾三疣梭子蟹5—7月主要集中在黄河口、龙口近岸,8—9月以潍坊及龙口近海密度最高,11月至翌年4月主要集中在湾口深水区.Pearson相关分析表明,莱州湾三疣梭子蟹数量分布与表层水温、溶解氧和水深的相关性最高,其次为盐度和浮游动物密度,与浮游植物密度及其他底层渔业生物个体数的相关性最低.与1981年同期对比,2011年莱州湾三疣梭子蟹的头胸甲长显著降低.建议适当降低捕捞强度,提高捕捞规格,进一步加强三疣梭子蟹增殖基础的研究,提出更加合理的增殖放流数量,以利于三疣梭子蟹资源的可持续利用.
Keywords: Laizhou Bay; Portunus trituberculatus; biological characteristics; environmental factors; temporal and spatial distribution.