海州湾方氏云鳚体长与体重分布特征及其关系

体长、体重是鱼类种群的基本生物学特征,能够反映鱼类个体生理状态以及所处环境条件的变化,但在实际研究中其时空变化往往被忽略。本文根据2011—2016年春、秋季海州湾8个航次的渔业资源底拖网调查数据,研究了方氏云鳚(Pholis fangi)的体长组成、体重组成,体长–体重关系和肥满度特征,并分析了上述指标的时空异质性。结果表明,海州湾方氏云鳚的群体有多个年龄组,体长、体重和体长–体重关系参数a、b及肥满度在时空上均有较大波动,且在年间差异显著。秋季各航次平均体长、体重呈现逐年增大趋势;肥满度的季节差异要大于年间差异,春季肥满度小于秋季;体长和肥满度在海州湾分布均是西南部大于东北部,但秋季肥满度分布则与此相反。调查的方氏云鳚群体基本符合正异速生长类型。体长体重特征的时空异质性可能与气候、摄食强度、性成熟比例与捕捞压力等有关,并在一定程度上反映了渔业生态系统和栖息地特征。相关研究应充分考虑体长、体重关系参数的时空变化,以为渔业资源评估提供精确参数。

Size distribution and length-weight relationships in Pholis fangi in Haizhou Bay

Body size is a basic biological characteristic in fish populations and can reflect individual physiology as well as changing environment conditions. Slight variabilities in some biological parameters may result in complex ecological effects, and affect food web link intensity in trophic cascades. However, the spatial and temporal het-erogeneity of size composition within populations have often been ignored in many studies of fish biology. We use Fang's gunnel (Pholis fangi) in Haizhou Bay as an example for studying the variability of body size on an annual scale. P. fangi is a low trophic fish and plays an important role in the food web and ecosystem of the Yellow Sea, with increasing dominance in Haizhou Bay. We collected annual bottom trawl surveys in Haizhou Bay in the spring and fall from 2011 to 2016. We used a range of statistical methods, included variable coefficient, covariance analysis, two-sample t-test, and Pearson correlation analysis to study the population size composition, length-weight relationship, and relative fatness of P. fangi in this area. We analyzed the annual and seasonal vari-ability as well as the spatial distribution of body length and relative body mass. The results showed that P. fangi had multiple age structure in Haizhou Bay. Their length frequency distributions were multi-modal and skewed, with the majority of captured individuals aged 2-3 years. Statistical analysis indicated that there were remarkable temporal and spatial variations in the average size and the parameters of body length-weight relationship of P. fangi, with significant differences across years (P<0.05). The average body length and relative fatness tended to be higher during autumn surveys than spring surveys. Variation in relative fatness was greater between seasons than among years. In spring, the spatial distribution of body length and relative fatness was larger in the southwest area than the northeast area of the bay. A t-test on the body length-weight relationship showed that the allometric growth patterns of P. fangi were generally positive. Correlation analyses between benthic water temperature and the length-weight relationship showed that temperature had a substantial influence on the relative fatness, body length-weight relationship, and mean body length. The spatiotemporal variability of fish size and other parameters may be attributed to their feeding intensity, maturation, fishing pressure, and environmental and habit variation, and is also likely to reflect changes in the fishery ecosystem. We suggest that the spatiotemporal variability of population size composition should be fully considered in fisheries resource management, as these basic parame-ters can contribute significantly to fishery ecosystem modelling and management strategy evaluation.