匙吻鲟越冬前后的生长特性研究

Growth Characteristics Study of Paddlefish(Polyodon spathula)before and after Overwintering

选择300尾均重（479.21±42.36）g的健康匙吻鲟（Polyodon spathula）进行90d的不投饵越冬试验,在越冬前后分别测定其体重、体长、体高、体厚,分析各体型指标在越冬前后的变化。结果表明,匙吻鲟在越冬后体重、体厚、体高和肥满度显著降低（P〈0.05）,其中体重比越冬前降低了9.7%,体长与体厚、体长与体高的比值显著提高（P〈0.05）;而其体长在越冬前后没有显著差异（P〉0.05）;越冬前三维图集中度较越冬后高,且出现明显迁移,体重的标准化使得越冬前后3个指标的三维图更加分散,但没有发生明显迁移。研究显示,匙吻鲟在越冬期间消耗自身的贮能物质为鱼体提供能量,导致越冬后体重显著低于越冬前,匙吻鲟越冬后体厚显著降低、体长与体厚比值显著提高、肥满度显著下降。三维图分析和多元逐步回归方程分析表明,匙吻鲟体型变化主要是由越冬后体重下降引起的。

The American paddlefish（Polyodon spathula）is a commercially valuable fish introduced to China in 1988.The species is adaptable,grows rapidly and is not aggressive.The paddlefish has been introduced in many provinces and cities,as it is easy to feed and catch and readily adapts to reservoirs,lakes and ponds.However,the paddlefish is a filter feeder,foraging primarily on zooplankton and management of overwintering is important for culturing.The effect of overwintering on fish has been researched,but the conclusions reached in different studies are not consistent and vary with species.In general,body weight,liver function and immunologic competence are affected by overwintering.To investigate changes in the body shape of paddlefish during overwintering,300 healthy paddlefish（average body weight,479.21±42.36 g）were fasted for 90 days in a natural pond.During the experimental period the pond was not ice covered and the fish were not fed,simulating natural overwintering.The body weight,body length,body height and body thickness were measured before and after fasting.All measured parameters except body length decreased significantly after fasting（P〈0.05）,as did the condition factor（ratio of body weight to body length）.Body weight decreased by 9.7%,while the ratios of body length to body thickness and body length to body height increased significantly（P〈0.05）.The differences were analyzed by plotting body length,height and width as points on three-dimensional figures before and after fasting.The concentration degree of the point in three-dimensional figure decreased,and shifted after the winter.After standardization by body weight,the points dispersed and displayed no obvious shifts.Three-dimensional and multiple regression analysis indicate that the change in paddlefish body shape during overwintering is caused primarily by weight loss.Our results show that paddlefish energy stores are adequate for overwintering,but overwintering results in significant decreases in body weight,body thickness and condition factor.