基于水声学方法的嘉陵江中游蓬安段鱼类资源研究

研究嘉陵江中游鱼类资源时空动态特征，了解变化过程及影响因素，提出嘉陵江鱼类资源保护的建议和措施，同时为长江上游及其支流的鱼类资源保护提供基础数据。运用Biosonics DT-X分裂波束科学回声探测仪于2018年7月（夏）、10月（秋）以及2019年1月（冬）、4月（春）对嘉陵江中游蓬安段金溪航电工程干流江段进行了水声学探测，并辅以常规渔获物调查。共采集到鱼类6科38种，其中蛇鮈、鲫、银飘鱼、黄尾鲴等中小型鱼类在数量上占优；鱼类密度分别为春季（0.8296±0.43）、夏季（0.8705±0.38 ）、秋季（0.5082±0.25）、冬季（0.3939±0.13）尾/m3；鱼体平均目标强度分别为春季（-63.15±5.03）、夏季（-52.85±14.45）、秋季（-46.42±15.85）、冬季（-44.77±15.28 ）dB；鱼体平均重量分别为春季0.03、夏季1.08 、秋季11.19 、冬季20.40 g/尾；鱼类资源量分别为春季0.4096、夏季0.2907 、秋季0.3919 、冬季0.5622 kg/m3；坝下鱼类密度显著高于坝上（F=12.67，P<0.05）；坝上（F=7.02，P<0.05）和坝下（F=19.99，P<0.05）3个水层之间的鱼类密度差异显著，中层鱼类密度显著高于上层和下层（P<0.05），且总体上夏季各水层的鱼类密度要高于其他季节。后续研究应加强对该江段鱼类资源的动态监测，并重点探讨引起鱼类资源动态变化的关键影响因子。

Fish Resource Assessment in the Peng'an Section of the Middle Jialing River Based on Hydroacoustic Surveys

Hydropower development on the Jialing River has changed the natural ecological environment, resulting in irreversible effects on the fish community. In this study, we explored the temporal and spatial dynamics of fish resources in the Peng ''an section of the upper and lower Jinxi Reservoir of Jialing River. The effect of environmental factors were analyzed and measures to protect and restore the fish resources of Jialing River were suggested. Our aim was to provide basic data for conserving fish resources in the upper Yangtze River and its tributaries. The study was based on a hydroacoustic survey using a Biosonics DT-X split-beam echo sounder in the Peng ''an section of Jialing River in July (summer) and October (autumn) of 2018, and January (winter) and April (spring) of 2019, supplemented with a fish catch investigation. The survey section stretched 8.3 km, from 4.5 km below the Jinxi dam to 3.8 km above the dam along a zigzag route. During the survey, a total of 23 738 individuals were recorded, including 38 species representing 6 families and 3 orders. Small and medium sized fish species, including Saurogobio dabryi Bleeker, Cyprinus auratus, Pseudolaubuca sinensis Bleeker, Xenocypris davidi Bleeker, were dominant. The density of fish in the Peng ''an section of Jialing River was relatively high in spring and summer (0.8296 ± 0.43 ind/m3, 0.8705 ± 0.38 ind/m3), and relatively low in autumn and winter (0.5082 ± 0.25 ind/m3, 0.3939 ± 0.13 ind/m3). The average target strengths of fish by season, from spring to winter, were (-63.15 ± 5.03), (-52.85 ± 14.45), (-46.42 ± 15.85) and (-44.77 ± 15.28) dB, the corresponding average weights were 0.03, 1.08, 11.19 and 20.40 g/ind, and the corresponding fish resource, based on fish density and average weight, were 0.4096, 0.2907, 0.3919 and 0.5622 kg/m3. The horizontal distribution of fish density varied by season and the fish density below the dam was significantly higher than above the dam (F=12.67, P<0.05). Vertically, there were significant differences in fish density among the three water layers above the dam (F=7.02, P<0.05) and below the dam (F=19.99, P<0.05). Multiple comparison (LSD) indicated that fish density in the middle layer was significantly higher than that in the upper and lower layers (P<0.05), and fish density in all water layers was generally higher in summer than in other seasons. In subsequent studies, we suggest strengthening dynamic monitoring of fish resources in this section, and carefully considering the key factors affecting fish resources.