中上层鱼类对过饱和总溶解气体的响应行为研究

China owns the most water conservancy and hydropower projects in the world. Total dissolved gas (TDG) supersaturation always generated along with the flood discharging, which threats the aquatic ecosystem downstream. That previous researches on the influence of TDG supersaturation to fish mainly focused on the lethal effect, such as fish’s gas bubble disease or tolerance characteristics. Few studies considered the response behavior of pelagic fish to supersaturated TDG. While it is a critically important link contributing to reveal the influence of supersaturated TDG to fish. In addition, researches in China before always chosen benthic fish as study object, and gave little attention on the pelagic fish. Nevertheless, pelagic fish is more susceptible to supersaturated TDG than the benthic. Fish’s response behavior to supersaturated TDG mainly includes: the variation of swimming performance in temporal range, the change of detection and avoidance characteristics in horizontal direction, and the fish’s ability of using compensation depth in vertical direction. Therefore, present study is carried out based on fish’s swimming performance, detection and avoidance characteristics, and fish’s ability of using compensation depth. Hypophthalmichthys molitrix and Aristichthys nobilis, two kind of pelagic fishes dwelling in the upper Yangtze River, are chosen as study objects to research the response behavior of pelagic fish to supersaturated TDG. Laboratory and field experiments are conducted in present research. These results provide important information that can be used in fish’s protection and contribute fundamental data for the establishment of water-related environmental standards.

中国建设了世界上最多的水利水电工程，其在运行的同时导致下游总溶解气体（TDG）过饱和，对河流水生生态产生严重影响。目前过饱和TDG对鱼类影响的研究主要集中在鱼类的气泡病和耐受性等致死效应上，对鱼类在过饱和TDG胁迫致死前的响应行为规律关注较少，然而这正是揭示过饱和TDG对鱼类影响的关键环节。此外，之前的研究多采用受过饱和TDG影响相对较小的底栖鱼类，而对更易受胁迫的中上层鱼类关注较少。过饱和TDG胁迫下鱼类在水体中相应的响应行为主要包括：时间上游动的变化、水平上感应与回避的变化、垂向上利用补偿水深的分布变化等。本项目以鱼类的游泳能力、感应回避能力、利用补偿水深能力为切入点，选择长江上游典型的中上层鱼类鲢鱼和鳙鱼为研究对象，利用室内实验和现场原位实验等手段，探究中上层鱼类对过饱和TDG的响应行为规律，研究成果可为鱼类保护措施的制定提供依据，并为有关水环境标准的制定提供建设性建议。

高坝泄水总溶解气体（TDG）过饱和严重威胁着鱼类生存，鱼类致死前的响应行为规律是揭示过饱和TDG对鱼类影响的关键环节。本项目以过饱和TDG环境中鱼类的游泳能力、感应回避能力、利用补偿水深能力为切入点，开展了鱼类对过饱和TDG的行为响应研究。结果表明：鲢鱼与鳙鱼在130%以上的高TDG饱和度水体中出现了明显的死亡，并伴随有眼球突出、鱼鳍出血与气泡等症状，不同TDG饱和度下鱼类的生存率存在显著差异，130%可认为是鱼类对过饱和TDG耐受性阈值；在7天的过饱和TDG非致死胁迫下鱼类临界游泳速度并未显著变化，而在130%以上的过饱和TDG致死胁迫下鲢鱼游泳能力显著降低，水温的变化也显著影响着过饱和TDG水体中鱼类的游泳能力；以大岗山水电站为例，其在泄洪期间引起的过饱和TDG最高达128.7%，显著降低了鱼类的临界游泳速度，在经历至少8h间歇期的115%以下低TDG过饱和恢复后，鱼类游泳能力最终能达到正常水平，表明高坝间歇泄洪可有效减缓鱼类游泳能力受到的过饱和TDG胁迫；当TDG饱和度在130%及以上时，鲢鱼对过饱和TDG的最终回避率达80%以上，而在较低饱和度的过饱和TDG水体中，鲢鱼的回避效应不明显；在145%TDG过饱和水柱中，鲢鱼能利用补偿水深有效回避过饱和TDG的影响，当TDG饱和为120%或130%时，鱼类不能有效利用利用补偿水深回避过饱和TDG。本项目的研究成果可为鱼类保护措施的制定提供依据，并为有关水环境标准的制定提供建设性建议。