鲢幼鱼对氨氮胁迫的行为响应特征研究

Behavioral Response of Juvenile Silver Carp to Ammonia Nitrogen Stress

为了深入揭示城市水体中氨氮胁迫对鱼类生存和栖息地的影响,有必要针对特定鱼类对氨氮胁迫的行为响应进行探究。选择对氨氮较为敏感的重要经济鱼类鲢作为目标物种,通过氨氮急性毒性预实验确定氨氮浓度范围,设计“静水多室”实验装置,开展鲢幼鱼对氨氮胁迫的行为响应实验。鲢幼鱼体长(5±1)cm;实验条件为水温(25±1)℃,pH 7.9±0.1,溶解氧>9.0 mg/L,电导率约400μS/cm。结果表明,鲢幼鱼对氨氮的96 h半致死浓度为16.8 mg/L。鲢幼鱼行为响应实验中,氨氮浓度为0、0.5、1.0、5.0、10.0、20.0 mg/L单元中的鲢幼鱼平均分布率分别为44.4%、13.9%、4.9%、13.2%、13.2%和10.4%,相应的鲢幼鱼平均回避率分别为-58.0%、-48.1%、68.9%、20.8%、33.3%和37.5%。鲢幼鱼对氨氮胁迫的回避阈值小于1.0 mg/L(相对应的非离子氨浓度小于0.05 mg/L)。当氨氮浓度超过1.0 mg/L后,鲢幼鱼回避率呈现先下降再上升的变化趋势。鲢幼鱼能够探测到水体中的氨氮产生回避行为响应,其表现类型为“低浓度吸引、高浓度回避”。此外,氨氮浓度过高会导致鲢幼鱼的应激反应能力降低。研究结果可为进一步探讨氨氮胁迫对鲢幼鱼生存活动的影响提供依据。

Silver carp,an important economic fish species that is sensitive to ammonia nitrogen was selected for study in this investigation.We studied the behavioral response of silver carp to ammonia nitrogen,aiming to better understand the effect of ammonia nitrogen toxicity on fish survival and habitat in urban waters.The concentration range of ammonia nitrogen for testing was determined based on the literature value of acute ammonia nitrogen toxicity.The 96-hour LC50 reported for silver carp[BL=(5±1)cm]is 16.8mg/L.Based on the result,six ammonia nitrogen concentrations(0,0.5,1.0,5.0,10.0,20.0 mg/L)were set for the test,and a"static multi-compartment"experimental device was designed for the behavioral response experiment,with a different ammonia nitrogen concentration in each compartment.The experimental conditions were as follows:water temperature(25±1)℃,pH(7.9±0.1),dissolved oxygen>9.0 mg/L,conductivity 400μS/cm.The fraction of test fish in each compartment was recorded and the avoid⁃ance rate was calculated.The average distribution of juvenile silver carp in the six compartments were,respectively,44.4%,13.9%,4.9%,13.2%,13.2%and 10.4%,and the corresponding average avoidance rates were,-58.0%,-48.1%,68.9%,20.8%,33.3%and 37.5%.The avoidance threshold of juvenile silver carp to ammonia nitrogen was estimated to be<1.0 mg/L,with a corresponding non-ionic ammonia con⁃centration<0.05mg/L.When the concentration of ammonia nitrogen exceeded 1.0 mg/L,the avoidance rate of juvenile silver carps decreased initially and then increased.Our study shows that juvenile silver carp detect and avoid ammonia nitrogen,and display a behavioral pattern of attraction at low concentration and avoidance at high concentration.The avoidance threshold is far less than the lethal concentration reported in the literature,so the avoidance response can effectively protect juvenile silver carps from ammonia nitrogen toxicity.However,at very high concentrations of ammonia nitrogen the behavioral response of juvenile silver carp is diminished and increases vulnerability toward ammonia-nitrogen toxicity.This study provide a basis for further research on the effect of ammonia nitrogen toxicity on the survival of juvenile silver carp.