Effects of acute ammonia nitrogen stress on behavior of juvenile Cichlidae

【Objective】The purpose of the study was to analyze the effects of acute ammonia nitrogen stress on anxiety behavior，clustering behavior and phototaxis behavior of juvenile Cichlidae，so as to provide a reference basis for the healthy development of Cichlidae aquaculture industry and the behavioral research and scientific management of Cichlidae.【Method】Three different concentrations of ammonia nitrogen（0，5.00 and 12.25 mg/L NH₄Cl）were used to stress the juvenile Cichlidae，and their anxiety behavior（latency time，total number of horizontal midline crossings，and total time spent in the upper half），clustering behavior（delayed time taken to leave the school of fish crossing the vertical midline，number of transitions，and total time spent away from the school of fish），and phototaxis behavior（residence time of individual juveniles in different brightness areas and residence number of multiple juveniles in different brightness areas）were observed and analyzed in the water body with different ammonia nitrogen concentrations.【Result】The experimental results of anxiety behavior showed that，with the increase of ammonia nitrogen stress concentration，the latency time of the juvenile Cichlidae first crossing of the fishtank horizontal midline was greatly shortened，and the number of times of crossing the fishtank horizontal midline was significantly increased（P<0.05，the same below）. With the increase of ammonia nitrogen stress concentration，the time of transition from the fishtank lower half to the upper half and staying in the upper half was significantly longer. The juvenile Cichlidae exhibited anxious behavior in response to ammonia nitrogen stress，with impatience more pronounced in the 12.25 mg/L concentration group. The experimental results of clustering behavior showed that the time taken by the juvenile Cichlidae to leave the school of fish crossing the fishtank vertical midline was shortened with the increase of ammonia nitrogen stress concentration. Meanwhile，the number times of crossing the fishtank vertical midline increased significantly，and the time of transition from the fishtank lower half to the upper half and staying in the upper half was significantly longer. The juvenile Cichlidae exhibited straying behavior in response to ammonia nitrogen stress. The experimental results of phototaxis showed that the percentages of residence time of control group（CK，0 mg/L）of juvenile Cichlidae in the individual experiment were 90.16%，5.67% and 4.17% for selecting the fishtank dark area，transition area and light area respectively. The population experiment showed that the percentages of the number of juvenile Cichlidae in the CK selecting the dark area，transition area and light area were 83.00%，12.00% and 5.00% respectively. The phototaxis of juvenile Cichlidae did not change significantly（P>0.05）at the ammonia nitrogen stress concentrations of 5.00 and 12.25 mg/L in the water body，indicating that juvenile Cichlidae had obvious negative phototaxis behavior.【Conclusion】When the ammonia nitrogen stress concentrations in the water body are 5.00 and 12.25 mg/L，the juvenile Cichlidae show anxious behavior and straying behavior，and they show more anxious behavior when the ammonia nitrogen concentration is 12.25 mg/L. When the ammonia nitrogen concentrations in the water body are 5.00 and 12.25 mg/L，the negative phototaxis of the juvenile Cichlidae is not greatly affected. Therefore，it is recommended that the ammonia nitrogen concentration in the water body of juvenile Cichlidae in artificial rearing should not exceed 5.00 mg/L.