Influence of Changes in Dissolved Oxygen Content on Fish Behavioral Trajectories During Water Eutrophication

Abstract

Fish is an important organism in the water and its living environment are a unified whole, interrelating and influencing each other. Changes in fish behavioral trajectories can directly reflect the deterioration degree of water. When the cyanobacteria in the water consume a lot of oxygen during reproduction, death and decomposition, which makes the dissolved oxygen content rapidly decrease, the fish swimming trajectory changes significantly and responds accordingly. In this paper, acoustic tag tracking technology was used to study the swimming ability of fish by simulating the eutrophication process in a simulating natural ecosystems tank and obtain its three-dimensional trajectory to determine the dissolved oxygen threshold when fish behavior changed. The variation regularity of fish behavioral trajectories was investigated with the change of dissolved oxygen content during water eutrophication. The experimental results showed that the individual behavioral response of adult carp was unobvious in the process of oligotropher to light eutropher, but at the state of middle and hyper eutropher was obvious. When the dissolved oxygen is 0.5 mg/L, adult carp began to breathe hard and float on the water surface. When the dissolved oxygen content dropped to 0.2 mg/L, adult carp began to die. During the process of dissolved oxygen content decreasing, the swimming trajectory of adult was convergent in space while they migrated from the bottom of water to surface in the direction of longitudinal water depth, and the swimming speed was slower and slower. Regression analysis was used to analyze the correlation between individual behavioral trajectories of adult carp and dissolved oxygen content. The results indicated that the swimming trajectory of water depth was highly negatively correlated with dissolved oxygen content. The swimming speed of adult carp and dissolved oxygen content had a strong negative correlation. The significant changes in the individual behavioral trajectories of adult carp indicated the environment of water has changed. It was suggested that dissolved oxygen content, which affected the changes of fish behavior, and individual behavioral trajectories of fish as a biological indicator were used to evaluate the water ecological restoration effect and ecological health status of water. It can more accurately reflect the current status of the aquatic ecosystem.

Ecology Health Evaluation System Based on Fish Movement Behavior Response

“…These water pollution incidents indicated that, under the conditions of limited monitoring, fish can reflect the actual pollution status of a water body more quickly and truly than environmental monitoring methods. Research on the fish movement behavior response during water quality change, particularly the toxicological behavior of fish [8], mechanism of fish movement behavior response under heavy metal stress [9], water quality evaluation factor model based on fish behavior characteristics [10], effects on fish behavior and death threshold of different pollutant concentrations [7], and others, have provided research basis for water quality monitoring systems based on fish behavior. Based on the fish movement behavior response, the potential impact on fish and the toxicity of water pollutants or toxic substances can be determined directly or indirectly.…”