A Delaunay Triangle Network Based Model of Fish Shoaling Behavior for Water Quality Monitor

Abstract

Fish actively form shoals, which is a behavior highly sensitive to experimental changes in environmental conditions. Here we evaluated the potential for using the shoaling behavior of red crucian carp as an early-warning biosensor system for assessing water quality. To reliably characterize shoaling behavior, we propose a novel method for determining the size of the shoal based on a Delaunay triangle network. We examined the effect of group size (two to 10 fish) in the shoaling paradigm and evaluated whether measurements of shoaling behavior could be used to assess water quality using test fish exposed to chemicals. The test chemicals were sodium hydroxide (NaOH), hydrochloric acid (HCl) and glyphosate, which are commonly used in agriculture or industry. There was a significant effect of group size on the shoaling behavior of unexposed fish. Furthermore, NaOH (20 mg/L), HCl (20 mg/L) and glyphosate at three concentrations (0.1 mg/L, 0.05 mg/L and 0.025 mg /L) significantly decreased shoaling behavior relative to controls. The average alarm time in response to a change in water quality was about 21 min. We conclude that the shoaling behavior of red crucian carp is a useful tool for monitoring water quality.