The Role of Phototaxis in the Initial Swim Bladder Inflation of Larval Yellow Perch (Perca Flavescens).

Abstract

The North Central Regional Aquaculture Center has designated the yellow perch (Perca flavescens) as a high priority species for culture. The demand for this species is high and it is estimated that the market could readily consume 50 to 100 million pounds per year. Tank culturing of yellow perch has several advantages over pond culture and this method has been growing in popularity, but is currently held back by problems in larval development. One of these problems, failed swim bladder inflation (SBI), is frequently reported in the literature as a bottleneck in the culture of many fishes. Unsuccessful SBI increases metabolic demands, inhibits prey capture, and increases a fish’s overall probability of death. Initial SBI can occur within a finite period during ontogeny, and missing this opportunity results in permanent malformation of the organ. Advances in this problem have been made, but the challenge of increasing SBI success remains. The literature suggests that light cues appear to trigger the response of rising to the surface to gulp air and initially inflate. The yellow perch is photopositive in the larval phase and this phototactic response correlates with the window of opportunity for SBI to occur. The goal of this research was to examine the role that phototactic behavior plays in initial SBI in yellow perch. The results of this study reveal that low-intensity nighttime light reduces the proportion of perch larvae to initially inflate. It seems that the photopositive response does not contribute to SBI success, and in fact it can significantly hinder the process when light sources exist below the water’s surface. This could potentially explain previous research where increased SBI is seen in tanks with less reflective internal surfaces, and suggests that nighttime lighting and below surface light should be reduced as much as possible to increase SBI success.