The role of phototaxis in the initial swim bladder inflation of larval yellow perch (Perca flavescens)

Abstract

The yellow perch (<em>Perca flavescens</em>) is a high priority species for aquaculture, with strong demand in the USA. Unfortunately, numerous developmental problems during larval rearing prevent its commercial viability. Failed swim bladder inflation (SBI) has been reported in the culture of numerous physoclistous fish species and is a prominent problem in the culture of yellow perch. Initial SBI occurs within a short period of ontogeny, and missing this opportunity results in permanent malformation of the organ. Lighting cues appear to play a role in triggering the response of rising to the surface to swallow the air required for initial SBI in several fishes including yellow perch. Larval yellow perch are photopositive, and this phototactic response seems to co-occur with the window of opportunity for SBI. Thus, we examined the role of phototactic behavior and low-intensity, moonlight-like illumination in initial SBI in yellow perch. Lights were positioned below and above the water surface in larval culture tanks to see if the presence of nighttime illumination impacted SBI success, and if the phototactic behavior of yellow perch helps them find the water surface when inflating at night. The results of this study reveal that even very low-intensity nighttime light reduces the proportion of yellow perch larvae to initially inflate regardless of the direction of the light source. Also, on treatment with no nighttime illumination, higher than expected SBI was observed, and the culture conditions that produced this success should be examined when focusing on improving SBI in the future. This research suggests that the photopositive response of yellow perch is not involved in SBI success, and lighting could play a role in hindering the process.