Ontogeny of light avoidance in juvenile lake sturgeon

Abstract

Hatchery-reared age 1+ and 4+ lake sturgeon (Acipenser fulvescens) were assayed to determine the effectiveness of coloured, strobing LED light guidance device (LGD) at achieving behavioural guidance for attraction or avoidance responses. Based on an initial y-maze dichotomous choice study in age 1+ fish during daytime, we selected green, blue, orange, and full-spectrum white light, all strobing at 1 Hz, for further testing. During nighttime light guidance trials, age 1+ sturgeon demonstrated the fastest entries and greatest proportion of entries to the cone of illumination in the experimental raceway when the LGD was producing blue light, and the lowest proportion of entries in response to orange light. Conversely, they also spent the greatest amounts of time under illumination during orange light trials. Blue light was associated with the greatest proportion and total numbers of complete passages through the illuminated zone, although passage rates through this area were observed during the unilluminated control trials. White light resulted in the least time spent in the illuminated zone, and the lowest rates of passage. Under the nighttime testing scenario, the age 4+ sturgeon, by contrast, demonstrated strong avoidance of blue light and white light. While their behaviour was negatively phototactic in general, orange light was the least repulsive. For the behavioural guidance of lake sturgeon moving at night, we recommend the use of blue light strobing at 1 Hz for the attraction of the 1+ age class and white light strobing at 1 Hz for their repulsion. For age 4+ fish, we recommend the use of blue light or white light strobing at 1 Hz for repulsion and caution that (a) light as a behavioural guidance tool appears most effective as a repulsive stimulus, and (b) further testing under both laboratory and field conditions are required.