Phototaxis of larval bonytail

Authors: Wade Massure, Chase Ehlo, Brian R. Kesner, Paul C. Marsh

Year: 2012 (xliv)

Abstract

Bonytail Gila elegans is a federally listed endemic fish species of the Colorado River basin. Recruitment in nature is precluded by non-native fish predation on early life stages. Although light traps have been successfully used to capture bonytail larvae, phototaxis has never been experimentally tested. Six larval fish traps were constructed of 5 cm ABS crosses, trap adapters, caps, LED lights, and 500 Á¬m Nitex cones. Lighted and dark traps were tested simultaneously and separately in aquaria in 2 and 4 h trials. Mean proportions of larval captures in lighted only trials were 62 and 68% of available larvae for 2 and 4 h trials, respectively, and lighted traps tested simultaneously with dark traps captured mean proportions of 49 and 73% of available larvae for 2 and 4 h trials, respectively. Combined for all trials, dark traps captured a total of one larva. Results from our study support phototaxis in bonytail at swim-up stage.