Comparing growth and body condition of wild and hatchery M YY brook trout in streams and alpine lakes

Abstract

Biologists have theorized that stocking YY males (created via in-hatchery hormonal sex-reversal and selective breeding; hereafter MYY fish) could be used to eradicate unwanted non-native vertebrate populations, but little is known about the fitness of MYY individuals once released into the wild. We compared growth and body condition of stocked hatchery-reared MYY brook trout (Salvelinus fontinalis Mitchell) to wild conspecifics in two streams and two alpine lakes. Maximum age for wild fish was age 6 at one stream and age 4 or 5 at the remaining waters, whereas for hatchery MYY fish, maximum age was age 5 at one stream and age 4 at the remaining waters. Total length ranged from 103 to 359 mm for wild brook trout and 115 to 353 mm for hatchery MYY brook trout. Growth rates and body condition of stocked MYY brook trout did not differ from wild fish in the same waters. Given that the success of MYY eradication programs is primarily contingent upon MYY individuals having fitness characteristics similar to wild conspecifics, our results provide further evidence that the stocking of hatchery-reared MYY fish may be a viable tool for eradicating unwanted non-native fish populations.