Failure of a Plant-and-Krill-Based Diet to Affect the Performance of Yellowstone Cutthroat Trout Broodfish

Abstract

We compared the performance of Yellowstone cutthroat trout Oncorhynchus clarki bouvieri broodfish when fed a diet with corn Zea mays gluten meal, wheat Triticum spp. gluten meal, and krill Euphausia superba protein sources relative to two fish meal diets. We hypothesized that the plant-and-krill-based diet would lead to a greater bioavailability of trace minerals and result in better broodfish condition, greater egg fertilization rates, increased survival of embryos to the swim-up stage, and increased egg mineral content. The three diets were fed to three replicate lots of 2-year-old, captive-reared fish for a 10-month period prior to spawning. None of the measured characteristics of broodfish condition differed significantly among diets. We found no significant differences among diets in rates of egg fertilization or survival of embryos to the swim-up stage. Manganese levels were lower in the eggs of fish fed one of the fish meal diets, but that was the only measure of egg content with a significant difference among diets. The experiment did not indicate that the plant-and-krill protein diet was better than fish-meal-based diets relative to the physiological condition of broodfish or the reproductive capabilities of Yellowstone cutthroat trout broodfish reared in captivity.