Yellow perch (Perca Flavescens) play a crucial role as both a food source and an ecologically significant species in the Midwest region of the United States. Despite their importance in aquaculture, cost-effective feed for yellow perch remains elusive. A common issue observed in yellow perch fed commercial feeds is the development of fatty liver and excessive visceral lipid accumulation. Addressing this challenge requires a comprehensive understanding of their nutrient requirements. The primary objective of this study was to determine the optimal carbohydrate-to-lipid (L/C) ratio in fish feed and assess its impact on growth performance, health, and stress tolerance in yellow perch.
Yellow perch (initial body weight, 8.9 ± 0.27g, n=21) were subjected to five lab test diets, all containing 50% protein, with varying lipid (11 to 19%) and carbohydrate (14-22%) levels to produce different L/C ratios (0.50, 0.65, 0.83, 1.06, and 1.36), and two commonly used commercial diets. A 12-week feeding trial was conducted within an indoor flow through aquaculture system (21-23°C) with three replicate tanks (20 fish per tank) for each treatment. The results revealed that fish fed a diet with a L/C ratio of 0.65 achieved the highest growth, significantly outperforming fish fed the test diet with a ratio of 1.36 and a commercial diet with a ratio of 0.80 (P<0.05). Although protein efficiency did not significantly differ among fish fed the five lab test diets, both the two commercial diets and the diet with a 0.65 ratio demonstrated better protein efficiency. Gender differences were observed in terms of morphology, with female fish showing a higher visceral fat index and hepatosomatic index than males. Conversely, males exhibited a higher gonadosomatic index than females. Additionally, males were found to be more sensitive to heat shock stress based on mortality compared to females across all dietary treatments. This preliminary study suggests that a diet with lipid and carbohydrate levels ranging from 11-15% and 18-22%, or a ratio of L/C at 0.65 is suitable for yellow perch under the current conditions. Diets with lipid content exceeding 16% may not be optimal for fish growth. Further validation of these findings will be conducted as the project progresses. The outcome of this study aims to offer a more comprehensive understanding of the nutritional requirements for yellow perch, benefiting aquaculture practices and ecological preservation.