Date of Award

August 2024

Degree Type

Thesis

Degree Name

Master of Science

Department

Freshwater Sciences and Technology

First Advisor

Dong-Fang DFD Deng

Committee Members

Ryan RN Newton, Chi CC Chen

Keywords

Aquaculture, Carbohydrate, Growth, Lipid, Stress, Yellow perch

Abstract

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. However, while wild populations of this fish have declined significantly in recent years, demand for this popular fish has remained high, necessitating their production through aquaculture. Despite their importance in aquaculture, cost-effective feed for yellow perch remains elusive. A common issue observed in yellow perch fed commercial feeds is suboptimal growth, the development of fatty liver and excessive visceral lipid accumulation due to feeding with current commercial feed designed for other species of fish. Addressing this challenge requires a comprehensive understanding of their nutrient requirements. The primary objective of this study was to determine the optimal lipid – starch (L/S) 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 ± 0.3g, n=21) were subjected to five lab test diets, all containing 46 % protein, with varying lipid (11 – 19%) and starch (14 – 22%) levels to produce different L/S ratios (0.5, 0.65 0.83, 1.06, 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 tank-1) for each treatment. The results revealed that fish fed a diet with a L/S ratio of L13/S20, or a ratio of 0.65, achieved the highest growth performance out of the five L/S test diets, based on weight gain (%). Lipid efficiency ratio significantly differed, as the L11/S22 and L13/S20 test diets demonstrated better lipid efficiency than the L17/S16 and L19/S14 diets. Significant differences (P < 0.05) in morphology were observed between males and females, with males having a significantly higher gonadosomatic index and females having a significantly higher visceral fat index. Conversely, no differences in morphology were observed between treatments. Differences in proximate composition were found, with moisture (%), ash (%), and lipid (%) significantly differing (P < 0.05) between treatments while there was no difference in protein (%). While an increase in dietary lipid inclusion correlated with an increase in whole body lipid content (%), this did not result in differences in visceral fat index or liver glycogen levels between any test diets. Lipid retention differences were also observed among treatments, with the L13/S20 diet having a significantly higher lipid retention than all other test diets. Comparisons of the best performing L/S test diet (L13/S20) and the commercial diets found that while growth performance metrics were similar, both commercial diets had significantly higher hepatosomatic indexes than the L/S test diet. Additionally, females were found to be significantly more tolerant to acute heat shock stress than males across all dietary treatments, based on mortality. This preliminary study suggests that a diet with lipid and starch levels ranging from 11 – 15% and 18 – 22% respectively, or a ratio of L/S near 0.65 is suitable for yellow perch cultured under the current conditions. Diets with lipid content exceeding 16% may not be optimal for fish growth. The outcome of this study offers a more comprehensive understanding of the nutritional requirements for yellow perch, benefiting aquaculture industry practices and ecological preservation of this culturally-valued fish. A longer-term feeding trial and practical feed formulation based on the current results are needed to validate these findings.

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