Date of Award

May 2020

Degree Type

Thesis

Degree Name

Master of Science

Department

Freshwater Sciences and Technology

First Advisor

Dong Fang Deng

Committee Members

Jerry Kaster, Ryan Newton

Keywords

Carbohydrate, Embryo, Nutrition, Perca flavescens, Salinity, Yellow Perch

Abstract

The development of effective culture techniques in the rearing of yellow perch (Perca flavescens) (Mitchill 1814) has multi-lateral benefits including enriching recreational resources, helping conservation efforts, as well as providing quality sea-food production. A myriad of challenges is yet to be remediated if yellow perch aquaculture is going to prosper. One of the challenges that hinders yellow perch aquaculture is the lacking supply of high-quality fingerlings. With current techniques employed by yellow perch hatcheries, the survival of yellow perch up to 30-day post hatch (DPH) age is typically less than 10%. Furthermore, larval culture has depended on imported dry feed developed for other species of fish, as well as live feed (artemia nauplii, rotifers, and even copepods), which may not be specific to yellow perch. Thus, it is critical to investigate new hatchery techniques and diets to increase larval survival during their early life stages. The overall goal of this research is to increase the yellow perch production efficiency by developing new culture techniques for yellow perch hatchery and fingerling production. Three experiments were completed in this study.

The objective of the first experiment was to determine the best feeding practices for the yellow perch. For this, yellow perch larvae were fed artemia which had undergone a decapsulation process, artemia which had not, as well as two formulated dry diets. These consisted of a popular commercial larval fish feed and a lab formulated larval feed. The live feed was fed in combination with dry feed as well. The diets were fed from 16 DPH to 30 DPH. The results showed that live feed performed better than the dry feeds in larval fish survival (p<0.05), but the decapsulated artemia had the best overall individual weight gain among live feeds. This suggests that, while non-decapsulated artemia can maintain larval perch survival, the larval perch may not be able to fully digest the unsoftened artemia, leading to less growth.

The objective of this next study was to assess whether 5-ppt saltwater had any effects on yellow perch embryos, as well as larval growth and survival, if used as an alternative to formalin for pathogen control. The conditions during embryo incubation were: Freshwater with formalin, 5-ppt saltwater with formalin, and 5-ppt saltwater without formalin. The embryos were photographed daily during development and measured for endogenous nutrition depletion from 0 days post spawn (DPS) to 7 DPS. The results showed a significantly higher endogenous nutrition diminishment among treatments with formalin than the 5-ppt saltwater without formalin (p<0.05). This implies that yellow perch incubated using formalin will have a lower endogenous nutrition reserve when they hatch as opposed to those that were not incubated using formalin. The second experiment also investigated the growth and survival of larval perch that were hatched after either being incubated in 5-ppt saltwater or freshwater and being reared in either a 5-ppt saltwater or freshwater environment. The feeding trial lasted for four weeks. The results of this study showed a significant increase (p<0.05) in growth and survival of fish in the 5-ppt saltwater environment, based on the measurement of body length and size of fish. This result implies it may be a potential approach to use 5-ppt salinity to increase larval production of yellow perch.

The third experiment determined if 5-ppt saltwater could enhance fingerlings previously grown solely in freshwater. Yellow perch fingerlings (192 DPH) were fed a high carbohydrate diet (25% wheat flour) containing 41% protein compared to a fishmeal-based diet containing 54% protein with no added carbohydrate. The feeding trial lasted for 8 weeks in a recirculating aquaculture system run with either freshwater or 5-ppt salinity water. The study showed no significant difference in growth between treatments reared at a 5-ppt low salinity and freshwater environment. The study did however find a significantly higher feed conversion ratio (FCR) in perch raised in saltwater as well as a higher hepatosomatic index (HSI). The protein efficiency ratio (PER) was higher in perch fed the wheat flour diet compared to those fed the fishmeal diet. These results conclude that more research into the optimal amount of carbohydrate inclusion in the yellow perch diet is needed, as well as the implementation of a low salinity environment.

Available for download on Thursday, October 21, 2021

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