Master of Science (MS), Wright State University, 2014, Biological Sciences

The metabolic rate of an organism is influenced by mass, temperature, and diet. Climate change is anticipated to increase ambient temperatures of aquatic systems and decrease the quality of food available to algivorous fish. We conducted a lab experiment and a field study to quantify the influence that temperature and diet have on standard and field metabolic rate of cichlids from Lake Tanganyika. The lab experiment demonstrated the effects of increased temperature and decreased food quality on the relative growth rate (RGR) and standard metabolic rate of an algivorous cichlid, Tropheus duboisi. We found that in all temperature treatments fish fed a high quality diet had significantly higher RGR than fish fed a low quality diet and that fish at the highest temperature (32 °C) grew at half of the rate of fish at the lower temperatures (26 °C and 29 °C). Neither food quality nor temperature significantly affected the standard metabolic rate of the fish. I conclude that the effects of decreased food quality on RGR from climate change will be a more immediate stressor than increased temperature on metabolic rate. I also measured the field metabolic rates of seven species of African cichlids from three trophic levels. Both mass-specific metabolic rate and gut-fullness scaled positively with activity level. The algivores had the highest metabolic rates, which may be a result of their higher levels of activity and increased gut-fullness relative to other trophic levels.

Committee: Yvonne Vadeboncoeur Ph.D. (Advisor); Lynn Hartzler Ph.D. (Committee Member); Volker Bahn Ph.D. (Committee Member) Subjects: Biology

Doctor of Philosophy, The Ohio State University, 2013, Environment and Natural Resources

Use of plant-based ingredients (PBI) to feed farmed fish is limited because of anti-nutritional factors and limiting amino acids especially lysine (Lys) and methionine (Met) which are the first limiting indispensable amino acids (IDAA) in plant sources. As one of the strategies to increase the limited use of PBI, we hypothesized that “interchangeable imbalanced-balanced feeding strategy” of IDAA with limited and complementary diets would increase the utilization efficiency of limiting amino acids. This feeding strategy of nutrient intake may in fact be similar to the situation in nature, where animals acquire food from different sources containing complementary nutrients. Diverse food sources may satisfy the nutritional requirement of animals in nature. This study addressed the effect of dietary level of limiting IDAA in relation to alternative feed sources and feeding strategies in Atlantic salmon juveniles. Four sub-objectives were addressed to accept or reject the hypothesis of: the essentiality and interaction of dietary lysine and methionine supplements in Atlantic salmon alevins (Chapter 2); the effect of dietary methionine concentrations, and evaluation of feeding strategies alternating methionine delivery with imbalanced IDAA (insufficient or enriched in methionine) and complete IDAA diets (Chapter 3); investigation of the efficiency of methionine under an alternative feeding strategy for practical diet and to determine the maximum use of soybean meals in Atlantic salmon starter diet (Chapter 4); and examination of the effect of dietary methionine deficiency on the activity of digestive enzymes that are critical in early life stages of fish (Chapter 5). In chapter 2, fish alevins (160±4 mg) at the swim-up stage were randomly distributed into eighteen tanks at a density of 44 fish/tank (3 replicates) at 15°C in a semi-recirculation system. A casein-gelatin (CG) based, semi-purified diet was formulated (control) and four free amino acid (AA) diets that replac (open full item for complete abstract)

Committee: Konrad Dabrowski (Advisor) Subjects: Animals; Aquaculture