Researcher(s)
- Hunter Christensen, Marine Science, University of Delaware
Faculty Mentor(s)
- Aaron Carlisle, School of Marine Science and Policy, University of Delaware
Abstract
This study aims to describe specific dynamic action associated with different diets in Clearnose Skates (Raja eglanteria). Specific dynamic action (SDA) is the energetic cost of digesting food, and it varies based on factors such as the animal’s diet. We find SDA by comparing the animal’s routine metabolic rate (RMR) to their metabolic rate after eating a meal. To calculate metabolic rates of skates we use static respirometry. This consists of a sealed tank and an oxygen sensor which records oxygen concentration over time. We equate oxygen concentration over time to oxygen consumption, which can then be used to calculate metabolic rate. We tested three skates each under two different treatments. Skates were fasted for at least 96 hours to obtain oxygen consumption for RMR. They then were fed and oxygen consumption was recorded continuously for about 8 hours to capture SDA. The Clearnose skate is a relatively abundant mesopredator in the Delaware bay, and is generally understudied. Clearnose Skates feed on a variety of prey such as squid, crustaceans and small fish. These prey vary in their composition of macronutrients such as fat and protein. In this experiment we fed the skates both shrimp and sardines, and compared the increase in metabolic rate between the two prey items. As results are forthcoming, I hypothesize that the prey with a higher amount of protein will require more energy to digest. Finding SDA is important to describing an animal’s total energy budget. If we can find out how much energy Clearnose Skates need it will give us an idea of how much they need to eat and, thus, how much energy they drain from the Delaware bay. Additionally, by finding prey that minimize the cost of digestion we can assume which prey allow Clearnose Skates to feed most efficiently.