Quantifying Diel Change in Metabolic Rate of the Clearnose Skate (Rostror eglanteria)

• Trinity Clifford, Marine Science, University of Delaware

• Aaron Carlisle, School of Marine Science and Policy, University of Delaware

The goal of this study was to measure the routine metabolic rate (RMR) for the Clearnose skate (Rostror eglanteria) throughout the diel cycle to understand when they are naturally most active, and determine if there is evidence of resting behavior. This evidence may lead to predictions about the circadian rhythms of this species (a cycle of behavior that shifts at predictable times within a 24 hour period in response to environmental fluctuations). The theory was that skates exhibit diurnal behavior (more active during the day) so the RMR would be higher during the day. The activity levels were tested using an intermittent flow respirometry system where the tank was sealed with a lid to prevent oxygen exchange between the air and water once the trial began. Oxygen consumption (dissolved oxygen percentage) levels were collected over a 1.5 hour period, then the system was flushed to prevent hypoxic conditions. Two flushes were conducted during the light hours (10am – 2pm) and two more flushes were completed during the dark hours (9:30pm – 1:30am). The average RMR for the day flushes was 183.5 kg/L/hour and the average RMR for the night flushes was 255 kg/L/hour. These numbers indicate that the skate was more active when exposed to darkness and less active in daylight. Thus, the skate exhibited nocturnal behavior which had not been seen in this species. Though this investigation needs a larger sample size, the skate’s activity levels are currently discrediting our initial theory.