Award: OCE-1156145

This multi-institution research project was designed to achieve a goal that has eluded researchers for decades: measuring the metabolic rate of free-ranging marine predators. Achieving this goal is crucial to quantifying a speciesÆ impact on their ecosystem, estimating the effect of their removal on lower trophic levels, and producing reliable bioenergetics models to aid fisheries management. To achieve this, we must have an understanding of how animals behave in their natural environment and the ability to reconcile differences between field and lab based experiments. The recent development and miniaturisation of animal-borne accelerometers can give us insight into the cryptic lives of animals through their movement. These devices are similar to the accelerometers found in the more modern smart phones that can monitor your step count or the wrist-worn activity trackers able to detect and distinguish your activities. Using this technology, the Bimini Biological Field Station Foundation (BBFSF) has successfully collected fine-scale body movement data for free-swimming juvenile sharks: the lemon shark (Negaprion brevirostris) and the nurse shark (Ginglymostoma cirratum). The juvenile lemon shark is a more active species, spending its time swimming the mangrove-fringed shorelines of Bimini, Bahamas. The juvenile nurse shark is more sedentary, readily found resting under shallow cave-like ledges during the day. This body movement data constitutes the field portion of the project for these two species, which can later be coordinated with lab-measured metabolic rates to determine the energy expenditure of these animals in their natural surroundings. Accelerometers were securely attached to the first dorsal fin of the individuals (attachment time <3 minutes), and began logging data 24 hours post release, for five days. Once data recording ceased, individuals were located and recaptured for device removal. Logging acceleration data in the three axes of movement (surge, sway and heave) at a rate of 30Hz, we have 2,520 and 2,280 hours of data recorded for the lemon and nurse shark respectively. That equates to 272,160,000 and 246,240,000 data points for our two model species! Additionally, temperature and pressure were recorded each second. Early data analysis indicates that from the acceleration data we can successfully identify typical behaviours, such as steady swimming, burst/fright response and resting for both species, with potential for semi-automated identification of successful predation events for the lemon shark with the upcoming release of new software. This provides us with the first real insight into what these species are doing from one second to the next, allowing us to reconstruct activity patterns of these free-ranging sharks on a daily and seasonal basis. For example, our data indicates that the lemon shark on average was found to spend approximately 11% and 16% of its time resting during the wet (April-September) and dry (October-March) season respectively. These activity patterns can be modelled against environmental factors such as temperature, time of day and tidal cycles to see which factors influence behaviour. Higher temperatures can yield increased metabolic rates, with the rate of increase varying between species and over temperature ranges. As such, field data was divided into two seasons, wet and dry, during which lemon sharks experienced a temperature range of 25.8-37.8ºC and 17.6-30.1ºC respectively. Preliminary analysis suggests that temperature has a significant effect on activity during both seasons, with the highest activity intensity for each season recorded at the top end of the temperature range. Additionally, average movement was found to be significantly higher during the warmer wet season than the dry season. The temperature recordings from the tags support published findings from another lemon shark nursery, indicating that juveniles of this species occupy increasingly warmer wa...