Huveneers, C. | bioRxiv Science

bioRxiv2021

Synergy of turbulence and fishing reduce aquatic biomass

A universal scaling relationship exists between organism abundance and body size1,2. Within ocean habitats this relationship deviates from that generally observed in terrestrial systems2-4, where marine macro-fauna display steeper size-abundance scaling than expected. This is indicative of a fundamental shift in food-web organization, yet a conclusive mechanism for this pattern has remained elusive. We demonstrate that while fishing has partially contributed to the reduced abundance of larger organisms, a larger effect comes from ocean turbulence: the energetic cost of movement within a turbulent environment induces additional biomass losses among the nekton. These results identify turbulence as a novel mechanism governing the marine size-abundance distribution, highlighting the complex interplay of biophysical forces that must be considered alongside anthropogenic impacts in processes governing marine ecosystems.

ecology↗

bioRxiv2017

A miniaturized threshold-triggered acceleration data-logger for recording burst movements of aquatic animals

Animal-borne accelerometers are effective tools for quantifying the kinematics of animal behaviors, such as swimming, running, and flying, under natural conditions. However, quantifying burst movements of small and agile aquatic animals (e.g., small teleost fish), such as during predatory behavior, or while fleeing, remains challenging. To capture the details of burst movements, accelerometers need to sample at a very high frequency, which will inevitably shorten the duration of the recording or increase the size of the device. To overcome this problem, we developed a high-frequency acceleration data-logger that can be triggered by a manually-defined acceleration threshold, thus allowing the selective measurement of animal burst movements. We conducted experiments under laboratory and field conditions to examine the performance of the logger. The laboratory experiment using red seabream (Pagrus major) showed that the new logger could measure the kinematics of their escape behaviors (i.e., body beat cycles and maximum acceleration values). The field experiment using free-swimming yellowtail kingfish (Seriola lalandi) showed that the loggers trigger correctly (i.e., of the 18 burst movements, 17 were recorded by the loggers). We suggest that this new logger can be applied to measure the burst movements of various small and agile animals, whose movements may be otherwise difficult to measure.

animal behavior and cognition↗