Thermal stratification drives movement of a coastal apex predator

Abstract

A characterization of the thermal ecology of fishes is needed to better understand changes in ecosystems and species distributions arising from global warming. The movement of wild animals during changing environmental conditions provides essential information to help predict the future thermal response of large marine predators. We used acoustic telemetry to monitor the vertical movement activity of the common dentex (Dentex dentex), a Mediterranean coastal predator, in relation to the oscillations of the seasonal thermocline during two summer periods in the Medes Islands marine reserve (NW Mediterranean Sea). During the summer stratification period, the common dentex presented a clear preference for the warm suprathermoclinal layer, and adjusted their vertical movements following the depth changes of the thermocline. The same preference was also observed during the night, when fish were less active. Due to this behaviour, we hypothesize that inter-annual thermal oscillations and the predicted lengthening of summer conditions will have a significant positive impact on the metabolic efficiency, activity levels, and population dynamics of this species, particularly in its northern limit of distribution. These changes in the dynamics of an ecosystem’s keystone predator might cascade down to lower trophic levels, potentially re-defining the coastal fish communities of the future.

Annual rhythms of temporal niche partitioning in the Sparidae family are correlated to different environmental variables

“…Counts of the common dentex ( D. dentex ) were significantly correlated to water temperature, salinity, and daily photoperiod with a clear peak in August. This observed pattern is also supported by recent telemetry studies in the NW Mediterranean Sea (at about 200 km north respect to the location of the OBSEA), which highlighted how this species has a clear preference for the suprathermoclinal warm water over the colder layer below the thermocline 38 . The common dentex is a predator occupying a high trophic level in coastal trophic niches, and mainly feeds on other coastal fishes and cephalopods 39–41 .…”

Response of small sharks to nonlinear internal waves

“…This enabled us to quantify shark distribution and behavior from hundreds of observations at temporal scales commensurate to NLIW variability. While shark (and other large nekton) spatial distribution and behavior can be measured by acoustic telemetry, and tagging studies have been used to measure top predator vertical movements in stratified waters (Eckert and Stewart ; Aspillaga et al ), tagging approaches have a number of limitations, including physical interference with the animals and the number of individuals that can be tagged. In order to generate data comparable to that obtained in this study, a very large number of individuals would need to be tagged to ensure a reasonable chance that those individuals were present at the time and location of NLIW.…”

Modelling the three‐dimensional space use of aquatic animals combining topography and Eulerian telemetry data

“…Data from an acoustic range test (detection probability measures at increasing distances from a receiver) were available for one location within the study site. The bathymetric raster map of the study area is from the Cartographic and Geologic Institute of Catalonia (http://www.icgc.cat; CC BY 4.0 license), fitted to a resolution of 10 × 10 m. More details about the data, the acoustic range test, and previous results on common dentex movements can be found in Aspillaga et al (, ) and Aspillaga ().…”

“…In addition, we applied and tested the performance of the method with real acoustic telemetry data from the common dentex and previous results on common dentex movements can be found in Aspillaga et al (2016Aspillaga et al ( , 2017 and Aspillaga (2017).…”