The relative importance of biological and environmental factors on the trophodynamics of a pelagic marine predator, the blue shark (Prionace glauca)

The decrease in number of pelagic sharks could have substantial cascading effects on wider marine communities. Concerns about these potential impacts, and the critical need for effective management, have led to an increased interest in assessing the trophic ecology of sharks. While stable isotope analyses have been used to provide relevant insights about the trophic ecology of sharks, the causal factors leading to trophic variation between individuals has been largely overlooked. Here, we investigated the relative effect of biological factors, geographic location, and environmental factors on the spatial trophodynamics of the blue shark (Prionace glauca). Specifically, stable isotope values of δ15N and δ13C, and the estimated trophic position (TP) were analysed for 180 blue sharks collected from south of the Canary Islands, to the north-western Mediterranean Sea. The results showed that models which included combined variables explained the variation in δ15N, TP and δ13C values better than models which considered only stand-alone predictors. The independent contributions of environmental variables and biological factors seemed to be more important than geographic location for δ15N and TP. Among environmental variables, chlorophyll-a, pelagic productivity, and sea-surface temperature proved to be reliable predictors, particularly for δ15N and TP, most likely due to their relationship with productivity and prey availability.

VIDAL Alba;  CARDADOR Laura;  GARCIA-BARCELONA Salvador;  MACIAS David;  DRUON Jean-Noel;  COLL Marta;  NAVARRO Joan; 

2022-12-01

ELSEVIER SCI LTD

JRC131718

0141-1136 (online),   

https://www.sciencedirect.com/science/article/pii/S0141113622002537,    https://publications.jrc.ec.europa.eu/repository/handle/JRC131718,   

10.1016/j.marenvres.2022.105808 (online),