Published 09/07/2018
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Behavioral responses of juvenile golden grey mullet liza aurata to changes in coastal temperatures and consequences for benthic food resources

C.Lefrancois , D.Christine , S.Como , E.Maggi , F.Antognarelli

If few studies have explicitly investigated the effect of temperature on the feeding behavior of fish , even less has been done to understand how these behavioral changes influence the spatial or temporal distribution of resources in coastal areas. Very little is known about the effects of temperature on the feeding behavior of other fish inhabiting coastal systems. However, whether or not grazing has negative effects on the mean and the spatial variance of the algal biomass depends on the time-scale of measurement and the interplay between the rates of algal removal and algal growth.
Temperature is an important factor for fish. Yet, little is known about its effects on the feeding behavior of fish and the subsequent consequences of these behavioral changes on the spatial distribution of resources. We analyzed the differences in the feeding behavior of two sizes of juvenile Liza aurata at two water temperatures , using laboratory mesocosms. We also examined whether temperature-induced changes in feeding behavior of the smaller size of L. aurata would affect the spatial distribution of the microphytobenthos biomass, an important resource in coastal systems. Both the number of feeding events and the swimming velocity during feeding in juvenile L. aurata were higher at 20C than at 10C, independently of the fish size. The time spent feeding did not vary between 10C and 20C, while the distance covered during feeding was significantly smaller at 20C than at 10C. Grazing did not affect the mean MPB biomass, but did increase its spatial variance at the smaller scale at 20C. A high number of feeding events, a high swimming velocity during feeding and a small distance covered during feeding in 20C-acclimated L. aurata most likely represented an adaptation to an increase in metabolism, as well as to the need to reduce the energy costs of feeding at 20C. Results also indicated that changes in feeding behavior of the 20C-acclimated L. aurata were responsible for the increase in small-scale spatial variability in the MPB biomass. We suggested that the enhanced spatial patchiness due to grazing by fish at 20C might yield a local increase in the mean MPB biomass, probably increasing photosynthetic efficiency of cells and algal growth that counterbalance the negative effect of algal removal by fish, and resulting in the lack of an overall significant effect on the mean.
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