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Trophic ecology of small pelagic fish in the northwestern Mediterranean / Ecología trófica de peces pelágicos pequeños en el Mediterráneo noroccidental
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[eng] In the northwestern Mediterranean anchovy and sardine are among the most ecologically and economically important species.
Both species are planktivorous during all their life stages, which could alledgedly lead to expect an overlap of trophic niches. However, trophic interactions between the two species had been, until now, poorly studied. This thesis aims to examine and compare the feeding behaviors of sardine and anchovy at different stages of their development, and during different seasons, in the Gulf of Lions.
In this work we have shown, through a detailed analysis of their diets and trophic dynamics, how these two species may interact with each other and with the environment, also considering the possibility of being affected by future climatic changes.
We explained that in the sardine, withan almost strictly carnivorous diet at the end of their larval stage and shortly after metamorphosis, the development of their gill rakers and pyloric caeca allow a change in the diet when sardines reach 4 cm standard length (SL), and at 7 cm SL, with these structures already fully developed, they are able to feed on phytoplankton with total effectiveness.
Juveniles of both species showed no interspecific trophiv competition, due to their marked differences in their gill rakers and pyloric caeca.
We also showed, with the analysis of stable isotopes, that there is dietary change along the development of sardine and anchovy, and that the analysis of stable isotopes (δ13C and δ15N) is essential to identify potential prey, such as appendicularians, whose contribution to the diet is often underestimated when stomach contents are directly analysed.
We assessed differences in the nutritional status of anchovy larvae found in summer and in December and estimated their growth rates. The nutritional condition of larvae in December was no different from the condition of larvae with the same size captured in summer. However, the higher daily growth rate of summer larvae suggests that sea temperature significantly influences the development of anchovy larvae.
This thesis showed that anchovy and sardine have adapted their abilities and ecological habits in the northwestern Mediterranean to avoid interspecific competition, not just by shuffling their reproductive periods but also adapting their trophic behavior.
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COSTALAGO MERUELO, David. Trophic ecology of small pelagic fish in the northwestern Mediterranean / Ecología trófica de peces pelágicos pequeños en el Mediterráneo noroccidental. [consulta: 13 de desembre de 2025]. [Disponible a: https://hdl.handle.net/2445/35328]