Non-competitive coexistence between Mediterranean grey mullet: evidence from seasonal changes in food availability, niche breadth and trophic overlap

Authors

  • L. Cardona

    Corresponding author
    1. Department of Biology, IUSC, C/Fontanella 19, 08010 Barcelona, Spain
      Tel.: +34 93 412 54 55; fax: +34 93 318 45 66; email: lcardona@iusc.es
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Tel.: +34 93 412 54 55; fax: +34 93 318 45 66; email: lcardona@iusc.es

Abstract

Five grey mullet species in the Albufera des Grau lagoon (Balearic Islands, Western Mediterranean), reacted to the spring-summer reduction in the organic matter content of sediment by expanding their niche breadth, mainly due to higher algae consumption. However, trophic overlap did not change for most of the studied species pairs and when it did, overlap was higher in the warm than in the cold season. When all the assemblage was considered, niche overlap distribution was significantly skewed towards values higher than those predicted by null models, both in the warm and the cold season. These results are not consistent with the predictions from the niche theory, which suggests that grey mullet are under carrying capacity and hence competitive exclusion does not operate in the studied assemblage.

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