MEPS 555:1-11 (2016)  -  DOI: https://doi.org/10.3354/meps11836

ABSTRACT: Zonation in marine fishes occurs along depth gradients in both temperate and tropical habitats, yet the importance of competition in causing these patterns has only been unequivocally demonstrated in temperate systems. Throughout Caribbean reefs, fairy basslets Gramma loreto and blackcap basslets G. melacara are segregated by depth with a narrow zone of overlap. Local populations of these planktivores are found under isolated reef ledges, where fairy basslets compete with conspecifics for access to prime feeding positions at the outer edges. I investigated the existence, mechanisms, and effects of interspecific competition on the local distribution and demography of basslets. I documented aggression and feeding rates of both species and conducted a reciprocal removal experiment comparing the response of each basslet in competitor-removal versus unmanipulated populations of both species. Positioning of both basslets under ledges was consistent with an overall size hierarchy, with larger fish progressively closer to the outer edges of ledges. Fairy basslets were more aggressive, yet competition had symmetrical effects on the juveniles of both species. Interference between species drove juveniles further back under ledges, where feeding and growth rates of individuals were reduced. Competition had no effect on the density of basslets during this 8 wk experiment. Aggression occurred between larger basslets, but with no consequential effects on any parameters measured. This study demonstrates symmetrical effects of interspecific competition on juvenile coral-reef fishes, a phenomenon that has rarely been documented previously.

KEY WORDS: Species interaction · Interference interaction · Distribution · Size hierarchy · Zonation · Basslets · Gramma loreto · Gramma melacara

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Cite this article as: Kindinger TL (2016) Symmetrical effects of interspecific competition on congeneric coral-reef fishes. Mar Ecol Prog Ser 555:1-11. https://doi.org/10.3354/meps11836 Export citation Share:    Facebook - - linkedIn