Seasonal fluctuations and dietary analysis of fouling caprellids (Crustacea: Amphipoda) from marinas of southern Spain

In marinas, native caprellids usually share their habitat with exotic species, and can eventually be replaced by them. The invasive Caprella scaura is spreading quickly and has successfully settled in many marinas of southern Spain, potentially threatening the native taxa. We selected two marinas (El Rompido, Huelva and La Linea, Cadiz) in which C. scaura has not yet been found, in order to explore the seasonal dynamic patterns of the resident species before the arrival of the non-native species. Sampling was carried out bimonthly from July 2010 to July 2011. Two caprellid species were recorded, Caprella dilatata and C. equilibra. In El Rompido, both caprellids were found on two substrates (the bryozoan Bugula neritina and the hydroid Ectopleura crocea), whereas in La Linea, B. neritina hosted only C. equilibra, and C. dilatata was absent. Caprella dilatata showed maximum densities in July, with a second peak of abundance in November, and was absent during the winter (January-March). Caprella equilibra showed differences in abundance patterns, body length and fecundity between the two marinas, probably due to differences in environmental measures between the marinas. The dominant component of the diet of the two species was detritus, followed by copepods, which were more abundant in specimens collected from E. crocea, suggesting the possibility of cleptocommensalist behaviour.