Composition and temporal dynamics of a temperate rocky cryptobenthic fish assemblage

Temporal variation in a temperate cryptobenthic fish assemblage at the Arrabida Marine Park (Portugal) was assessed by visual Surveys during 2002 and 2003. A total of 9596 fish from 11 families and 30 species was recorded. There were no changes in structure or density at the assemblage level between years, whereas diversity changed significantly due to a higher number of abundant species in the second year. A similar seasonal trend was found between years, with a significant overall density increase in autumn. This is partially explained by the arrival of new recruits of some of the most abundant species in the assemblage. Assemblage diversity and structure also changed across seasons. A group of species encompassing Gobius xanthocephalus, Tripterygion delaisi, Parablennius pilicornis, Gobius paganellus, Lepadogaster candollii and Lepadogaster spp. were analysed in detail. The temporal patterns of two of the most abundant species, G. xanthocephalus and T delaisi, mimicked the overall temporal patterns of the assemblage. We suggest that the inter-annual stability in density of this subtidal fish assemblage may be similar to what has been reported for the intertidal and that strong post-settlement processes are probably shaping this assemblage.