Distribution and habitat use patterns of benthic decapod crustaceans in shallow waters: a comparative approach

摘要

Coastal areas are widely considered to be nurseries for many marine species. New approaches to this concept take into account interactions among environmental variables and ecological variation related to geographical location, as well as the complex life cycles of marine invertebrates. We present a comparative approach to assessing the association between environmental variables and patterns of distribution and the habitat use of benthic decapod species in coastal areas. Through this approach we infer which processes underlie these patterns and identify appropriate habitat-use models. An intensive fine-grain sampling design was used to account for environmental gradients occurring at different spatial scales (defined by substrate type, depth, exposure and geographical location) in a temperate oceanic bay (Ria de A Coruna, NW Spain). A high proportion of juveniles occurred in most populations, but our results did not allow us to generally designate coastal areas as nurseries, except for a few species, which showed marked spatial segregation between juveniles and adults. Coastal habitats are predominantly used as nurseries by juveniles of larger species, while, for smaller decapods, they seem to constitute habitats for the entire population. Larval transport may account for mesoscale distribution patterns, while microscale distribution may respond to the complex interaction among different processes, i.e. habitat selection at settlement, differential mortality among habitats, post-settlement dispersal and ontogenetic habitat shifts. Sandy substrates were characterised by low-diversity communities dominated by hermit crabs. In rocky bottom communities, variability in spatial patterns was mostly related to substrate type and geographical location. Caridean shrimps had higher densities on flat rock surfaces, with similar juvenile and adult patterns. Anomuran species occurred mainly on cobbles. Distribution patterns of brachyurans varied among species, but did not change greatly from juveniles to adults.