Diel patterns of seagrass decapods depend on the sampling technique

Supervisor: Fernando Tuya (University of Las Palmas de Gran Canaria)
Diel patterns in the decapod community associated to seagrass meadows have been often reported. However, these patterns depend on some behavioural traits that might not affect all samplers the same way. The aim of this study was to compare the abundance, diversity and structure of seagrass-associated decapod assemblages between day and night and to address whether these patterns were consistent between three sampling techniques. The structural parameters of the meadow were recorded in order to assess the potential influence on the assemblage. Twenty taxa were identified, members of the family Hippolytidae being the dominant species of the assemblage. Processa edulis and Athanas nitescens were also important members of the night community. The three sampling techniques provided a different, but complementary, picture of the decapod assemblage. The hand-net preferentially sampled the foliar stratum, and this was reflected into marked diel patterns, in terms of increased total abundance, total biomass, species richness and variation in assemblage structure. Captures by this technique were strongly influenced by the structural architecture of the seagrass, due to the link between foliar stratum and captured organisms. The airlift pump sampled both the foliar and rhizome strata, only presenting diel differences in terms of total biomass, and showing no connection to the morphological variations of the seagrass habitat. Baited traps are a passive fishing gear, that depend on the activity of the target organisms and were thus unavoidably bound to behavioural diel patterns, but manifested no influence of the small-scale structural variability of the meadow. The first record of Cronius ruber in the Canary Islands was made.