Fish communities associated with FADs

Two groups of six fish aggregating devices (FADs) were deployed at two loca tions off the eastern coast of Majorca (Western Mediterranean). Samples wer e obtained fortnightly throughout a two-year period by means of hauls perfo rmed with an experimental purse seine. Two control areas were established t o check the aggregation efficiency of the FADs. A total of 16 families and 26 species of fishes were recorded beneath FADs. Pelagic fishes, largely Tr achurus picturatus, T. mediterraneus, T. trachurus, Naucrates ductor, Serio la dumerili and Coryphaena hippurus, dominated the fauna. The total fish ab undance, number of species and length range of the species confirmed that t he FAD community was significantly related to season (recruitment period), resulting in a sequential fish colonisation of the FADs during the study pe riod. Some of the species were present only during a particular period, suc h as Trachnrus spp. in spring and summer. Other species, although evident f or a longer period, were more occasional in catches (Schedophilus ovalis, B alistes carolinensis and Polyprion americanus), and some others were also p resent in small quantities. Diversity and equitability of the fish communit y associated with FADs were higher in summer than in winter. Many species w ere more abundant around FADs than in open water controls. The species that showed the most distinct recruitment phase beneath the FADs were N. ductor , S. ovalis, Trachurus spp., P. americanus, S. dumerili, C. hippurus and B. carolinensis. FADs can be considered nursery structures for many pelagic a nd demersal species, thus having an effect on the redistribution of juvenil es. In the deployment of artificial structures as aggregators for fishing p urposes one should consider the patchiness and seasonal characteristics of these communities as well as the redistribution aspect for fishery manageme nt.