The Senegalese sole is a marine pleuronectiform that naturally occurs in Southern Europe and Mediterranean region where it is being produced in aquaculture, in particular in Portugal and Spain. The aim of this study was to assess the quality of hatchery-reared larvae in comparison with those reared in the wild, and determine to which extension wild growing larvae are also a¡ected by skeletal deformities. The main structures a¡ected included those forming the axial skeleton, the caudal ¢n complex and both anal and dorsal ¢ns, with the most prevalent anomalies a¡ecting caudal vertebrae and arches. Hatchery-reared ¢sh presented a higher incidence of deformities (79%) compared with the 19% observed in wild specimens. In wild postlarvae collected in Autumn no deformities were observed. This work clearly shows that wild Senegalese sole present less skeletal deformities than those hatchery-reared during larval stages, indicating a selective mortality of wild deformed ¢sh and/or an e¡ect of aquaculture-related rearing conditions in the development of skeletal deformities in sole.

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The composition and distribution of the benthic macroinvertebrate community in a lagoon fish-pond system in the Bay of Cadiz. Spain, were studied by taking monthly samples at 4 sites during 1991. A total of 29 macroinvertebrate species, representing 16 orders. were identified. Gastropods, amphipods and chironomid larvae dominated the macrofauna in term of numbers of individuals, while in biomass terms gastropods, bivalves and polychaetes were dominant. The diversity (H') and evenness (J') indices of this community were low, ranging from 0.58 to 1.85 and 0.30 to 0.75 respectively (natural log base). Monthly total invertebrate density showed considerable seasonal variation, with a main peak in winter. Taking the most abundant species only, the densities of Hydrobja minoricensis, H. ventrosa, Microdeutopus gryllotalpa and Chironomus salinarius were positively related, and the density of Nereis diversicolor negatively related, to the biomass of benthic macroalgae (Ulva lactuca and Cladophora sp.). The density of C. salinarius was also positively related to the silt content in the sediment. Mean annual production varied between 13.3 g m-' yr-' ash-free dry weight (50.7 g m-2 yrr' dry weight) and 27.3 g m-' yr-' AFDW (122.0 g m-'yr-' DW) depending on the sampling site, yielding production/biomass (P/B) ratios between 1.08 and 1.37 yr-l. The annual production estimate for the whole system was 19.5 g m-' yr-' AFDW (66.6 g yr-' DW).

The successful settlement of the African pea crab Afropinnotheres monodi in the Bay of Cadiz was analysed to get new insights into the evolution of pea crab parasite life history traits. The pea crab lives symbiotically and with high prevalence in the bivalves Cerastoderma glaucum and Mytilus galloprovincialis, and with low prevalence in Scrobicularia plana. A remarkable monopolisation of host (one crab/bivalve) occurred irrespective of host species and crab demographic categories (males, hard females, soft females), probably as an optimisation of resources in smallsize hosts. However, there was a clear asymmetry in host use by the different crab 2 categories. A 1:1 sex ratio was found in crabs harboured by C. glaucum and S. plana, with most of the female crabs being small and hard specimens, whereas crabs inhabiting M. galloprovincialis were primarily large reproductive females. Ovigerous females were found throughout the year in M. galloprovincialis and there was a strong correlation between female size and fecundity, suggesting that the females harboured by this host were the major contributors to the reproductive effort of the studied population. Conversely, most of the new crabs recruiting to the population were harboured by the remaining two host species. We hypothesise that such a generalist but asymmetrical usage of bivalve hosts by pea crabs may have clear benefits for species in geographical expansion as A. monodi, facilitating its dispersal to new locations and its successful settlement in sheltered systems, as the Bay of Cadiz.