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Biodiversitat i estructura de la comunitat íctica litoral del substrat rocós del Parc Natural de serra Gelada (sud-oest del mar Mediterrani) Aquest estudi analitza la comunitat íctica litoral sobre substrat rocós del Parc Natural de serra Gelada (Alacant) i s’aporten dades de base que permetran avaluar a llarg termini els canvis deguts a diverses mesures de gestió. Es van fer censos visuals en transsectes lineals sobre fons rocosos entre 1 i 32 m de profunditat. A les set localitats estudiades es van comptar 44 espècies. El nombre d’espècies, l’abundància, la biomassa i l’estructura de talles van ser similars entre les zones amb alta i baixa protecció. La composició d’espècies observada va ser similar a les d’altres àrees marines protegides del Mediterrani occidental. Les diferències entre localitats podrien ser causades per l’alta heterogeneïtat i complexitat de l’hàbitat a petita escala.

The effects of stocking density on fish welfare are complex and involve many interacting parameters. This complex relationship between fish welfare, stocking density and influencing factors make it challenging to define a specific optimal (“golden”) stocking density. Indeed, previously published recommendations on stocking density for different species of aquaculture interest are incredibly variable even at the same life stage, and can also vary widely within a rearing unit. Production density can be estimated quite accurately if the farmer has good biomass control and a known water volume, but it is difficult to set minimum and maximum stocking density levels that will protect welfare. However, there is little doubt that stocking densities that are too low or too high can have negative impacts on welfare and/or production. Here, we propose how to select density on captive fish and monitor its potential effects integrating 1) solid welfare assessment based on operational welfare indicators and 2) good management practices. Regulation directly limiting stocking density is likely to be unworkable and ineffective, and a more rational option might be to prescribe acceptable levels of different welfare indicators (e.g., water quality, health, nutritional condition and behavioral indicators), which together with a positive economic balance of the company, allow to estimate the most suitable range of fish density for each particular species, life-stage and production systems.

Current production systems of finfish aquaculture, and in particular intensive farming systems, can cause welfare problems leading not only to poor condition of the fish but also to a decrease in product quality. Adding structural environmental enrichment (EE) to bare rearing environments may improve the welfare of certain cultured fish. In this study we experimentally demonstrate the positive effects of adding structural EE on rearing environments of juvenile seabream (Sparus aurata). Fish maintained for 35 days with EE showed less aggression and interactions with the net pen, and lower erosion of pectoral and caudal fins, compared to fish kept in bare conditions (non-enriched, NE). In addition, EE modified the horizontal distribution of fish in the experimental cage, increasing the use of the inner areas. Non-significant effects of EE were observed on fish body condition and growth, and on brain monoamines levels and mortality. Nevertheless, this work highlights the potential use of structural EE to improve welfare of juvenile seabream, which might be feasible to apply at larger-commercial scale. Keywords: Structural complexity, Aggressiveness, Spatial use, Fish welfare, Aquaculture management

Abstract Trace elements in otoliths of sea bass (Dicentrarchus labrax L.) and sea bream (Sparus aurata L.) from fish farms and coastal wild populations in the western Mediterranean Sea were analysed by inductively coupled plasma-mass spectrometry. Results showed that concentrations of Mg, K, and Mn differed significantly between wild and farmed sea bass, while concentrations of Mg, K, Mn, Fe, Zn, Sr, and Ba varied significantly between wild and farmed sea bream. Discriminate analysis and cross-validation classification showed that the trace element profile in otoliths can be used to separate farmed fish from wild stocks with high accuracy on both sea bass (individuals correctly classified: 90.7 %) and sea bream (individuals correctly classified: 96.6 %). Moreover, trace elements in otoliths resulted to be useful to discriminate among wild fish stocks within each species.