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A small escape incident of gilthead seabream Sparus aurata tagged with acoustic transmitters (N = 25) from a commercial farm located in a coastal bay of the eastern Adriatic Sea was simulated to enable evaluation of recapture strategies and escapee management. Over a 3 mo monitoring period, tagged individuals showed spatial distribution closely related to fish farms, where 76 and 68% of tagged fish were present at the farm during the second and third weeks post-release respectively. Upon initial release, escaped seabream had a small total home range (0.142 km2) that encompassed the farm site. Short-term residence differed among tagged fish. Few fish (28%) remained in the proximity of the fish farm for longer than 1 mo; most were likely angled or moved outside the acoustic array. Fish that moved elsewhere have the potential to cause substantial ecological and genetic impact, as they likely are able to quickly adapt to natural conditions. Considering the capture impact of the limited recreational fishery on this small-scale escape event, fish recapture by this type of fishery within 2 wk of escape could be feasible and is highly recommended.

A spatially explicit capture-recapture (SCR) model was applied to estimate simultaneously population parameters and individual activity (i.e. home range size) of O. vulgaris, based on experimental mark-recapture data in a human-altered Mediterranean coastal area. Seventy-two octopuses were captured, tagged with subcutaneous PIT-tags and released. Nineteen tagged individuals were recaptured (recapture rate: 26.4%) in the same area over the study period, which spanned over 6 months. Population sizes and densities decreased over the study period, from 337 octopuses (8 ind. ha−1) in September-October to 105 octopuses (2.5 ind. ha−1) in February-March. The highest recruitment probability was estimated to occur at the beginning of the study but it clearly decreased over time, while mortality probability during a fishing period slightly increased. Mean specific growth rate was 0.82 ± 0.11 day−1. Individual home range or activity area ranged from 2.8 ha to 7.3 ha (median home range radius: 121.8 m). Overall, these results suggest that human-altered coastal habitats, which are characterized by abundant shelters, abundant food and absence of predators, can act as settlement and growth areas for juveniles and adults of O. vulgaris. Furthermore, the methodologies applied in this study are recommended as innovative tools to improve management actions of coastal resources. [ABSTRACT FROM AUTHOR]

Sea trout face growth-mortality trade-offs when entering the sea to feed. Salmon lice epizootics resulting from aquaculture have shifted these trade-offs, as salmon lice might both increase mortality and reduce growth of sea trout. We studied mortality and behavioural adaptations of wild sea trout in a large-scale experiment with acoustic telemetry in an aquaculture intensive area that was fallowed (emptied of fish) synchronically biannually, creating large variations in salmon lice concentrations. We tagged 310 wild sea trout during 3 years, and gave half of the individuals a prophylaxis against further salmon lice infestation. There was no difference in survival among years or between treatments. In years of high infestation pressure, however, sea trout remained closer to the river outlet, used freshwater (FW) habitats for longer periods and returned earlier to the river than in the low infestation year. This indicates that sea trout adapt their migratory behaviour by actively choosing FW refuges from salmon lice to escape from immediate mortality risk. Nevertheless, simulations show that these adaptations can lead to lost growth opportunities. Reduced growth can increase long-term mortality of sea trout due to prolonged exposure to size-dependent predation risk, lead to lower fecundity and, ultimately, reduce the likelihood of sea migration. [ABSTRACT FROM AUTHOR]

Gilthead sea bream and European sea bass aquaculture is widely established in the Mediterranean and North-eastern Atlantic regions, and rearing is mainly in coastal net-pen facilities. The rapid growth of the fish farming industry increases the potential number of farmed fish in the wild. Escape-related issues are likely to increase unless escape-management policies are included into the aquaculture legislation in the near future. This review summarizes the potential direct interactions among escaped fish and nearby farmed fish stocks, wild conspecifics, and coastal fish populations, since these interactions could compromise sustainability in coastal areas. Socioeconomic implications are also addressed, given that escape events can also lead to economic losses for farmers and may alter local fishery landings. Fish markets and consumers might be also affected. This review compiles the current knowledge on the potential effects of escapees in coastal areas, and contributes to the existing risks analyses regarding sea bream and sea bass escapes. Eventually, the need to design management policies to prevent or minimize escape events and to mitigate further impacts, applicable to Mediterranean countries and of special interest in areas where these species are locally absent, is discussed in the context of sustainable fin-fish aquaculture. [ABSTRACT FROM AUTHOR]

The assessment of trace metal content in our fish diet is important due to the adverse effect on human health. Despite the increasing interest about the fish quality, little information is available for Southern Spain, a region characterized by high seafood intake. Nine species from the Bay of Cádiz with high commercial value were selected. Similar values were measured in the nine studied species for most of the elements, except for the macroelements Ca and S, and the microelements Fe, Mn and As, which showed significant differences among species. Metal Pollution Index (MPI) did not differ among species, and it was similar to those obtained for other Atlantic and Mediterranean locations. The values measured for the nine species were below the health limits provided by World, European and Spanish legislations, indicating that, in general terms, consumption of these species is safe in the study area. • Trace and major elements are measured in nine commercial fish species. • Similar values are obtained for most elements, except for Ca, S, Fe, Mn and As. • Metal Pollution Index does not differ among species. • Values are below the limits provided by World, European and Spanish legislations. • Consumption of these fish species is safe in the study area. [ABSTRACT FROM AUTHOR]

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The population of meagre ( Argyrosomus regius) has increased dramatically around the Western Mediterranean, accompanied by a higher seasonal incidence of the species in fishery landings. Presumably because of escapes, this new predator is gaining ground in marine habitats where it was normally not found. Given the lack of knowledge about the potential impact of this locally absent species on ecosystems and fishery resources, the objective of this study was to analyse the diet and predation behaviour of A. regius in order to evaluate its capability to adapt to a new environment as well as to identify its main prey. Stomach contents of 159 individuals were analysed and the identifiable prey items classified into major groups. Results showed that the diet of meagre was remarkably size-dependent. The commercially important decapod Melicertus kerathurus (Index of Relative Importance IRI: 798.53), and to a lesser extent other crustaceans, were preferred to smaller sizes, while larger individuals gradually shifted to a piscivorous diet, particularly to Platichthys flesus (77.99 IRI). The potential ecological effects on the prey species are discussed, and management measures preventing the establishment of new local populations are suggested in order to harmonize coastal zone management policies with a sustainable production of meagre. [ABSTRACT FROM AUTHOR]

The article presents a study which offers evidence of whether sea bass escapees are short- or long-lived and to assess the feeding habits of externally-tagged sea bass recaptured by local fishermen in the Mediterranean Sea. The application of the tagging method in which the fishermen were provided with the fish information is cited. It is inferred that the presence of particulate organic matters in the stomachs indicate the aggressive feeding behaviour of escaped sea bass.

The present study compares fin damages in gilthead seabream ( Sparus aurata) and European seabass ( Dicentrarchus labrax) according to their wild, escaped or farmed origins. In addition, the potential applicability of fin condition indices (Fin Erosion Index ' FEI' and Fin Splitting Index ' FSI') as identification tools is discussed. Farmed seabream fins evidenced more erosion and splitting ( FEI ± SD: 2.1 ± 0.3; FSI ± SD: 1.9 ± 0.6) than wild seabream fins ( FEI: 0.8 ± 0.6; FSI: 1.2 ± 0.9), a result of farming conditions in open-sea cages. Escaped seabream fin erosion was between that of farmed and wild seabream ( FEI: 1.6 ± 0.4), which could indicate that fins in farmed fish recover over time from farming abrasions once they are in the wild. However, the fins of escaped seabream seem to be weaker than those of the wild fish, and therefore might be more susceptible to suffer other types of erosion such as splitting or nipping ( FSI: 2.3 ± 0.7). No significant differences were found in seabass FEI according to their origins, although wild seabass presented significantly more split caudal fins ( FSI: 3.3 ± 2.8) than the farmed seabass ( FSI: 1.2 ± 1.1) and escapees ( FSI: 2.5 ± 1.6). Therefore, FEI for seabream could be used as tools not only to distinguish between wild and farmed fish, but also to identify recent escapees, improving further assessments on the contribution of seabream escapees in fishery landings. However, the healing potential of damaged fins must be considered for the proper identification of escapees. Use of fin condition indices from both species could be helpful for aquaculture management, to assess fish welfare in fish farms stocks, and improve the knowledge of handling, stock densities and open-sea cage environment conditions. [ABSTRACT FROM AUTHOR]