Aggregations of wild fish were counted around 9 floating sea-cage fish farms along a 300 km stretch of the Spanish coastline in the southwestern Mediterranean Sea. Each fish farm cultivated Sparus aurata and Dicentrarchus labrax in 6 to 16 floating sea cages between 10 m and 7.4 km from the coast. During September and October 2001, assemblages of fish were counted on 3 separate days at each of 9 farms. Six 5 min rapid visual counts using SCUBA and covering 11 250 m 3 were performed within each farm complex and at open water control sites 200 m distant from farms. Abundance (52 to 2837×), biomass (2.8 to 1126 ×) and number of species (1.6 to 14 ×) were greater in fish farm counts than control counts at all locations. Twenty-seven species were recorded at fish farms, with 2 families, Sparidae (12 species) and Carangidae (4 species), being particularly abundant. Over 85% of farm-associated fish were of adult size. Assemblages of wild fish differed greatly between farms separated by 10s to 100s of km, although there was some evidence to suggest that similar assemblages occur at farms separated by 100s of m to several km. Abundance, biomass and number of species differed among fish farms, with all 3 variables negatively correlated with distance of farms from shore and positively correlated with size of farms. Limited variability of wild fish assemblages and abundance of the dominant taxa at each farm among times sampled indicated some degree of temporal stability on a scale of several weeks. Due to the strong aggregative effect of fish farms, possible residence of fishes for periods of weeks to months and the prohibition of fishing within farm leasehold areas, we suggest that coastal sea-cage fish farms may act as small (up to 160 000 m 2), pelagic marine protected areas (MPAs). Furthermore, at farms where wild fish are abundant, ecological interactions that may influence both wild fish stocks and the impact of farms must be considered.

Abstract. Marine reserves are assumed to protect a wide range of species from deleterious effects stemming from exploitation. However, some species, due to their ecological characteristics, may not respond positively to protection. Very little is known about the effects of life history and ecological traits (e.g., mobility, growth, and habitat) on responses of fish species to marine reserves. Using 40 data sets from 12 European marine reserves, we show that there is significant variation in the response of different species of fish to protection and that this heterogeneity can be explained, in part, by differences in their traits. Densities of targeted sizeclasses of commercial species were greater in protected than unprotected areas. This effect of protection increased as the maximum body size of the targeted species increased, and it was greater for species that were not obligate schoolers. However, contrary to previous theoretical findings, even mobile species with wide home ranges benefited from protection: the effect of protection was at least as strong for mobile species as it was for sedentary ones. Noncommercial bycatch and unexploited species rarely responded to protection, and when they did (in the case of unexploited bentho-pelagic species), they exhibited the opposite response: their densities were lower inside reserves. The use of marine reserves for marine conservation and fisheries management implies that they should ensure protection for a wide range of species with different life-history and ecological traits. Our results suggest this is not the case, and instead that effects vary with economic value, body size, habitat, depth range, and schooling behavior.

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Coastal aquaculture is a globally expanding enterprise. Currently, 1200 salmon farms operate in coastal Norway, yet their capacity to aggregate and subsequently modify wild fish distributions is poorly known. Aggregations of wild fish at 9 farms and 9 control locations were counted on 3 separate days in June to August 2007. On each sampling occasion, 6 counts were made at 5 distinct depth-strata at each farm and control location. Wild fish were 1 to 3 orders of magnitude more abundant at farms than at control sites, depending on the location. Gadoid fish (Pollachius virens, Gadus morhua and Melanogrammus aeglefinus) dominated farm-associated assemblages and were present across a wide range of sizes, from juveniles to large adults. Estimated total farmaggregated wild fish biomass averaged 10.2 metric tonnes (t) per farm across the 9 farms (range: 600 kg to 41.6 t). Applied across the geographical range of Norway's 1200 salmon farms, our estimates indicate that salmon farms attract and aggregate over 12 000 t of wild fish into a total of just 750 ha of coastal waters on any given day in summer. Possible consequences of these persistent, substantial aggregations of wild fishes at farms include a heightened potential for the transfer of pathogens from salmon farms to wild fish and among adjacent salmon farms, and altered availability of wild fish to fisheries. Restrictions on fishing in the immediate surrounds of salmon farms may avoid farms acting as ecological traps, particularly for species with depressed populations such as G. morhua, which are highly attracted to farms.

In situ visual surveys using a hierarchical sampling design were carried out at 36 sublittoral rocky locations along the central-east Atlantic Canarian Archipelago to find relationships among (1) benthic primary producers, (2) the demographic structure of the herbivorous sea urchin Diadema antillarum Phillipi and (3) the trophic structure of coastal fish communities. Our correlation approach displayed a relationship between the lack of large macroinvertebrate-eating predatory fish and the increase in density of sea urchins, in addition to a decrease in fish richness. In contrast, increases in fast-growing plankton-feeding fish species were detected. The size structure of D. antillarum is dominated by small-to-intermediate sized sea urchins in environments with a high density of individuals, whereas low sea urchin density locations are characterized by the dominance of large sized individuals. The physical complexity of the substrate seems to play an important role in determining the local patchiness of D. antillarum. Finally, a non-linear decrease in the percentage of fleshy macroalgal cover with increasing density of D. antillarum was observed. We therefore propose D. antillarum as a key herbivorous species, which plays an important role in determining the structure of shallow, hard-substratum, infralittoral benthic communities throughout the Canary Islands. KEY WORDS: Urchin-fish interactions · Trophic cascades · Diadema antillarum · Sea urchins · Fish assemblages · Macroalgae · Canary Islands Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 278: [157][158][159][160][161][162][163][164][165][166][167][168][169] 2004 tourist industry and the increased demand of fishery resources (Bortone et al. 1991, Falcón et al. 1996. However, no empirical evidence of the effect of these disturbances is available, as there are no data on the nearshore fish populations during the predevelopment era of the 1960s (Falcón et al. 1996). Personal observations and several local studies have suggested that the long-spined sea urchin Diadema antillarum Philippi has experienced a significant increase in abundance throughout the central-east Atlantic (FAO fisheries region #34) in the last decades (Casañas et al. 1998, Alves et al. 2001, Tuya et al. 2004b. Although D. antillarum has been extensively studied in the western Atlantic, where it has a great impact on benthic community structure (e.g. Sammarco et al. 1974, Carpenter 1981, Lessios 1988, little research has been undertaken in the eastern Atlantic to link the demographic structure of this echinoid species with the abundance and biomass of rocky-reef fish assemblages in the Canarian Archipelago. Moreover, no study has addressed the above along with the coastal trophic cascades within this area (Pinnegar et al. 2000).The general aim of this study was therefore to determine whether there is an association between the structure of Diadema antillarum populations and the community structure of macroalgae and fish. This potenti...

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Fernandez-Jover, D., Sanchez-Jerez, P., Bayle-Sempere, J. T., Valle, C., and Dempster, T. 2008. Seasonal patterns and diets of wild fish assemblages associated with Mediterranean coastal fish farms. – ICES Journal of Marine Science, 65: 1153–1160. Fish are attracted to floating structures, including coastal cage fish farms, sometimes in dense aggregations. To understand better the influence of aquaculture on wild fish stocks, we carried out seasonal visual censuses around three southwestern Mediterranean farms over 2 years to assess the temporal patterns of the aggregated fish assemblage. In addition, we analysed the diet of the five most abundant species. Aggregations around all farms were large throughout the year, although species composition and abundance differed among farms and seasons. Fish farms are attractive habitats for certain species of wild fish in specific seasons. Adult fish of reproductive size dominated the assemblages, and stomach content analysis revealed that 66–89% of fish of the five most abundant taxa had consumed food pellets lost from the cages. We estimated that wild fish consume up to 10% of the pellets used at farms, indicating that food is a key attractant. Regional monitoring of farm-associated wild fish assemblages could aid management of the interaction of aquaculture and wild fish resources, because changes in feeding behaviour may have consequences for fish populations and local fisheries.