A hierarchical sampling design, spanning five orders of magnitude (from 10s of metres to 100s of kilometres) was created in order to quantify the multi-scale spatial variability of visually censused ...rocky reef fish assemblages in the western Mediterranean Sea. Specifically, we tested the hypotheses that species abundance and the biomass of reef fish populations is higher within than outside marine reserves, and that a north-to-south geographical gradient of these variables exists. We also explored the relationship between the fish assemblage and habitat structure, as an environmental factor likely to account for an important part of the observed variability. The mixed analyses of variance revealed that total abundance and biomass, species richness and abundance and biomass of several target species reached higher average values within marine reserves. Nevertheless, some non-protected localities (e.g. Aguilas) harboured richer and more abundant fish assemblages than some marine reserves. In addition, regional variation, attributable to differences in local carrying capacity and hydroclimatic conditions, are also shown across the studied area. Moreover, the studied assemblage is patchy at small and/or intermediate spatial scales, considering both assemblage descriptors (total abundance and biomass, species richness), and the abundance and biomass of fish species and spatial categories. Detected patterns were different depending on the species and assemblage variables analysed. Differences in habitat structure account for a significant proportion of total variability of the studied variables, and are likely to be responsible for a large part of the observed differences, especially at small-to-intermediate spatial scales. Other factors—spatial variability in larval distribution, settlement and/or post-settlement survival–are discussed in order to explain the observed differences. We concluded that causes of the observed patchiness of Mediterranean reef fish assemblages are probably multiple. Long-term, multi-scale spatial and temporal monitoring actions, as well as process-oriented manipulative experiments are urgently needed in order to ascertain the relative importance of each factor.
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 size-classes 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.
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 morhuaandMelanogrammus aeglefinus) dominated farm-associated assemblages and were present across a wide range of sizes, from juveniles to large adults. Estimated total farm-aggregated 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 asG. morhua, which are highly attracted to farms.
Particulate wastes drive benthic organic enrichment from cage fish farming. Differentiation between faeces and uneaten feed estimates at cage level are of great value to both economize the feeding ...process and reduce waste. This study estimates the particulate waste outflowing cages at different depths and orientations, and the wasted feed component by combining in situ measurements and modelling. Particulate matter flux (PMF) was greater vertically through the cage bottoms (60.89%), but lateral outflow was also substantial (39.11%). PMF occurs all around the cages, and the influence of the mainstream current was low. Wasted feed was greatly variable, reaching high values (about 50% of supplied feed. The self-application of feed wastage monitoring and estimates by fish farmers is recommended to improve sustainability.
•Particulate waste sampler was designed to study solid wastes exiting from fish cages.•Wasted feed fraction was measured combining in situ measurements and modelling.•Particulate wastes flow out all around the cages, and mainly through the bottom.•Wasted feed is not predictable and strongly depends on feeding practices.
Spatiotemporal patterns of distribution of sea bass, Dicentrarchus labrax, and sea bream, Sparus aurata, and their influence on artisanal fisheries are explored before and after an escape event that ...released 1.5 million fish into the wild off La Palma (Canary Islands). Data were collected by in situ visual census and first sale data as a proxy of artisanal fisheries landings. Permutational anova of escapee abundances in shallow coastal habitats revealed consistent spatial patterns that linked densities of these fish to distance from escape point, whereas temporal patterns were related to a higher biomass released during winter. A nearby marine protected area did not show different densities of escaped fish. Local artisanal fleet catches accurately reflected the massive escape event and offer the main contingency force to mitigate the potential negative effects of massive escape events over shallow coastal habitats.
We demonstrate that the anodization of copper in alkaline water/ethylene glycol media containing fluoride ions generates nanostructured copper oxide films. By modifying the anodization conditions ...(fluoride and OH– concentrations, applied voltage and anodization time), nanofibrillar Cu2O as well as highly rough nanofibrillar network or nanoporous mixed Cu2O/CuO films are obtained. Raman and X-ray Photoemission Spectroscopy (XPS) results indicate that in fluoride presence, Cu(I) oxide is obtained when anodization takes place applying low voltages at a relatively low OH– concentration. In comparison, the subsequent oxidation to obtain Cu(II) species (CuO and Cu(OH)2) is promoted by increasing the OH– contents. According to the present results, an oxidation reaction scheme is proposed in order to gain a deeper understanding in the preparation of controlled nanostructured copper oxide films.
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•Nanofibrillar Cu2O films are obtained in fluoride-containing media.•Oxidation to Cu(II) is promoted by OH– and the underlaid surface roughness.•Roughness and morphologic evolution from fibrillar to a noticeable porous surface•Porous and hydrated mixed copper oxide is obtained at high voltages.•Fluoride assisted dissolution compete with the oxide formation.
Fish escaping from net pens have always been considered a major source of socioeconomic and ecological issues entitling high economic loses for farmers. Local artisanal fisheries have proved the ...ability to mitigate escape events by recapturing escapees, but its effectiveness has always been questioned. However, the knowledge regarding the interaction of large scale escape events and local fisheries remains scant. The recapture dynamics of a massive escape of nearly 100 tones taking place in Western Mediterranean was analysed. The artisanal fishery showed efficient in recapturing escaped fish as 64.7% of the escaped biomass was recovered. The spatial distribution of escaped gilthead seabream along the shore was studied as well as the efficiency of the fishing fleet distinguishing between fishing gears. The recapture of escaped fish showed well correlated with the distance to the escape point. Moreover, a high recapture success (64.7%) was registered being fish traps (53.8%) more efficient in recovering escapees than nets (10.9%). Concluding, management implications and data-based measures to be implemented on further regulations of escape events are discussed.
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.
Gilthead sea bream (Sparus aurata L.) aquaculture has rapidly spread around the Mediterranean Sea. Fish escapes from sea cages are one of the major problems for the industry and also represent a ...threat to the marine environment. Fishery catches are also influenced by escape events, being mirrored in increased landings of cultured species. However, within the Mediterranean, studies shedding light on the incidence of escaped individuals in fisheries landings are scarce. Firstly, the present study describes a simple scale‐examination methodology to distinguish escaped from wild S. aurata landed by coastal fisheries. Secondarily, the incidence of escapees is assessed within landings of the species in the western Mediterranean. The scale readings revealed a monthly incidence of escapees between 11.2 and 20.8%, representing 6.8% of the total income derived from these landings. Moreover, morphological differences between wild fish captured near and far from fish farms point towards escape events as a source of potential genetic admixture between cultured and wild genotypes. Socio‐economic and ecological implications of escapees are discussed, and a set of management guidelines proposed, to prevent and/or mitigate the negative influences of escaped fish on the ecosystem and traditional users of the coast such as fisheries.
Aquaculture's struggle for space Sanchez-Jerez, P.; Karakassis, I.; Massa, F. ...
Aquaculture Environment Interactions,
01/2016, Volume:
8
Journal Article
Peer reviewed
Open access
Aquaculture is an increasingly important food-producing sector, providing protein for human consumption. However, marine aquaculture often struggles for space due to the crowded nature of human ...activities in many marine coastal areas, and because of limited attention from spatial planning managers. Here, we assess the need for coastal spatial planning, emphasising the establishment of suitable areas for the development of marine aquaculture, termed Allocated Zones for Aquaculture (AZAs), in which aquaculture has secured use and priority over other activities, and where potential adverse environmental impacts and negative interactions with other users are minimised or avoided. We review existing examples of marine aquaculture spatial development worldwide and discuss the proper use of site selection in relation to different legal and regulatory requirements. National or regional authorities in charge of coastal zone management should carry out spatial planning defining optimal sites for aquaculture to promote development of sustainable marine aquaculture and avoid conflict with other users, following a participatory approach and adhering to the principles of ecosystem-based management.
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