Veštačka staništa kao potencijalne nove naseobine mlađi riba: efekat ribnjaka na ishranu i rast otolita

Cilj ovog rada je identifikacija razlika u sastavu populacije i brojnosti morskih riba koje žive u blizini kaveznih sistema u poređenju sa kontrolnim lokacijama. Njihova identifikacija je pokušana analizom oblika otolita

Seasonal patterns and diets of wild fish assemblages associated with Mediterranean coastal fish farms

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.The study forms part of the ACUFISH project (Unidad de Biología Marina, University of Alicante) and was funded by Spanish Ministry of Science grant MYCT-REN2003-00794

Coastal aquaculture and conservation can work together

Current fishing practices are regarded as unsustainable (Pauly et al. 2002), yet our appetite for seafood grows. To meet the growing gap, there are increasing calls for mankind to tame the oceans through aquaculture (Marra 2005). Close to the coast, rapid expansion of marine aquaculture is underway throughout the world. Sea cages enclose 2.5 million tons of fish, while 12 million tons of mussels, oysters and clams hang from floating ropes or grow on racks or trays (FAO 2004). Aquaculture structures are now ubiquitous to many coastlines. As the expansion continues, how can we best manage the interaction between natural communities and aquaculture

Potential retention effect at fish farms boosts zooplankton abundance

Coastal aquaculture activities influence wild macrofauna in natural environments due to the introduction of artificial structures, such as floating cages, that provide structural complexity in the pelagic system. This alters the abundance and distribution of the affected species and also their feeding behaviour and diet. Despite this, the effects of coastal aquaculture on zooplankton assemblages and the potential changes in their abundance and distribution remain largely unstudied. Traditional plankton sampling hauls between the farm mooring systems entail some practical difficulties. As an alternative, light traps were deployed at 2 farms in the SW Mediterranean during a whole warm season. Total zooplankton capture by traps at farms was higher than at control locations on every sampling night. It ranged from 3 to 10 times higher for the taxonomic groups: bivalvia, cladocera, cumacea, fish early-life-stages, gastropoda, polychaeta and tanaidacea; 10–20 times higher for amphipoda, chaetognatha, isopoda, mysidacea and ostracoda, and 22 times higher for copepoda and the crustacean juvenile stages zoea and megalopa. Permutational analysis showed significant differences for the most abundant zooplankton groups (copepoda, crustacean larvae, chaetognatha, cladocera, mysidacea and polychaeta). This marked incremental increase in zooplankton taxa at farms was consistent, irrespective of the changing environmental variables registered every night. Reasons for the greater abundance of zooplankton at farms are discussed, although results suggest a retention effect caused by cage structures rather than active attraction through physical or chemical cues

Guía de buenas prácticas para la gestión de escapes en acuicultura marina. Vol. I. Prevención

Los escapes en acuicultura son un problema que pueden evitarse con la formación del personal que trabaja en las instalaciones en mar abierto. Este libro proporciona los puntos más importantes que tener en cuenta para prevenir los escapes en acuicultura.Cofinanciado por el Fondo Europeo de Pesca y la Fundación Biodiversidad, del Ministerio de Agricultura, Alimentación y Medio Ambiente

Assessment of the impact of Atlantic bluefin tuna farming on Adriatic benthic habitats by analysing macroinvertebrate assemblage structure at family level

The rapidly expanding Atlantic bluefin tuna fattening industry is characterized by high stock densities and a high input food biomass in the form of whole bait seafood. The environmental impact of this activity must be effectively monitored within a proper sustainable development framework, to address concerns about the potential adverse effects. However, evaluation of monitoring tools for tuna farming has received less attention than other activities. Based on the principles of key taxa (Pocklington & Wells, 1992), we tested the potential use of changes in benthic macroinvertebrate assemblages, polychaetes and amphipods for this purpose. Applying a non-parametric multivariate approach for monitoring the impact of this aquaculture activity on the benthic habitat, we checked for correlations with the physicochemical environmental variables of the sediment. A hierarchical spatial design was followed, using multiple controls. Amphipods and polychaetes showed dissimilarities between impacted and control locations, with significant differences for total assemblage structure at a taxonomic level of families. Total nitrogen (TN) and total sulfur (TS) concentrations were the variables best associated with these changes for amphipods, and d 13C and total phosphorus (TP) were the best for polychaetes. However, total free sulfides (TFS) and TP were the chemical variables that best indicated the effects on sediment. Using this approach, surrogating the whole benthic assemblage to a single taxocene, our data suggest that monitoring tuna farming impact by comparing the changes in amphipod and polychaete assemblages at family level could be an optimal procedure with an excellent cost/benefit ratio.The study was funded by the Postdoctoral program of the Generalitat Valenciana for DFJ (APOSTD/2012/044)

Monitoring the influence of marine aquaculture on wild fish communities: benefits and limitations of fatty acid profiles

Fatty acids (FA) have been applied as indicators of the influence of coastal sea-cage fish farming on wild fish communities in several recent scientific publications. Due to the relatively high conservation of FA composition throughout the food web, they are useful for characterizing trophic relationships. The increasing utilization of vegetable or alternative animal oils in the production of aquafeeds results in cultivated fish exhibiting higher levels of terrestrial FAs in their tissues. As previously reported, wild fish ubiquitously aggregate around fish farms as a consequence of the introduction of new habitat and the easy availability of food—fish farms act as enhanced fish aggregation devices (FADs). The influence of food pellets on the composition of wild fish has been detected in recent studies on salmon, sea bass and sea bream aquaculture, with increased levels of linoleic acid (18:2n-6) and a low n-3/n-6 ratio as clear indicators of the consumption of food pellets from the farms. The potential ecological and physiological effects on wild fish are presently unknown. In the present article, guidelines are proposed for the investigation and use of terrestrial FAs to track the effects of coastal aquaculture on wild fish communities and local fisheries, as well as the benefits or limitations of this technique

Proxy Measures of Fitness Suggest Coastal Fish Farms Can Act as Population Sources and Not Ecological Traps for Wild Gadoid Fish

Background: Ecological traps form when artificial structures are added to natural habitats and induce mismatches between habitat preferences and fitness consequences. Their existence in terrestrial systems has been documented, yet little evidence suggests they occur in marine environments. Coastal fish farms are widespread artificial structures in coastal ecosystems and are highly attractive to wild fish. Methodology/Principal Findings: To investigate if coastal salmon farms act as ecological traps for wild Atlantic cod (Gadus morhua) and saithe (Pollachius virens), we compared proxy measures of fitness between farm-associated fish and control fish caught distant from farms in nine locations throughout coastal Norway, the largest coastal fish farming industry in the world. Farms modified wild fish diets in both quality and quantity, thereby providing farm-associated wild fish with a strong trophic subsidy. This translated to greater somatic (saithe: 1.06–1.12 times; cod: 1.06–1.11 times) and liver condition indices (saithe: 1.4–1.8 times; cod: 2.0–2.8 times) than control fish caught distant from farms. Parasite loads of farm-associated wild fish were modified from control fish, with increased external and decreased internal parasites, however the strong effect of the trophic subsidy overrode any effects of altered loads upon condition. Conclusions and Significance: Proxy measures of fitness provided no evidence that salmon farms function as ecological traps for wild fish. We suggest fish farms may act as population sources for wild fish, provided they are protected from fishing while resident at farms to allow their increased condition to manifest as greater reproductive output.Funding was provided by the Norwegian Research Council Havet og kysten program to the CoastACE project (no: 173384)

Comparison of diet and otolith growth of juvenile wild fish communities at fish farms and natural habitats

Juvenile fish of >20 different species use offshore floating sea cages as settlement habitats in the Mediterranean Sea. In the present work, surveys were conducted to identify differences between species composition and abundance of new settlers among farms and control rocky-shore environments and to test for variation in their diets. Along with this, otolith growth and morphology analyses were also applied to better understand the consequences for the ecology and growth performance of several fish species that use coastal farms as recruitment habitats in the southwestern Mediterranean Sea. Results showed that fish farms are acting as a new habitat for the settlement of juvenile fish and that detected abundance could be compared with that found at natural habitats such as shallow rocky environments. However, a consistent pattern for all the studied species was a significant variation in otolith-shape descriptors, principally identified through the Aspect Ratio index, which was lower for the farm-associated species Atherina boyeri, Oblada melanura, and Sarpa salpa. Otolith modifications were effectively detected by elliptic Fourier descriptors since multivariate analysis correctly identified farm or control origin at 78.8, 85.1, and 86.1% for A. boyeri, O. melanura, and S. salpa individuals, respectively. According to these results, fish farms may offer new settlement habitat for several fish species on open coastal areas and provide resources equivalent to rocky habitats, but at the same time causing some effect on fish growth as a potential consequence of the availability of particulate organic matter derived from feed pellets.The study forms part of the FATFISH project (Department of Marine Science and Applied Biology, University of Alicante) and was funded by the Ministry for Science (Project Reference CTM2009-14362-CO2-01/2)

Ecological relationship between wild fish populations and Mediterranean aquaculture in floating fish cages

Floating fish farms are associated, with important aggregations of wild fish around them. Several studies have shown that there is an important aggregation around all of the Mediterranean farms throughout. The most abundant families are clupeids, sparids, carangids, mugillids and pomatomids, although the dominant species varied markedly among farms and seasons. This important aggregation affects the behaviour and physiology of the local ichthyofauna, and may have important consequences for wild fish populations and local fisheries on a regional scale. Aggregated fish change diet, using aquafeed as main resource, which increases the biological condition but also affects the fatty acid composition, increasing vegetal fatty acids. Floating cages also aggregate post-larvae and juveniles of several pelagic and benthic species which find protection around the floating structures. Wild fish reduce environmental impact on the benthic communities by feeding on the lost food pellets. In addition, protection of this aggregation around Mediterranean fish farms can promote biomass exportation and enhance local fisheries. Therefore, the aggregation of wild fish around fish farms is an important aspect to take into account for coastal managers.CIES