This study analyses the temporal and spatial changes in abundance and distribution of the warm water species round sardinella (Sardinella aurita) in the western Mediterranean over the last decades in relation to sea water temperature. In the western Mediterranean basin , a significant positive relationship was found between round sardinella landings and temperature anomalies. Along a latitudinal gradient off the Mediterranean Iberian coast (1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004), a gradual increase in species abundance was observed from south to north, with a certain time lag going northwards, associated with the increase in sea water temperature. The abundance of round sardinella in the two warmest and southernmost areas was positively and significantly correlated with sea surface temperature registered during the start of gonad maturation the previous year. In addition, the positive relationship established between water temperature and abundance of round sardinella in the coldest and northernmost study area demonstrates that there is a temperature limit for the distribution of this species in the western Mediterranean. In addition, this study analyses round sardinella larvae distribution and abundance in the summers of 2003 and 2004, and conducts a comparison with the situation 20 years ago (summer 1983). Results show a marked increase in larval abundance during the last decades and the present appearance of larvae in the northernmost study areas, where they did not occur 20 years ago. This indicates the successful reproduction of round sardinella in the northern part of the Mediterranean, where the species has expanded, confirming its establishment in the area.

This study investigates the connections between climate fluctuations and sardine and anchovy production in the NW Mediterranean, taking the Western Mediterranean Oscillation index (WeMOi) as an indicator of climate variability. The basic working hypothesis is that sardine and anchovy productivity is influenced by the WeMOi, a proxy for the local environmental conditions such as sea surface temperature (SST) and river runoff. Sardine and anchovy landings in the Catalan Coast and landings per unit of effort (LPUE) were used as proxy for recruitment. The results demonstrated a clear link between climate fluctuations and sardine and anchovy production. Positive WeMOi values were significantly correlated with low SST, high river runoff and high LPUE, that is, with betterthan-average recruitment of sardine and anchovy. Conversely, negative WeMOi values were associated with high SST, low river runoff and low LPUE. During the negative WeMOi phases (such as that at the end of the analyzed period), environmental conditions are unfavourable for the overall biological productivity in the NW Mediterranean and would decrease the survival, growth, condition and reproduction of sardine and anchovy during their life cycle. Despite the evidences on the appropriateness of the NAOi as an indicator of the climate in Europe and its impact on some biological variables, we suggest that using a regional index, such as the WeMOi, can provide a more accurate representation of the environmental conditions affecting small pelagic fish production in the NW Mediterranean.

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Predicting the impact of climate change on marine ecosystems or how fish and other species are adapting to rising sea temperatures is still subject to much uncertainty, despite considerable progress in recent years. In this study we assess whether our understanding of the impact of sea warming on marine fish can be enhanced with an interdisciplinary approach that collates data from fisheries, fishermen and scientific research. By doing this, we aim to shed light on the major changes in the abundance and diversity of warm and cold water fish in recent decades in relation to sea warming. Location: This study was conducted in the north-western Mediterranean, where the impacts of global warming are particularly critical because range shifts are physically constrained. Methods: We collected and combined statistical data from fisheries, the traditional ecological knowledge of fishermen (TEK), reproductive data (histological gonad analyses and ichthyoplankton surveys) and extensive research into the relevant literature (including systematic catalogues and museum collections and their databases). Results: We have found that changes in the abundance of fish have followed a particular spatio-temporal sequence, with three different phases of colonization in the case of warm-water species (occasional occurrence, common presence and establishment), and three phases of regression (abundance reduction, range contraction and disappearance from the catch) in the case of cold-water species. Main conclusions: Overall, the results show that this multidisciplinary approach, combining qualitative and quantitative information from different sources, provides new insight into the observed changes in fish diversity and abundance in relation to climate changeThis study was financed by the Abertis Foundation (http://www.fundacioabertis.org/). In addition, J.L. benefited from a Ramon y Cajal Research contract from the Spanish Ministry of Economy and Competitiveness. A.S. was partially supported by the project MAR-CTM2010-1887

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The exploitation patterns of three target species (Merluccius merluccius, L. 1758, Mullus barbatus, L. 1758, Mullus surmuletus, L. 1758) of the western Mediterranean demersal fisheries were compared. The study was carried out in five ports along the Italian and Spanish coasts. These three species are fished simultaneously or sequentially by a number of gears, their use during the year being different depending on the area. The trawl catches dominated the landings, both in number and weight, but varied greatly during the year. The size ranges of specimens in the catches were in their major part different among the types of gear. Artisanal methods (gillnet and long line for M. merluccius, trammel net for Mullus spp.), used seasonally, contributed primarily to landings of larger, adult specimens, whereas trawl catches consisted mainly of smaller sized individuals, recently recruited to the fishery. In M. merluccius, individuals of less than 20 cm total length accounted for 80 to 95% of the annual catch in numbers, and between 15 and 60% of the catch in weight, depending on the port. This situation indicates a substantial over‐exploitation and a high risk of long‐term unsustainability in stock development and production.

Sabatés, A., Martín, P., and Raya, V. 2012. Changes in life-history traits in relation to climate change: bluefish (Pomatomus saltatrix) in the northwestern Mediterranean. – ICES Journal of Marine Science, 69: 1000–1009. This study shows the strong relationship between the increasing surface temperature in the NW Mediterranean and the expansion northwards of the bluefish distribution range with the species reproducing in the new distribution areas. Two shifts in temperature were detected: the first one in the early 1980s and the second around 1997. This last shift, explained by warmer springs (April–June), when the species migrates for spawning, led to the observed changes in bluefish. In the western Mediterranean basin, a significant increase in bluefish landings was observed by the mid nineties, whereas in the Catalan coast, the northern edge of the species distribution, a northward expansion was observed from 2000. At present, spawning takes place all along the Catalan coast (June to September), including the new distribution areas, being 21°C the threshold for the presence of larvae in the plankton. This temperature was not attained in June two decades ago. The highest concentrations of larvae were located near the mouth of the Ebro River and their distribution to the north did not extend beyond the thermal front. Bluefish has taken the advantage of the changing environmental conditions and is established in new northernmost distribution areas.