Climate modulation of fish populations: the role of the Western Mediterranean Oscillation (WeMO) in sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) production in the north-western Mediterranean

Abstract

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.

Long-term (1998 vs. 2010) large-scale comparison of soft-bottom benthic macrofauna composition in the Gulf of Lions, NW Mediterranean Sea

“…In 1989, Conte et al (1989) years of time-series (Martín et al, 2012); on the other hand, no correlation was observed between landing of Sepia officialis and WeMO over 45 years of time-series (Keller et al, 2014).…”

Seabirds and climate: knowledge, pitfalls, and opportunities

“…In addition, time lags in climate indexes relative to survival and population change, for example, appear reasonable when climate effects on adult survival are mediated by the food-web, because seabirds are top-predators, and some delay between climate, physical forcing and a large part of the food chain is to be expected (Thompson and Ollason, 2001;Arnott and Ruxton, 2002;Lloret et al, 2004;Martín et al, 2012). Furthermore, this delay may depend on the species, with some taxa feeding on relatively low trophic levels (e.g., fish larvae), whereas some species feed on higher food web prey (e.g., squid).…”

Effects of climate change on Mediterranean marine ecosystems: the case of the Catalan Sea

“…This may be explained by the increase of planktonic productivity as a result of river inputs, and vertical mixing due to wind and low temperature, favouring spawning, feeding and survival of larvae. Recently, Martín et al (2011) indicated that the WeMO regional index could provide an accurate representation of the environmental conditions affecting small pelagic fish production in the Catalan Sea. In this area, the abundance of these 2 species has fluctuated in synchrony over the last 30 yr.…”