Early stages of Sardina pilchardus and environmental anomalies in the Northwestern Mediterranean

Abstract

The influence of environmental conditions on the spatial distribution patterns of the early stages of Sardina pilchardus off the Catalan coast (Northwestern Mediterranean) during November 1998, February 1999 and November 1999 was investigated. As a general rule, eggs were found on the continental shelf, while larvae displayed a wider cross-shelf distribution. The local circulation during autumn–winter 1998–1999 was dominated by an anticyclonic eddy of new Atlantic Water that remained stationary at the centre of the Catalan Sea from September 1998 to the end of February 1999. Such a situation is very infrequent and the influence of these waters extended to the continental shelf zone, modifying the slope current by diverting the flow and even reversing the direction of the flow. On the third cruise, carried out at the beginning of the spawning season of 1999 (November), the circulation and water mass distribution in the region was typical, with the old Atlantic Water occupying the whole region. Abundance of pilchard eggs and larvae during this last cruise was higher than in the previous surveys. In November 1998, the abundance of pilchard eggs and larvae was relatively low in the zones affected by the new Atlantic Water. The most interesting result of these surveys was the very low concentrations of eggs and larvae found in February 1999, possibly due to the anomalous situation created by the eddy, which had remained almost stationary during the 1998–1999 spawning season.