Co-occurrence of European sardine (Sardina pilchardus), anchovy (Engraulis encrasicolus) and sprat (Sprattus sprattus) larvae in southern North Sea habitats: Abundance, distribution and biochemical-based condition

Spawning populations of European sardines (Sardina pilchardus) and anchovies (Engraulis encrasicolus) have become re-established in the southern North Sea after a ~30-year absence and now co-occur with sprat (Sprattus sprattus). Consequently, little is known concerning potential interactions among these three species in this region. Based upon parallel cruises conducted in June/July 2005, we compared the larval abundance, size-distributions and biochemical-based condition of these species among 1) nearshore (Wadden Sea) areas and offshore (German Bight) areas that were 2) vertically mixed, 3) frontal zones, or 4) stratified waters. In general terms, larval condition (RNA:DNA) was relatively high at all stations. Although fronts clearly acted to concentrate larvae, larval condition was not necessarily higher. For example 9% of sardines captured at the tidal mixing front were categorised as starving, while no starving larvae were sampled in the stratified water masses. Habitats of sardine and sprat larvae were similar, whereas anchovies were primarily restricted to nearshore areas. This is the first study examining the potential role of near- and offshore habitats as nursery areas and the extent to which resource (habitat) partitioning exists among the larvae of sprat and newly established anchovy and sardine in the North Sea.