Capelin larvae (Mallotus villosus) and community structure of zooplankton off the coast of northern Norway

Abstract

Capelin larvae (Mallotus villosus) and mesozooplankton were collected in May 2001 in the southern part of the Barents Sea. During the period of hatching and first feeding, capelin larvae experience high mortality rates. In order to understand the underlying mechanisms influencing larval survival, we monitored a selected site for 10 days using a variety of different sampling approaches. Hydrological parameters conductivity-temperature-depth-fluorescence (CTDF) were recorded and zooplankton samples obtained simultaneously using MOCNESS at three time periods. The mesozooplankton consisted essentially of copepods (85%), dominated by Calanus finmarchicus. The zooplankton community consisted of different assemblages derived from different areas (i.e. different water masses; Atlantic and coastal). Capelin larvae were found in surficial coastal waters. Copepod nauplii and C. finmarchicus were less abundant in coastal waters where small copepodites (such as Acartia spp. and Temora longicomis) were found together with early stages of coastal invertebrates that are possible prey for capelin larvae. We suggest that capelin larvae base their foraging on small prey organisms frequently found among the coastal zooplankton and that these larvae are less dependent on the propagation of the recruiting generation of C. finmarchicus present from April to June.