Effects of predation from juvenile herring (<i>Clupea harengus</i>) on mortality rates of capelin (<i>Mallotus villosus</i>) larvae

Predation has been suggested as a cause of substantial mortality of fish larvae to the degree that it might influence recruitment. This field-based study concludes that juvenile herring ( Clupea harengus ) as small pelagic predator can significantly affect mortality rates of the planktonic larvae of capelin ( Mallotus villosus ) in the Barents Sea. Surveys were carried out in the summers of 2001 and 2003. In 2001, juvenile herring were widely distributed and overlapped with capelin larvae over a wide area, whereas in 2003, the herring were more aggregated. The study focused on predation in the areas of predator–prey overlap. Capelin larvae were observed in the herring stomachs at 11 of 24 stations and at 8 of 16 stations where herring were caught in 2001 and 2003, respectively. At those stations, an estimated 7.3% and 9.9% of the capelin larvae were eaten by herring per day in 2001 and 2003, respectively. Statistical models revealed that density of capelin larvae and copepods and occurrence of euphausiids in the stomachs affected the number of capelin larvae per predator stomach. A simplified model with only capelin larvae density as predictor was converted to a functional response relationship using an experimentally derived digestion rate estimate for capelin larvae in herring stomachs.