Laboratory feeding experiments on zoea of northern shrimp Pandalus borealis fed with natural zooplankton

A series of experiments was carried out in spring 2001 and 2002 in order to investigate the effects of prey concentration, prey type and size, predator life stage, predator starvation, and temperature on predation rates of larvae of the northern shrimp Pandalus borealis reared in the laboratory. Stage IV shrimp larvae that were offered a natural zooplankton assemblage showed a significant trend of linearly increasing predation over the full range of 3 to 250 prey l(-1). This followed the Holling type I functional response model. Individual Stage IV shrimp larvae ingested up to 14 prey d(-1) at the highest initial prey concentration offered (250 prey l(-1)). Temperature effects were investigated with Stage 11 shrimp larvae as predators. The predation rate increased significantly, from 11 (at 3degreesC) to 21 (at 5degreesC) prey per predator d(-1), but stayed stable at 24 prey per predator d(-1) at 8degreesC. The majority of the prey eaten by the Stage II shrimp larvae were small (copepod nauplii; other invertebrate eggs and nauplii) while those eaten by the Stage IV larvae were larger (Calanus finmarchicus CI, CII, CIII and body parts of CIV, CV, CVI). However, Stage IV larvae also ate small prey (copepod eggs and nauplii, other invertebrate nauplii).