Abstract
Otolith and somatic growth of herring (Clupea harengus L.) larvae were studied in laboratory experiments (500-litre tanks) in autumn 1995 and spring 1996. The larvae were kept at 8 °C and offered natural zooplankton at low (20–40 prey I-1) or high prey densities (1200–2000 prey I-1), and simulated seasonal photoperiods were used. Mean growth rates in length were higher in spring than in autumn both when offered low (0.12 mm d-1 v. 0.08 mm d-1) and high (0.35 v. 0.24 mm d-1) prey densities. Average weight-specific growth rates (G) were 1.7 % d-1 at low and 6.7 % d-1 in the high density groups. Autumn spawned larvae showed a dome-shaped growth pattern with a maximum in growth about 3–4 weeks post hatching, whereas spring spawned larvae grew at approximately constant rates during the same period. Daily mortality rates were less than 2.5 % in all groups. Otolith radii were not significantly different at similar lengths in autumn- and spring-spawned larvae.