ENVIRONMENTALLY-INDUCED SHORT-TERM VARIABILITY IN THE GROWTH-RATES OFLARVAL HERRING

The growth of herring Clupea harengus larvae within a patch tracked fo r approximately 20 d in the Orkney-Shetland area (north of Scotland) w as investigated using otolith microstructure and, in a supporting role , condition factor analyses. Daily otolith growth responded conservati vely to external factors, there being significant autocorrelation with in individual otolith increment sequences. Past growth history explain ed most of the variation of the data. Both otolith microstructure and condition factor analyses yielded consistent results, indicating that short term variations in growth rate were related to environmental fac tors such as wind-induced turbulence level, and changes in illuminatio n and prey concentration. A dome-shaped effect of wind-generated turbu lence on larval growth was detected, which indicated a maximum respons e at a wind speed of approximately 14.5 m s(-1), a value very close to the speeds predicted by theoretical studies to generate maximum inges tion rates of larval fish.