Abstract
Ocean thermal energy conversion (OTEC) facilities will bring large volumes of deep, cold water to the surface, where it will be mixed with warm surface water after the utilization of the thermal differential. Mixing of these two water types will result in exposure of larval and juvenile fishes entrained in the warm water intake to lowered temperatures. A time course of cold shock from simulated entrainment was used to determine potential effects upon egg and larval mahimahi, Coryphaena hippurus, manini, Acanthurus triostegus, and juvenile striped mullet, Mugil cephalus. Experiments were designed to test varying exposure times and temperature changes upon different early life stages of tropical fishes.
Earlier stage eggs were more sensitive to temperature shock, with mortality increasing with increasing delta T as compared to controls; exposure time, however, did not exert a significant effect. Significant excess mortality for all stages of eggs occurred at the range of times and temperatures used in the experiments, although in some cases these exceed values proposed in current OTEC engineering plans. For mahimahi larvae, excess mortality increased with age to values higher than for latest stage eggs, but we consider this to be caused by stress associated with yolk exhaustion. A single size range of juvenile mullet was exposed to the same experimental protocol as the eggs and larvae. Although exposure time was not significant, delta T had a significant effect upon mortality, and there was a significant interaction between exposure time and delta T.