NON-AVOIDANCE OF HYDROCARBON LADEN SEDIMENTS BY JUVENILE FLATFISHES

Behavioural tests were used to determine whether juvenile flatfishes w ere capable of detecting and avoiding sediment containing various conc entrations of petroleum hydrocarbons. Three species of juvenile Alaska n flatfishes: rock sole (Pleuronectes bilineatus), yellowfin sole (P. asper), and Pacific halibut (Hippoglossus stenolepis) were tested in l aboratory chambers containing contaminated mud or sand offered in comb ination with clean mud, sand or granule. The flatfishes were able to d etect and avoid heavily oiled (2%) sediment, but they did not avoid lo wer concentrations of oiled sediment (0.05%). Oiled sediment was favou red over unoiled sediment if the unoiled sediment was of the grain siz e not preferred by that species. Oiled sand or mud was always preferre d over unoiled granule. The observed lack of avoidance at concentratio ns likely to occur in the environment may lead to long-term exposure t o contaminated sediment following a spill. Recruitment of juveniles ma y be affected if the exposure to oil is long enough to affect growth a nd survival.