Feeding reduction and recovery in cunner Tautogolabrus adspersus following exposure to crude oil

Cunners, T. adsperus, from Portugal Cove, Newfoundland were acclimatized in flow through seawater tanks, under seasonally ambient conditions of photoperiod and temperature, over a period of 8 months. The fish were then weighed, measured, tagged and separated into 2 equal groups. During May-September (active feeding period) the experimental group was exposed to water soluble fractions of Hibernia P-15 crude oil with an initial concentration of 200 ug per litre and a further 50 ug per litre added at weekly intervals from week 3 to week 11. Records of consumed feed (freshly thawed capelin) were collected for both groups of fish by removing the uneaten food before each new feed. After 15 weeks no significant differences in feeding were observed between exposed and control groups. A significant reduction of feeding was observed by week 11 and was the signal for termination of oil exposure. This study showed that a concentration in the 150-250 ug per litre range for 4-5 weeks was required for the onset of feeding depression and that recovery could occur in as few as 2-3 weeks.