SPONTANEOUS SWIMMING ACTIVITY OF ATLANTIC COD GADUS-MORHUA EXPOSED TOGRADED HYPOXIA AT 3 TEMPERATURES

The spontaneous swimming activity of Atlantic cod Gadus morhua was inv estigated at graded levels of hypoxia at three temperatures (5, 10 and 15 degrees C) by using a computerized system monitoring animal activi ty. The fish were tested individually, and swimming distance was used as a measure of activity. No significant effect of temperature on swim ming distance in normoxic water was found. At all temperatures, activi ty level decreased with decreasing oxygen saturation. Swimming behavio ur at normoxia and 50% and 25% oxygen saturation is described. No appa rent avoidance of hypoxic water was found based on the distribution of swimming speeds and turning angles. The possible benefits of a decrea sed activity level in a hypoxic environment are discussed.