SURVIVAL OF LAKE TROUT EGGS ON REPUTED SPAWNING GROUNDS IN LAKE-HURONAND LAKE-SUPERIOR - IN-SITU INCUBATION, 1987-1988

Lake trout reproduce widely in Lake Superior but little in Lake Huron. We examined whether survival of lake trout eggs and fry in either lak e was reduced by physical disturbances and swim-up mortality. Eggs wer e collected from feral lake trout in Lake Superior and placed in 108 p lastic incubators. A total of 48 incubators was set at Partridge Islan d Reef in southern Lake Superior, 48 were set at Port Austin Reef in s outhern Lake Huron, and 12 were held as controls in flowing well water at a laboratory. Survival-to-hatching of these eggs at Partridge Isla nd Reef (18%) was significantly different from that at Port Austin Ree f (43%) and significantly different in the laboratory (88%) from that at either reef (P < 0.05). During egg-fry incubation from 28 October 1 987 to 5 May 1988, 11-18 cm of sediment accumulated in sediment traps placed on the reefs but < 1 cm of sediment was present on each reef in May 1988. Analysis showed that 44% of the eggs at Port Austin Reef an d 28% of those at Partridge Island Reef were buried and killed by sedi ments. During the first week after deployment, mean wave energy was 90 % higher at Partridge Island Reef and significantly different from tha t at Port Austin Reef. Wave energy may be a habitat condition that mak es Partridge Island Reef less suitable than Port Austin Reef for incub ation of lake trout eggs. Fry from eggs incubated at all three sites e xperienced no swim-up mortality. We conclude that in 1987-88 habitat c onditions required for survival of lake trout eggs were more suitable at Port Austin Reef than at Partridge Island Reef.