EFFECTS OF SALINITY ON AEROBIC METABOLISM AND DEVELOPMENT OF EGGS AND ALEVINS OF STEELHEAD TROUT (ONCORHYNCHUS-MYKISS) AND FALL CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA)

Metabolic rates, hatching success, alevin survival, time to hatch, and growth were measured for steelhead (Oncorhynchus mykiss) and fall chinook salmon (Oncorhynchus tshawytscha) embryos incubated in salinities of 0, 4. 8, and 12 parts per thousand (ppt) from the eyed stage. Metabolic rates of eyed steelhead trout eggs, and chinook salmon eggs and alevins were not significantly affected by the salinities tested. The metabolic rate of newly hatched steelhead trout alevins, however, was significantly lower in 8-ppt, and significantly higher in 12-ppt, than in 0- and 4-ppt salinities. Egg hatchability was high in all four salinities, but newly hatched alevins of both species showed decreased survival and were smaller in 12-ppt salinity. Salinity effects on alevin survival and size were greater for steelhead trout than for chinook salmon. The results suggest that 8-ppt salinity is the upper limit for the normal development of steelhead trout and chinook salmon eggs and alevins.