Two Devices to Assess Incubation Survival and Emergence of Salmonid Fry in an Estuary Streambed

Survival of eggs of chum salmon Oncorhynchus keta was determined at Carnation Creek, British Columbia, with two devices that were designed to help assess factors influencing incubation and to cause minimum disturbance of natural stream gravels. Three variations of the incubation technique were assessed with perforated plastic cylinders (incubation capsules). Survival rates of 0–47% were obtained when (1) water exchange through the capsules was adequate, (2) egg density was limited to 30 eggs/capsule, (3) eggs were distributed throughout the capsules, and (4) eggs were planted within 1 h of fertilization. Variation in survival was partially attributed to differences among stations in salinity, substrate composition, and dissolved oxygen concentrations. The technique was simple and inexpensive, so many replicates could be used. A capped and inverted plastic pipe (intragravel fry releaser) was developed to introduce alevins into the streambed. From 0 to 69% of them emerged. No differences in timing and pattern of emergence were observed between wild and experimental fry. Results compared favorably with other techniques that had been designed to assess instream survival of salmonid eggs, but those techniques required extensive gravel disturbance during installation.