Results of rotary auger trap sampling in the Nanaimo River, 1999 / by D.A. Nagtegaal and E.W. Carter.: Fs97-4/2502E-PDF

"In 1999, a study of juvenile chinook salmon (Oncorhynchus tshawytscha) productivity was conducted by Fisheries and Oceans Canada, Pacific Biological Station together with the Nanaimo First Nations. The three key elements of this yearly project are: i) enumeration of juvenile out-migrants, ii) monitoring growth of hatchery and naturally-reared fry, iii) monitoring hatchery releases and interaction between hatchery and naturally-reared fry in the river. A rotary screw trap was used to estimate fry production. Bismarck Brown dyed naturally-reared fry were released above the trap site and recapture results of these marked fry were used to expand trap catches to estimate total production. The minimum estimate of production of naturally-reared juvenile chinook for the 1998 brood year was 25,424 (95%CL: 22,822 - 27,966). Minimal recapture data were obtained from hatchery fry. A total of 1,691 hatchery fry were recovered from three hatchery fry releases which occurred (May 9, 12 and 13) while the project was active. It was assumed that these hatchery fry emigrated out of the river shortly after release and those that remained in the river for a period of time did not migrate down to the trap site prior to the end of the project. The other hatchery release (May 28) occurred after the project completion. It is believed therefore that hatchery and naturally-reared fly interaction is minimal. Based on hatchery records, releases of chinook fry and smolts in 1999 totalled 608,425"--Abstract, page v.

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