Research Document - 1999/166

Assessment of Coho Stocks on the West Coast of Vancouver Island, 1998.

By S. Baillie, B. Patten, J. Till, K. Simpson, W. Luedke, and P. Tschaplinski

Abstract

This working paper summarizes the abundance, exploitation rates and marine survival of coho stocks originating from streams on the west coast of Vancouver Island in 1998. Also included is a summary of the coho fry survey work that was completed in 1998. Returning adult coho salmon ('escapement') were either enumerated at counting weirs (e.g. Carnation Creek) or estimated from visual counts.

The two wild indicators, Carnation and Kirby Creek, had coho adult escapements of 272 and 323 respectively. At the Stamp Falls Fishway 70,711 adult coho were counted. Of these, 36,658 returned to Robertson Hatchery and the rest (34,053) were considered as the 'wild' return. The increases over the brood year for Carnation Creek and Stamp Falls Fishway counts are 55% and 385% respectively. Visual surveys were conducted in 57 rivers and tributaries this year. The results indicate a 370% increase from the brood year. Most streams showed dramatic increases in coho escapement during 1998; likely due to severe fishing restrictions imposed in 1998 and the possibility that smolt outputs may have been better in 1997 as well.

The exploitation rate for Robertson and Conuma Hatchery stocks was 1.9% (excluding freshwater fishery) and 1.2% respectively. The cessation of directed coho fishing has resulted in these rates dropping from recent years (they reached 75.5% in 1993). The marine survival for Robertson and Conuma Hatchery, and Carnation Creek stocks was 3.6%, 0.27%, and 5.6% respectively. The marine survival remained relatively poor compared to long term means. The Robertson Hatchery survival rate continues to slowly increase since the low survival year of 1994. The survival rate of Carnation Creek, the wild indicator, continues to fluctuate without a trend in the 5% - 10% range. The Conuma Hatchery survival rate reached the lowest level since 1986, and was lower than the 1994 return of 0.28%.

In 1998, 19 new fry survey sites were added in areas that have been under-represented in past years. Coho fry densities are trending upward in Area 24 and south, and stable in Area 25 and north.

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