Abundance of Spawning Pacific Salmon in Two Lake Superior Streams, 1981–1987

Abstract

We examined, by mark and recapture procedures, the abundance of Pacific salmon entering two Lake Superior tributaries to spawn between 1981 and 1987. In 1987, abundance of pink salmon in the Carp and Pancake rivers declined to 50 and 25%, respectively, of that observed in 1981. In contrast, abundance estimates and catch records indicated that coho and chinook salmon had increased since 1981. The construction of a lowhead barrier dam on the Carp River in 1983/84 allowed passage of coho and chinook but precluded passage by pink salmon. Construction of the barrier dam did not appear to be the major cause for changes in abundance of pink salmon. Most mature pink salmon (>50% of total abundance) entered the spawning streams during a 2-week period following either onshore wind or a heavy rainfall. We submit that it is premature to suggest a lake-wide decline in pink salmon abundance.