Evidence of Decreasing Spatial Diversity in British Columbia Salmon Stocks

Abstract

Escapement records indicate a severe decline since 1950 in the number of streams contributing significantly to salmon production in southern British Columbia. To account for 90% of the escapement for chinook (Oncorhynchus tshawytscha), coho (O. kisutch), pink (O. gorbuscha), and chum (O. keta), one need examine only about half as many streams now as in 1950. The deterioration has been most pronounced for coho; only 40 of 350 south coast streams now account for 80% of the recorded escapement. The apparent changes are due partly to reduced monitoring effort rather than actual stock declines, but deterioration in the monitoring system is itself a cause for major concern.