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A comparison of land use and Coho salmon abundance in the Georgia Basin, British Columbia Morlin, Maria Gabrielle Tamara

Abstract

Coho salmon (pnayrhynchus kisutch) declines in the Strait of Georgia, British Columbia have been attributed to overfishing, marine survival, and habitat loss; however, the relative impact of each is difficult to ascertain. In many cases of commercial fish population declines, factors other than fishing are blamed. In British Columbia considerable funding is allocated to habitat restoration projects; however, if spawners fail to colonize streams, then funding and effort may be wasted. I investigated the contribution of freshwater habitat loss in the Georgia and Lower Fraser Basins of British Columbia to a substantial decline in coho salmon abundance from mid-1970 to 1995. I used land use as an indicator of potential habitat loss and degradation for an index set of watersheds and measured land use change over four decades using aerial photos and a Geographic Information System. I compared land use to coho escapement and coho fry for sixteen watersheds and over three time periods (1955, 1975 and 1995) using linear regressions. I found no significant relationships between mean coho escapement and land use for each time period. Land use change over time was not related to the realized rate of population growth (g) for coho or coho fry. Coho fry abundance was positively related to proportion old growth in a watershed, and negatively related to proportion urban land use in the 1995 time period.

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