Watershed restoration to reconcile fisheries and habitat impacts at the Keogh river in coastal British Columbia

Reconciling fisheries, climate, and habitat impacts with conservation may be possible with ecosystem restoration. Riparian logging decreased large woody debris in most British Columbia streams, reducing fish cover, overwinter refuges, and bank stability. Salmon survival at sea declined dramatically in the 1990s in southern British Columbia, at some places accompanied by declines in yield from freshwater life stages. Watershed restoration may offset poor survival. At the oligotrophic Keogh River, approximately 500 habitat structures were installed, off-channel ponds developed, nutrients added annually, and logging roads storm proofed and stabilized. Treatment effectiveness was evaluated stepwise by annual monitoring of juvenile fish in stream, and steelhead Oncorhynchus mykiss and coho O. kisutch salmon smolts, in comparison to the adjacent Waukwaas River. Mean juvenile sizes and densities were highest where treated with nutrients and habitat structures. By 2003, 90% (previous mean, 32%) of steelhead smolts were age-2 or younger with average previous size of age-3 smolts, as found in the nutrient-enriched river in the mid-1980s. Yields exceeded (coho) or approached (steelhead) the average smolt yield of an earlier more productive decade (1980s), despite exceptionally low returns. Steelhead smolt yield per spawner improved substantially in the Keogh River, compared to a pretreatment extirpation trajectory. Regardless, covariance analysis indicated that steelhead smolt recruits per spawner were lower than that of the earlier regime (1980s) and not significantly different from those in the recent (1990s) regime, prior to treatment. The latter was confounded by differing levels of spawners. Nonetheless, based on the density and growth studies in river, earlier age of steelhead smolts (with no change in mean size), and observations on other species, we conclude that populations are in better condition after watershed restoration to respond to low survivals of smolts in the ocean, potential harvest impacts, and climate shifts.