Abstract.-To understand how logging of second-growth forests affects populations of coastal cutthroat trout Oncorhynchus clarkii clarkii, we examined trout relative abundance, body condition (mass relative to length), and physical and thermal habitat in the summer and winter in four headwater streams (two treatment streams and two nonlogged control streams) over a 6-year period (2 years prelogging [1997][1998]] and 4 years postlogging [1999][2000][2001][2002]). This is one of the first efforts to conduct a multiyear, replicated stream, before-and-after experiment on this scale to assess the effects of logging on fish and habitat. In the treatment streams, 21% of the watershed area was logged by clear-cutting (no scarification or slash-burning). Careful logging approaches were employed to remove most of the riparian overstory (i.e., no machines were used within 5 m of stream, logs were felled and yarded away from riparian zones, all shrubs were left behind, and large wood was left in streams). Because a cooler summer climate occurred coincidentally with our postlogging period (the mean daily average summer air temperature was 1-28C cooler than the temperature during the prelogging period), the mean average and mean maximum daily stream temperatures declined after the logging period in the control streams and remained the same in the treatment streams. After accounting for the effects of climate, logging had warmed treatment streams by about 18C. We could not detect any logging treatment effects on summer or winter relative abundance or condition, nor were any changes evident to instream physical habitat associated with the logging treatment. These results were probably attributable to the careful logging approaches employed and the cooler climate that occurred during the postlogging period.

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Understanding the conservation status of native fish populations is increasingly important because they are put at risk by mounting anthropogenic pressures, including climate change. Conventional approaches to assess fish populations can be logistically challenging and cost-prohibitive. As a result, resource managers often make assumptions about the status of fish populations based on limited information. The watersheds of Washington's San Juan Islands were considered too small to support wild salmonid populations. Many streams flow only seasonally, and all have been subjected to varying degrees of anthropogenic impacts affecting their ecological integrity. Nonetheless, we found that at least five watersheds in the archipelago support populations of coastal cutthroat trout (Oncorhynchus clarki clarki). To better understand the conservation status of coastal cutthroat trout populations there, we genotyped approximately fifty trout in each of three watersheds: Cascade and Doe Bay creeks on Orcas Island and Garrison Creek on San Juan Island. Results suggest that two watersheds support native populations and one supports naturalized hatchery fish. The likely native coastal cutthroat trout diversity documented in the two watersheds contributes to the overall diversity of the species, demonstrates that species' resiliency, and provides justification for conservation measures. Effective management and conservation planning in data-limited situations requires the use of a precautionary approach. Population genetics provide a useful tool for identifying vulnerable fish populations and understanding their relationships with other conspecific populations. This information can inform restoration goals and help identify and prioritize restoration and protection measures.