Recent studies suggest that freshwater turtle populations are becoming increasingly male-biased. A hypothesized cause is a greater vulnerability of female turtles to road mortality. We evaluated this hypothesis by comparing sex ratios from published and unpublished population surveys of turtles conducted on-versus offroads. Among 38 166 turtles from 157 studies reporting sex ratios, we found a consistently larger female fraction in samples from on-roads (61%) than off-roads (41%). We conclude that female turtles are indeed more likely to cross roadways than are males, which may explain recently reported skewed sex ratios near roadways and signify eventual population declines as females are differentially eliminated.

WILLOW CREEK VEGETATION No Active Management Alkrncrtive Vrgetation Key U.S. Army Corps of Engineers, Seattle District. 1984. Wetland Plants of the Pacific Northwest. 85pp. U.S. Department of Energy, Bonneville Power Administration, ~ivision of Fish and Wildlife. 1987. A Wildlife Habitat Protection, Mitigation, and Enhancement Plan for Eight Federal Hydroelectric Facilities in the Willamette River Basin. U.S. Fish and Wildlife Service. 1978. Habitat suitability index models: ~aliforaia ~uail. Draft. U.S. Fish and Wildlife Service. 1980. ~abitat suitability index models: Red-tailed Hawk. Draft.

This report was funded by the Bonneville Power Administration (BPA), U.S. Department of Energy, as part of BPA's program to protect, mitigate, and enhance fish and wildlife affected by the development and operation of hydroelectric facilities on the Columbia River and its tributaries. The views in this report are the author's and do not necessarily represent the views of BPA. BURLINGTON BOTTOMS HABITAT EVALUATION

Each gear has a characteristic catchability range depending on species, size, and environment, that relates actual abundance or biomass density to catch-per-unit-effort (CPUE) with catch as numbers or weight of fish, respectively. A consistent protocol does not guarantee constant catchability, but makes it minimally variable in given habitats across floodplain units. Maintaining protocols will also permit the future application of catchabilities estimated from efficiency calibrations on-site, or with similar gear, species, and habitats elsewhere. This would transform CPUE data to actual abundance or biomass estimates. Where smaller water bodies exist, standardized protocols using backpack electrofisher or electric seine will be employed and maintained at those sites and seasons.