Response of larval lost river and shortnose suckers to wetland restoration at the Williamson River Delta, Oregon

摘要

Population declines of the federally endangered Lost River sucker Deltistes luxatus and shortnose sucker Chasmistes brevirostris have been linked to several factors, including the loss of larval nursery habitat associated with lake fringe and riparian wetlands. Restoration of deltaic wetlands in the Williamson River delta, Oregon, is regarded as one strategy that may increase larval nursery habitat and survival. This study examined larval sucker presence, growth, development, and feeding in pilot restoration wetlands at the Williamson River delta to determine whether wetland restoration provides habitat that is conducive to larval rearing. We compared results from the restoration wetlands to those in riparian and lacustrine wetland reference sites during 2003 and 2004. The seasonal timing of larval Lost River and shortnose suckers captured in the restoration wetlands was similar to that in reference sites during the April-July study period. The frequency of occurrence in the restoration wetlands was comparable to that in reference sites; larvae were collected in 90-100% of transects during periods of peak abundance. These data are an indication that restored wetlands provide critical habitat for larval suckers. Larval sucker length, developmental phase, and gut fullness in the restoration wetlands indicated that larvae were feeding, growing, and hence, rearing, in those areas. Water temperatures in the restoration wetlands were 3-4 degrees C higher than those in reference sites, especially early in the season, which may have increased the restoration sites' suitability for larval rearing compared with reference sites. Our results indicate that initial wetland restoration efforts at the Williamson River delta have successfully created suitable rearing habitat for larval Lost River and shortnose suckers and suggest that further large-scale wetland restoration in the delta will increase larval rearing opportunities and contribute to the recovery of these two endangered species.