AMPHIBIAN USE OF CHEHALIS RIVER FLOODPLAIN WETLANDS

The use of isolated emergent wetlands by amphibians has been well documented. However, amphibian habitats such as emergent wetlands in floodplains may differ from isolated wetlands because of their high disturbance (water fluctuation) related to riverine flooding, presence of fish species, and increased connectivity among aquatic habitats. We compared the amphibian assemblages at 6 freshwater wetland habitats in the Chehalis River floodplain and examined the effect of wetland restoration on amphibians. We sampled 6 wetlands during the breeding season in 2003 and 2004 and captured over 15,000 adults, tadpoles, and larvae from 6 species. The red-legged frog (Rana aurora) was the most abundant species captured. The rough skinned newt (Taricha granulose) was the only amphibian captured at all sampled sites. Although it is more desirable to prevent wetland degradation from occurring, restored and enhanced wetlands in floodplains do provide breeding habitat for amphibians. Amphibian species captured in reference wetlands were also captured in restored wetlands. Water control structures, which were used to facilitate wetland restoration, did not seem to influence utilization by amphibians; however, hydroperiod seemed to affect amphibian abundances. Wetlands with intermediate hydroperiods had the highest amphibian abundance compared to wetlands with temporary or permanent water. Fish were captured in all wetlands, and those with the greatest abundance of native non-game fishes had the highest abundance of amphibians. Our results suggest that emergent wetlands in floodplains are dynamic habitats that can offer breeding opportunities, but microhabitat suitability needs to be considered when managing amphibian habitats.