RESPONSE OF MIGRATORY SCULPIN POPULATIONS TO BARRIER REMOVAL IN FOUR SMALL LOWLAND URBAN STREAMS IN THE LAKE WASHINGTON BASIN.

We examined changes in density, distribution, and size of migratory sculpins (Coastrange Sculpin [Cottus aleuticus] and Prickly Sculpin [C. asper]) in 4 small lowland urban tributaries following the removal of instream barriers. In 3 of the streams, a complete or partial barrier to upstream movements of migratory sculpins was removed. In the 4th stream where sculpin were not known to be present, the lower reach was daylighted (stream channel was reconfigured from an underground culvert to a more natural stream channel at the surface). In Lyon Creek, where a partial barrier was removed, sculpin densities upstream of the barrier site increased only slightly. Poor habitat conditions in this stream section may have limited recovery. In Taylor and Zackuse Creeks, where barriers were also removed, Coastrange Sculpin quickly colonized the stream section upstream of the barrier site and densities became similar to or higher than downstream study sections. In the daylighted Mapes Creek, both sculpin species were common throughout the new channel shortly after the project was completed. In both Lyon and Taylor creeks, body size of migratory sculpin in the upstream section decreased dramatically following barrier improvement. Prior to barrier removal, only a few large sculpin migrated upstream; whereas, after barrier removal sculpin of all sizes were able to move upstream except young-of-the-year. Our results indicate that migratory sculpin have the ability to recolonize new habitats shortly after connectivity is restored, but habitat quality may limit sculpin use of newly accessible areas. [ABSTRACT FROM AUTHOR]