Distribution, Abundance, and Size of Migratory and Non-migratory Species of Sculpin in Relation to Barriers in Puget Sound Lowland Streams, Washington

We examined the effects of barriers on populations of migratory sculpin (have pelagic larvae; Coastrange Sculpin C. aleuticus and Prickly Sculpin C. asper).  We compared sculpin populations immediately upstream and downstream of small barriers in 18 Puget Sound, Washington lowland streams. All streams had populations of Coastrange Sculpin or Prickly Sculpin or both in stream reaches downstream of the barrier.  In 7 of the 18 streams studied, at least one species of non-migratory sculpin (have benthic larvae; Riffle Sculpin C. gulosus, Torrent Sculpin C. rhotheus, and Shorthead Sculpin C. confusus) was also present.  In all streams examined, the abundance of migratory sculpin immediately upstream of the barrier was substantially lower than immediately downstream of the barrier.  In 11 of the 18 streams, migratory sculpin were not present immediately upstream of the barrier.  The few migratory sculpin collected upstream of the barrier were considerably larger than those collected downstream of the barrier.  In most streams with non-migratory sculpin populations, non-migratory sculpin were rare downstream of the barrier and abundant upstream of the barrier.  Overall, barriers appear to have a strong effect on the distribution of migratory and non-migratory sculpin and need to be taken into account when assessing stream fish communities.