Streams of the size in this study are often not considered salmon habitat because many flow seasonally and do not provide habitat for spawning salmon. However, we found that numerous small streams entering the Whidbey Basin do provide rearing habitat for fry migrant Chinook salmon originating from the three nearby rivers (Skagit, Snohomish, and Stillaguamish). These same small streams are not well mapped and may be subject to inadequate protection as fish habitat. Better mapping of small streams and a predictive model for juvenile Chinook salmon potential would help managers better protect this unique habitat type.

Statistical analysis suggests that four factors influence whether juvenile Chinook salmon are present within Whidbey Basin small streams: 1) distance to nearest Chinook salmon bearing river, 2) stream channel slope, 3) watershed area, and 4) presence and condition of culverts at the mouth of a stream. Streams further from Chinook salmon bearing rivers and with steeper channel slopes had lower juvenile Chinook salmon presence rates. A minimum watershed size of approximately 45 hectares with channel slopes less than 6.5% may be necessary before juvenile Chinook salmon potential exists. We found culverts at stream mouths likely cause upstream migration problems for small fish such as Chinook salmon fry.