Effects of cover and mesohabitat type on the abundance of young-of-the-year Chinook salmon

Snorkel surveys were conducted on the Sacramento River to investigate the relative importance of microhabitat and mesohabitat scales on the abundance of young of the year (YOY) Chinook salmon (Oncorhynchus tshawytscha), while taking into account temporal and segment-scale spatial variations. Sites, with 13 different mesohabitat types, were sampled nine times from April to September in 1996. Both the sites and cells within the sites were classified by cover type. The analyses revealed that the microhabitat scale, specifically woody cover, best explained YOY abundance, versus the mesohabitat scale. Temporal and large-scale spatial patterns reflect the timing and abundance of different runs of Chinook salmon, while microhabitat scale patterns reflect cover preference of YOY Chinook salmon.