Diel and seasonal movements by adult Sacramento pikeminnow (Ptychocheilus grandis) in the Eel River, northwestern California

In late summer and fall, radio‐tagged adult Sacramento pikeminnow (Ptychocheilus grandis) at three sites in the Eel River of northwestern California moved more at night than during the day. Fish moved up to 535 m at night and returned to their original positions the following morning. Adult Sacramento pikeminnow at all sites occupied only pools during the day, but at one site moved through high gradient riffles and occupied fast water habitats at night. Adult Sacramento pikeminnow at the upstream limit of their range in one Eel River tributary moved downstream up to 23 km during the winter and tended to return to their original position the following spring, where they remained through the summer. Fish radio tagged at downstream sites exhibited more variable behavior, moving 2‐92 km over >393 days. Our observations suggest that the most appropriate scale of consideration for attempts to manage this species or estimate population size includes entire river drainages.