Structure, abundance, and movements of an allacustrine population of rainbow trout in the Naknek River, Southwest Alaska

摘要

Allacustrine rainbow trout move downstream from Naknek Lake into the Naknek River to spawn, and become vulnerable to angling during the spawning season. Regulations, including an annual angling closure from 10 April through 7 June, have been implemented to protect spawning fish from angling mortality, but the synchrony of the angling closure to the time when sexually mature fish are present in the river was unknown. We describe (1) the length structure and abundance of sexually mature fish in the spawning population and (2) the post-spawning movements of sexually mature fish. We sampled sexually mature fish ranging from 424 to 860 mm fork length during 2000 and 2001. The spawning population was estimated to be similar to 3,000 fish. Of 70 radio-tagged fish, 80% moved from the river to the lake by 8 June 2001, but several fish remained in the river throughout the summer. More than half of the radio-tagged fish that moved to the lake returned to the river during the fall and early winter. A substantial portion of the spawning population was protected by the annual angling closure, but some fish were not protected because they remained in the river through the summer or returned to the river before it froze in the fall.