Abstract:
We monitored larval Lost River and shortnose suckers from natal beds in the
Williamson and Sprague rivers to nursery grounds in Upper Klamath Lake.
Downstream movements occurred at night, in the middle of the channel, and on the
falling limb of the hydrograph. Ages, sizes, and developmental stages of larvae from
spawning beds and the river mouth were similar, while larvae collected
contemporaneously from the lake tended to be larger and better fed. Our results
indicate in-river rearing was rare, that a rapid outmigration to the lake was favorable
for larval survival, and that modification of the lower Williamson River does not
appear to have prohibited rapid entry or preclude access to Upper Klamath Lake.
Within the Williamson River and Upper Klamath Lake, emergent macrophytes
supported significantly higher abundance, larger mean sizes, and better fed larvae than
submerged macrophytes, woody vegetation, or open water areas. Analysis of seven
years of larval sucker production and survival corroborated the habitat analysis by
identifying a positive relationship with emergent macrophyte availability as well as a
positive relationship with air temperature and a negative relationship with high wind.
These findings illustrate the importance of fast growth, appropriate habitat and calm
hydrological conditions for larvae, and are highly consistent with other larval fish
studies.
