9523 - Laserfiche WebLink

Home Browse Search

conditions that persisted through the summer. Razorback sucker grew from 110mm, 111 mm and 96mm averages at stocking to ~ 317mm, 341 mm and 310mm averages in September/October for the three sites. Weight gains averaged 336g, 442g, and 347g in the three sites. Growth rates averaged from 1.3 mm/day to 2.2 grams/day. Following the second growing season, fish stocked in 1999 averaged 409mm/722 grams to 410mm/863 grams. Growth rates for the second growing season r averaged 0.3mm/day and 1.2 g/day to 0.5mm/day and 2.6 g/day. Growth rates for age- 1 fish stocked into Baeser Bend in the spring of 2000 were similar to 1999 growth rates. This far exceeded the growth of a control group of fish that were held at the Ouray hatchery. Although conditions were not ideal, and nets were not entirely effective, some ~ data on razorback sucker movement from the sites was collected. Only two razorback sucker were caught leaving the sites during the first connection with the river following stocking, suggesting age-1 fish preferred to remain in the sites. Survival estimates confirm that most fish remained in the sites after this first river connection, and therefore for at least one growing season. Significantly more razorback sucker left the . floodplain the second year. During connection in 2000, 31 razorback sucker were caught in outgoing traps at Baeser Bend, 10 at Above Brennan, and one at The Stirrup. Considerably more movement occurred than was measured in these nets. Numerous floodplain stocked razorback sucker that were not captured in outgoing traps were captured in the river. Floodplain razorback sucker caught with river sampling totaled 41 in 2000 and 148 in 2001. i Stocking age-1 razorback sucker into floodplain depressions can potentially contribute healthy fish to the river population. Perhaps more importantly, this study demonstrated that floodplain depressions containing an abundant non-native fish community can still provide viable rearing habitat for wild razorback sucker. Efforts to determine if larval razorback sucker can survive in nonnative fish dominated floodplain ~ habitat should continue. The following recommendations are made: 1. Continue studies to quantify larval razorback sucker survival to recruitment in floodplain sites. Efforts should focus on enhancing larval fish entrainment into the best floodplains, testing survival following a reset of nonnative fish ~ populations, determining larval densities necessary to survive predation, options for nonnative fish control, and quantify other sources of mortality such as water quality and food availability. Entrainment and survival of larval razorback sucker in floodplain habitats represent one of the critical links in self-sustaining razorback sucker populations. 2. Monitor the contributions to the spawning population of floodplain reared ~` razorback sucker. 3. Use floodplain depressions for razorback sucker grow-out ponds during years when average and above average flows are predicted. -vi-