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Author:
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Category : Anadromous fishes
Languages : en
Pages : 78
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Author:
Publisher:
ISBN:
Category : Anadromous fishes
Languages : en
Pages : 78
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Author: Casey M. Baldwin
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ISBN:
Category : Anadromous fishes
Languages : en
Pages : 62
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Author:
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Category :
Languages : en
Pages :
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Pelagic fishes, such as kokanee and rainbow trout, provide an important fishery in Lake Roosevelt; however, spawner returns and creel results have been below management goals in recent years. Our objective was to identify factors that potentially limit pelagic fish production in Lake Roosevelt including entrainment, food limitation, piscivory, and other abiotic factors. We estimated the ratio of total fish entrained through Grand Coulee Dam to the pelagic fish abundance for September and October, 1998. If the majority of these fish were pelagic species, then entrainment averaged 10-13% of pelagic fish abundance each month. This rate of entrainment could impose considerable losses to pelagic fish populations on an annual basis. Therefore, estimates of species composition of entrained fish will be important in upcoming years to estimate the proportion of stocked pelagic fish lost through the dam. Food was not limiting for kokanee or rainbow trout populations since growth rates were high and large zooplankton were present in the reservoir. Estimates of survival for kokanee were low (0.01 annual) and unknown for rainbow trout. We estimated that the 1997 standing stock biomass of large (1.1 mm) Daphnia could have supported 0.08 annual survival by kokanee and rainbow trout before fish consumption would have exceeded available biomass during late winter and early spring. Therefore, if recruitment goals are met in the future there may be a bottleneck in food supply for pelagic planktivores. Walleye and northern pikeminnow were the primary piscivores of salmonids in 1996 and 1997. Predation on salmonid prey was rare for rainbow trout and not detected for burbot or smallmouth bass. Northern pikeminnow had the greatest individual potential as a salmonid predator due to their high consumptive demand; however, their overall impact was limited because of their low relative abundance. We modeled the predation impact of 273,524 walleye in 1996, and 39,075 northern pikeminnow in 1997 because diet data revealed predation on salmonids during these years. We could not determine the absolute impact of piscivores on each salmonid species because identification of fish prey was limited to families. Our estimate of salmonid consumption by walleye in 1996 and northern pikeminnow in 1997 shows that losses of stocked kokanee and rainbow trout could be substantial (up to 73% of kokanee) if piscivores were concentrating on one salmonid species, but were most likely lower, assuming predation was spread among kokanee, rainbow trout, and whitefish. Dissolved oxygen was never limiting for kokanee or rainbow trout, but temperatures were up to 6 EC above the growth optimum for kokanee from July to September in the upper 33 meters of water. Critical data needed for a more complete analysis in the future include species composition of entrainment estimates, entrainment estimates expanded to include unmonitored turbines, seasonal growth of planktivorous salmonids, species composition of salmonid prey, piscivore diet during hatchery releases of salmonids, and collection of temperature and dissolved oxygen data throughout all depths of the reservoir during warm summer months.
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Category :
Languages : en
Pages : 362
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This project began collecting biological data from Lake Roosevelt starting in 1991, with a long term goal of developing a computer model which accurately predicts biological responses to reservoir operations as part of the System Operation Review Program. In conjunction with the Lake Roosevelt Monitoring Project, this study collected limnological, reservoir operation, zooplankton, creel, net-pen rainbow trout and kokanee tagging data in 1994. Results obtained from current and past years data allow for the quantification of impacts to lake limnology, zooplankton, fish species and fisherman caused by reservoir drawdowns and low water retention times. in Lake Roosevelt, reservoir operations influence lake morphology as well as habitat availability for fish and their food. Lake elevations reached a yearly low of 1,263.90 feet above sea level in April and a yearly high of 1,288.50 feet in October. Lake Roosevelt experienced a peak in Daphnia spp. densities during July and August including the peak density of nearly 9,000 organisms per m3. High densities of zooplankton were found in the lower end of the reservoir which supports the hypothesis that flushing of reservoir water increases downstream plankton densities and biomass as well as increasing entrainment of fishes. In 1994, a total of 26,975 net-pen rainbow trout were tagged at locations throughout the reservoir. Anglers fishing in Lake Roosevelt or below returned 448 tags, of which 399 tags were from fish tagged in 1994. Trends in tag returns continue to indicate that entrainment of Lake Roosevelt net-pen fish are influenced by water retention times and release times. Creel surveys of Rufus Woods were conducted over a six month period in 1993 and seven months in 1994 to estimate entrainment loss of tagged fish, however no tags were observed. Harvest estimates for the creel period were 46, 0 and 55 fish for rainbow trout, kokanee and walleye in 1993 and 384, 5 and 4,856 fish per year respectively in 1994.
Author:
Publisher:
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Category : Fisheries
Languages : en
Pages : 214
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Book Description
Report on activities in the divisions of research.
Author: Matt Polacek
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Category : Fish stock assessment
Languages : en
Pages : 24
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Author:
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Category :
Languages : en
Pages : 96
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The Lake Roosevelt Fisheries Evaluation Program is the result of a merger between two projects, the Lake Roosevelt Monitoring Program (BPA No. 8806300) and the Lake Roosevelt Data Collection Project (BPA No. 9404300). These projects were merged in 1996 to continue work historically completed under the separate projects, and is now referred to as the Lake Roosevelt Fisheries Evaluation Program. Creel and angler surveys estimated that anglers made 196,775 trips to Lake Roosevelt during 1998, with an economic value of $8.0 million dollars, based on the Consumer Price Index (CPI). In 1998 it was estimated that 9,980 kokanee salmon, 226,809 rainbow trout, 119,346 walleye, and over 14,000 smallmouth bass and other species were harvested. Creel data indicates that hatchery reared rainbow trout contribute substantially to the Lake Roosevelt fishery. The contribution of kokanee salmon to the creel has not met the expectations of fishery managers to date, and is limited by entrainment from the reservoir, predation, and possible fish culture obstacles. The 1998 Lake Roosevelt Fisheries Creel and Population Analysis Annual Report includes analyses of the relative abundance of fish species, and reservoir habitat relationships (1990-1998). Fisheries surveys (1990-1998) indicate that walleye and burbot populations appear to be increasing, while yellow perch, a preferred walleye prey species, and other prey species are decreasing in abundance. The long term decreasing abundance of yellow perch and other prey species are suspected to be the result of the lack of suitable multiple reservoir elevation spawning and rearing refugia for spring spawning reservoir prey species, resulting from seasonal spring-early summer reservoir elevation manipulations, and walleye predation. Reservoir water management is both directly, and indirectly influencing the success of mitigation hatchery production of kokanee salmon and rainbow trout. Tag return data suggested excessive entrainment occurred in 1997, with 97 percent of tag recoveries from rainbow trout coming from below Grand Coulee Dam. High water years appear to have substantial entrainment impacts on salmonids. The 1998 salmonid harvest has improved from the previous two years, due to the relatively water friendly year of 1998, from the harvest observed in the 1996-1997 high water years, which were particularly detrimental to the reservoir salmonid fisheries. Impacts from those water years are still evident in the reservoir fish populations. Analysis of historical relative species abundance, tagging data and hydroacoustical studies, indicate that hydro-operations have a substantial influence on the annual standing crop of reservoir salmonid populations due to entrainment losses, and limited prey species recruitment, due to reservoir elevation level fluctuation, and corresponding reproductive success.
Author:
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Category : Environmental chemistry
Languages : en
Pages : 834
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Author: Keith D. Underwood
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Category : Grand Coulee Dam (Wash.)
Languages : en
Pages : 340
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Author: Thomas A. Cichosz
Publisher:
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Category : Grand Coulee Dam (Wash.)
Languages : en
Pages : 331
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