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7/14/2009 5:02:32 PM
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5/24/2009 7:32:18 AM
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UCREFRP
UCREFRP Catalog Number
8026
Author
Berry, C., R. Bulkley, D. Osmundson and V. Rosen.
Title
Survival of Stocked Colorado Squawfish with Reference to Largemouth Bass Predation.
USFW Year
1985.
USFW - Doc Type
Logan, Utah.
Copyright Material
NO
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populations (Figure 2). Conductivity was generally higher in the <br />ponds than in the adjacent river as evidenced by the drop in values <br />during the flood period. Fish Chalet Pond had much higher conductivity, <br />values than the other four ponds (Figure 3). Secchi disk transparency <br />was always less than 2 m in four of the ponds, and fell to as low as <br />0.1 m during the spring flood. However, during this time, the one pond <br />not affected by the flood, Fish Chalet, became so clear that details <br />of the benthic region could be readily discerned when viewed from the <br />surface (Figure 4). <br />4. Squawfish Stocking <br />Squawfish were stocked in the ponds on October 13, 1983, and on July <br />24 and October 31, 1984. Stocking data and pond conditions at the time <br />of-stocking are given in Tables 5,.6, and 7. Samples of squawfish held <br />in live-cages at each pond at the time of each stocking all had 1001 <br />survival when checked 48 hours later, indicating that transport stress <br />was not critical. <br />5. Bass Stomach Contents <br />Only bass stomach contents collected during fall of 1983 have been <br />analysed to date. Those contents were collected from bass at Terry <br />and Island ponds. In both cases, diets of the bass switched almost <br />entirely to squawfish immediately after stocking. Within two weeks, <br />squawfish had disappeared from the diet of Terry Pond bass, possibly <br />indicating their disappearance from the community (Figure 5). Also, <br />the mean volume of the contents increased when squawfish were stocked, <br />indicating that squawfish were more vulnerable or abundant than the <br />customary food items (Tables 9 and 10). By using both ends of the <br />confidence intervals for the bass population estimates and the mean <br />number of squawfish per stomach for each size class of bass, it can <br />be estimated that between 21 and 79 percent of the squawfish stocked <br />were eaten the first night at Terry Pond. <br />6. Squawfish Growth <br />Squawfish stocked in October, 1983, did not grow during winter. Those <br />remaining in Fish Chalet Pond were monitored through the following <br />summer. They demonstrated, for the first time, their growth potential <br />under ideal circumstances. In five months they more than tripled in <br />mean total length (Figure 6). One individual was 304 mm long by the <br />end of September. The reputation the squawfish has of being a slow <br />grower is apparently based on growth rates observed in the upper <br />portion of its historic range where water temperatures are not optimal. <br />Warm pond water and abundant food supplies of young carp produced <br />squawfish growth in Fish Chalet Pond that may be indicative of growth <br />in the once warmer waters of the southern portion of the fish's <br />historic range. <br />7. Overall Survival <br />Survival of squawfish varied greatly according to the pond and season <br />of stocking (Table 8). Overall survival is not correlated soley with <br />densities of largemouth bass, and yet, bass predation is obviously a <br />8
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