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<br />December 2008
<br />
<br />Bestgen et aL-Ecology of Gi/fl e/egans
<br />
<br />491
<br />
<br />TABLE I-Number, me,m totallength (mm) and range (in parentheses), and stocking dates and locations for
<br />bony tails (Gila elegans) released in the Green River study area, Colorado and Utah (river km 597-554.6), 2002-
<br />2005. Fish were produced at the John W. Mumma Native Aquatic Species Restoration Facility, Colorado Division of
<br />'Wildlife, Alamosa, Colorado. Bony tails recaptured or obseIVed were all from fish stocked the same year,
<br />
<br /> Year
<br />Locality 2002 2003 2004 2005
<br />Brovms Park (river km 597) 8,600
<br />Mean total length 224 (119-351)
<br /> 4 October
<br />Recaptured 1
<br />Echo Park (river km 554.6) 5,000 1,592 6,6EiO 2,580
<br />Mean total length 209 210 (156-332) 229 (143-596) 234 (180-365)
<br /> 10 October 7 October 12 and 16 September 10 June
<br />Recaptured or obseIVed 0 0 84+ 45
<br />
<br />1988 and 1989. Of the 86 bony tails released to
<br />obtain habitat-use information, 64 fish (74%)
<br />were documented mortalities. p, V. Badame and
<br />]. M. Hudson (in litt.) had slightly higher
<br />recapture success in 1996-2001, when larger
<br />numbers offish were stocked; 0.8% (n = 663) of
<br />bonytails stocked in the Colorado River (n =
<br />84,603) were recaptured and 0.02% (n = 17)
<br />had over-wintered ~6 months. In the Green
<br />River, 0.4% (n = 523) of bony tails stocked (n =
<br />127,714) were recaptured and 0.05% (n = 59)
<br />had over-\\Iintered ~6 months. Most fish released
<br />were relatively small (82% < 140 mm total
<br />length), and most recaptures were of larger fish,
<br />which led them to recommend stocking of fish
<br />~300 mm in total length.
<br />Many bony tails captured in September 2005
<br />had multiple Lernea infections or fungus, and
<br />their general appearance, color, and condition
<br />was poor. The ANCOVA of weight as a function
<br />of length between bony tails recaptured in 2004
<br />(weight = -255.9 + totallength*1.54, F = 79.0,
<br />df I, 19, P < 0.001, y2 = 0.81) and those in 2005
<br />(weight = -328.9 + totallength*1.74, F = 175.0,
<br />df I, 35, P < 0.001, y2 = 0.83) did not detect a
<br />significant group-length interaction term (F =
<br />0.67, P = 0.420), but there was a significant
<br />difference among intercepts (F = 12.81, P <
<br />0.001), After correcting for differences in lengths
<br />of bonytails for samples in 2004 and 2005 (mean
<br />= 261 mm total length), least-squares means
<br />suggested bony tails captured soon after stocking
<br />in 2004 were 17% heavier (147 g) than those
<br />recaptured 4 months after release in 2005
<br />(126 g). Using a length:weight relationship
<br />developed for wild bonytails Vanicek and Kramer
<br />
<br />(1969), predicted weight for an average 261-mm-
<br />long fish was 132 g, which was slightly heavier
<br />than bony tails recaptured in Septem bel' 2005
<br />that were at large 4 months but less than just-
<br />stocked fish recaptured in September 2004.
<br />Bonytails recaptured by electrofishing in Au-
<br />gust 2005 grew an average of 11.6-mm total
<br />length (1-20 mm) following their release in
<br />June, which was similar to the rate of growth of
<br />10.4 mm in total length for smaller bony tails
<br />(mean total length = 124-130 mm, 1996-1998
<br />year classes) observed by P. V. Badame and]. M.
<br />Hudson (in litt.) over a 58-70 day period.
<br />Bony tails recaptured in our study in September
<br />2005 and 4-months post-release grew an average
<br />of 29.5 mm in total length (7-55 mm). SimiIar-
<br />sized age-4 wild bonytails (mean = 258 mm total
<br />length) had an average annual growth increment
<br />of 89 mm in total length (Vanicek and Kramer,
<br />1969). Reduced condition of bonytails at large
<br />for 4 months relative to just-stocked fish and
<br />relatively slow growth rates of stocked bony tails
<br />in 2005 compared to wild fish may indicate
<br />stocked fish are not able to acquire adequate
<br />food, which likely contributed to susceptibility to
<br />disease and other stressors.
<br />Bonytails captured or observed in 2004 and
<br />2005 were mostly collected in eddies and pools
<br />1-3-m deep, but also used backwaters and swifter
<br />runs and riffles with current velocity ::SO.7 m/s.
<br />Bon}tails from riffles in 2004 apparently were
<br />feeding, as several fish excreted algae and insect
<br />parts during post-capture handling. P. V.Ba-
<br />dame and J. M. Hudson (in litt.) also found
<br />bon}'tails using a wide variety of habitat types,
<br />with smaller (mean total length = 95 IllIll)
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