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Last modified
7/14/2009 5:02:36 PM
Creation date
5/17/2009 11:30:51 PM
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UCREFRP
UCREFRP Catalog Number
9489
Author
Mueller, G.
Title
The Role of Stocking in the Reestablishment and Augmentation of Native Fish in the Lower Colorado river Mainstream (1998-2002).
USFW Year
1998-2
USFW - Doc Type
03-288,
Copyright Material
NO
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<br />I <br />:1 <br />,I <br />I <br />I <br />I <br />I <br />I <br />I <br />,I <br />I <br />I <br />'I <br />II <br />.t <br />I <br />il <br />I <br />I <br /> <br />2001 Effort <br /> <br />The sampling effort in 2001 increased and started 19 January, which was earlier and began prior to the <br />spawning season. This resulted in 36 sets that did not collect any fish larvae. We captured a similar number <br />(3,602) oflarvae from the 30 samples that did collect fish (Table 1.4). Most (>95%) were cyprinids (common <br />carp) and centrarchids (<5%). Traps were placed at the tailrace of Davis Dam, Laughlin Lagoon, Boy Scout <br />Camp, Park Moabi, Topock Bay, Pulpit Rock (Topock Gorge), and Blankenship Bend. <br />Six razorback suckers were captured, four at Park Moabi and two at Blankenship Bend. Eight flannelmouth <br />suckers were captured, all in the Bullhead City region. Traps also attracted dense swarms of zooplankton, <br />Odonate and Mayfly nymphs, diving beetles, and freshwater prawns or glass shrimp (Palaemonetes spp.). <br />Water temperatures averaged 14"C (10-1 T C) during the period. <br /> <br />2002 Effort <br /> <br />Fifty-three light trap samples were collected between 16 January and 25 April (Table 1.5). Four larval <br />razorback suckers were captured near Park Moabi and Pulpit Rock. No larval flannelmouth suckers were <br />captured. <br />The presence of sucker larvae showed that both species had successfully spawned but larvae were <br />geographically separated, suggesting species were spawning in different areas. All sexually active <br />flannelmouth suckers and their larvae were collected in the upper 16 Ion region of the study area. It is believed <br />spawning extended downstream another 8 Ion; however, this area was not sampled due to an absence of <br />backwaters. It is interesting to note that flannelmouth larvae were not captured in the lower 40-Ion river reach. <br />Likewise, razorback sucker larvae were also site specific. A total of 12 were collected during the 3 years. All <br />were found in the lower 40-Ion reach, between the Park Moabi and Blankenship BeIi.d areas. This coincided <br />with where sexually active adults were collected. <br /> <br />Larval Emergence <br /> <br />The timing that fish larvae emerged provides compelling evidence that razorback suckers may be more <br />vulnerable to predators. Razorback sucker larvae appeared prior to other fishes, making them vulnerable to <br />predators emerging from their winter fast. Flannelmouth suckers on the other hand, spawn later, well into the <br />spawn of other species (Figure 1.2). Emerging with thousands of other larvae may increase their chance for <br />survival as more food becomes available to predators. <br /> <br />Table 1.4. Summary of the location, effort, number, and species taken in the 2001 larval light trap effort. <br />Location # of sets Effort (h) RZB FMS Cyprinids Centrarchids <br />Davis Dam 2 32 0 0 6 0 <br />Laughlin Lagoon 14 224 0 3 2,951 120 <br />Big Bend Park 3 48 0 0 240 0 <br />Boy Scout Camp 5 80 0 5 403 25 <br />Park Moabi 4 64 4 0 19 9 <br />Blankenship Bend 2 32 2 0 0 4 <br />Total 308 480 6 8 3,619 158 <br />a Total number of samples was 66 but only 30 contained fish. Total effort was 1,056 hr. <br /> <br />7 <br />
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