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<br />C) <br />C:J <br />....~ <br />CD <br />(, -j <br />o <br /> <br />Table 3.9. <br /> <br />Number of young-of-the-year (YOY) and juvenile wild Colorado pikeminnow <br />collected annually from 1987 to 1997 in the San Juan River during monitoring <br />studies Source: Converse and Holden 1999). <br /> <br /> <br />Platania <br />(1990) <br /> <br />18 <br /> <br />o <br /> <br />-' <br /> <br />Buntjer et ai, <br />(1993,1994) <br /> <br />o <br /> <br />2" <br /> <br />o <br /> <br />Lashmett <br />(1993,1994, <br />1995) <br /> <br />o <br /> <br />11 <br /> <br />o <br /> <br />Archer et al. <br />(2000) <br /> <br />5" <br /> <br />o <br /> <br />o <br /> <br />7' <br /> <br />Platania et ai, <br />(2000) <br /> <br />2" <br /> <br />2" <br /> <br />o <br /> <br />Number of <br />seine hauls <br />8Data not collected or available. <br />bLarval fish taken in drift nets or by seining. <br />cTwQ of the fish collected in 1994 were captured in April and were 1993 year-class fish. <br /> <br />? <br /> <br />? <br /> <br />235 <br /> <br />240 <br /> <br />135 <br /> <br />103 <br /> <br />? <br /> <br />1,390 <br /> <br />892 <br /> <br />796 <br /> <br />29 <br /> <br />Population size is an important limiting factor for both razorback sucker and Colorado pikeminnow in the <br />San Juan River, Although the small Colorado pikeminnow population appears to be able to maintain itself <br />through a low level of recruitment, it may be too small to respond to improvements in its environment. <br /> <br />Management Implications <br />Because of the lack of razorback sucker in the San Juan River, the SJRIP initiated experimental <br />augmentation in 1994 (Ryden 2000b), The intent of the study was to determine if stocked razorback <br />sucker would survive, grow, and reproduce, Past razorback sucker augmentation efforts had not been <br />successful, and one of the reasons may have been the size offish stocked (Marsh and Brooks 1989, <br />Minckley et al. 199 I), Previously stocked fish may have been too small to avoid predation or may not <br />have been able to withstand the riverine environment. The experimental stocking of razorback sucker in <br />the San Juan River was very successful, Ryden (2000b) recommended stocking larger-sized razorback <br />sucker in the spring, although this would require holding them an additional winter in grow-out facilities. <br />Hence, if such facilities are not available, stocking in the fall at a smaller size would be acceptable. Ryden <br />(2000b) also recommended stocking as far upstream as possible, since stocked razorback sucker exhibited <br />relatively large downstream movements shortly after stocking. His studies suggested that programs to <br />reduce the potential of stocked fish loss to predatory nonnative fish species were important and that <br />younger fish (less than 3 years of age) appeared to be better able to adapt to the riverine situation than <br />older captive-reared razorback sucker. The success of experimental stocking between 1994 and 1996 <br /> <br />September 2000 <br /> <br />3-58 <br /> <br />Program Evaluation Report <br />