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<br />Ij~~.~~."~.' <br /> <br />. <br /> <br />RESULTS AND bISCUSSION <br /> <br />Animas River <br /> <br />The Animas River running through Durango has had no documented natural <br />reproduction of trout of any species for many years. Any number of factors <br />(or combinations of factors) including siltation, sewage pollution, or heavy <br />metal toxicity could be the reason(s) for the lack of reproduction. ,The <br />Colorado Division of Wildlife, (CDOW) has managed this river for most of the <br />past decade with a mix of catchable rainbows augmented by large annual <br />plants of Snake River cutthroat trout (SRN) and brown trout fingerling <br />plants. <br /> <br />After several years under this Jnanagement plan, it was determined that <br />survival of the brown trout fingerling plants was much better than the SRN <br />plants. In particular, the survival of larger brown fingerlings (10 cmor 4 <br />in. averag~ size) appeared to be much better and more cost effective than <br />2-inch (5 em) fingerling plants (Nehring 1986). As a result of these <br />preliminary investigations, it was decided to include the Animas River as an <br />additional stream in this study beginning in 1987. CRR and' TAS rainbow <br />fingerling plants were to be included in the evaluation together with the <br />continued plants of brown trout fingerlings, as shown in Table, 5. <br /> <br />The data in Table 8 contains the population estimates for all unmarked <br />brown trout for both stations (Animas land 2) combined since 1981. 'The <br />highest densities recorded (for brown trout at age l+) prior to the time <br />when the sizes of the fingerlings stocked were increased were in '1982 and. <br />1984, when t~e age 1+ brown, estimates were 7ll and 757, respect~vely. <br />~ehring (1986) reported that 75-90% of the 711 age l+,browns captured in <br />1983 were from a plant of 2,088 brown fingerlings that ranged in size from <br />7.6-15.2 cm (3-6 in.), while those from the 1984 plant averaged 5.9 em (2.33 <br />in.) at stocking. The age l+ survivor's estimate from the 1985 plants were <br />1,071 from a plant that averaged 7.47 cm (2.94 in.) in length and were the <br />largest brown fingerlings planted'up through 1985 (Tables 5 and 8). <br /> <br />Table 8. Animas River, brown trout life table 1977-87 from 32nd Street Bridge <br /> to Purple Cliffs for unmarked browns. <br />Year/ <br />date 1986 1985 1984 1983 1982 1981 1980 1979 1978 1977 <br />12/81a 116 444 236 45 3 <br />11/82 711 354 369 l23 30 0 <br />12/83a 271 484 204 64 2 0 <br />l2/85 25 78 242 116 46 8 <br />12/86 l,O71 757 236 274 184 78 11 <br />12/87 31 86 237 l38 35 30 2 0 <br /> <br />al981 and 1983 estimates went only from Durango Hatchery to Purple Cliffs; <br />thus, estimates are probably low when compared to 1982 and 1985. <br /> <br />c ;: ~~. <br /> <br />.:L:': <br />.~. c <br /> <br />(\ <br />H <br /> <br />II rJ0002401 <br />