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<br />.oOD1'S <br /> <br />. <br /> <br />Beginning in 1986 and continuing through 1987, the average size of the <br />brown fingerling plants were increased to approximately lO em (4 in.) in an <br />effort to further increase the survival rate. In addition, both the 1986 <br />and 1987 plants were given an adipose clip to discover once and for all what <br />portion of the brown 'trout population was coming from natural reproduction, <br />either in the Animas River proper or side tributaries such as Hermosa <br />Creek. As showncin Table 8, estimated density of unmarked browns from the <br />1986 year-class captured during the December 1987 electroshocking operation <br />was3l for the entire section. In contrast,the estimate of adipose-clipped <br />brown trout from the 1986 plant was 958. Thus, out ofa total estimate of <br />989 brown trout from the 1986 year-class, 97% (958) were from the <br />adipose-clipped hatchery plant and 3% (3l) were from unknown sources. <br /> <br />The population estimates for the 1987 plant of adipose-clipped brown <br />trout for Animas 1 and 2 were 62 and, l,35l, respectively. The 1987 plant of <br />adipose-clipped brown trout averaged l4.7 cm and ranged in 'size from II cm <br />to,20 em. They averaged 9.65 cm when stocked in late August 1987. The <br />average increase in length was 5.09 cm in slightly more than 90 days after <br />stocking. ,One hundred percent of all browns under 20 cm in length sampled <br />in Decemberl987 were adipose-clipped. <br /> <br />Tasmanian (TAS) rainbow fingerlings were also stocked'in the Animas <br />River (sections land 2) in late August 1987. These fingerlings were not <br />marked and averaged 8.7l cm in length at stocking. They ranged in size from <br />11-2l em total length and averaged 16.3 cm. Population estimates for the <br />TAS rainbows for the Animas River, sections 1 and 2, were ll6and l,324, <br />respectively~ Reiterating, the population estimates for the,l987 <br />adipose-clipped ,plants of brown trout fingerlings were 62 and l,35l for <br />Animas River sections land 2, respectively. If the sections were stocked <br />with equal ,numbers of both species as shown in Table 5, what could be the <br />explanation for the poor survival of the fingerlings planted in section 1 of <br />the ,Animas River? Th~ most likely explanation is that those stocked in <br />section 2 were hand-stocked in small numbers evenly throughout the entire <br />reach out of a Jon boat. In contrast, those fingerlings stocked in section <br />1 were planted out of hatchery trucks at fewer distribution points and much <br />higher densities at each point. This technique probably leads to high <br />losses to predation by larger brown trout and/or avian predators such as <br />king fishers and mergansers. Heavy'predation losses to brown trout were <br />noted in the fingerling plants made on the Coller Wildlife area of the Rio <br />Grande in both 1985 (Nehring 1986) and in 1987. <br /> <br />It is gratifying to see that' both rainbow and brown trout fingerlings <br />stocked in the Animas River in 1986 and 1987 are surviving at least as well <br />as expected, if not better. <br /> <br />Blue River <br /> <br />The Blue River (between Dillon and Green Mountain reservoirs) was first <br />stocked with fingerling rainbows (both CRR and TAS strains) in late-August <br />1987. Due to their small size at stocking, the slow growth rates in the <br />Blue River (high elevation and cold water temperatures), and only 45 days <br />between stocking and our population estimates, no population estimates were <br />possible. However, we did collect some fingerlings of both (CRR and TAS) <br />strains at the three electroshocking sites in October 1988. A few were also <br /> <br />..., <br />c, <br /> <br />Ii (10002402 <br />