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<br />002J38 <br /> <br />Bcth populations began to spawn by 1990, with growth averaging only 20 mm for <br />Sandbeach from September 1989 to September 1991, and 16 mm for Pear from <br />September 1989 to July 1991. <br /> <br />Tag studies conducted on the Hunters Creek historic population, indicated that <br />growth for sUt greenbacks (178-252 I\1I'l\ in length), averaged only 6 '1 from June <br />1988 to June 1989 with no measurable change in length. Hunters Creek is 2,896 <br />m in elevation, and has a large (118 kg/ha) stable fish population that is <br />used fcr egg collections and is closed to fishing. <br /> <br />Diaeaa. and paraait.a <br /> <br />The first mcdern fish pathology work on wild greenbacks was conducted prior to <br />the transfer of 64 Como Creek greenbacks to the USFWS, Fish Technology Center <br />in 1977. Fecal material, ovarian fluid and seminal fluid from 78 como Creek <br />pre-and post-spawning greenbacks failed to show any viral activity when <br />inoculated cnto susceptible tissue cultures. One moribund greenback collected <br />from como creek on June 22, 1977, had numerous Gvrodactvlus .!!l!e. .and <br />Glossatella.!!l!e. covering the body, with Hexamita.!!l!e. and CreDidostomum. <br />farionis within the intestinal tract. Although bacteria were present within <br />the kidney, they were nonobligate to salmonids. Following the transfer of the <br />COmo Creek greenbacks to the FTC, 11 greenbacks were lost within six months. <br />Examinaticn of these fish revealed no viral activity, and no clinical <br />bacterial infection was found although Pseudomonas .!!l!e. and Aeromonas <br />hvdroDhilia were isolated. Additional non-lethal fish disease samples (fecal, <br />seminal fluid, ovarian fluid) ccllected.from Hunters Creek, Upper Hutcheson <br />Lake and South Fork of the poudre River from 1983 to 1990, found no viral <br />activity and no obligate fish bacterial infecticns. Fish diagnostics work was <br />performed by the USFWS, Fish Disease COntrol center, Fort Korgan, colorado. <br /> <br />Due to the concern over the recent .introduction of whirling disease (Kvxobolus <br />cerebralis) to COlorado, experiments were conducted on the response of <br />greenbacks to whirling disease at the USFWS, Naticnal Fish Heath Research <br />Laboratory, in conjunction with the Cclorado Divisicn of Wildlife. The <br />experimental exposure cf two to three month old greenbacks to a light exposure <br />of whirling disease (Kvxobolus cerebralis), indicated that greenbacks produced <br />7.5 times less H. cerebralis spores than rainbow trout after three months, and <br />15.6 times less spores than rainbows after sut months. However, infected <br />greenbacks weighed about 45' less than the infected rainbowS, with greenback <br />mortalities 26' tc 32\, compared to 3 percent tc 4 percent for infected <br />rainbows. These results indicate that although. greenbacks showed no overt <br />signs of infections (skeletal deformities and tail chasing), mortalities for <br />infected greenbacks were higher than for infected rainbow trout. Kortalities <br />of unexposed controls were cne percent for both species (Karkiw 1990). <br /> <br />s.naitivitv to DB <br /> <br />Research conducted by Woo~ward (1991), indicated that the threshold <br />concentration cn greenbacks in the absence of aluminum was pH 5.0. However, <br />adverse effects were cbserved at pH 6.0 when 50 ug/l of aluminum was present. <br />Greenback alevin and swim-up larva were found to be more sensitive to acidic <br />pH and elevated aluminum than eggs and embryos. However, growth of greenbacks <br />waS not reduced .t low pH, as was observed in Snake River and Yellowstone <br />cutthroats. Reduced pH is a concern, because most of the historic greenback <br />populations and greenback restoration projects are located in alpine habitats <br />that are susceptible to acid precipitation. <br /> <br />11 <br />