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<br /> <br />C) <br />CJ <br />...~ <br />CD <br />1"'.., <br />--.] <br /> <br />drain locations in the San Juan Basin on larval razorback sucker and Colorado pikeminnow. They <br />concluded that copper and mixtures of inorganics could adversely affect larvae of both species in specific <br />sites where these contaminants were found in high levels, but in other sites, waterborne levels were not high <br />enough to cause adverse effects, Drainages from irrigation fields in the Shiprock, New Mexico, area and <br />streams such as the Mancos River and McEImo Creek, which were primarily irrigation return flow in late <br />sununer, were the major areas of concern. <br /> <br />The second study involved the effects of individual inorganics and five mixtures of inorganics on <br />flanneImouth sucker larvae (Hamilton and Buhl1997b). Copper was again found to be the major toxic <br />component-singly and in four of the mixtures tested--and zinc was the major toxic component in the other <br />tested mixture. Hamilton and Buhl (I997b) hypothesized that these elements and mixtures may be <br />adversely affecting flanneImouth sucker recruitment in some localized portions of the river, but that the <br />overall health and size of the flanneImouth sucker population in the river masked these detrimental effects. <br />They also noted that elevated levels of selenium in flanneImouth sucker and in the San Juan River may be <br />a causative agent for abnormalities noted in the Fish Health section of this report. <br /> <br />The third study investigated the effects of both elevated levels of waterborne selenium and selenium in the <br />diet of adult Colorado pikeminnow on reproductive success (Buhl and Hamilton 2000). Different levels <br />of waterbome and dietary selenium were used as different treatments in the experiment. The fish were <br />spawned, and the survival of eggs and larvae was determined. Buhl and Hamilton (2000) found that <br />elevated levels of waterborne and dietary selenium did not affect adult fish growth or survival. Not all <br />females in the experiment spawned, so not all of the treatments in the study had replicate spawns. Selenium <br />levels in eggs and newly hatched larvae were two-to-five times greater than those seen in the female <br />parents. Table 3,8 shows the survival and growth of the larvae produced in the experiment. Larvae in the <br />high-selenium treatments (both waterborne and dietary) had survival rates and growth similar to those <br />larvae in control treatments. Although lack of replications did not allow Buhl and Hamilton (2000) to draw <br />conclusions from their data, the results suggested that selenium, at the levels tested, had little effect on <br />reproductive success of Colorado pikeminnow, This indicates that selenium was not a major limiting factor <br />for this species in the San Juan River. <br /> <br />In 1993, the USFWS concluded in a Biological Opinion to the BLM that oil and gas leasing and <br />development activities were reducing survival of the endangered fish species in the San Juan River, This <br />resulted in the BLM joining the SJRIP and conducting a study evaluating the potential impact of oil and gas <br />activity in the San Juan Basin. The study had several phases, including developing a baseline for <br />polynuclear aromatic hydrocarbon (P AH) contamination in the basin, determining sites with the highest <br />potential contamination risk, sampling for P AHs in the river, and conducting studies of P AH toxicity to <br />native fishes. Samples in streams, dry arroyos, and well locations showed some P AH contamination, but <br />contamination tended to be spotty and generally low level (Odell 1997). The BLM concluded that oil and <br />gas activities were not contributing significant levels of P AHs to the San Juan River. <br /> <br />September 2000 <br /> <br />3-55 <br /> <br />Program Evaluation Report <br />