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5 The DBO points out that data simply are not available from the Grand Canyon to unequivocally prove that the use of backwaters and other nearshore areas in the mainstem by larval through juvenile humpback chub would make a significant difference to the Grand Canyon population, because they have never occurred to allow the fish to respond to them. The Service hypothesizes that once improved habitat is formed through regulated floods, low steady summer flows would provide warmer water creating needed backwater habitat. The LCR is presently the only significant source of larval and young of the year humpback chubs. Since most of the predation and mortality of the larval fish occurs at the transition zone at the confluence of the mainstem Colorado River, it is doubtful many of these young fish could negotiate cold temperature of the mainstem to reach the warmer mainstem backwaters proposed to be created by low steady summer flows, and furthermore would be subject to predation from non- natives which would also seek out these warmer backwaters. Testing of this type of hypotheses would best be accomplished through the scientifically based Adaptive Management Program, particularly with the concern for reactions of non-native fishes to the low steady flow which may have negative ramifications for natives. Reclamation believes that these scientific issues should first be addressed through appropriate field and laboratory research to identify limiting factors. From a basis of data, we will then be able to determine and implement actions to improve habitat, provided endangered fish are able to successfully access and occupy it. New information resulting from this research and research from other areas could be the basis for reconsultation. The Service's only mandate in the Section 7 process is to consider whether the proposed agency action will cause jeopardy to the existence of an endangered species or cause destruction or adverse modification of critical habitat, and if so to develop an RPA which would alleviate such impact. The Service has stated that all elements of the RPA must be fully implemented to remove jeopardy. Some of these elements may not be achievable, such as establishment of a second spawning population, so theRPA may never remove jeopardy. The Service seems to be attempting to make a jUdgement call as to which operational scheme, MLFF or Seasonally Adjusted Steady Flows, would best benefit endangered fish. Inclusion of actions intended to maximize benefits for endangered species in the RPA goes beyond the Service's authority in the Section 7 process. In summary, we believe that the species would benefit more from a well defined and quantitative research and monitoring program rather than the adhoc initiation of steady flows. Reclamation proposes to implement as the Preferred Alternative, the MLFF Alternative with the change in maximum flow and ramp rate recommended by the Cooperating Agencies (see Enclosure 1). We also Rropose to-Accelerate studie~ to determine the feasibility and desirability of warming mainstem water temperatures through use of a Selectiv Withdrawal Structure at Glen Canyon Dam. A risk assessment would be complete so that knowledgeable predictions can be made regarding the impact of steady flows on the non-native fish community, and potential for competition and predation on native fish. In concert with the Adaptive Management Program, monitoring native and non-native fish response would be developed before initiating experimental steady flows. Research designs .for studying native/non-native interactions would be developed as well. Finally, and perhaps most importantly, a threshold criteria for adjusting or abandoning # H ~