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Federal Regi&-~ / Vol, 58. No, 18 / Friday. January 2~~93 I Proposed Rules 6583 Pursuant to section 4(b)(2) of the Act, critical habitat is to be designeted on the basis of the best scientific data available. and after considering. the economic and other impacts of designation, Areas may be excluded from the designation if the Secretarv detetmin.. that the benefits of exclusion outweigh the benefits of critical habitat d..ignation, unless the exclusion will result in the species' extinction. This designation of critical habitat for the Colorado River endangered fish consisted of three major steps, The first step was to complete a biologically-, based determination of potential critical habitat areas. The second step will detennine the impacts of this designation. Tha third step will ba to decida which areas, if any. should be excluded based upon economic or other relevant impacts and to detennine the costs and benefits associated with the final designation, The first step required an inventory of areas needed for the survival and recovery of the four species, For the razorback sudeer. the biological delennination was based on the primary constituent elements. additional selection criteria determined by the Service, 'past Service findings. and other published and non published sources, These constituent elements and selection criteria were then applied throughout the historical range of the razorback sudear, For tha Colorado squawfish. humpbade chub. and bonytail chub, the biological datennination was based on the primary constituent elements. recovery plans for these speci... past Service findings. and other published and nonpublished sources, The biological support document will provide the details of the biological detanninations, The second step will be to detennine the potential Impacts of the proposed designaticns. These impacts will be addressed in the economic analysis, The third step will be to decide which areas, if anv. should ba excluded based upon a detOrmination that tha benefits of the axclusion outweigh the benefits of designation unless the axclusion will result in the extinction of eny of the four species, Any changes in critical hahitat areas resultins from the exclusion process will be noted in,the final rule, Additional Selection Criteria for the Rozorbock Sucker Bacause a recovery plan for the razorback sucker has not yet been prepared, additional selection criteria were developed to assist the Service in malting e determination of which areas to propose as critical hebitat. Previous Service findings. other publishad and unpublished literature sources. and discussions with individual membera of the Colorado River Fishe. Recovery Teem were utilized to deveiop the constituent elements and additionel selection criteria. The razorbade sudeer hes displayad a degrae ofversatility in its ability to survive and spawn in different habitats. However. razorback sucker populations continue to decline and are considered below the survivellevel. Thus. a. versatile as the razorback sucker appears to be in selecting spawning habitat. there has been little or no recruitment of yaung to the adult population. Therefore. special consideration was given to habitats required for its reproduction and recruitment. The following selection criteria were used by tha ServiCllto help detennine areas necessary for survival and recovery of the ruorback sudear, 1, Known or suspected wild spawning populations. although recruitment may be limiting or nonexistent. 2, Areas where juvenile razorback suckers have been collected or whicn could provide suitable nursery habitat (backwaters. flooded hottomlands. or coves). 3, Areas presently occupied or that were historically occupied that are considered neCllssary for recovery and that have the potential for establishment of razorback sucker, 4, Areas and water required to maintain rangewide fish distribution, and divarsity under a variety of physical. chemical, and biological conditions. 5, Areas that need special management or protection to insure razorback survival and recovery. These areas once met the habitat needs of the razorback sudeer and may be recoverable with additional protection and management.. Summary The primary constituent alements were applied throughout the historical range of the Colorado River endangered fishes,ln addition. the five selection criteria described above were also used to evaluate potential razorback sudeer critical habitat areaa. The proposed critical habitat designations are based on the primary constituent elements. published and unpublished sources, Service reports and other findings,. recovery plans (for Colorado squawfish, bumpback chub. and bonytail chub). additional selection criteria. and the preliminary recovery goal. being presenlly discussed far the razorback sucker by the Colorado River Fishes Recovery Team. Proposed Critical Habitat Designation The resuits of the critical habitat inventory process described above are presented'in this section. The presence of one or more primary constituent elements did not automatically result in inclusion es proposed 'critical habitat, Section 3(5llC) of the Act stat.. that "Except in those circumstances determined by the Secretary. critical habitat shell not include the entire geographical area which can be oceu pied by the threatened or endangered speci~." ThIs proposal is in compliance with the provisions of the Act, as only a portion of the historical range is proposed for designation. A detailed discussion of the biological basis for selection of each river reach proposed for critical habitet will be included in the biological support document. This will includea discussion of which attributes of tho constituent elements may need to be enhanced. The critical habitat areas proposed below are those that the Service believes are required for the survival and recovery of each speci.., Figure 1 displays the total extent of proposed critical hahitat for ell four species combined, This includes the considereble overlap of proposed critical bahitat between species. A specific description of the location of aach area proposed for critical habita.l is provided later in this rule, B1WNO CODE 431o...a-M