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<br />922
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<br />COPEIA, 1998, NO.4
<br />
<br />(3/7) of the captures, whereas 43% of the time
<br />it was called X. texanus hybrid. Once it was des-
<br />ignated as X. texanus. During the data collection
<br />process, biologists noted on two different occa-
<br />sions that it possessed "a definite keel" or "a
<br />small, distinct keel." Similarly, individual
<br />"7F7F33064D" was captured four times. It was
<br />designated as C. latipinnis in 75% (3/4) of its
<br />captures. Yet, in its final capture, it was desig-
<br />nated as X. texanus hybrid with "a small but def-
<br />inite keel." From the above, one point is clear.
<br />The ability in this study to recapture (and thus
<br />reexamine) potential hybrids was a great aid in
<br />their eventual diagnosis.
<br />Results from our study underscore the pau-
<br />city of baseline data for these species in Grand
<br />Canyon (as per Miller, 1946). Two areas of ad-
<br />ditional research are recommended. The first is
<br />a Grand Canyon-wide genetic study to estimate
<br />patterns of variability and divergence among en-
<br />demic fishes. This is especially necessary for C.
<br />latipinnis, which may encompass several forms
<br />within Grand Canyon [Minckley, 1973; unpubl.
<br />(cited in Minckley, 1991:159); Minckley and
<br />Holden, 1980]. Genetic research is also re-
<br />quired to ascertain extent of hybridization and
<br />backcrossing between C. latipinnis and X. texan-
<br />us.
<br />Long-term monitoring of these (and other)
<br />big-river fishes is also required. Research should
<br />focus at confluences of major tributaries (Paria
<br />and Little Colorado Rivers; Bright Angel, Shin-
<br />umo, Tapeats, Kanab, and Havasu Creeks). Our
<br />data show X. texanus/C. latipinnis hybrids move
<br />extensively into and from the LCR. Monitoring
<br />of other low-gradient tributaries (Paria River
<br />and Kanab Creek, for example) may discover
<br />similar aggregations. Catostomus latipinnis also
<br />has a demonstrated propensity to congregate at
<br />(and enter into) a variety of tributary outflows,
<br />and it is there it can be most parsimoniously
<br />monitored.
<br />Like X. texanus, C. latipinnis is also capable of
<br />long-range movements (S. Weiss, M. Douglas, B.
<br />Persons, and R. Valdez, unpubl.), Sampling
<br />should thus be extensive enough to statistically
<br />verify these movements within Grand Canyon
<br />yet possess sufficient resolution that local (or
<br />tributary) year classes can be adequately moni-
<br />tored. Knowledge of the latter is particularly im-
<br />portant as benchmarks for recruitment and on-
<br />set of senescence. In this way, C. latiPinnis can
<br />be adaptively managed and protected within
<br />Grand Canyon before it is pushed into endan-
<br />germent.
<br />
<br />ACKNOWLEDGMENTS
<br />
<br />Numerous individuals were involved in data
<br />collection: G. Aldridge, B. Bagley, N. Brian, J.
<br />
<br />Cook, G. Doster, J. Dunham, B. Dunnigan, A.
<br />Fegley, E. Gustafson, M. Horn, R. Larson, E.
<br />Montoya, C. Minckley, R. Mose, D. Oakey, D.
<br />Palmer, R. Reed, P. Ryan, R. Shepherd, R. Tim-
<br />mons, D. Valenciano, and R. Van Haverbeke. C.
<br />Weber entered and edited data. Grand Canyon
<br />National Park (GCNP) allowed research within
<br />the park's boundaries. GCNP and Arizona
<br />Game and Fish Department (AGFD) provided
<br />permits to collect fish at the confluence, where-
<br />as Nav~o Fish and Wildlife Department (Navajo
<br />Nation) supplied a permit for the Little Colo-
<br />rado River. The U.S. Fish and Wildlife Service
<br />(USFWS) allowed us to engage in endangered
<br />fish research as a sub-permitee under Federal
<br />Permit 676811. The cooperation and assistance
<br />of these organizations and agencies are appre-
<br />ciated. The biology of endemic Colorado River
<br />fishes was discussed earnestly and often with W.
<br />Minckley and T. Dowling (Arizona State Univer-
<br />sity), C. Minckley (USFWS), R. Miller (Univer-
<br />sity of Michigan), P. Ryan (Navajo Natural Her-
<br />itage Program; NNHP) , T. Hoffnagle and W.
<br />Persons (AGFD), B. Masslich and R. Valdez
<br />(Bio/West, Inc.), and D. Wegner and M. Yard
<br />(Glen Canyon Environmental Studies, Bureau
<br />of Reclamation). Reviews were provided by R.
<br />Miller, C. Minckley, and M. R. Douglas; N. Ar-
<br />nason expedited analyses using POPAN-4; and
<br />D. Buth and T. Dowling shared genetic data on
<br />X. texanus. A bibliography of endemic fishes in
<br />Grand Canyon (compiled by C. Minckley under
<br />BOR I-FC-40-10500; Special Collections, Hay-
<br />den Library, ASU) was an important source of
<br />unpublished information. This project was
<br />funded by Bureau of Reclamation under Con-
<br />tract BOR-I-FC-90-10490 to ASU/NNHP (D. L.
<br />Wegner, Project Manager).
<br />
<br />...
<br />
<br />LITERATURE CITED
<br />
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<br />BROWNIE, AND K. H. POLLOCK. 1987. Design and
<br />analysis methods for fish survival experiments
<br />based on release-recapture. Am. Fish. Soc. Monogr.
<br />5:1-437.
<br />BUTH, D. G., R. W. MURPHY, AND L. ULMER. 1987.
<br />Population differentiation and introgressive hybrid-
<br />ization of the flannelmouth sucker and of hatchery
<br />and native stocks of the razorback sucker. Trans.
<br />Am. Fish. Soc. 116:103-110.
<br />CAROTHERS, S. w., AND B. T. BROWN. 1991. The Col-
<br />orado River through Grand Canyon: natural history
<br />and human change. Univ. of Arizona Press, Tucson.
<br />CHART, T. E., AND E. P. BERGERSEN. 1992. Impact of
<br />mainstream impoundment on the distribution and
<br />movements of the resident flannelmouth sucker
<br />(Catostomidae: Catostomus latipinnis) population in
<br />the White River, Colorado. Southwest. Nat. 37:9-15.
<br />DOBSON, A. P., J. P. RODRIGUEZ, W. M. ROBERTS, AND
<br />
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