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Species Accounts The following descriptive species accounts, except that for longnose sucker, are reproduced or updated from the earlier edition of this guide (Snyder and Muth 1990). Each 8-page account begins with an illustration of the adult fish, map of its distribution in the Colorado River Basin, brief summaries of adult diagnosis, reproduc- tion, and early life history, and a table of adult meristics. Much of this information was extracted from literature (and occasionally personal com- munications) listed at the bottom of the first page. Each account continues with description of the larvae and early juveniles. Page one con- cludes with a table of size at apparent onset of selected developmental events. Page two con- sists of a table of size at developmental-interval and gut-phase transitions and a table of morpho- metrics and meristics summarized by develop- mental phase. The next 4 pages illustrate eight stages of development from just hatched proto- larvae through early juveniles about 30 mm SL. The last two pages of each account consist of illustrations of selected skeletal characters and a table of frontoparietal fontanelle dimensions. Regarding reproduction, all seven catosto- mids are classified according to Balon's (197 5a, 1981) reproductive guilds as non-guarding, open-substrate, lithophils. Lithophils prefer to spawn over predominately rock or gravel sub- strates. Their recently hatched larvae are photo- phobic and usually hide or remain in the sub- strate for at least a few days before emerging and drifting with the current. Although consid- ered broadcast spawners, razorback sucker in reservoirs prepare discrete, nest-like depressions or redds (Bozek et al. 1984), which suggests a tendency toward a brood-hiding guild. 27