Reproduction of three species of suckers, Catostomus catostomus, the longnose sucker, Catostomus commersoni, the white sucker, and Catostomus macrocheilus, the largescale sucker, has been studied in British Columbia during the summers of 1956 and 1957. These species spawned in the spring months depending on locality and annual differences in climate. 'White and longnose suckers spawned primarily in inlet streams although moderate runs of the former to outlet streams have been noted. Largescale suckers usually spawned in outlets. No lake spawning was observed. Overlap of breeding seasons and co-habitation of the same spawning stream by white and largescale suckers may explain occasional hybridization between these species. Spawning females matured a year later, were larger and lived longer than the males of all three species. Detailed work at Baker Lake, near Quesnel, indicated males entered the spawning stream before the females and generally remained till the females had returned to the lake. In 1956 the sex ratio of white suckers was 1:1. In 1957, 2 males to 1 female were present in the spawning stream. Low water levels may have prevented larger females, which were predominantly marked, from moving upstream. As a result of these conditions fish may have spawned in other streams thus masking any tendency to return to the same stream in successive years. The longnose suckers sex ratio of 2 marked females : 1 marked male suggests that a differential mortality acting either from hatching or after first spawning is in effect. Numbers of unmarked fish were not significantly different. Factors associated, with migrations at Baker Lake were studied. Adult migration was primarily at night. Numbers of white suckers migrating into the inlet stream were dependent on temperature change from one day to the next. A similar situation prevailed during the main portion of the longnose sucker run but no such relationship existed at the beginning of the run. Limno-logical conditions in the lake may have influenced migration to the creek. Fry in the inlet streams moved downstream at night. The migration was halted by placing a gas lantern over the creek. Juveniles remained in the outlet- stream up to four years before entering the lake. Their migration into the lake was related to rising temperature. / Science, Faculty of / Zoology, Department of / Graduate

Catostomus commersonii and Catostomus macrocheilus are sympatric in three major drainages of British Columbia. Morphological analysis employing a character index and discriminant function analysis of allopatric and sympatric populations revealed that hybrids occurred in nine lakes, representing virtually every lake examined where both species occur. Presumed F1 hybrids made up an average of 7% of the combined populations where hybrids occurred. There was no evidence of backcrossing or swamping. Spawning migrations were studied in eight confined inlets of lakes which have both species. Four inlets supported migrations of both species. Collecting was also done throughout the spawning migration in Cluculz River, an outlet with diversified habitat supporting both species. Postmating isolating mechanisms were studied from artificial crosses of the species, two back-crosses involving hybrid females, and microscopic examination of hybrid testes. An interaction of temporal, habitat, and postmating isolating mechanisms was not considered sufficient to prevent swamping. Ethological isolation is inferred to be of major importance in reducing initial hybridization, while selection against hybrid crosses is inferred to prevent swamping. Hybridization could not be attributed to environmental factors commonly noted in the literature to be associated with hybridization. Males of one species entering the spawning act with males and a female of the other species is considered the main cause of hybridization. Mis-mated individuals, however, have much opportunity for conspecific matings at other times. There was no evidence of reinforcement of isolating mechanisms despite the probable occurrence of hybridization in some areas for at least several hundred years. Natural selection against individuals producing hybrids is apparently low. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.)--Oregon State University, 2004. / Typescript (photocopy). Includes bibliographical references (leaves 118-127). Also available on the World Wide Web.

Thesis (M.S.)--University of Wisconsin -- La Crosse, 2007. / Includes bibliographical references (leaves 31-36)

The white sucker, Catostomus commersoni, is among the many fishes classified as minnows (order Cypriniformes). Minnows are a morphologically diverse teleost (bony fish) group whose brains have been examined previously in both a morphological and experimental context. Two species of minnows, goldfish (Carasius auratus) and European carp (Cyprinus carpio) have been commonly used as model systems for experimental neuroanatomical studies.The purpose of this present study is to catalog the brain of the white sucker for its use in future studies and as a comparative reference for the study of other catostomids. In particular, the neuronal connections of the cranial nerves could be explored once the brain has been characterized. This species was chosen because of its position as the outgroup for all other members of the genus Catostomus, and the fact that it is relatively easy to obtain. This study focuses on two areas: descriptions of the gross morphology of the brain of the white sucker, and histological characterizations of the nuclei of the brain of the white sucker. / Department of Physiology and Health Science

Selected aspects of the life history of desert suckers were examined in four southeastern Arizona streams. Diet, age class structure, reproduction, and habitat use were analyzed from field data obtained from April 1987 through October 1988. Adults fed primarily on plant matter, while fry fed almost exclusively on diatoms. Aging of suckers by scales was not possible and length frequencies were too evenly distributed to determine age class structure. In 1988, ovary and teste development occurred from late January through April, with spawning commencing in May. Suckers primarily used pools with high water flow and significant (∼80%) cover formed by tree limbs, branches, leaves, and other debris. Deterioration or loss of suitable habitat is reducing the range of the sucker due to reductions in and manipulations of surface waters.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 39-47). Also available on the World Wide Web.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed May 8, 2007). PDF text: xi, 207 p. : ill. (some col.), maps ; 2.21Mb UMI publication number: AAT 3237058. Includes bibliographical references. Also available in microfilm and microfiche formats.

Fish of the family Catostomidae, consisting of 11 genera and about 57 species, comprise a significant part of the fish fauna of Western North America. Life history information of some species is available (Bailey, 1969, and Brown and Graham, 1953, Catostomus catostomus; Dence, 1948, .f. commersoni; Douglas, 1952, Xyrauchen texanus; Geen et al., 1966, C. catostomus and C. coI!Dllersoni; Greenfield et al., 1970, .f. santannae; Harris, 1962, C. catostomus; Hauser, 1969,C. platyrhynchus; MacPhee, 1960, .f. macrocheilus; Nelson, 1968, .f.cotmnersoni and C. macrocheilus; Raney and Webster, 1942, C. commersoni; Smith, 1966, entire subgenus Pantosteus; Spoor, 1938, C. commersoni; Willsrud, 1966, C. tahoensis). Utah suckers, except those in Utah Lake, have received little attention (Frogley, 1950; Hatton, 1932; Lowder, 1951; Smith, 1966; Standing, 1954; Stubbs, 1966; Tanner, 1936). Reproductive studies of suckers have been limited to a description of spawning activities and estimates of fecundity (Geen, 1958, C. connnersoni C. catostomus and C. macrocheilus; Hauser, 1969, C. platyrhynchus; Mcswain and Gennings, 1972, Minytrema melanops; Wagner and Cooper, 1963, Erimyzon oblongus).

Thesis (M.S.)--University of Wisconsin -- La Crosse, 1976. / Includes bibliographical references (leaves 72-76).