Clark Hubbs

An Annotated Checklist of the Freshwater Fishes of Texas, With Keys to Identification of Species

University of Texas at Austin, University of Texas - Pan American, Texas Parks and Wildlife Department

Some Effects of Introduced Fishes on the Native Fish Fauna of Southern Nevada

(Gregory 1933, Fig. 283). Development of the upper jaw in the Iniomi is similar initially to that in the Isospondyli, but while still in the larval stage the premaxillaries continue to grow posteriad and force the maxillaries completely out of the gape. The presence of transitory teeth on the maxillaries in larval Scopelosaurus may be indicative of a close phylogenetic association of this family with the Isospondyli. Representatives of other, higher orders of fishes studied develop the upper jaw structure in a manner similar to that in the Iniomi. This indicates that fishes in most of the

FECUNDITY AND EGG SIZE IN TWO CENTRAL TEXAS DARTER POPULATIONS

More than 1500 measurements were made of mature eggs from females obtained from two populations of central Texas darters (Etheostoma spect- abile from the Llano River at Junction and Etheostoma lepidum from the South Concho River 4 miles south of Christoval). Junction eggs averaged 1.515 + 0.002 mm and those from the South Concho 1.301 ? 0.031 mm. Female size did not seem to influence egg size, with small eggs as likely in large as in small females. Eggs from females collected in November and April were smaller than those from fish of the same population collected in December through March. More than 2500 counts were made of egg complements of females from the same two populations. The number of eggs increased geometrically with female size, and the rate of increase approximates a squared relationship. Apparently digestive absorptive surface is more limiting than coelomic space. The largest females may have fewer eggs than medium sized females, especially toward the end of the breed- ing season. Females collected in February and adjacent months have more eggs than those obtained in other months. The difference is caused by more eggs in equivalent sized females. The fecundity of an animal is the product of frequency of spawn- ing and number of eggs produced per spawning interval. Although egg number would appear to be rather easily ascertained, little is known about spawn variability or factors causing it. The potential maximum number of eggs in a female is the result of available dis- tended coelomic space divided by average egg volume. Either volume varies among females or maximum potential is seldom achieved, be- cause spawn variation has been demonstrated and is obvious in our counts. Therefore, egg number in fishes may be limited by several factors including available coelomic space and nutrition. Sviirdson (1949) pointed out that equivalent-sized females can pro- duce large numbers of small eggs or small numbers of large eggs. A female could concentrate her nutrients in a few eggs, each of which would have a high survival potential, or spread them over many small eggs, each with low survival potential. Genetically controlled differ- 301

Distributional patterns of Texas fresh-water fishes.

Distribution patterns of most fresh-water fishes in Texas closely resemble those of terrestrial organisms, though there are 3 exceptional groups: (1) those limited by stream divides, (2) those of marine and freshwater forms meeting in fresh waters near the coast, and (3) certain species of northeastern Texas (Austroriparian) whose ranges include outliers or extensions into other biotic provinces. It is concluded that the basic factors controlling distribution patterns of fishes are climatic and geological, these determining the properties of the water. In recent treatments on the biogeography of Texas, many distributional patterns have been delimited (Blair, 1950, and Tharp, 1939 and 1952). Although Tharp divided the state into more subdivisions than did Blair, the demarcation lines for his Vegetation Regions conform closely to those for Blairs Biotic Provinces and Districts (Fig. 1). In addition, Tharp emphasized differences associated with the coastal prairie more than Blair, who in turn separated the district known as the lower Rio Grande Valley more distinctly. Their areas approximate those of Johnson (1931) as both authors correlated the biologic distributions with geologic and climatological data. Obviously, the edaphic and climatic factors are critical to the survival of organisms in any region. Both Blair and Tharp base their conclusions chiefly on the distribution of terrestrial organisms. At least one group of aquatic organisms, the fishes, has distributional patterns that closely resemble those derived from terrestrial studies. Correlation of fresh-water fish distribution with Life Zones in Texas as given by Bailey (1905) is not very close. The life-zone boundaries of Bailey that approximate the boundaries of Blair and Tharp fit the, distribution patterns of fresh-water fishes, whereas no correlation is noted where Baileys boundaries differ. Additional support for the general validity of these boundaries can be derived from the geographic distribution of historic Indian groups. Kroebers (1939) maps for Indian tribal areas roughly correspond with Blairs and Tharps regions. T. N. Campbell (personal communication, 1957) reports that the correlation at about 1500 A.D. is perhaps even better than indicated by Kroeber. He would locate the Caddo and Atakapa Indians in the Austroriparian Biotic Province with occa-

INTERFERTILITY BETWEEN TWO SYMPATRIC FISHES, NOTROPIS LUTRENSIS AND NOTROPIS VENUSTUS

The redhorse shiner, N otropis lutrcnsis (Baird and Girard) and spottail shiner. N otropis uenustus (Girard) are among the most abundant fishes in southwestern North America. They are considered to belong to separate subgenera, Moniana and Erogala respectively, by Hubbs (1955). The close relationship between the subgenera is shown by their adjacent position among the twelve subgenera of N otropis recognized by that author. The two species do not occupy entirely identical geographic ranges. N otropis uenustus is the more eastern in distribution. Populations are found from the Devils River and the adjacent section of the Rio Grande, Texas, to the coastal streams emptying into the Gulf of Mexico near Houston. It is apparently absent from the Tamaulipan Biotic Province of Blair (1950). From Houston the range extends eastward in the coastal streams to the Apalachicola River in Georgia and Florida. Spottail shiners are found northward in the Mississippi River Valley to southern Illinois. The eastern and northern limits of the geographic range of the spottail shiner is taken from that given by Bailey, Winn, and Smith (1954). We have noted no pronounced morphologic variations of spottail shiners in those Texas populations we have studied. The northern limit of the range of Notropis Iutrensis extends from southeastern Wyoming, through Nebraska, southeastern South Dakota, western and southern Iowa, to central Illinois. The eastern limit extends from central Illinois southward in small numbers along the Mississippi River to southeastern Mississippi, and thence in fresh and even slightly brackish water along the western Gulf of Mexico to northern Mexico. It has not been recorded from the Ozark Highlands. Small populations are found in sandy streams along the Arkansas River as it passes through the Ozarks. On the west the redhorse shiner ranges from southeastern Wyoming through central Colorado and central New Mexico to Mexico. The southern extent of the range, in northern Mexico, is incompletely worked out. The problem there is complicated by the presence of many isolated populations that may be conspecific with N. lutrensis. The variability shown by the isolated populations in Mexico is continued over the adjacent semiisolated drainages in Texas and New Mexico. All of the individuals of the

Fertilization, Initiation of Cleavage, and Developmental Temperature Tolerance of the Cottid Fish, Clinocottus analis

Eggs from coldwater stations are more cold adapted than are the warm adapted eggs from warmwater stations. Eggs exposed to diurnal temperature changes have survivals approximating that occurring at the more optimal temperature. Thermal lethalities are associated with failures at gastrulation, initiation of circulation, hatching, and perhaps melanophore formation. Hatching appears to be stimulated by agitation. Developmental rates are nearly equal above 20? C but double with an increase of 7 or 8? C at lower temperatures.

Effects of Thermal Fluctuations on the Relative Survival of Greenthroat Darter Young from Stenothermal and Eurythermal Waters

Adaptation of a stenothermal spring population of greenthroat darter young to thermal fluctuations is compared experimentally with that of eurythermal stream populations of the same species. A constant temperature locality was chosen for the stenothermal population collection site. Stocks of the stream population were obtained from 3 nearby areas in the same stream system. Experiments were carried out on zygotes derived from gametes removed from wild—caught parents and the resulting developmental stages through late larvae. Results showed increased resistance to thermal shock with increased temperature fluctuations. See full-text article at JSTOR

Developmental Rates of Menidia audens with Notes on Salt Tolerance

Abstract Fertilized eggs of Menidia audens were incubated at temperatures from 10.2 to 36.4 C, normal development occurred between 13.2 and 34.2 C, high survival was between 17.0 and 33.5 C, and optimal development seemed to be between 20 and 25 C. Cold lethality was associated with depletion of yolk supply prior to hatching. Eggs in 1/4 sea water did as well as those in fresh water; development through eye pigmentation was normal even in full strength sea water. Adults were more salt tolerant with critical salinities being near full sea water.

RELATIVE VARIABILITY OF HYBRIDS BETWEEN THE DARTERS, ETHEOSTOMA SPECTABILE AND PERCINA CAPRODES

INTRODUCTION on great variability of wild fishes. Moreover, F 1 hybrids between two minnows, The frequency and degree of natural N otropis lepidus and N. uenustus, have hybridization between fishes recently has also been shown to be much more variable been reviewed by Carl L. Hubbs (1955). than their controls (Clark Hubbs, 1956). Although many hybrids between species The hybrid swarms reported in the lit(and genera) have been reported, relaerature may still involve hybrid fertility tively few have been reported as fertile. as many valid fish species have been Most of the reported hybrid fertility is shown to produce fertile hybrids. Conbased, at least in part, on the relatively siderable work has been done on fertility increased degree of variability of the wild of hybrids between Turkish cyprinodonts. hybrids. These include those between Four species, Kosswigichthys asquamaN otropis rubellus and N. cornutus (Ibid.: tus, Anatolichthys splendens, Anato10), Hesperoleucas symmetricus and Lalichthys transgrediens, and Aphanius vinia exilicauda (Ibid. : 10), Lepomis chanteri, are considered to be of hybrid macrochirus and L. cyanellus (Ibid. : origin by Aksiray (1952), and both 2), N otropis lutrensis and N. venustus species of Anatolichthys by Kosswig (Clark Hubbs, Kuehne, and Ball, 1953: (1953). These authors have demon226), Siphoteles mohavensis and Gila strated experimentally that many of the orcutti (Carl L. Hubbs and Miller, female hybrids between these forms and 1943). With the exception of the N 0their near relatives (parental types?) are tropis lutrensis and N. venustus hybrids occasionally fertile, but they have only reported on by Clark Hubbs and Strawn produced fertile males from the cross be(1956), the fertility of the above hytween A. splendens and A. transgrediens. brids has not been confirmed experimenIn addition many partially fertile hybrids tally. As one of the F 1 hybrid samples have been produced experimentally behere reported is much more variable than tween poeciliids of the genera Xiphoits controls, doubt is cast upon the validphorus by Gordon and other workers and ity of assuming hybrid fertility based only M ollienesia by Carl L. Hubbs, although

Life History Dynamics of Menidia beryllina from Lake Texoma

Life history calculations for Lake Texoma Menidia beryllina (Cope) show that female fecundity is size-dependent with egg numbers ranging up to ca. 2000 eggs per female per day of a 3-month breeding period. During that time female growth cannot be demonstrated and extensive mortality results in virtually no adults surviving to spawn a 2nd year. Growth is density-dependent and reproduction can occur if youngof-the-year achieve minimum spawning size before water temperatures exceed the maximum breeding limit of ca. 30 C. INTRODUCTION Detailed life-history summaries are available for few fishes, especially for small species with short life spans. Substantial background information is available on feeding and reproduction that can facilitate life-history calculations for Menidia beryllina (Cope) inhabitating Lake Texoma. Most of the published reports on Menidia in Lake Texoma reference the Mississippi silverside (Menidia audens); however, Chernoff et al. (1981) demonstrate extensive integration with the tidewater silverside (Menidia beryllina). I agree with their conclusion that the two morphs are conspecific and use the latter name to comply with scientific name priority. Lake Texoma was formed by Denison Dam in 1942 and filled to power pool level in 1945. At this level, the lake has a surface area of 36,000 ha and a shoreline of 933 km (Patten et al., 1975). When first filled, Lake Texoma had dense populations of the brook silverside (Labidesthes sicculus). The first reported collection of Menidia in Lake Texoma was in 1953 (Riggs and Bonn, 1959). By 1955 Menidia had attained population densities equivalent to those of Labidesthes in earlier years. It seems apparent that Menidia were inadvertently released into Lake Texoma in the early 1950s from an unknown source. This hypothesis of introduction is supported by the first known occurrence of Menidia in Oklahoma in 1949 (Moore and Cross, 1950) and by the absence of Menidia at inland locations in Texas prior to 1950 (Bonn and Kemp, 1952). Tilton and White (1964) demonstrate and document a spread of tidewater silversides in the Colorado River Basin in Texas. The Lake Texoma stock of Menidia was the source of the silversides stocked into Clear Lake, California (Carl D. Riggs, pers. comm.). Food habit studies by Saunders (1959), Elston and Bachen (1976) and R. Drenner (pers. comm.) have shown that the Lake Texoma stock of Menidia feeds extensively on copepods, cladocerans and chironomids. Elston and Brachen (1976) reported they feed mostly during daylight hours (0700-2000 hr) in August and they suggested a 1-hr stomach retention time. If so, they have ca. 14 daily feedings. If those feedings average only 1 % of total biomass, a daily ingestation of 14% of the biomass occurs. Observations during May, June and July 1980 (the Lake Texoma breeding period) suggest more nighttime feeding by Menidia (Michael Bleakley, pers. comm.).