Description and ecology of larvae and juveniles of three native cypriniforms of coastal southern California

Larval series of the Santa Ana sucker, Catostomus santaanae (Federally Threatened), arroyo chub, Gila orcutti (California Species of Special Concern), and Santa Ana speckled dace, Rhinichthys osculus (California Species of Special Concern) are described from wild-caught specimens from the Los Angeles and Santa Ana river drainages. Santa Ana sucker larvae are elongate, having 41–46 myomeres and a distinctive paired-triangle patch of melanophores over the midbrain. Melanophores present on the snout, dorsal body, lateral midline, dorsal gut, postanal ventral body, and caudal fin. Preanal length 74–79% in body length (BL), typical of catostomids. Arroyo chub larvae relatively deep-bodied, 36–39 myomeres, and a heart-shaped patch of melanophores over the midbrain with a line of melanophores trailing posteriorly. Heavy pigment present on the snout, lower jaw, dorsal body, lateral midline, gill arches, dorsal gut, postanal ventral body, and caudal fin; short preanal length of 65–72% BL, typical of native North American cyprinids. Santa Ana speckled dace are similar to arroyo chub except for having less pigment on the ventral gut, large distinct melanophores on the ventrolateral caudal peduncle, a wedge-shaped patch of midbrain melanophores with no distinct line trailing posteriorly, and lateral midline melanophores that do not extend anteriorly. These three species often occur together and with nonnative cyprinids. Characters distinguishing them from other local larvae, including southern fathead minnow, Pimephales promelas confertus and red shiner, Cyprinella lutrensis, are discussed with their habitat preferences.     

Swimming Performances of Four California Stream Fishes: Temperature Effects

The critical swimming velocity (U_crit) of four California stream fishes, hardhead, Mylopharodon conocephalus, hitch, Lavinia exilicauda, Sacramento pikeminnow, Ptychocheilus grandis, and Sacramento sucker, Catostomus occidentalis was measured at 10, 15, and 20°C. Hardhead, Sacramento sucker, and Sacramento pikeminnow swimming performances tended to be lowest at 10°C, higher at 15°C, and then decreased or remained constant at 20°C. Hitch swimming performance was lower at 10°C than at 20°C. There were no significant differences among species at 10 or 15°C, although pikeminnow and hitch were ca. 20% slower than hardhead or sucker. At 20°C hardhead, Sacramento sucker, and Sacramento pikeminnow had remarkably similar U_crit but hitch were significantly (by 11%) faster. We recommend that water diversion approach velocities should not exceed 0.3ms^–1 for hitch (20–30cm total length) and 0.4ms^–1 for hardhead, Sacramento pikeminnow, and Sacramento sucker (20–30cm TL).     

Alcohol dehydrogenase variability in Hypentelium nigricans

The alcohol dehydrogenase enzyme system of Hypentelium nigricans has been analyzed by means of starch gel electrophoresis yielding two electrophoretically distinct alleles. Clinal variability is suggested with apparent fixation of alleles at the extremes of the sampled range.     

Effects of prey density on growth and survival of white sucker,Catostomus commersoni,and pumpkinseed,Lepomis gibbosus,larvae

Synopsis Growth and survival of white sucker and pumpkinseed larvae were examined in the laboratory in relation to prey density. Mortality of both species was greatest during the transition from endogenous to exogenous nutrition. Mortality prior to yolk absorption was substantial for white suckers and was not related to prey density whereas, pumpkinseed mortality during the same period was low. After yolk absorption, however, pumpkinseed suffered considerably higher mortality rates than white sucker larvae and, in both species, mortality and growth were directly related to prey density. The minimum prey density supporting 10% survival of pumpkinseed larvae was estimated at 0.16 plankters ml^-1 whereas, for white suckers it was 0.15 plankters ml^-1. Significant growth of both white sucker and pumpkinseed larvae, however, occurred only at prey densities higher than 0.25 plankters ml^-1. We suggest that since egg size and yolk reserve are greater in sucker larvae, suckers are better adapted to survive short term declines in prey abundance during the transition to exogenous feeding than pumpkinseed larvae. The reproductive strategies of each species seems to reflect this, with suckers spawning over a short time interval, but producing young with large yolk. Pumpkinseed, in contrast, spawn intermittently over an extended period but produce young with relatively small volk reserves.     

Biochemical identification of Moxostoma rhothoecum and M. hamiltoni

The acid phosphatase, glycerol-3-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and glucosephosphate isomerase enzyme systems of Moxostoma rhothoecum and M. hamiltoni have been analyzed by means of starch gel electrophoresis. The Roanoke River population has been biochemically identified as M. rhothoecum. Glycerol-3-phosphate dehydrogenase and glucosephosphate isomerase polymorphisms are described in M. rhothoecum.