Fish morphologically intermediate between Acrocheilus alutaceus and Ptychocheilus oregonensis have been collected infrequently from the Columbia River system. Morphological comparisons of wild Acrocheilus, Ptychocheilus, and intermediates, with artificial inter- and intra- species crosses indicated that wild intermediates were of hybrid origin. Observations of spawning habitat and behavior of the parent species suggest that hybridization in most localities is accidental. In Missezula Lake an unusually high incidence of hybrids, pronounced spatial separation of spawning groups of the parental species and presence of stray Ptychocheilus in the school of Acrocheilus all suggest that interspecific mating occurs. Hybrids are largely sterile, but hybrid males produce fertile sperm infrequently. The parent species show no evidence of gene flow, but a few intermediates are apparently backcrosses. Gene flow is probably blocked by the rarity and partial sterility of hybrids and by selection against backcrosses. The presence of wild backcrosses and partial fertility of hybrids suggest a large amount of genetic similarity between Acrocheilus and Ptychocheilus. This contention is strengthened by similarity in chromosome morphology and the presence of dominance effects in the inheritance of some parental characters in hybrids. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Diel substrate preferences were tested in artificial stream experiments for six cyprinids: redfin shiner (Lythrurus umbratilis), silver shiner (Notropis photogenis), spotfin shiner (Cyprinella spiloptera), central stoneroller (Campostoma anomalum), striped shiner (Luxilus chrysocephalus), and bluntnose minnow (Pimephales notatus). We used experimental pools containing two of three substrate types (sand, cobble, and gravel) per trial to test if habitat preferences differed in day and night observations. Over 85% of specimens were observed over cobble substrate during the day, and all species switched substrate preferences at night for the tanks containing cobble. Our results suggest that day-night differences in habitat use may occur in other small-bodied species. Interpretations for habitat use of these species in the majority of studies that are based on daytime observations may need to be modified. Interpretations for habitat use by fish assemblages in the majority of studies that are based on daytime observations may need to be modified. / Department of Biology

Thesis (Ph. D. (Ichthyology & Fisheries Science))--Rhodes University, 2004.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains v, 50 p. : ill. Includes abstract. Includes bibliographical references.

The dace (Leuciscus leuciscus (L.)) is a small, shoaling, rheophilic, lithophilic cyprinid fish, and is an important component of chalk stream ecosystems. Historical recaptures of marked dace in the River Frome suggested that some individuals were mobile, however it was unclear whether these movements occurred predictably in time or space. Migrations, defined as deliberate, temporally predictable translocations in space, allow individuals to exploit new resources, avoid predators and find a mate. However, energy is generally utilised during locomotion, and there are potential costs associated with moving to an unfamiliar environment, including reduced foraging opportunities, and increased predation risk. To be successful, individuals must find food, avoid predation and reproduce. If adult dace can solve these problems efficiently in one section of river, then considering the potential costs associated with migration, it would be most profitable for them to remain in this area. A range of techniques were used to study the migrations and habitat use of adult dace in the River Frome, covering both daily and seasonal cycles. The movements of 32 radio-tagged dace were tracked over a period covering over 16,000 hours. During this period 6864 radio locations were made, and radiotagged fish covered a combined minimum distance of over 109 km. A further 1724 dace were individually or batch marked, of which 128 were recaptured. In addition over 4000 dace were recorded on video as they passed through a fish counter. The daylight habitat use of 377 adult dace was visually observed from the bank, and habitat suitability indices created. The nocturnal habitat use of 11 adult dace was assessed using radio-active isotope tags, which were located on 247 occasions over a period covering 121 "fish nights". The adult dace observed in this study moved extensively, and their movements were both temporally and spatially predictable, and therefore constituted migrations. Of the 30 fish released at their capture sites, at least 19 moved more than 500m fi-om this site during the observation period. Spawning occurred in millstreams, and was preceded by an upstream migration. After spawning, slow flowing shaded sites out of the main river were selected by at least five out of six radio-tagged dace. A substantial upstream migration was observed in late spring, and diel migrations between separate distinct day and night habitats were observed during the summer. In autumn adult dace moved downstream and formed aggregations in the tidal reaches. Consequently, the hypothesis that dace occupy one section of the river throughout the year was rejected.

Chapter One Introduction Research in the structure, biochemistry, electrophysiology and mechanical properties of fish muscle is reviewed. A variety of mechanisms underlying temperature acclimation and adaptation is described. Chapter Two The effects of temperature acclimation on muscle relaxation in the carp (Cyprinus carpio L.1 1. Common carp were acclimated to either 7 or 21 ° for a minimum of one month, and the twitch contraction kinetics of a nerve-muscle preparation investigated. 2. A significant compensation for the acute effects of a temperature change was achieved in twitch kinetics by acclimation to 8 °. An acute drop in temperature from 20 to 8 ° in 20 °-acclimated preparations led to approximately 2 and 3 fold increases in the half times for activation and relaxation. Chapter Three The effects of temperature acclimation on the pCa-tension relationship of slow myotomal muscle fibres from the carp 1. Common carp Cvprinus carpio L.) were acclimated to either 7 ° or 2 3 ° for at least one month. 2. The pCa-tension relationship of skinned slow fibres isolated from the anterior myotomes was investigated at pH 7.0, 7.6 and at 0 ° and 15 °. 3. Sigmoid pCa-tension curves were obtained with 'n' (i.e. Hill coefficient) values between 2 and 3. 4. Temperature acclimation did not alter the sensitivity of the contractile apparatus to calcium under any of the conditions of pH or temperature investigated. Chapter Four The role of thyroid hormones in temperature acclimation 1. Common carp (Cyprinus carpio L.) were acclimated to either 8 ° or 22 ° for at least one month. 2. One group of cold-acclimated fish were made hypothyroid by treatment with methimazole (80mg/100ml 0.9% NaCl) 0.5?g/g body weight once every two days. 3. The level of T3 and T4 in the plasma of carp was determined using a radioimmunoassay technique. 4. Frozen sections of m. hyohyoideus muscles were cut and stained for the activity of succinic dehydrogenase and alkali-stable myosin ATPase to determine the percentage cross-sectional area of different fibre types. 5. m. hyohyoideus muscles from cold-acclimated fish had a higher proportion of slow oxidative fibres and fast oxidative glycolytic fibres than similar muscles from warm-acclimated carp. 6. The ultrastructure of slow myotomal muscle was investigated by electron microscopy. The volume fraction of mitochondria was higher in fibres from cold- than warm-acclimated fish (P < 0.01). The volume fraction of myofibrils decreased in the series cold-acclimated > warm-acclimated > cold-acclimated, hypothyroid (P < 0.01). The mean cross sectional area of individual myofibrils decreased in the series, warm-acclimated > cold-acclimated > cold-acclimated hypothyroid. 7. Hypothyroidism did not affect the total volume fraction of mitochondria in cold-acclimated fish. The volume fraction of mitochondria in the intermyofibrillar zone was higher in cold-acclimated euthyroid than hypothyroid fish (P < 0.001). 8. Neither temperature acclimation nor hypothyroidism affected the volume or surface density of cristae within mitochondria. 9. The effects of temperature acclimation and hypothyroidism on the performance, composition and ultrastructure of muscle are compared and the involvement of thyroid hormones in temperature acclimation is discussed. Chapter Five General Discussion The results presented in this report are discussed in the context of providing mechanisms that may compensate for the effects of low temperature on the rate of diffusion of small molecules through the cytosol.

Chapter 1. Part A reviews the current knowledge of temperature acclimation in teleost fish,with particular emphasis on skeletal muscle. There appear to be two types of response to low temperatures, dormancy or a homeostatic response. The homeostatic response serves to compensate for the reduced reaction rate usually seen at lower temperatures. In some species both responses occur depending on the water temperature. Part B reviews polymorphism in muscle proteins. All the myofibrillar proteins have been shown to exist as isoforms, which are differentially expressed in muscle types and with development. The isoforms expressed appear to be related to the contractile properties of the muscle. Chapter 2. The parvalbumin content, isoforms, and calcium binding characteristics were studied in the white muscle of 5° and 25° acclimated carp (Cyprinus carpio). The total parvalbumin concentration was 0.61-0.68mmols/kg wet weight. Two calcium binding sites per molecule and a dissociation constant of 2.1-2.4x10^-6 M were measured. No differences related to acclimation temperature were observed. Chapter 3. The myofibrillar ATPase from white muscle of 8° and 20°C acclimated carp (Cyprinus carpio) u/as shown to increase in cold-acclimated fish at both high and low assay temperatures. Electrophoretic analysis of the myofibrillar proteins showed a unique myosin light chain isoform to be present in cold-acclimated fish, and a unique troponin I isoform to be present in warm acclimated fish. The presence of tropomyosin and troponin T isoforms in carp white muscle was also noted. The (MLC3 + extra MLC):MLC1 ratio was found to be lower in cold- than in warm-acclimated fish Chapter 4. Myosin heavy chains and actin from the white muscle of carp (Cyprinus carpio) acclimated to 2°, 5°, 8°, 11° C, 15°, and 23° were studied by peptide mapping. No differences were found between fish from any of the acclimation temperatures for either protein. Chapter 5. The major findings of the study are discussed, in relation to the mechanisms that produce protein isoforms, and with reference to further studies.

The hybrid grass carp, a cross between the male bighead carp (Hypothalmichthys nobilis) and the female grass carp (Ctenopharyngodonidella), was first produced in the United States in 1979 for biocontrol purposes. Unlike the fish produced in 1979 and 1980, the hybrid grass carp spawned in 1981 were assumed to be uniform, triploid, and to have growth and feeding rates comparable to those of grass carp. A comparison study to determine differences in the morphology of the 1979, 1980, and 1981 hybrid grass carp revealed that the hybrid grass carp spawned in 1981 have a longer relative gut length, fewer deformities of the gill rakers, and fewer diploid fish than the previous spawns. In feeding trials, the growth rate of the 1981 hybrid grass carp (2.5 to 3.9 g fish-1 day-1) were similar to that of the 1979 and 1980 fish (2.8 and 3.9 g fish-1 day-1, respectively). In field tests, their mortality rate ranged from 20.8 to 97.4% and was similar to that of other hybrid grass carp. Due to the increased gut length, low feeding rate, and high mortality, the 1981 hybrid grass carp were unable to control (eliminate) the growth of aquatic vegetation in field trials in Blue Lake and in a detention pond which had been treated with herbicide prior to stocking. The 1981 hybrid grass carp has proven to be less effective than previous hybrid grass carp spawns as a biocontrol agent.

No description available.