Interconnected freshwater habitats are essential for many fish populations, which allow fish to migrate between areas to fulfil their life-cycle and maximize their fitness. Currently, such populations are negatively affected by human habitat exploitation. As a result, the biodiversity in freshwater ecosystems is decreasing. In this study, I use data from surveys of two Asp (Leuciscus aspius) populations in Uppland to see how a representation of day length, water temperature and water current influence their spawning migrations. I also determine the difference in timing of migration between males and females, and if the individual body size matters. I found that day length, water temperature and water current affect the migratory behavior of Asp. I also found a significant difference in migratory timing between males and females, where males on average arrive 5-6 days earlier than females to spawning areas.

Dactylogyrus vastator Nybelin, 1924 is a common, economically significant pathogenic monogenean parasite of European carp, Cyprinus carpio L. D. vastator attaches to the gills by means of an attachment organ, the opisthaptor, which carries two large hamuli, a connecting bar and fourteen peripheral marginal hooks. Experiments during the present study have shown that populations of D. vastator on young carp reach peaks of abundance at 12°C, 19°C and 22°C within 5,3 to 4 and 6 weeks, respectively, followed by a decline to a lower level. Parasite abundance was greatest at 19°C and lowest at 12°C. Principal component analysis was used to investigate the effects of temperature on sclerite measurements. It was shown that the basic length and internal root length of the hamuli are the major factors by which populations of the parasite reared under different temperature regimes can be discriminated. Parasites reared at 12°C were clearly separated from those reared at 14°C and 19°C. Scanning and transmission electron microscopic studies were carried out on D. vastator. The outer layer of the epidermis is a syncytial structure. Circular and longitudinal muscle is found beneath this outer layer. The muscle bands are not of uniform thickness. Epidermal secreting cell bodies are located below the muscle layer and communicate with the outer layer via ducts or channels. Possible. epidermal sensillae are unequally distributed over the worm's body. The parasite has four cephalic lobes each of which is provided with a cup-like opening at the border; the unicellular cephalic gland cells empty their contents into a collecting duct. D. vastator shows protandous gonadial development. The female reproductive system has an oval shaped ovary, uterus, ootype, accessory glands, whereas the male reproductive system has a single lobed testis located in the posterior region of the body. Clean sclerites prepared by using an ultrasonication technique were examined under the electron microscope. The hamuli of adult and immature dactylogyrids are divided into internal and external processes and a shaft which ends in a spike. Marginal hooks have a blade and spike. The adult and immature worms can be differentiated by the structure of the auxiliary sclerite. In mature specimens the outer and the inner surfaces of the auxiliary sclerite remain separate. The surface of the hamuli has an interlocking array of striations. The two hamuli are of unequal size in both adult and immature worms. The parasites are not randomly distributed over the gill apparatus. There were no significant differences between gill arches but parasites aggregated in certain areas of the gills, in particular the ventral proximal secondary filaments on both sides of the hemibranch are favoured. Smaller D. vastator which are found in higher numbers on fish presumably represent worms which have recently invaded the host. Larger worms are found in lower numbers. This may be due to competition or an age related mortality in which mature worms die off. D. vastator does not need to be attached to the host tissue to initiate egg laying. In-vitro oviposition was observed and described, however the egg laying rate varies with the environmental temperature. The first eggs that are produced in-vitro are of a large size but as time continues the size of the eggs becomes smaller. A severe hyperplastic tissue response was observed two weeks after the start of an experiment where fish infected with D. vastator were mixed with naive fish. Damage to the host gills caused by D. vastator was observed. Hyperplasia of gill tissue led ultimately to fusion of the secondary lamellae. Affected fish became lethargic and gulped air at the surface. Challenge experiments were carried out to investigate whether there is an acquired immunity by carp to D. vastator infections. The challenged fish had a significantly lower parasite burden compared to the naive fish. The infection causes a change in the blood proteins, as was clearly shown by comparison of infected and uninfected fish, the former having very visibly separable additional bands using gel electrophoresis.

Oviposition-site decisions can have disproportionate effects on offspring survival and success, and while the effects of these decisions are frequently investigated, the processes underpinning these decisions and the cues used are often less well understood. The aim of this thesis was to understand the mechanisms associated with making oviposition decisions, and their consequences, using the European bitterling (Rhodeus amarus), a small freshwater fish that lays its eggs in the gills of freshwater mussels. Using an artificial mussel, females were shown to respond to dissolved oxygen, relating to offspring survival, while males attend to water flow velocity, with implications for sperm competition. Oviposition decisions by either sex were unaffected by olfactory cues associated with sperm release, though males and females were responsive to visual cues associated with ejaculation. An analysis of the placement of eggs within the mussel gills by females failed to show evidence of “handedness”, though there was a tendency to place eggs in a mussel's inner gills, which may be adaptive in avoiding competition with the mussel's embryos. Male response to oviposition sites showed inter-population variation, with males from a population with high levels of mean crowding showing an elevated frequency of mussel inspection and probability of ejaculation. Males also increased the frequency of mussel inspection in response to the presence of a gravid female, suggesting a role for sperm competition and fertility assurance. Social network analysis was used to investigate how male interactions affect oviposition decisions. This approach showed that male mating tactics could be understood by quantifying how males distributed their sperm among oviposition sites. Findings are discussed in the context of our understanding of the bitterling mating system and research on oviposition-site decisions.

M.Sc. (Zoology) / Milt and blood samples of Aarbus aeneus were collected during November in order to perform chemical analyses of the blood and seminal plasma. Physical analyses were also carried out on milt. Throughout the year testes were collected in order to determine the stages of testicular development. This was done by means of histological analyses. The sperm counts averaged 8,41 x 10-3 cells rom while the spermatocrit value varied between 44% and 82% (average of 61,9%). All the milt samples collected were white in colour showing a high viscosity. Sperm motility gradually declined after activation and stopped after 82,5 seconds. Chemical values of the components tested in the blood plasma were statistically compared to those in the seminal plasma and no statistically significant differences were recorded between sodium, potassium, chloride, calcium, magnesium, glucose, total lipid, total proteien concentrations, osmolality and pH. The only component where a difference in concentration occured was fructose (30% probability). Sodium, calcium, magnesium, glucose, fructose, total lipid and total proteien concentrations in the blood plasma were significantly lower than the corresponding concentrations in the seminal plasma. In contrast the potassium concentration were higher in the seminal plasma. The pH of the seminal plasma (8,63) was alkaline while a pH of 7,5 was recorded for blood plasma. In the two lobe testis of Barbus aeneus semen is collected with seminiferous ducts into the vas deferens which together with the blood vessels are housed within a hilus. The testis is surrounded by a tunica albugenea and the seminiferous lobules are filled with cysts. The testis of the smallmouth yellowfish appears to be lobular and sperm are deposited into lumens which exist between the cysts. During the resting phase the interstitial tissue is very difficult to distinguish and is seen as a thin layer of cells between the lobules seperating them from one another...

Minnows of the genus Dionda (Cyprinidae, Teleostei) inhabit spring-fed streams in the southwestern United States and Mexico. Five nominal species of Dionda (D. argentosa, D. diaboli, D. episcopa, D. nigrotaeniata and D. serena) are found in streams and rivers in central and west Texas. Because Dionda require clean, flowing water, they serve as aquatic indicator species of biological impacts of drought and human water use. Consequently, the ecological and conservation status of species of Dionda are important relative to monitoring habitat deterioration. This study used genetic data from geographic samples of the five nominal species of Dionda in Texas waters to document the conservation-genetics status of populations in each species. Fish were collected in cooperation with the Texas Parks and Wildlife Department and the U.S. Fish and Wildlife Service. Data from 585 base pairs of the mitochondrially encoded, protein coding ND-5 gene and from 21 to 33 nuclear-encoded microsatellites were used to assess genetic variation, population structure, historical demography, and genetic effective size of samples of each of the five species. The sample from Independence Creek, initially assumed to be D. episcopa because of its location, was found to be D. argentosa. Results of genetic assays indicate that each geographic sample in each species should be treated as a separate population and managed in a way that preserves the natural diversity found within each species. Genetic data revealed that all of the populations evaluated may be compromised genetically and should be monitored further.

Thesis (M.S.)--Texas State University-San Marcos, 2008. / Vita. Includes bibliographical references (leaves x,40-42). Also available on microfilm.

I studied habitat preferences of Gila chub in a canyon-bound system (Bonita Creek) and a marsh system (Cienega Creek). Gila chub in Bonita Creek, frequently occurred in a broader range of habitat types and conditions than Gila chub in Cienega Creek. Gila chub in Cienega Creek were highly pool oriented. In contrast, Gila chub in Bonita Creek generally preferred, or used in proportion, swifter shallower habitat types. Segregation between size classes in relation to habitat variables was noted, but was less than expected. I studied other life-history characteristics as well and found reproduction commencing in February, peaking in spring, and dropping off as summer begins. Spawning in the fall is suggested by the presence of small YOY and gonad development. I also evaluated methods to spawn and rear Gila chub. Following initial spawning, Gila chub spawned consistently in the laboratory without hormonal, chemical, photoperiod, or drastic temperature and substrate manipulation, during all times of the year. Spawns were noted at temperatures ranging from about 15 to 26°C but spawning above 24°C occurred infrequently. Larval Gila chub fed a commercial diet grew the same or slightly better than those fed thawed Artemia sp. nauplii, and significantly better than those fed chicken Gallus domesticus egg-yolk powder, but survived significantly better when fed Artemia. Despite the latter, observations suggest Artemia nauplii may be difficult for first-feeding larval Gila chub to handle. Thawed chironomid sp. larvae clearly outperformed prepared commercial feeds for small and large juvenile Gila chub with respect to growth. Growth of larval Gila chub was highest at 28ºC and lowest at 32ºC, while survival of larval Gila chub was highest at 24ºC and lowest at 20ºC. Spinal deformities were common (about 47%) for larval Gila chub reared at 32ºC but generally uncommon for those reared at lower temperatures. Water temperatures from 20-28ºC appear suitable for rearing larval Gila chub, with temperatures from 24-28ºC more optimal. Water temperatures from 20-29ºC appear suitable for rearing juvenile Gila chub. My data strongly support increasing rearing density having a negative effect on growth and survival (larval only) of Gila chub. Although populations of Gila chub share many natural history traits, my data suggests habitat use can vary among systems. It is possible unique preferences and strategies exist between different populations of Gila chub. Thus managers should be cautious about applying information based on one population to others. The future of Gila chub may someday depend in part on hatchery propagation to provide specimens for restocking formerly occupied habitats and establishing refuge populations. Information from my study can aid future efforts to successfully spawn and rear Gila chub and related species.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 247-250).

The biology of three large cyprinid fishes, Barbus holubi, B. kimberleyensis and Labeo capensis, was studied in a large turbid man-made lake on the Orange River, South Africa. The influence of environmental fluctuations on population dynamics was examined in relation to biological adaptations. On this basis inferences were made about the effect exploitation would have on the populations, and management alternatives were considered. Lake Ie Roux is situated in a semi- arid area, downstream from another large reservoir, Lake Verwoerd. In the pristine river, flooding is seasonal, and floodwaters carry a heavy silt load. Lake Verwoerd acts as a silt-trap and changes in turbidity in Lake Ie Roux (Secchi disc readings range from 15 to 160 cm) are influenced by hydrological management and are not necessarily seasonal. Water temperatures in the regulated river connecting the two lakes depend on the pattern of water release, and fluctuations in Iake levels depend on management practices. Reproduction was studied by examination of gonads and from the distribution of newly hatched juveniles. Age and growth was interpreted from the reading of scales and otoliths. Relative year class strength, dispersal and mortality were monitored using catch data from a regular, standardized gillnetting survey. The Barbus species spawn in the regulated river in spring or summer. Spawning is coordinated for a large part of the population and B. holubi spawn four to six weeks earlier than B. kimberleyensis. The juveniles are 'initially found along the shoreline, but later move into the pelagic zone and disperse throughout the lake. Year class strength is dependent on time of spawning and a late spawning results in a poor year class. For this reason, year class strength of B. kimberleyensis is generally poor, but there is a greater variation in year class strength of B. holubi, which is the dominant large Barbus. The two Barbus species exploit the pelagic zone, visually predating on zooplankton. When turbidity increases large scale mortalities occur, especially in B. holubi. Mortalities more than compensate for the reduction in carrying capacity, and the size of the reduced population may be inversely related to initial abundance. Growth rate is similarly affected by turbidity and density, and size at sexual maturity in B. holubi is reduced when growing conditions deteriorate. Labeo capensis do not form a homogenous population in Lake le Roux. Spawning occurs throughout the lake, but is erratic, probably depending on local rainfall. At each locality, more than one spawning may occur during spring and summer because of temporal variation in gonadal development. Juvenile survival appears to be mainly dependent on water level fluctuations, and strong year classes were formed when the lake was filling during the first two years. Subsequent year classes were weak. Subadult and adult B. capensis are herbivorous and depend on autochthonous production for food. They are relatively sedentary, but when turbidity increases fish smaller than 200 mm disperse, probably in response to food shortages. Mortality rates may be accelerated but mortalities are not as high as in B. holubi. The growth rate of B. capensis is variable and depends on turbidity and population density. Size at sexual maturity remained relatively constant during the study period. B. holubi has a relatively fixed reproduction cycle in Lake le Roux and exploitation is likely to dampen fluctuations in population density. Population growth and stability could be further promoted through hydrological management. B. kimberleyensis does not represent an exploitable population in Lake le Roux, although the large size obtained by this species (>3 kg) may be an attraction to anglers. B. capensis does not appear to have the potential to withstand sustained exploitation because of its erratic and generally poor reproductive success. However, the species is long-lived and can sustain relatively high densities under harsh conditions because of its relatively low mortality rates. It was concluded that harvesting of B. holubi must be flexible to promote maximum benefits to commercial and recreational fisheries, but B. capensis which is not an angling species, should chiefly be exploited when catches of B. holubi are poor, but left to recover in between. An alternative management strategy would be to commercially exploit the fish populations of several reservoirs. A monitoring programme could be established to decide when each reservoir is to be exploited to see to the interests of commercial and recreational fishing alike.

The southern African yellowfish (Barbus aeneus, B. capensls, B. kimberleyensis, B. natalensis and B. polylepis) are very similar, which limits the utility of traditional taxonomic methods. For this reason yellowfish similarities were explored using multivariate analysis and karyology. Meristic, morphometric and Truss (body shape) data were examined using multiple discriminant, principal component and cluster analyses. The morphological study disclosed that although the species were very similar two distinct groups occurred; B. aeneus-B. kimberleyensis and B. capensis-B. polylepis-B. natalensis. Karyology showed that the yellowfish were hexaploid, B. aeneus and B. kimberleyensis having 148 chromosomes while the other three species had 150 chromosomes. Because the karyotypes of the species were variable the fundamental number for each species was taken as the median value for ten spreads. Median fundamental numbers were B. aeneus = 196, B. natalensis = 200, B. kimberleyensis = 204, B. polylepis = 206 and B. capensis = 208. The lower chromosome number and higher fundamental number was considered the more apomorphic state for these species. Silver-staining of nucleoli showed that the yellowfish are probably undergoing the process of diploidization. Southern African Barbus and closely related species used for outgroup comparisons showed three levels of ploidy. The diploid species karyotyped were B.anoplus (2N=48), B. argenteus (2N=52), B. trimaculatus (2N=42-48), Labeo capensis (2N=48) and L. umbratus (2N=48); the tetraploid species were B. serra (2N=102), B. trevelyani (2N=±96), Pseudobarbus afer (2N=96) and P. burgi (2N=96); and the hexaploid species were B. marequensis (2N=130-150) and Varicorhinus nelspruitensis (2N=130-148). The taxonomic implications of polyploidy for the African cyprinids were considered, and its effect on species was discussed.