The visual biology and its relevance to orientation was examined in fishes in the subfamily Salmoninae (salmon, trout, and char) by characterising the spectral and polarisation sensitivity of their visual systems. Integrated spike activity of axons from the optic nerve was used as a measure to determine the polarised-light sensitive mechanism underlying the ability of rainbow trout (Oncorhynchus mykiss) to orient in down-welling, linearly-polarised light. Relative sensitivity curves were then obtained for the five types of photoreceptor cells in this trout's retina: rods, ultraviolet sensitive cones (UV), short wavelength cones (blue-sensitive) (S), medium wavelength cones (green-sensitive) (M), and long wavelength cones (red-sensitive) (L). Under scotopic conditions (dark adapted), no sensitivity to e-vector was apparent. Under photopic conditions (light adapted), trout parr exhibited on-responses with e-vector sensitivity in two orthogonal channels. No evidence of polarisation sensitivity was observed in the on-responses of larger fish (50–78 g smolts) under UV-isolating background conditions, whereas the off-responses were unchanged.M and L cones, in contrast, retained their unimodal response. The decrease in UV-polarisation sensitivity in larger fish was found not to be attributable to size-related changes in the ability of the ocular media of the eye to transmit polarised light. Rainbow trout was used as a model species and spectral and polarisation sensitivity were compared with steelhead (an anadromous form of O. mykiss), cutthroat trout (O. clarki), kokanee (land-locked form of O.nerka), and brook char (Salvelinus fontinalis ). Visual pigment templates from rainbow trout were corrected for ocular media absorbance and overlaid on the spectral sensitivity curves for the purposes of comparison. Some differences in sensitivity were observed among species. In particular, on-responses were dominated by L-cones in most species.However, in kokanee, the M- cone was dominant.These differences may be related to the photic environments from which these fish originate. The first physiological evidence of near-UV sensitivity in the genus Salvelinus is also provided. It was therefore concluded that UV sensitivity is ubiquitous in the subfamily Salmoninae. Polarisation sensitivities in the above species were modelled using periodic regression analysis. Comparisons suggest that all of these species have a similar dual-channel polarisation detection system. The effect of the tuberculostatic drug Ethambutol on the visual physiology of rainbow trout was also examined. This drug appears to cause a decrease in sensitivity analogous to chromatic adaptation. Fish were fed daily for one month and then spectral sensitivity and polarisation sensitivity of Ethambutol-treated fish were compared to control fish. Relative to controls the visual systems of treated fish were dominated by the M-cone mechanism. Spectral and polarised light sensitivity of UV and L-cones were reduced. Finally, orientation responses of juvenile rainbow trout, steelhead, and brook char to a polarised-light stimulus were examined under controlled laboratory and semi-natural field conditions. Trained fish of all species oriented to the plane of polarised light, whereas untrained fish could not. Fish trained in the lab were tested at twilight and were found to be able to orient under natural skylight. Under semi-natural conditions, fish in floating net-pens in a lake were provided food rewards at a specific compass bearing. Their orientation responses were assessed under various natural and artificial conditions. When the sun was visible the fish typically had a unimodal distribution. However, they were typically not oriented when presented with only brightness and spectral cues at Zenith or on cloudy days. In contrast, both steelhead and sockeye were oriented correctly at civil twilight if the horizon was not obscured by heavy cloud or if blue sky was visible at Zenith. / Graduate

Vertical distribution and onshore movement of maturing kokanee were studied by means of extensive gill net sets in Nicola Lake between 1958 and 1961. In late spring of 1959 maturing kokanee were found largely in the upper 30 feet of the lake but gradually dispersed to occupy all depths to 100 feet by mid-summer. A diel vertical migration occurred in which maturing kokanee moved surfaceward during the day and downward at night in 1959. In 1961 the reverse condition was observed wherein kokanee avoided areas of bright illumination during the day but moved surfaceward at night. No effect on vertical distribution of kokanee by extensive and rapid fluctuations of the thermocline, initiated by wind induced seiches, was noted in 1959 or 1961. The 1961 vertical distribution appeared closely associated to light intensity. Seasonal and diel changes in diet were observed in 1959. Chironomid pupae were the dominant food organisms eaten in late spring and summer. Planktonic crustaceans were consumed in greatest numbers in late summer, autumn and spring. Kokanee captured in mid-summer in the surface water (0-25 feet) generally had been feeding on planktonic crustaceans whereas those taken from below 25 feet contained largely chironomid pupae and larvae. Onshore movement of mature kokanee toward a spawning stream was initiated by falling light intensity and intensified by strong onshore winds. Possible mechanisms of location of the spawning stream were investigated. Migration to an inlet spawning stream and movement within the stream were recorded at two traps, one situated at the stream mouth, the other 1000 feet upstream. Movement into the spawning stream occurred only at night and was unaffected by changes in stream temperature and flow. A significant correlation was found between daily number of kokanee entering the stream and strength of onshore winds. Differences in sex ratio of the spawning runs and length of mature kokanee were recorded and possible causal agents discussed. / Science, Faculty of / Zoology, Department of / Graduate

Relations between the diversity of juvenile anadromous salmonids and pool features were examined in a managed and a pristine watershed in Oregon during the summer of 1990. There were no differences (p>0.05) in pool depth, velocity or pool wood volumes between streams. However, the pristine system had twice the number of pools within similar lineal distances. Pools in the pristine system also had larger substrates (percent dominant within pools) and smaller pool area (p=0.01). Fish diversity was found to be greater in pools in the pristine system than in the managed system using the Simpson's Diversity and Shannon Evenness indicies (p=0.01). The Shannon-Wiener Diversity index did not show any differences between streams. The difference in assemblage diversity was due to differences in relative abundance and not species richness. Relative abundance of juvenile steelhead and cutthroat trout and coho salmon was more even in Cummins Creek, the pristine system, than in Cape Creek, the managed system. Relative abundance of coho increased in the managed system possibly due to a change in pool habitat characteristics, whose conditions favored coho salmon, but this relationship was not clear. This study emphasizes the importance of assessing communities of juvenile anadromous salmonids as opposed to studies involving a single species. Past land management activities have focused upon single species' with regards to a particular habitat component, which has decreased biodiversity and changed stream habitat characteristics through cumulative effects. Resource managers should examine interactions between habitat characteristics and salmonid communities in order to maintain biological diversity or risk creating favored habitat for a single species within stream systems. / Graduation date: 1997

Detection and treatment of bacterial kidney disease (BKD) was investigated. Experiments were conducted to evaluate the quantitative, fluorescent antibody technique (QFAT) that is used to detect, identify, and quantify both typical and 'bar form' Renibacterium salmoninarum cells. Smears of kidney tissue from naturally and artificially infected salmonids, both with and without chemotherapy, were quantitatively examined throughout the course of R. salmoninarum infections. Detection and quantification by QFAT has been reported to provide assessments of prevalence and severity of R. salmoninarum of individual fish. These assessments and the occurrence of 'bar forms' of R. salmoninarum have been used as an indication of recovery within a population. 'Bar forms' were observed in kidney tissue smears of fish that survived bacterial challenge when treated with erythromycin. The 'bar form' was also detected when rainbow trout were artificially infected with lower doses of live R . salmoninarum and in fish that were injected with irradiation-inactivated R. salmoninarum cells. By examining R. salmoninarum cultures in vitro by QFAT, it was determined that 'bar forms' did not occur on artificial media even when antibiotics were incorporated into the agar. When QFAT was compared to direct fluorescent antibody technique (DFAT) and quantitative enzyme linked immunosorbent assay (ELISA), it was determined that QFAT had similar sensitivity as ELISA but was more sensitive than DFAT. QFAT was also used to predict minimum mortality. Experiments were also conducted to evaluate drug regimes to treat both artificial and natural R. salmoninarum infections. Erythromycin was administered by intraperitoneal injection in different doses and at selected days post infection. Erythromycin decreased percent mortality and increased mean day to death, but did not completely eradicate R. salmoninarum from infected test animals. Sarafloxacin and erythromycin were incorporated into daily ration of artificially infected test animals. Contrary to erythromycin, sarafloxacin did not decrease mortality or increase mean day to death when tested in vivo against R. salmoninarum. A new drug, A-77143, was tested in vitro to determine if it was bactericidal and its minimum inhibitory concentration. When A- 77143 was compared to other antibiotics, it had a relatively low minimum inhibitory concentration and was shown to be bactericidal against the eight strains of R. salmoninarum tested. / Graduation date: 1993

Philonema (Nematoda; Philometridae) from anadromous hosts, sockeye salmon (Oncorhynchus nerka), and non-anadromous hosts, rainbow trout (Oncorhynchus mykiss) , were studied in order to determine if hosts with different life histories were infected with the same or different species of Philonema. Worms from the two host species were morphologically indistinguishable. However, electrophoretic banding patterns produced by restriction enzyme digestion of DNA extracted from Philonema demonstrated the presence of two genetic types corresponding to the two host species. This supports the idea that at least two species of Philonema are endemic in British Columbia. Philonema oncorhynchi Kuitunen-Ekbaum, 1933 is a parasite of sockeye salmon which undergo a long ocean migration before returning to freshwater to spawn, while P. agubernaculum Simon and Simon, 1936 is a parasite of rainbow trout (and other salmonids) which live in lakes. Kokanee (O. nerka kennerlyi), a non-anadromous offshoot of sockeye, were infected with the same worm as sockeye probably because the two hosts have similar life histories. Steelhead smolts, anadromous O. mykiss, contained worms identified as P. agubernaculum. This likely represented an accidental infection because steelhead do not usually contact Philonema. Philonema were examined from various localities in B.C. Philonema agubernaculum showed population divergence corresponding to the different geographic localities from which it was collected. This likely reflects the isolation of these parasite populations in unconnected watersheds. Philonema oncorhynchi showed polymorphisms spread throughout many of the populations. The lack of population divergence probably results from gene flow between parasite populations brought about by wandering hosts. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

No description available.

The powan, Coregonus lavaretus (L.) is endemic to only two British waters, Loch Lomond and Loch Eck, Scotland. This thesis describes the seasonal and longer term growth processes of the two populations, concentrating on growth in length back-calculated from scales, factors affecting recruitment and mortality, reproductive cycles, and seasonal deposition and mobilisation of storage products, particularly lipid. The interrelationships of these cycles is discussed. The populations differ in their diet and duration of feeding, and it is shown that most of the inter-population differences in seasonal cycles of growth relate to these feeding differences. The Loch Eck population is the more variable. In addition to adult and immature powan, a third category is identified, termed adolescents. These are fish which are entering their first reproductive cycle. Immature and adolescent fish are analysed separately and compared with the adults. There are some differences in seasonal cycles between the juveniles and adults, mainly in relation to the presence or absence of the reproductive cycle. A preliminary histological study of the ovaries of adolescent females is carried out. Comparison of historical data with the results of the present study shows that there has been little change in the Loch Lomond powan in the past 200 years. Both lochs are coming under increasing human pressure, and conservational measures urgently need to be taken if the powan populations are to survive.

No description available.

Graduation date: 1990