The spontaneous spike activity of the primary afferents was statistically analysed in order to gain insight into its origin and to provide a basis for examining its modulation by sound. The responses to pure tone stimulation were investigated by examining the change in spike rate, degree of synchrony and the phase locking angles, to pressure and velocity stimuli at different stimulus intensities, over a range of frequencies. The 3-dimensional directional characteristics of the units were studied by presenting vibrational stimuli on different axes around the animal. It was found that most spontaneous spike activity showed serial dependence and thus the ISI histogram is an incomplete description of the activity. There is evidence of resonance of the hair cell/primary afferent complex, both from certain patterns of spontaneous spike activity and from the relationship between the driven spike activity and the phase of the stimulus. The phase angle of response to pure tone stimulation increased or decreased as the stimulus intensity increased depending on the whether the stimulus frequency was above or below the best frequency of the unit. It is shown for the first time that cod primary afferent units respond to sound in 3 dimensions.

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The impact of the source of n-3 fatty acids on cardiovascular disease has not been fully investigated. This study was carried out to investigate cardiovascular benefits of diets with a low ratio (2:1) of n-6:n-3 fatty acids from different sources, either fish or flaxseed oil, in C57BL/6 mice. Twenty-one mice were divided into 3 groups (n=7) and fed an atherogenic diet supplemented with either a fish or flaxseed oil-based ‘designer oil’ with low n-6:n-3 fatty acid ratio (treated groups) or safflower oil-based formulation with a high ratio (control group) for 16 weeks. Plasma cholesterol levels declined significantly in both treated groups, by greater than 30%, compared to those in control. The ratio of n-6:n-3 fatty acids in liver was significantly lower in fish and flax groups as compared to control. Our data suggest that lowering dietary ratio of n-6:n-3 fatty acids may significantly reduce cardiovascular risks regardless of the source of n-3 fatty acids.

Oil and gas exploration in Northern Canada uses explosive-based seismic techniques to locate hydrocarbon reserves beneath waterbodies not frozen to the bottom. The use of explosives in, or near, waterbodies has the potential to harm fishes, primarily through instantaneous pressure changes (IPCs) generated from the detonations. These IPCs can damage soft tissues through the rapid compression and expansion of the swimbladder as the pressure wave passes. In Canada, a document entitled Guidelines for the Use of Explosives In or Near Canadian Fisheries Waters recommends that peak pressures not exceed 100 kPa for the protection of fish, however damage has been reported below this level. To simulate seismic exploration and examine potential pathological changes surrounding the current Guideline, fish across different developmental stages and with varying degrees of swimbladder presence were exposed to a variety of explosive based IPC levels in field experiments. Early life stages of rainbow trout (Oncorhynchus mykiss) including eyed eggs, sac fry, and juveniles were caged and exposed to discrete detonations from 0 to 280 kPa in the Mackenzie Delta, NWT. These fish were subsequently examined for both gross pathological and histological changes to cranial structures as well as swimbladder, kidney, liver and gill tissue. Results showed changes in both the area and circumference of the cranial region of eyed eggs, as well as swimbladder, ocular and kidney damage in juveniles. Additionally, caged adult swimbladder bearing lake trout (Salvelinus namaycush) and non-swimbladder bearing slimy sculpin (Cottus cognatus) were exposed to explosive based IPCs ranging in peak pressure from 0 to 127 kPa at the Experimental Lakes Area, Ontario. Fish were later examined grossly and blood, liver, kidney, intestine, and spleen were examined to determine the presence of any traumatic based pathological changes. Results indicated the occurrence of swimbladder hemorrhage in lake trout exposed to IPCs near the current Guideline level. Finally, a risk assessment for lake trout of the Mackenzie Delta exposed to IPCs was undertaken; to examine the potential for adverse risk to individuals and populations, and the likelihood of populations being unable to recover. Based on the findings of the aforementioned studies, the recommended Guideline level is not protective of early life stages of rainbow trout and furthermore represents the threshold at which damage to the swimbladder in adult lake trout does not occur, as such, a re-examination of the recommended Guideline level is warranted.

This thesis presents the findings of a physical modeling study examining the hydraulic characteristics within the inlet region of a corrugated steel pipe (CSP) culvert with common inlet treatments. Also examined are the effects of embedding the culvert below the stream bed and backfilling the culvert with granular material. Velocity and turbulence distributions were examined in an effort to better understand how these inlet treatments may affect fish passage. The velocity field of each inlet configuration was dominated by a central jet of high velocity surrounded by low velocity boundary areas. Based on percent area analysis the various projecting end inlet configura-tions presented the largest area with streamwise velocities less than Uavg. The usefulness of the low velocity boundary areas may be limited by significant vertical and spanwise velocities and associated elevated turbulence levels.

Open net-pen aquaculture allows for free exchange of materials between farm and wild environments. Increased habitat complexity in the form of farm infrastructure produces effects similar to fish aggregating devices and artificial reefs, altering the distribution and abundance of fish species within the greater area. The continuous input of nutrients via fish waste and uneaten food pellets can amplify such effects, leading to large and persistent aggregations of wild fish near aquaculture sites. These aggregations have been quantified in numerous geographical locations but data are lacking for salmon farms in coastal British Columbia. The footprint of the attractive effects is also poorly understood in all cases as research has focused on fish populations directly associated with the infrastructure. In this study wild fish populations were quantified at shallow rocky ecosystems adjacent to salmon farms in the Broughton Archipelago and compared to paired reference sites with similar habitat characteristics to test for aggregating effects. Two SCUBA divers performed visual surveys along six 25x4x4m transects at each site, three at each of two depth ranges: deep (12-16m) and shallow (6-10m). Species, abundance, and estimated total length, as well as temperature, salinity, rugosity, and visibility were examined. A combination of multivariate and univariate statistical analysis were performed to compare the physical characteristics, community composition, number of individuals, and biomass between farms and reference sites. The overall community composition was significantly different at farm sites despite no difference found in the physical habitat characteristics between treatments. This difference was predominantly driven by five fish species, yellowtail rockfish (Sebastes flavidus), copper rockfish (Sebastes caurinus) quillback rockfish (Sebastes maliger), shiner perch (Cymatogaster aggregata) and striped perch (Embiotoca lateralis). Presence/absence data showed no significant difference in species identity between farms and references, implying that the difference in community composition was primarily driven by changes in abundance rather than species identity. The total number of fish and biomass of all fish species was also significantly higher at farms. These results suggest that salmon farms in the Broughton Archipelago alter the community structure and increase the abundance of near-field wild fish populations. The aggregating effects are asymmetric within the community, with higher trophic level species showing the greatest increases in abundance. The potential implications of these results include a greater risk of disease and parasite transfer between farm and wild fish, as well as within each population. The ecological relationships among species may also be compromised with predator amplified communities potentially exhibiting top-down effects on the rest of the food web. Changes to wild fish communities seen up to 170m away from farm infrastructure suggest that the mechanism of the attractive effects may be driven more by nutrient subsidies than the presence of infrastructure. This work underscores the need to determine the full spatial extent and mechanisms of attractive effects as well as the ecological implications of persistent aggregations of wild fish near salmon farms. / Graduate

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