Two similar salmonids, coho and steelhead, cohabit many coastal rivers of British Columbia. Field collections reveal that the distributions of underyearling coho and steelhead are similar along the length of these streams. However, the microhabitat distribution of the two species is different. In spring and summer, when population densities are high, coho occupy pools, trout occupy riffles. In autumn and winter, when numbers are lower, both species inhabit the pools. Nilsson (1956) stated that segregation (such as that shown by coho and trout in spring and summer) may be indicative of competition resulting from similar ecological demands. To test this hypothesis the distribution and behavior of coho and steelhead were compared in a stream aquarium at different seasons with gradients of light, cover, depth or depth/velocity and in experimental riffles and pools. Distributions, and preferences of the two species in the experimental environments were most similar in spring and summer, the seasons when segregation occurred in nature, and least similar in autumn and winter, the seasons when the two species occurred together in nature. Spring and summer segregation in the streams is probably the result of interaction which is produced by ecological similarities of the species and accentuated by dense populations and inherently high levels of aggressiveness. The species do not segregate in streams in winter because certain ecological demands are different, numbers are lower and inherent levels of aggressiveness are low. When the two species were together in the experimental riffle and pool environment, trout were aggressive and defended areas in riffles .but not in pools; coho were aggressive in pools but less inclined to defend space in the riffles. These differences in behavior probably account for the distribution of trout and coho in natural riffles and pools. The data support the basic contention of Nilsson (1956) and illustrate the role of behavior in segregation produced by competition for space. / Science, Faculty of / Zoology, Department of / Graduate

Changes in population size are governed by the birthrate, the sex ratio and the death rate. In pink salmon the average egg-production per female is about 1700 and variations from this average are insufficient to account for observed changes in adult populations. The sex ratio is approximately 50-50. Survival during the freshwater phases of the life cycle has been found to vary from approximately 1% to 24%,the average survival being significantly different in different streams. Variation is relatively greater in streams in which average survival is low. Natural survival in the ocean is considered, to average about 5% of the number of young fish reaching the sea. In the central region of the British Columbia coast the annual catch averages about 60% of the adult fish, this percentage being relatively constant for both small and large runs. Pink salmon maturing in "even" and "odd" years represent separate populations. These populations vary in size independently but may maintain a relatively constant ratio for a series of generations. This ratio varies from near equality to extreme disparity. Marked changes in the level of abundance may occur suddenly. Three types of mortality are recognized: (a) mortality which becomes relatively heavier as populations increase in density (compensatory) (b) mortality which becomes relatively heavier as populations decrease in density (depensatory) (c) mortality which is independent of density (extrapensatory). (a) is especially identified with the period of spawning and incubation;(b) is considered to occur mainly during the period of fry migration and to be due to predation;(c) may occur at any stage but is probably most variable during the period between entrance of the adults into fresh water and emergence of the fry. Population changes initiated by extrapensatory factors, among which stream-flow conditions are considered to be important, are exaggerated by depensatdry factors (notably predation on fry) but tend to be resisted by the compensatory influences which operate during the period of spawning and incubation. Stabilization of a level of abundance depends on a balance between these processes. In general, freshwater mortality is more variable than ocean mortality and plays a greater part in inducing population changes. It is suggested that the average freshwater survival of an un-fished population would approximate 2.4% and that this efficiency must be raised to about 6% to permit a sustained catch of 60% of the adult population. A lower freshwater output is likely to result in a reduction in size of the stock. Large runs in both even and odd years are not fundamentally incompatible. The possibility, of promoting a low-level stock to a persisting higher level of abundance is indicated. Chum salmon are subject to the same types of mortality as pink salmon but the results are modified by the higher average egg-production (ca.2700) and the variable length of the life cycle. The species tends to occupy streams in which physical conditions are less stable. Compensatory influences are frequently obscured by these conditions, resulting in irregular fluctuations in abundance. In the application of remedial measures similar principles apply to both species. / Science, Faculty of / Zoology, Department of / Graduate

The relative abundance of coho salmon (Oncorhmchus kisutch) in the Kains island troll fishing area was computed, for the years 1943 to 1951 inclusive, on the basis of the average catch per boat per day each year. The resulting figures varied from a minimum of 75, pounds per boat per day in 1946 to a maximum of 231 pounds per boat per day in 1951. These yield per unit effort figures were then statistically compared with the average surface salinity, or average surface temperature, for various periods in the life history of the coho taken by the fishery in these years. It was found that a very high correlation (r = 0.85, p = 0.01 - 0.001) existed between the average "summer" salinity (June to September inclusive) and the poundage yield per unit effort during that same year. It is suggested that this correlation is explainable in terms of varying growth rates in different years, and by variations in the numbers of fish taken in these years, both of these factors being governed by the availability of food, as evidenced by surface salinity. / Science, Faculty of / Zoology, Department of / Graduate

Rainbow trout {Oncorhynchus mykiss) and coho salmon (0. kisutch) produce males which mature at an abnormally early age. The objectives of this study were to critically describe the role of growth rate in early sexual maturation of male salmonids by monitoring growth rate and precocious sexual development in individually identified fish. Underyearling rainbow trout were individually identified using coded tags. These fish were reared at 9°C and 15°C and growth was monitored twice a month in both groups over a 9 month period starting January 24, 1989. The number of precocious males in the 9°C and 15°C groups were 11% and 18% respectively. Yearling coho salmon were similarly tagged, reared at ambient temperature, and monitored for growth over an 8 month period starting March 22nd, 1989. Ten percent of the coho salmon matured precociously. In both experiments there was a similar relationship between fast growth in early spring and precocious maturation. The growth rate of fish that matured declined in autumn relative to non-maturing individuals. Condition factor (length to weight relationship) was greater among those fish that matured precociously. Plasma growth hormone was monitored in the coho salmon. Most samples fell below the detection limits of the assay (1.5. to 3.0 ng/ml). A strategy to reduce the number of precocious males in cultured salmonids is suggested. / Land and Food Systems, Faculty of / Graduate

In the first experiment, sexually immature male and female coho salmon were exposed for 21 days to dietary DDT at a level of 10 or 100 parts per million (ppm), or to methoxychlor at a level of 100 ppm. Exposure to 100 ppm DDT was found to increase the level of liver microsomal Cytochrome P-450 from a control level of 1.32 ± .04 nmoles/1000 mg liver to a level of 1.98 ± .04 nmoles/1000 mg liver, a statistically significant difference (P<.001). None of the treatments were found to affect the hepato-somatic index. In the second experiment, liver slices from sexually maturing male and female coho salmon fed 100 ppm DDT for 21 days or a control diet were incubated with 4-C¹⁴-estradiol-17β in vitro. Metabolites produced were extracted with dichloromethane, separated by thin-layer chromatography and assayed using scintillation counting techniques. Produced in the incubation were estrone, estriol and one other unidentified polar metabolite. DDT treatment was found to significantly increase the amount of estriol and unidentified metabolite produced (P< .001). In the third experiment, sexually maturing male and female coho salmon fed 100 ppm DDT for 21 days or for 7 days or a control diet were injected with 625,500 dpm 4-C¹⁴-estradiol-17β and permitted to metabolize the hormone in vivo. Serial blood samples were extracted, chromatographed and subjected to scintillation counting techniques to obtain values for Metabolic Clearance Rate, Half-life Time and Volumes of Distribution of the injected steroid. It was found that ingestion of DDT had no significant effect upon any of these parameters (P<.001). The pattern of metabolites produced in vivo closely resembled that produced in vitro. The evidence presented in this study suggests that enhancement of the activity of the Mixed Function Oxidase system in coho salmon may occur upon ingestion of an organochlorine insecticide, but that the phenomenon may have little significance in vivo. / Science, Faculty of / Zoology, Department of / Graduate

This study was aimed at providing information that could be used to estimate the predation effect of squawfish on sockeye salmon. Initial studies at Griffen Lake revealed that the percentage of the population acting as predators, and the average stomach volume, increased with increasing size in non-spawning squawfish. Squawfish in Griffen Lake appeared to be most active at night. For the most part, a force fed volume (2.0 ± .1 gms) was digested by all sizes of squawfish in less than 24 hours. Further studies at Cultus Lake in the laboratory revealed that the rate of digestion was dependent on temperature, volume of food, and size of fish. At 6°C a lag prior to digestion commencing was observed and digestion was not complete for the medium volume in less than 52 hours. On an average the medium fed volume was digested in less than 24 hours for temperatures greater than 15°C. Medium volume corresponded to approximately twice the smallest volumes recorded in stomach contents in the field. A life span of ten years for males and 14 years for females with no differential in the growth rate was determined from the banding patterns and sections of pharyngeal teeth. Consumption rates and periodicity of feeding and activity were within the limits of data from Griffen Lake. Laboratory calculated routine metabolic rate was approximately twice the theoretical rate for pooled species. A tagging experiment at Cultus Lake revealed a population of approximately 20, 000 squawfish greater than 720 cm that, on an average, grew less than 0.36 cm during the winter. Growth during the summer was assessed to be in the form of weight increase of body tissue and gametes. Trap catches and temperature preference experiments indicated that squawfish are found within particular temperature regimes in different phases of the year. Within Cultus Lake, distance did not prevent squawfish aggregation on concentrations of sockeye smolts. There was increased consumption of smolts during smolt migration from the lake. In the field a significant difference in rate of digestion for different sizes of squawfish could not be demonstrated; however, there was a difference in the volume voluntarily consumed. With these findings and other theoretical information, it is possible to determine quantitatively the predation effect of a squawfish population on sockeye. Having established a population estimate, an estimate of annual mortality (55.2 per cent per year), and the temperature specific phases (early smolt phase, peak smolt phase, spawning phase, summer phase, fall phase, winter phase), two methods for the assessment of the predation effect were possible. First, knowing proportion of the size classes acting as predators, the numbers and frequency distribution of squawfish remaining within any phase, the duration and temperature characteristics of the phase, the effect of temperature on the rate of digestion, and the volumes that can be digested in 24 hours, it was possible to get an accumulated volume consumed for the population. For the 20, 000 squawfish greater than 20 cm fork length in Cultus Lake, this represents an approximate consumption of 1.4 million sockeye smolt equivalents. The second estimate of consumption was based on the energy requirements converted to consumption rates using conversion coefficients for the same population. The energy requirements to complete spawning, growth and mean metabolism were summed, then converted to a consumption volume for the population. The findings revealed that approximately 2.8 million sockeye equivalents are required. / Science, Faculty of / Zoology, Department of / Graduate

The fry of the very similar salmonids, coho salmon (Oncorhynchus kisutch) and steelhead trout (Salmo gairdnerii), live in very close association with each other during their first year of life in fresh water. The present study was designed to measure the effects of competition between these species. Populations of different densities of coho and steelhead fry in four identical artificial stream-channels were studied. Observations were made on survival, growth rates, and some aspects of behavior. Among the various groups of fry, survival was apparently dependent upon interspecific factors; the presence of another similar species had no observable effect. Low-density populations survived well, even when another species was present at a high-density. Survival of the fish at high-densities was always depressed, even when the companion species was present at low density. Steelhead fry demonstrated a faster initial growth rate than the coho, enabling them to exceed the coho in growth despite the latter’s earlier hatching and consequent initial size advantage. Growth rates were inversely related to density, both inter- and intraspecific effects being noticeable. The two species tend to be spatially segregated, coho occupying positions in the middle and upper layers of the streams, and steelhead remaining close to the bottom. This stratification was reflected in their feeding behavior and diet. Emigration activity occurred to a greater degree among the coho than the steelhead. Emigrants of both species were observed, to undergo substantial weight loss subsequent to their disappearance from the stream-channels. It was concluded that coho and steelhead fry live in close association with one another without experiencing extensive interspecific competition. This is because of segregation of the species by having differing habitats, feeding habits, growth and survival rates, and consequent population dynamics. / Science, Faculty of / Zoology, Department of / Graduate

Various aspects of rainbow trout (Salmo gairdneri) predation on migrating sockeye salmon (Oncorhynchus nerka) fry and rainbow trout eggs were studied during 1970-71 in specially-constructed artificial streams, and in the laboratory. Tests involving sockeye fry as prey were conducted near Babine Lake, British Columbia, while those using rainbow trout eggs were done near Abbotsford, British Columbia. Examination of the effects of physical factors such as water velocity, water turbidity, and light intensity on predation on migrating sockeye fry showed mortality to be inversely related to water velocity and water turbidity; inversely related to light intensity at low light levels but directly related at very low levels. Other stream tests showed mortality to be inversely related to the amount of exposure of predators to fry, before the beginning of a nightly fry migration. Exposing predators to abnormal light for varying periods of time, immediately prior to fry migration, reduced over-all mortality during fry migration. Mortality was not proportional to the length of exposure of predators to abnormal light. Fry experience with predators was shown to increase the ability of fry to escape or avoid predation on subsequent predator encounters. Additional experience served to further increase their ability to escape or avoid predators. Conclusions drawn from stream tests and a behavioral study are that experienced fry migrate in a manner rendering them less susceptible to predation and the migration pattern (compact and in mass) is influenced in part, or completely, by encounter and escape from predator-prey interactions experienced earlier. "Handling" or other fright-evoking stimuli appeared to have similar effects. Rainbow trout feeding on colored fish eggs indicated color preference patterns which are influenced by background coloration (color contrast between food and background), and light intensity. Preference was for colors showing the most contrast with the background at a particular light intensity. At low light levels, on a pale-blue background, preference was for lighter colors, while it was for darker colors at high light levels. Mortality differences increased proportionately with contrast between colors. Finally, trout displayed what appears to be a behavioral preference for red, and possibly blue, regardless of surrounding environmental conditions. In a food deprivation study rainbow trout displayed an S-shaped hunger response curve when fed on eggs. Indications were that rainbow trout will feed to gut capacity when given the opportunity. Finally, beyond an upper limit of food deprivation, the amount of food eaten by an individual remains fairly constant. / Science, Faculty of / Zoology, Department of / Graduate

Data from five conductivity-temperature-depth (CTD) surveys collected during 1985 and 1986 in support of project MOIST -Meteorological and Oceanographic Influences on Sockeye Tracks- are used to describe the salient oceanographic features of the waters lying between Vancouver Island and the British Columbia mainland coast. Using these data, four oceanographic regimes are clearly defined on the basis of salinity structure. Temperature-Salinity diagrams are used to discuss water types and mixing ratios in these regimes. Vigorous tidal mixing over shallow sills and/or in narrow channels produces tidally mixed fronts that separate oceanographic regimes. The tidal evolution of two of these fronts located near Weynton Passage and Cape Mudge are discussed by means of 24-hour CTD stations. Seasonal variability of the residual estuarine circulation is examined and estimates of the seaward flow in the upper layer of a very simple two-layer geostrophic model were found to be in reasonable agreement with the few direct measurements made in this region. Seasonal variability of the general hydrography is described. Ultrasonic telemetry provided horizontal and vertical distribution time series data for return migrating sockeye salmon (Oncorhynchus nerka). Concurrent high spatial resolution CTD data was used to specify the ambient temperature and salinity fields in the immediate vicinity of the tagged sockeye. Spectral analysis of the depth and ambient oceanographic data time series revealed periodic vertical movements at approximately 15 and 33 minutes per cycle for fish tracked in the slightly stratified regimes of Queen Charlotte Strait, western Johnstone Strait and the Strait of Georgia. High frequency large amplitude periodic vertical movements were characteristic of fish that did not make significant progress towards the Fraser River: low frequency small amplitude vertical movements were characteristic of well oriented fish. Aspect ratio, defined as the horizontal distance travelled divided by the vertical distance travelled, gave an indication of the relative degree of homeward orientation. Vertical distribution and orientation were also related to the frequency and duration of successive vertical excursions. Fish depth and vertical swimming velocity were found to be positively correlated in regions of weak stratification and/or for well oriented fish. Ambient density gradients were not found to inhibit vertical movements as the rate of doing work against hydrodynamic drag was several orders of magnitude greater than that of doing work against a varying buoyancy force. In the presence of strong temperature and salinity gradients, tracked sockeye were most often observed at depths not associated with the maximum gradients. In stratification regimes where temperature and salinity gradients were nearly uniform with depth, tracked sockeye were observed at depths uniformally distributed throughout the thermo- and haloclines. Minimum vertical swimming velocities were generally associated with minimum vertical gradients. These observations suggest that the tracked sockeye frequently swam through but did not reside in the region of the maximum gradients. Dimensional analysis suggested that physical variables alone are insufficient to specify the vertical distribution of the tracked sockeye. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The primary objective of this study was to evaluate quantitatively the effects of a mixture of agricultural and non-agricultural land use practices on the chemical characteristics of the Salmon River, near Fort Langley, B.C. Present land use and geomorphic unit maps were used to determine appropriate stream sampling sites which would give an indication of the combined and separate effects of land use and geologic materials on water quality. Chemical characteristics of the Salmon River and its tributaries were monitored over a 10 month period from May 1974 until April 1975. Eighteen chemical variables were analyzed in the laboratory using Standard Methods and 5 were monitored in the field. The in situ parameters included pH, temperature, oxidation-reduction potential, specific conductance and dissolved oxygen levels. Also monitored were 7 trace metals, Cr, Cu, Fe, Mn, Ni, Pb and Zn. Atmospheric precipitation collectors were installed at the end of June 1974 and precipitation samples collected monthly from July 1974 until April 1975. Eighteen separate chemical variables were monitored at these sites using standard methods. Stream bed sediment grab samples were taken in May and again in July 1974. These_ samples were analyzed for total elemental composition as well as total nitrogen, total carbon, total sulfur, total cation exchange capacity, exchangeable cations (Ca, Mg, Na, K) and pH. The major geologic materials in the watershed were sampled in 6 sites located in undisturbed and cultivated areas on marine, glacial outwash, and alluvial materials. The monitoring of some selected chemical characteristics of the Salmon River revealed in general the mean values of pH, specific conductivity, temperature, total alkalinity, total HC03 alkalinity, total hardness (CaCO₃ equivalent), total dissolved solids, total Kjeldahl N, organic C, NO₃ -N, CI, Na, and K were consistently higher at low streamflows than at high (>750cfs) streamflows. Oxidation reduction potential and dissolved oxygen mean values were consistently higher at high flows than at low flows. The other variables measured remained relatively constant on average across all levels of streamflow. There was, however, considerable variation at specific point samples. Data derived from collection of atmospheric precipitation indicated a significant input of many chemical factors to the watershed. Bed sediment and soils chemical characteristics give a general indication of the amounts and distribution of the various chemicals potentially available for contribution to stream waters. Analysis of the results obtained in comparison with water quality standard acceptable levels revealed water quality problems with pH, temperature, phosphorus, iron, copper, and manganese. Significant statistical correlation exists between water quality variables and glaciomarine, marine and beach overlying marine or glaciomarine materials; glacial outwash materials; agricultural field crops; low density residential areas; and schools. In order to identify specific point and non-point sources more detailed information is needed on groundwater characteristics and the streamflow characteristics of tributary streams. Some general management alternatives are recommended bearing in mind that each site must be evaluated on its own merits and specific suggestions made on-site. / Land and Food Systems, Faculty of / Graduate