This study was undertaken to try to delay gonadal maturation of pink salmon for one year beyond their normal two year life cycle. This would allow these fish to spawn in years of low or nonexistent escapement and possibly increase these "poor" year populations. Three experiments were conducted to investigate the efficacy of the antigonadotropic drug, methallibure, in inhibiting gonadal maturation in pink salmon. Gonadosomatic index, oocyte diameter, and stages of cell maturation in the testis and oocyte maturation in the ovary were measured. The first or pilot experiment involved a range of doses of methallibure (0.10 mg., 0.32 mg., and 1.0 mg./gm./2wks.) to determine the optimal dose for subsequent experiments. All doses had only a slight slowing effect on maturation. This result and possible undesirable effects of higher doses prompted the decision to use the 0.10 mg./gm. dose for subsequent experiments. The second or long-term experiment investigated the effects of methallibure and a constant 12 hours light:12 hours dark photoperiod on gonadal maturation of males and females for a period of ten months. Methallibure completely inhibited testicular maturation by preventing the transformation of primary into secondary spermatogonia. Ovarian maturation, however, was only slowed. The treated ovaries possessed oocytes in the oil globule stage while control ovaries had oocytes in the secondary yolk globule stage. Methallibure had an antithyroidal effect under natural photoperiod but not under constant 12L:12D photoperiod or at a high dose (1.0 mg./gm). Stress from kidney disease may have been operative in this effect. Methallibure also slowed the rate of increase in body weight. The constant 12L:12D photoperiod slowed gonadal maturation in both males and females. It is suggested that a specific day-length and an endogenous rhythm stimulate the initiation, maintenance, and termination of gonadal maturation and that the seasonal daylength fluctuations function as a synchronizer. The difference in effect of methallibure on males and females may be due to treatment beginning prior to the start of testicular maturation but after the start of vitellogenesis. To investigate this possibility, methallibure treatment was begun at successive intervals prior to the start of vitellogenesis in the third or sequential experiment. This treatment had no effect on ovarian maturation which suggests that the females are less sensitive to methallibure than are the males. Treatment with a higher dose started early in juvenile life may inhibit ovarian maturation. From this study, only the males could be delayed and, therefore, possibly spawn in "poor" years. However, Funk and Donaldson (1972) were able to achieve the same goal by maturing males in the year of hatching, thus making a three year program impractical. The value of a long program would be the delay of ovarian maturation since Funk et al. (1973) were unable to advance maturation of females by one year. / Science, Faculty of / Zoology, Department of / Graduate

Eggs of Pacific herring were exposed to air for different periods of time in simulation of tidal effects on spawn deposits at varying beach heights. The maximum exposure range was 2/3 of a 24 hour day corresponding roughly to the exposure of eggs at 4 meters above mean low tide on the British Columbia coast. Egg size, spawning fish length, and egg clump size were examined as secondary factors modifying the effect of exposure. Incubation time dropped from 19 to 18 days with only two 2-hour periods of exposure per day and thereafter fell slowly. It is suggested that oxygen deprivation triggered a hatching response for the initial drop, whereas the gradual decrease was due to a higher air temperature increasing metabolism. Hatching mortality rose steadily from an unexposed 13% to 31% at maximum exposure time, with significantly higher contributions from eggs of smaller fish and smaller egg clumps. Larval length at hatching for the unexposed eggs was 7.7 mm.; lengths for all degrees of exposure were similar (7% less than for no exposure). Larval weight (body plus yolk) remained relatively constant (0.099 mg.) until the longest exposure period when it dropped to 0.087 mg. This decrease coincided with similar sharp trends in incubation time and hatching mortality, and suggests a "critical point" near the upper experimental range of exposure, above which eggs stand little chance of normal development or survival. Beach surveys to note possible egg size stratification, although suggesting the deposition of larger eggs at the top levels, proved inconclusive, but point up the possibility that a heavy fishing pressure which reduces mean fish size might detrimentally affect potential stock recruitment via the intertidal exposure effect on the spawn. / Science, Faculty of / Zoology, Department of / Graduate

The temporal and spatial variations in the activity of cutthroat trout in a small coastal British Columbia lake (49°19'N, 122°34’W) were examined in order to determine the Impact of activity on the production of fish, and the factors controlling activity. Sonar tracking, diving, netting and tagging, rise observation, stomach content-prey distribution comparision, and echo sounding were used in the Investigation. Average activity levels were at least an order of magnitude below any published values. Energy values were correspondingly low; the maximum estimate of annual energy expenditure in activity (including routine metabolism) was 2330 kCal/kg/yr, which is well below the accepted 'rule' of field metabolism being twice the routine metabolism (3860 kCal/kg/yr). Fish behavioral problems and methodological shortcomings are considered responsible for this result. Activity over 5 min intervals was quite variable. Daily activity peaked during dawn and dusk. The level of activity decreased in late fall and early spring, and there was a shift from the littoral zones during summer. The cutthroat in the lake appear to maintain home ranges-for up to 5 months. Factors affecting activity can be broken into 3 categories: Temperature, light, and oxygen primarily determine the depth zones that are accessible to fish. Substrates such as Potamogeton beds and logs may act to concentrate fish within accessible depth zones; attraction is likely due to the higher food levels and/or increased cover found in these areas. Bottom slope, by affecting foraging efficiency in the productive littoral areas, might also affect the summer offshore distribution of fish within an accessible depth zone. It is suggested that the indirect effects of activity (specifically, the offshore movement of fish in summer) can be equally or even more important to the production of fish than is the direct use of energy for activity. higher food levels and/or increased cover found in these areas. Bottom slope, by affecting foraging efficiency in the productive littoral areas, might also affect the summer offshore distribution of fish within an accessible depth zone. It is suggested that the indirect effects of activity (specifically, the offshore movement of fish in summer) can be equally or even more important to the production of fish than is the direct use of energy for activity. / Science, Faculty of / Zoology, Department of / Graduate

The effect of impoundment size on fish has been investigated. Investigators have reported that greatest growth has taken place in large in some instances and in small impoundments in others. The effect of varying space on the cichlid Aequidens pulcher Gill, was examined in four tanks of equal volume. Each tank was divided into two replicates in the compartment ratios 9:3:1 and each contained 90:30:10 fish respectively. A higher density tank had twice the fish number in all compartments and had lowest growth due to either reduced oxygen availability, increased biomass, increase in activity or stress due to small nearest neighbour distances. Fish in a tank with mirrors on all compartment walls had a reduced growth possibly due to visual stress compared to a control lacking mirrors. A further tank had twice the surface area of the control, a greater distance between nearest neighbours and greatest fish growth. Growth was significantly greater, at the 95 percent confidence limit, in all small compartments of tanks and activity was significantly greater in large compartments. In an identical treatment design to that of the control fish were shown to lose weight while being starved. The fish in the larger compartments were more active and lost most weight. A strong suggestion that the lower growth rate in large compartments was due to greater activity, possibly this was related to the total available swimming space per fish. Fish aggression was greatest in small compartments and decreased over time, possibly as a result of conditioning. / Science, Faculty of / Zoology, Department of / Graduate

This study compared three methods used to measure aggression in the male three-spined stickleback. These methods have been used in different studies without the certainty that they measure the same behavioural phenomenon. A number of different measures of aggression must be highly correlated if aggression in the male stickleback is to be regarded as a unitary drive. The methods consisted of recording the behaviour of an experimental male when: (i) a tube containing another male (or a female in some tests) was visible for 5 min; (ii) another male was visible across a glass partition at all times; (iii) a fish-shaped wax model was visible for 2 min. Each method showed that in the 12 days after fertilization of an egg-mass, there was a U-shaped trend in frequency of biting, frequency of charging and the rate of biting per minute spent oriented towards the other fish or the model. In Method (i), total oriented time formed about 70 % of a test period and this measure was not correlated with frequency of biting, nor did it follow a U-shaped trend. In Methods (ii) and (iii), total oriented time formed less than 50 % of a test period, was correlated with frequency of biting, and did follow a U-shaped trend. In Methods (i) and (ii), the measures, frequency of biting and bites per min of oriented time were at a maximum in the first 15 min after fertilization. Method (iii) did not show this maximum in biting. All methods showed that frequency of biting, of charging, and bites per min of oriented time were higher for fish with nests than for fish which had yet to build nests. Gonadectomy of fish with nests reduced all measures to the levels found for intact fish that did not have nests. An experiment using only Method (i) showed that a male with a nest attacked another male more than a non-gravid female. A male without a nest attacked both a male and a non-gravid female equally. The use of more than one measure for a behaviour pattern improved both the comparisons between methods and the analysis of changes in behaviour of the male. Examples of this are given for biting and parental fanning. Results from Method (iii) were not always consistent with those from Methods (i) and (ii). Method (iii) was exceptional in the number of charges the experimental males made with both dorsal and ventral spines erect. A wider range of behaviour patterns were recorded more regularly in Method (ii) than in Method (i). But these two methods consistently showed the same trends in frequency of biting, charging and bites per min of oriented time. In spite of the similarities in the results from the three methods there was not sufficient evidence to conclude that aggression in the male stickleback is a unitary drive and that all potential measures of aggression will be equivalent. / Science, Faculty of / Zoology, Department of / Graduate

Supervisor: N. R. Liley The endogenous and exogenous factors contributing to a diel rhythm of locomotor activity in juvenile sockeye salmon Oncorhynchus nerka (Walbaum) were examined in the laboratory. The basic measure employed in the investigation was spontaneous locomotor activity. High frequency sound (800 kHz) was used as a monitoring technique to collect continuous activity records. Three major areas received attention. First, a description and analysis were provided for the entrained diel activity pattern under three different temperatures (5°, 10°, and 15°C) and three different photoperiods (8L 16D, 12L 12D, and 16L 8D). The combined effects of temperature and photoperiod upon the basic 24 hour response were recorded and analyzed. Juvenile sockeye salmon were nocturnally active immediately after emergence from the gravel. A diurnal activity pattern was gradually acquired during the following 14 days and was maintained for 12 months. Photoperiod was the primary environmental synchronizer for either diurnal or nocturnal activity. The endogenous component of the activity rhythm was examined in constant environmental conditions. Constant light (34.4 lux at 10°C) facilitated the free-running response while constant dark inhibited it. The spontaneous frequency in constant light was 23.30 hours but this could be altered by light intensity or periodic feeding. The final experiments focused upon the relationship between the environmental stimulus (photoperiod) and the physiological sensory mechanisms mediating the entrained response. The eyes were the primary photoreceptors mediating information about the light-dark environment. The entrained activity response disappeared when the retina was not illuminated. When the pineal body was removed or shaded, juvenile sockeye responded with increased activity. Intraperitoneal injections of melatonin (N-acetyl-5-hydroxy-tryptamine) or serotonin (5-hydroxy-tryptamine) selectively altered the activity amplitude in either the light or dark respectively. Juvenile sockeye salmon possess an endogenous circadian activity rhythm which is synchronized by the photoperiodic cycle. The fish are generally light active, except for the period immediately after emergence. However, interactions between daylength and temperature can result in temporary dark active responses. Mediation of the photoperiodic information occurs via the retina, but without transmission by optic nerve pathways. Chemical agents (melatonin and serotonin) produced by the retina and/or pineal might control the activity amplitude in light and dark, thus resulting in the characteristic entrained pattern. / Science, Faculty of / Zoology, Department of / Graduate

The blue gourami, Trichogaster trichopterus, is a small, freshwater tropical fish, native to Southeast Asia. Parental behavior is normally shown only by males after spawning. Females and non-parental males eat small numbers of test eggs which they are given, while parental males retrieve them to their nests. The goal of this thesis was to investigate the factors responsible for the sudden change in behavior from egg-eating to parental care which takes place at the time of spawning. In the initial section, the patterns of parental behavior are described, and quantitative data on the development and maintenance of parental behavior in male fish spawning for the first time are presented. The experimental studies reveal that stimuli from the eggs are an important factor in the induction of parental behavior. Many naive males developed parental behavior within 0.5-2.5 min when given eggs spawned by other fish. This response was dependent upon the number of eggs presented: a large proportion of fish became parental when given 2000-3000 eggs, a smaller proportion did so when given 500-1000 eggs, and none did so when given 100 eggs. However, even 100 eggs evidently affected parental responsiveness because some fish eventually developed complete parental behavior when repeatedly given 100 eggs. These results indicate that eggs can induce parental behavior, not that they do so in the natural spawning situation. However, tests of males spawning with females whose oviducts were plugged indicated that exposure to eggs was an important component in the natural development of parental behavior. Spawning by itself did not induce fish to become parental, but it did reduce the number of eggs necessary for parental behavior to develop. Besides spawning and stimuli from the eggs, androgens also play a role in the development of parental behavior. It was shown that, after spawning, males performed more parental behavior than females, although detailed observations of females revealed that they had some capacity to perform parental behavior. The masculinization of females by means of methyl testosterone implants allowed them to develop parental behavior in response to large numbers of eggs. Whether castration of males eliminated their capacity to perform parental behavior could not be determined with certainty. The presence of young facilitates the maintenance of parental responsiveness to eggs when males with developing broods are compared with males whose broods have been removed. Apparently, physical contact with the young is necessary because males lose their parental responsiveness when their broods are placed in baskets which allow only visual and chemical contact. An important result of this study is the demonstration of the significance of stimulus strength in the induction of parental responsiveness. This factor has not often been taken into consideration in other studies of parental behavior. By varying stimulus strength, repetition of stimuli, and sexual experience, patterns of the induction of parental behavior were found in gouramis which were similar to those observed in other studies on a variety of mammals, birds, and fish. That is, parental behavior developed either almost immediately or gradually with the presentation of young to non-parental fish, or it was shown only if the young were presented during the "sensitive period" after spawning. The finding of such different patterns in a single species as a result of varying the strength of stimuli from the eggs suggested that the motivating effects of eggs and young on parental responsiveness may represent a common pattern underlying the control of parental behavior in a variety of vertebrate species. This possibility and the relationship between hormones and stimuli from the young in the control of parental behavior are discussed in the final chapter. / Science, Faculty of / Zoology, Department of / Graduate

Samples of Gasterosteus aculeatus from 16 areas in the Fraser Valley and environs were examined for plerocercoids of Schistocephalus solidus. Fish at Coal Harbour and Alouette Lake were sampled several times over a twelve month period. The number and sizes of worms present in the Alouette Lake fish samples were recorded, and it was found that infected fish less than 45 mm. total length carried on average more worms than those over 45 mm., and that uninfected adult fish were caught only during the breeding season. In another lake, infected fish were found in a different area from the uninfected ones. The fish intermediate host was shown to be affected by the infection in four ways: (i) Infected fish died sooner than uninfected fish, (ii) Heavily infected fish were lighter in weight of fish tissue than controls of the same length, (iii) The total standard respiration rate of infected fish was higher than that calculated by combining values obtained from uninfected fish and published values for in vitro plerocercoids. (iv) Heavily infected fish required up to twice as much oxygen per gram fish weight per hour when swimming at the same speed as control fish. Other aspects were examined but the results were inconclusive or negative. The observations on natural populations are discussed in the light of the experimental findings. / Science, Faculty of / Zoology, Department of / Graduate

Behaviour to increased water velocity is examined in fast stream fish (Otocinclus, Hypostomus, Pterygoplichthys, Chaetostoma and Gyrinocheilus) and a slow water form (Farlowella). Behaviour can be divided into two stages; resting and adhesion (Chapter I). In Otocinclus a third fin extension stage is apparent. Based on the slipping velocity of live and dead fish it is determined that Gyrinocheilus has the greatest station holding ability on a smooth perspex surface. This is attributed to a complete seal produced by its oral sucker lips (closed sucker). Station-holding ability is also examined on rougher surfaces. Slipping does not occur in any of the genera at water velocities up to 90 cm s⁻¹. Morphological adaptations (eg. oral sucker, pectoral fins, frictional pad and odontodes) that may contribute to increasing slipping velocity are examined. In Otocinclus these structures are analyzed using a Scanning Electron Microscope. Otocinclus is the only genera with the ventral dermal plates between the pelvic and pectoral fins organized laterally into a frictional pad. Drag on fish is directly measured with strain gauges and used to calculate drag coefficients (0.10 - 0.94; Chapter II). Drag coefficients for low fineness ratio (length/height < 10) forms at Reynold's numbers below 10⁴ compare poorly with literature values for technical bodies. Drag coefficients determined for fish are high due to roughness and interference drag produced by the fins. Using morphological measurements, dead slipping velocities, drag coefficients, static frictional coefficients and submerged body weight, lift coefficients (-0.55 - 1.23) calculated. Fast stream fish maximize slipping speed by having high frictional coefficients (0.67 - 0.95, on a smooth perspex surface), density (1.03 -1.10 g cm⁻³), rheotactic suction pressure (13 - 173 N m⁻²) and negative lift Although Farlowella has high density (1.129 g cm⁻³) and a low drag coefficient (0.23), its lift to drag ratio is high (6.71) and rheotactic suction pressures (2 - 27 N m⁻²) are low. In general Farlowella does not exhibit hydrodynamic, behavioural or morphological characteristics that enhance station-holding. / Science, Faculty of / Zoology, Department of / Graduate

Aurelia aurita passes through several life cycle stages during its development. Sexual reproduction occurs in the adult jellyfish and results in the free-swimming planula, which develops into the sessile scyphistoma (polyp). The polyp, which reproduces asexually by budding, develops into a strobila which, also asexually, produces free-swimming ephyrae (the initial medusoid stage) through transverse fission. In the planula, the nervous system consists of ectodermal sensory cells and neurons and their fibres. Anti-FMRFamide antibodies label both sensory and neuronal cells in the anterior region of the planula; the neuronal processes are mostly arranged longitudinally along the anterior/posterior axis, and a few fibres run transversely. Labelled neurons do not appear to make contact with one another in the early, i.e. just released, planula and do not have the appearance of a nerve net until the late planula, i.e. just prior to metamorphosis. Metamorphosis of the planula can be induced by exogenously applied thyroxine (10−⁷M) and iodine (10−⁷M) and, to a lesser degree, by retinoic acid (10−⁷M). MgCl₂ (0.13M) and FMRFamide (10−⁷M), on the other hand, inhibit or reduce, respectively, the induction of metamorphosis. Less than 50% of planulae cut into anterior and posterior halves are undergoing metamorphosis after 10 days, and thyroxine fails to enhance the rate of metamorphosis in those larvae. In the scyphistoma, the nervous system consists of sensory cells and neurons in the ectoderm and the endoderm. The somata of cells labelled with anti-FMRFamide are located mostly in the oral disc and the tentacles, where they, together with their processes, have the appearance of a nerve net. Nerve fibres are also found on the four muscle bands that extend the length of the scyphistoma from the pedal to the oral disc. In the developing and adult jellyfish, conventional techniques such as methylene blue staining distinguish between a diffuse nerve net and a giant fibre system. Neuronal subsets are identified by immunohistochemical techniques such as labelling with anti-FMRFamide and a monoclonal antibody generated with ephyral tissue as the immunogen. Anti-FMRFamide labels a subset of neurons of the diffuse nerve net, whereas the monoclonal antibody labels a separate subset of neurons, some of which belong to the giant fibre system, while others do not, and none of which co-label with the anti-FMRFamide antibodies. In contrast to the subset of FMRFamide-positive neurons, which has the appearance of a nerve net in all jellyfish stages, the number of neurons labelled with the monoclonal antibody increases during the development of the jellyfish from a few scattered neurons in the ephyra to an interconnected population of neurons forming a nerve net in the adult. Whereas elements of the diffuse nerve net and the FMRFamide label are present in all life cycle stages, the giant fibre system, which innervates the swimming muscles, and the monoclonal antibody label only occur in the jellyfish stages. Rhodamine B, which has been used as an indicator of neuronal activity in other phyla, was found to also stain neurons in the jellyfish stages of Aurelia. The number of stained neurons was significantly higher in ephyrae treated with FMRFamide or Artemia when compared to ephyrae treated with MgCl₂ and FM[D-R]Famide. The data indicate that the nervous system of Aurelia aurita is more complex than previously assumed, in that a separate nerve net or subset of neurons is present in the jellyfish whose characteristics are neither solely that of the giant fibre system nor that of the diffuse nerve net. No indications were found for neuronal cell death during the development of the nervous system. / Graduate