No description available.

The fact that fish possess a sense of smell has been known for some time. Fabricus (1780) described how lampreys and sharks would follow rotting meat and Mono, (1744) demonstrated that fish would react to a worm in the water and show adaptation to its odour. Bateson (1890) showed feeding responses in both elasmobranchs and teleosts to hidden food and juices squeezed through cloth. These reactions are present in both seeing and blind fish. Copeland (1912)and Parker (1914) shoved that dogfish were able to localize hidden food by olfaction, thus proving that it could be a directional sense. Initially the study of chemosense had been performed by observing the occurrence of a definite feeding reaction either as a result of detecting food odour or to extend the type of stimulus studied when the reaction had been conditioned to another stimulus (Göz, 1941; Teichmann, 1959). Conditioning is a long process and requires a suitably hardy species. In many cases where a stimulus not connected with feeding is used to condition a feeding reaction we may learn of sensory acuity in absolute terms but nothing of the natural use of the reaction. To examine more subtle reactions to stimuli. especially those not related to feeding, specialized apparatus had to be developed. This allowed workers to look at how a response would be used by the fish in nature. As well as showing reactions to food and prey organisms fish have been shown to use olfaction in social behaviour both with other species and conspecifics of both sexes. Göz (1941) managed to condition a single, blinded, minnow Phoxinus phoxinus to show a feeding reaction to the odour of another fish species Ictalurus nebulosus not the prey of the minnow. This took many weeks using even the easily-trained minnow. Because of the difficulties and limitations many workers have adopted more direct approaches, Wrede (1932) found blinded minnows (a shoaling species) preferred to visit a compartment in an aquarium where the odour of a conspecific lingered rather than a control compartment. Hemmings (1966a) used a more complex preference trough derived from that of Shelford and Allee (1914) and found that the shoaling, freshwater roach (Rutilus rutilus) showed a preference for the end which had the odour of other roach. By analysis of movement in the trough he showed that this preference was due to increased turning rate. Investigating these pheromones in char, D6ving, Nordeng and Oakley (1974) used electrophysiological methods, recording electrical impulses from the olfactory tract, and found the char was able to identify racial differences in this social identifier. Doving,Enger and Nordeng (1973) proposed a component of mucus to be the pheromone. Interest in amino acids as a possible stimulus to feeding in marine organisms began when Steven (1959) found that glutamic acid produced a feeding reaction in two species of tropical marine fish. Case and (iwilliam (1961) found that a range of amino acids would stimulate a blinded crab to feed when applied to the cheiae This reaction was confirmed electrophysiologically on isolated dactyl preparations, responses being obtained from the dactyl receptors to a range of amino acids. Many workers including Hara et al (1973), Hashimoto et al (1968), Haynes et al (1967) and Suzuki and Tucker (1971) have found similar reactions from the olfactory nerves of teleosts. The long, easily accessible olfactory tract in some teleost species makes them ideal subjects for electrophysiological investigation. The technique of monitoring nerve impulses enables a large number of amino acids to be rapidly tested; the thresholds obtained however may not be those which will stimulate a feeding reaction and hardy species are needed. Most work on chemosense in teleosts has been performed on adult and juvenile fish; this is not surprising since rearing beyond the non-feeding yolk sac stage of many important marine species has only been successful in the last decade. The histology and morphology of the development of the olfactory system has also received little study since Holm (1894) described this process in Salmo salar. He showed that in Salmo salar, which took 90 days from fertilization to hatch, there was no nervous connection between epithelium and brain at 60 days post fertilization but one was found at 83 days post fertilization. The olfactory nerve appeared as the groove closed. Attention has been drawn to this lack of knowledge by Hasler (1957), Johnson and Brown (1962) and Branson (1963). In many of the teleosts so far studied the olfactory system is undergoing development not only for the whole of larval life but beyond into juvenile development. Larval development is a valuable time to study this, and indeed any organ system, since it is changing in physical structure, increasing in complexity and possibly changing in acuity and function. The role of a larva can be in many cases to give the early stages of an organism a different ecological niche from the adult, preventing intraspecific predation and competition for food. Therefore its senses may be used for different purposes to the adult, (for example the use of chemosense and touch in the settlement of Balanus nauplii (Crisp, 1974) a system obviously of no use to the adult). In the case of a nektonic shoaling fish such as the herring with a planktonic non-shoaling larva, there would be a possibility of larvae dispersing over a large area prior to onset of shoaling behaviour. There would obviously be some value in keeping larvae together in loose groups and it is likely chemosense may play some part in this. Aggregations of planktonic marine organisms are a well documented phenomena (Barnes and Marshall, 1951; Weibe & Holland, 1968) from the longevity of these aggregations it seems unlikely that this is caused by physical boundaries of water parcels. It seems possible that chemosense acts to keep aggregations intact and in some organisms is retained in adult shoaling life, perhaps to maintain aggregations when the shoals disperse at night (Harden-Jones, 1962). Feeding patterns in larvae and adults can also differ; for example herring and plaice larvae will snap at food organisms in the water column, taking selected individual prey; in the case of herring almost stalking. As adults, herring mainly feed by filtering, although evidence from other filter feeding fish suggest a proportion of particulate feeding will also occur depending on prey size and density (O'Connell, 1972), and plaice move along the sea bed eating epibenthic organisms, mollusc siphons and sedentary worms, Both modes of feeding require good vision. Newly hatched herring (Blaxter and Jones, 1967) and plaice (Blaxter, 1968a) have very different eyes from the adult, the eye developing throughout larval life. In Sardinops caerulea, Schwassmann (1965), the eye is a very rudimentary structure when feeding begins. Although the feeding act is visual, the volume which can be searched using sight alone is small (in herring 0.3- 2.0 litres per hour and in plaice 0.1-1.8 litres per hour (Blaxter and Staines, 1971). It seems possible that olfaction could assist in the search for food either by directionally guiding the fish larva to a concentration of food organisms or restricting energy-requiring searching behaviour to periods when food organisms can be detected by presence of their odour. With these possibilities in mind the outline of study below was adopted.

Thesis (Ph.D.) -- McMaster University, 1999. / Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1954. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 118-121).

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 29-31.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. Includes bibliographical references.

Inaug.-diss.--Basel. / "Literatur": p. 50-52.

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

No description available.

Cohorts of larval Pacific herring, Clupea harengus pallasi Valenciennes 1847, were studied from hatch during the spring of 1985, 1986, and 1987 in the Strait of Georgia, British Columbia. The main objectives were to study the patterns in the larval dispersal process, to study a major spawning area for Pacific herring to determine whether this site may act as a nursery area for the resulting year-class, and to evaluate the current hypotheses concerning survival of the larval year-class for their applicability to Pacific herring. Results indicated a significant proportion of larval herring which hatched in Lambert Channel quickly dispersed into Baynes Sound, probably through a combination of tidal movements and wind driven surface currents. Baynes Sound was shown to be much more stable than Lambert Channel due to strong stratification through freshwater input and protection from wind mixing by the surrounding land masses which may also have resulted in an earlier spring plankton bloom. Baynes Sound also had significantly higher densities of microzooplankton important to the early feeding herring larvae than Lambert Channel and outside waters. The suite of potential predators was also different between the two channels with Baynes Sound having more hydromedusae and Lambert Channel having more chaetognaths and polychaetes. Analysis of larval growth rates using an RNA/DNA ratio technique on individuals from the yolk sac stage onwards indicated the larvae initially grew very slowly but, by postflexion were growing over 25 %•d⁻¹ in protein. Starvation did not appear to play an important role in mortality. The RNA/DNA ratio was demonstrated to be directly correlated with a morphometric condition factor Pacific herring larvae indicating it can also be used as a condition factor. There was a significant positive correlation between the mean protein growth rate measured with RNA/DNA ratios and the mean nauplii density. Feeding larvae in Baynes Sound were found to be growing faster than those in Lambert Channel suggesting Baynes Sound was being used as a nursery area. Analysis of otoliths suggested there was a significant increase in survival of larval herring having higher growth rates over as little as a 3-week period. / Science, Faculty of / Zoology, Department of / Graduate