Typescript. / Thesis (Ph. D.)--University of Hawaii, 1966. / Bibliography: leaves [180]-199. / xxiv, 297 l illus. (part mounted), tables

Life history events of chinook salmon preclude determination of a critical size for this species by established methods. The use of size, rather than age, as a basic correlate of growth rate is discussed and compared to analagous treatment of physiological rates described in literature. Ecological opportunity and physiological opportunity are visualized as the two interacting components that determine growth, both of which are related to size attained. Growth opportunity occurs in stanzas which are entered at "threshold" sizes. The function, dw/dt = kw(x) is developed into a growth equation for linear dimentions, 1(z/t+1) = ɑ + (1z/t) and three methods of fitting this equation to growth data are demonstrated. Application is explored and discussed using steel-head trout and chinook salmon as examples. Significant differences in growth rate were found between life history types and sexes. The chinook data were then treated on a 1(t+1), 1(t) plot and it was shown how an apparent fit of the von Bertalanffy type growth equation can result from selectively fishing for the larger fish of any brood year. Accordingly, life history subgroups of a year class must either be treated separately or weighted according to relative abundance in determining critical size. The former alternative is followed in lieu of necessary weighting data. Natural mortality of a chinook population is estimated from the pattern of tag recoveries, taking advantage of the fact that maturity occurs at different ages for individuals of a year class and that the fishery operated mainly on maturing individuals. Annual instantaneous natural mortality was estimated to lie in the range 0.3 to 0.4. The growth equation was then transformed to a length-specific average annual instantaneous growth (weight) rate and critical size was observed to occur at maturity for each life history type. Since fishing is presently allowed on the immature stock, a size limit protecting the older life history types causes a loss in yield from the younger life history types. This loss might be offset, depending on the relative abundance of life history types in the stock, providing mortality due to hooking and releasing is negligible. Capture by trolling was found to subject feeding coho and chinook salmon to hyperactivity which may lead to a distressed condition or death, and death cannot be predicted from examination of individual fish at time of capture. Mortality of coho was estimated to be in the 0.95 confidence interval of 34 percent and 52 percent; of chinook in the 0.95 confidence interval of 40 percent and 71 percent. Time of maximum death rate is shown to coincide with the period of maximum blood lactate response. Survival occurred either when blood lactate did not reach critical levels (above 125 mg%) or reached critical levels and subsequently subsided. Holding salmon in a live box for 8-14 hours before release did not improve tag recovery, suggesting additional indiscriminant stress was caused at release. Adult coho in freshwater did not appear capable of lethal hyperactivity. This led to the hypothesis that cessation of feeding during spawning migration has adaptive significance for survival of Pacific salmon. The combination of natural mortality, mortality from hooking injury and delayed mortality from fatigue gave a total instantaneous first year mortality rate (exclusive of fishing) greater than 1.0 and possibly as high as 2.5. This mortality rate results in a critical size of not more than 22.5 inches and most likely about 15.0 inches fork length. It is thus concluded that for maximum yield in pounds (1) fishing for chinook should be restricted to their ultimate year (maturity) and (2) the use of non-selective gear should be encouraged. These recommendations are opposite to present practices. If fishing is to be allowed on the immature stock, size limits should be abolished. / Science, Faculty of / Zoology, Department of / Graduate

Typescript (photocopy). / Digitized by Kansas Correctional Industries

The richness of nervous systems represented by extant fishes has not yet been determined; the brain morphology of many species, indeed, many groups, remain undescribed. For this reason we have examined esociform teleosts and focused on three goals: 1) to provide the first basic descriptions of the brains of two esociform teleosts, Esox masquinongy (muskellunge) and Esox lucius (northern pike); 2) to describe the development of E. masquinongy brains; and 3) to compare the neuronal features between E. masquinongy and E. lucius in light of the ontogenic pattern of E. masquinongy. We demonstrate that a suite of differences exists between the brains of these two congeners. Relative to the brains of E. lucius, the brains of E. masquinongy exhibit a number of paedomorphic features. This heterochronic shift parallels the differences in non-neuralmorphological features previously described between these two species. We identify three features that cannot be explained by this heterochronic shift: 1) the optic nerves of E. masquinongy and E. lucius cross oppositely, E. masquinongy have optic nerves that cross left nerve dorsal, E. lucius cross right nerve dorsal; 2) Esox lucius have a consistent cellular discontinuity in the telencephalon between Dm, and Dd that is not present in E. masquinongy; and 3) adult E. lucius retain a neural canal opening that closes in larval E. masquinongy, a peramorphic exception to the paedomorphic pattern. / Department of Physiology and Health Science

Ph.D. / A genetic study of seven fish species within the chubby and goldie barb groups of minnows was done by means of starch-gel electrophoresis. These two groups of minnows are widely distributed within the temperate rivers of southern Africa. Because of little morphological differentiation between the species within these two groups of barbs, their taxonomy has not yet been settled. Subsequently, species within these two groups of minnows could not always be identified with certainty and caused some problems for conservation bodies concerning the distribution and status of the different species. To make a contribution towards the taxonomy and conservation of these fish species, 330 specimens of goldie and chubbyhead barbs were analysed to determine the genetic variation within and between 17 populations comprising seven species. The heterozygosity values obtained in the present study within populations is similar to the values obtained for fish in other studies (Nevo et al., 1984; Alves and Coelho, 1994). The highest heterozygosity values were observed in fish populations collected from the eastern Cape, which could possibly be an indication of a relationship between this specific habitat and genetic diversity. In contrast, relatively low heterozygosity values were observed in some populations, for example Barbus brevipinnis (Marite River) and B. gurney! (Mgeni River), which could possibly be attributed to a degraded habitat. This assumption is supported by the fact that these populations were infested with parasites, which is often an indication of stress.

No description available.

M.Sc. (Zoology) / The histomorphology of the ovaries of Cyprinus carpio L., as well as the histomorphological changes that occur in these ovaries during the breeding cycle, were investigated. Concurrently, the blood plasma and ovarian cytosol were analized for the presence of gonadotropin (GtH), FSH, LH, Oestriol, Cortisol and Progesterone, with the aid of Test Kits which are commonly used for determining the levels of these hormones in human blood plasma. C. carpio possesses cystovaria which are continuous with the oviducts which unite before opening to the exterior via a gonopore. The results clearly show that C. carpio has a four season breeding cycle and that egg laying occurs during Spring and Summer. Furthermore morphological changes of the ovary (which occurred during the breeding cycle) as well as the oocyte developmental stages, closely resemble those respectively described for teleosts in general by Kesteven (1960) and Malhotra et al., (1978). The endocrinological tests clearly indicated the presence of GtH, FSH, LH, Oestriol and Cortisol, while all the tests for Progesterone were negative. A comparison between the presence of the abovementioned hormones and the histomorphological development of the ovaries during the breeding cycle indicate that the endocrinological control mechanisms are similar to those which have been described for other teleosts. However, a clear distinction was found between FSH and LH which is a possible indication that C. carpio does not possess a single gonadotropin, but rather that FSH and LH have evolved in this species.

M.Sc. / Please refer to full text to view abstract

An experiment was designed to determine whether the response of fish to graded dietary levels of essential fatty acids (n3) was affected by the total dietary lipid concentration. Juvenile coho salmon were fed practical diets varying in lipid source and total lipid content. The diets were fed in duplicate during a 27-week and a 12-week period ran in succession. The effects of the different dietary fatty acid concentrations on body fatty acids composition were determined after each period. The dietary fatty acid classes were expressed either as percent of the dry diet or percent of the dietary lipid. Analysis of the body lipid fatty acid composition was performed for neutral and polar lipid fractions. The effect of dietary fatty acid concentration on growth and mortality was determined over a 12-week growth study (period 2). A 24-hour saltwater challenge was performed at the end of period 2. It was used to examine the effect of dietary fatty acid concentration on saltwater tolerance. Dietary n6 and n3 fatty acids appeared to be selectively incorporated into the body polar lipid pool. Linoleate and linolenate underwent elongation and desaturation which resulted in the inhibition of the elongation and desaturation of 18:ln9. The neutral lipid pool served as a source of n3 fatty acids for the polar lipid when dietary intake was limited by low temperatures during period 1. The body neutral monounsaturated and 18:1 monounsaturated fatty acids consistently reflected the composition of the diet. The n3 fatty acid concentration in the neutral lipid was also directly related to the dietary fatty acid composition during period 2. The effect of dietary fatty acids on the body neutral or polar fatty acid composition did not depend on the manner in which the dietary fatty acids were expressed. There was also no significant effect of dietary total lipid concentration on the relationship between dietary fatty acids and their incorporation into the body lipids. The growth response was difficult to interpret because of the high mortality. There was a significant difference in mortality among treatments. A positive relationship between dietary concentrations of total n3 fatty acids or n3 highly unsaturated fatty acids and mortality became evident following analysis of the regression of mortality as a function of dietary fatty acid composition. The dietary fatty acid composition did not appear to alter the saltwater tolerance of the 1+ coho salmon. / Land and Food Systems, Faculty of / Graduate

M.Sc. (Zoology) / Tilapia sparrmanii (Smith) obtained from the Provincial Fishery in Lydenburg was used for toxicological studies. The haematology of T. sparrmanii was investigated after exposure to sub-lethal doses of atrazine, zinc and iron for 72 hours in a continuous flow and static system, as well as prolonged (4 weeks) exposure in the continuous flow system. After exposure the blood of the experimental fish were sampled. Mean values and standard errors were obtained for several haematological parameters such as number of red and white blood cells, haematocrit, haemoglobin, mean corpuscular volume, pH, plasma glucose-, protein-, lipid- and lactate concentrations, as well as plasma Na+, K+, eland Ca+. Statistically significant differences were found between the values of haematological parameters of experimental and control fish. A tendency towards haemoconcentration was observed when fish were exposed to the low pollutant concentrations, while signs of haemodilution was found at higher concentrations. The results in this study demonstrate that, after prolonged exposure, T. sparrmanii develops a tolerance and partially recovers from the stress condition. The bioconcentration of atrazine in the blood of T. sparrmanii after exposure were determined by liquid chromatography and zinc and iron by atomic absorption spectrophotometry. During this study it was found that atrazine, zinc and iron concentrated in the blood of T. sparrmanii after short- and prolonged exposure to the pollutants. The routine oxygen consumption of "!'. sparrmanii exposed to atrazine, zinc and iron were determined in a continuous flow apparatus over 72 hours. The oxygen consumption of the experimental fish fluctuated for the first 8-12 hours during the acclimation period. The influence of atrazine on the routine oxygen consumption was not so drastic as that of zinc and iron. Zinc caused a decrease in the routine oxygen consumption of the experimental fish over 72 hours, while iron increased the routine oxygen consumption...