Thesis (PH. D.)--University of Michigan, 1941. / Reprinted from Papers of the Michigan academy of science, arts, and letters, vol. XXVIII, 1942. Published 1943. Literature cited: p. 308-312.

Thesis (M. Sc. (Ichthyology and Fisheries Science))--Rhodes University, 2006.

Thesis (M.S.)--University of Puerto Rico, Mayaguez Campus, 2006. / Includes bibliographical references.

The effects of stocking density, size grading, feeding frequency and ambient temperature on the growth performance and size variation of spotted grunter, Pomadasys commersonnii were investigated. The time that would be required to rear the species to market size was modelled. An area where maximum growth rate could be achieved under ambient temperature conditions, and therefore the location of a commercial farm within the distribution range of spotted grunter along the coast of South Africa, was predicted. The growth performance of spotted grunter was not significantly affected by stocking density. Growth performance seemed to improve with increasing stocking density. Competitive behaviour was absent among fish in the various stocking densities. Growth in terms of fork length and body weight was not significantly different between stocking densities. The highest specific growth rate, best food consumption, food conversion ratio and protein efficiency ratio of the fish were recorded at a density of 6.4 kg/m³, whereas the best condition factor was recorded at a density of 3.8 kg/m³. The lack of significant difference in many of the growth parameters between the various stocking densities suggest that juvenile spotted grunter could be reared at densities higher than 6.4 kg/m³. Further investigations are needed to determine the optimal initial stocking density of juvenile spotted grunter under ambient temperature and photoperiod conditions. Replacing the largest fish with average sized fish did not have a significant effect on the specific growth rate and competitive behaviour based on the relationship between the coefficient of variation and average size. Feeding frequency had a sIgnificant effect on food consumption, food conversion and protein efficiency ratio, and not on size increase, specific growth rate and condition factor. Its effect on competitive behaviour could not be conclusively explained. The best food conversion ratio recorded when feeding once a day showed that although the fish consumed a limited amount of food, they utilised the food that was fed most effectively. It is suggested that the fish be fed three times a day. The survival of juvenile spotted grunter was 95.6 % when feeding three times a day compared to 90 and 90.2 % when feeding once and five times a day, respectively. Fluctuating ambient temperature had a dramatic effect on specific growth rate and food consumption of spotted grunter. Growth modelling showed that the fish could be reared to a market size of 550 g (270 mm FL) in 19 months under ambient temperature conditions (23.2°C) at Richard's Bay. The optimal predicted rearing period of 19 months is approximately seven months less than that calculated for fish in the wild, and can possibly, be reduced further by feeding a balanced diet. The overall food consumption (on a dry weight basis) in the three size classes ranged from 0.15 ± 0.16 to 0.38 ± 0.35 % body weight per day. Food conversion ratio improved with increasing fish size. This relationship was attributed to diet quality and more specifically, the protein : energy ratio. As a result, fish in the large size class had the best overall protein efficiency ratio. Maximum specific growth rates of1.5, 0.84 and 0.74 % body weight per day were recorded from the small, medium and large size classes in the peak of summer with average daily temperature ranging from 21 to 22°C. Positive slopes in the coefficient of variation against fish size in the large size class indicated the presence of competitive behaviour which was attributed to the onset of adolescence. The information from this study can be used for pilot production of spotted grunter. Further research should be undertaken to investigate captive reproduction of the species.

[No abstract available] / Science, Faculty of / Zoology, Department of / Graduate

[No abstract available] / Science, Faculty of / Zoology, Department of / Graduate

Any mathematical formulation for depicting the growth of organisms must yield an empirical fit that is reasonably good. Its validity is enhanced if the equation yields information of biological interest. This investigation is aimed at applying the Parker-Larkin (1959) growth equation to a number of aquatic organisms to describe the problems encountered in making use of this technique. The data are also analysed by the Von Bertalanffy growth equation to bring out the similarities of the constants of both the equations. The data pertaining to three species of marine fish, brill, halibut and herring, four species of freshwater fish, rainbow trout, cutthroat trout and sturgeon and to a lamelli-branch species scallops, have been analysed. It is pointed out that the exponent of the length-weight relationship should not be taken as 3. It is shown that the length-weight relationship of rainbow trout varies depending on sex, maturity and size. In many species the Parker-Larkin growth equation predicted the lengths at various ages accurately. Von Bertalanffy’s equation progressively overestimated the sizes. In white sturgeon the growth increments decrease at first and then become equal. In such a situation it is suggested that the data be split into two stanzas for analysis since the analysis without splitting underestimates the sizes in the early years and overestimates in the older ages. The anterior radius of the scale grows relatively slower than the length of the fish in herring. The regression equation of the body-scale relationship is used only to obtain the value of the intercept. The back calculation of lengths is made by keeping the intercept constant with variable slopes for the individual fish. The Parker-Larkin equation gave an excellent fit for the data on halibut. This is because the observed values of halibut are actually calculated values from a linear logarithmic regression of weight on age - an algebraic equivalent of the Parker-Larkin equation in which the slope is the reciprocal of (l-x). The range of values of z between 1.0 and 1.5, when the line of best fit on a Walford plot approaches the 45° diagonal, is true for salmonids only and in similar situations for other species a value as high as 3.6 for z is obtained. The variability of z depending on the density of the population and/or availability or non-availability of food material is shown for rainbow trout. This dependence of z on the food available is similar to that of L₀₀ or W₀₀. There is an inverse relationship between L₀₀ and z as that of L₀₀ and Κ. It is tentatively suggested that z might be a parameter of physiological importance in the Parker-Larkin equation. Further work of an experimental nature is suggested to establish the physiological significance of the parameters of the Parker-Larkin equation. / Science, Faculty of / Zoology, Department of / Graduate

A description of a new strigeid metacercaria of the Neascus group responsible for the production of black spot in the lake shiner, Richardsonius balteatus is given. The metacercaria is distributed over the body in melanistic integumentary cysts. All attempts to obtain the adult flukes by feeding infected fish to pigeons, ducklings, rats, and cats failed. Black spot is erratically though widely distributed throughout British Columbia. Thirty-six of the forty- four lakes examined showed the disease to be present in the shiners. Ptycholeilus oregonensi, Mylocheilus caurinus, Catastomus macrocheilus, Cottus asper, Salvelinus fontinalis, Salmo gairdneri kamloops and Prosopium williamsoni are also infect by black spot. / Science, Faculty of / Zoology, Department of / Graduate

The following report is a summary of an investigation undertaken on behalf of the Canadian fishing industry, more especially the inland fisheries of the Prairie provinces, by the Fisheries Research Board of Canada. The investigation was allotted to the Pacific Fisheries Experimental Station at Vancouver, the actual work being performed in the Physics Department of the University of British Columbia. The application of physical methods to biological and other problems is becoming more prevalent. The case in hand is an example of the application of physics, more particularly the laws of light scattering, to determining the infestation of fish by Triaenophorus crassus. The arguments wherever possible have been stated in everyday language and notwithstanding the possibility of boring the informed reader, all experiments are described in detail. This, it is hoped, will accomplish two purposes. Firstly the biologist will have a better understanding of the investigation and secondly the application of physics to similar problems can be assessed. Included at the end of the section on candling is an attempt to explain the formation of shadows by objects imbedded in turbid media. The argument is first given, in simple language followed by a mathematical discussion. The complexity of the theory of scattered light in terms of ultimate processes need not be stressed. A treatment based on the theory of M. Born is found in Appendix I. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Food study based on the stomach content analyses of spring and coho salmon collected from various localities along the southern British Columbia coast during the summer of 1957 revealed that herring followed by Crustacea formed the most important item of the diet of the two species. Coho salmon exhibited more pelagic and varied diet than spring salmon caught in the same area. Definite seasonal fluctuations in the composition of food and feeding intensity were noticed, considerable amounts of Crustacea were taken in early summer months and after that fish assumed importance. July and August mark the period when the feeding activity is intense in both the species. Qualitative and quantitative differences in the feeding conditions on the east and west coasts of Vancouver Island warrant the establishment of two food type areas. The differences in growth of fish on the two coasts as related to feeding conditions are discussed. Although, herring is the major food item of both spring and coho salmon, evidences are presented in support of the hypothesis that a reduction in herring stock abundance due to predation would not affect salmon catches. Based on ova measurements and maturity index values fish have been classified into immature and maturing. It appears that almost all coho salmon available to the commercial fishery are maturing, spring catches on the other hand include large percentage of both immature and maturing fish. Immature and maturing female springs divide at a fork length of 74 cm., cohos do so at an approximate fork length of 52 A volume method for the determination of egg numbers present in the ovary has been developed, the average percentage error between the calculated and actual counts being 5.3. it was found that the absolute fecundity is positively correlated to fish length and negatively to egg size but the magnitude of the effect of fish length on absolute fecundity is about four times greater than that of egg size. / Science, Faculty of / Zoology, Department of / Graduate