Taxonomic differences exist between Thyasira gould! and T. flexuosa both in conchological features and in the soft parts, perhaps the best of these differences are those concerning the sperm which are easily seen even in badly curated specimens. The occurrence of a population of T. gouldi within Loch Etive on the west coast of Scotland extends the known distribution of this arctic bivalve considerably further south. The development is nonpelagic and this, associated with the non-synchronized reproductive activity , means that independence is gained from plankton blooms and other external triggers allowing the characteristic dense but patchy populations to be built up. Salinity and sediment particle size both limit the distribution of T. souidi within L. Etive, the VI naturally occurring sediment is altered by the inhabi tants of the area into a sediment vlhich is better suited to the needs of T. gouldi. Asynchronized breeding, slow growth rate, longevi ty of life and 10\'1 adul t mortality all combine to give a characteristic bimodal population, the modes of which do not appear to shift with time. A method is described whereby an indication of both the mean state of the population and the state of the individual can be obtained for any period of the year. The biochemical composition varies with size and time of the year as well as with gonad state. Dry weight fluctuations are, however, not entirely explained by variations in the stage of gonad development as seasonal variations in the amount of somatic tissue do exist. Thyasira gouldi is one of the Lucinaceans infected by the much modified copepod parasite Axinophilus thyasirae. The life cycle and infective stage of this parasite are described as is the external morphology of the nauplius copopedite and adult. The reproductive system of both the male and the female are also described. The first infected parasite is always female and only rarely does more than one female reach maturity within anyone host even though up to five parasites may be present. The parasite has been shown to affect the biochemical composition of the host, reducing the amount of each of the components present, but tending to reduce the amount of nitrogenous material in preference to the amount of carbohydrate. VII The parasite affects the gonad of the host resulting in castration probably as an indirect effect of 'food robbing'. The interference to the host's food supply by the parasite is thought to be so great as to reduce the host to starvation levels of food,

The thesis is concerned with the strategic analysis of carp culture development in Iran, based on an assessment of the supply potential from various forms of carp farming, and on the potential demand, market features and price determinants for carp and carp products. Based on a sample of 188 farms from the three main carp farming provinces plus two case studies, all farmers in all locations and categories made a profit, with feed and fertiliser dominating variable costs. Considerable variation in production costs and profitability was observed. Where some degree of investment and support services have been provided, major increases in output have occurred. The culture of carp is technically possible in a variety of conditions within the country, though, expanding large scale farming mainly depends on reducing the cost of feed and fertiliser. Future targets could be to integrate with other agricultural activities, intensify smaller farms in the Caspian area, and consider developing larger scale commercial production in Khuzestan. A market and consumer survey was conducted, including a sample of 357 consumers in Tehran and Karaj, and 96 sellers in 11 main cities from 6 provinces. Younger consumers had the strongest preferences for ready meals product, while to increase consumption, a rise in income and decline in price will have a greater effect on older groups, larger sized families and educated people. The growing willingness to buy new product forms, particularly by younger consumers, educated groups, inland urban dwellers and high-middle income groups might be expected to increase demand. A range of supply/demand scenarios has been presented, offering projections for the year 2010, suggested target levels of 284,000-348,000t. In broad terms a policy for carp production was described to meet these targets. As in developing markets elsewhere, the traditional wholesale sector may lose its position as multiple retailers and supermarket chains become increasingly important outlets for carp and its products, and opportunities may arise for adding value in a range of ways. Within rural areas, and smaller cities, consumers may also increase their ability to buy fresh fish at the farm gate or at local outlets.

Nakambala Tilapia Farm commenced operations at the Nakambala Estate of the Zambia Sugar Company near Mazabuka, Zambia in early 1982. The farm used an intensive tank system designed to produce 50 tonnes of tilaplas per annum to provide fish for feeding the labour force on the sugar estate. The project had to manufacture fish feeds on site. A wide range of feed raw materials were used over the course of the project, with formulations designed to aim to supply the nutrient levels suggested by the University of St iIng, Institute of Aquaculture. The raw materials included microalgae from a pilot scale algae culture project funded by the Overseas Development Administration, dried fish, blood meal, carcase meal, soyabeans, cottonseed, hydrolysed feather meal, sunflower oilcake, lucerne, leucaena, yeast, wheatings and maize. Dis involved identification of raw material supplies, development of appropriate feed processing methods, formulation of feeds and manufacture of the feeds. Seventeen feed trials were carried out to evaluatet he use of different feed formulations. Many of these trials concentrated on the supply of vitamins in the feeds as the provision of a vitamin supplement was made impossible by restrictions on foreign exchange allocations. The main conclusions were 1. The poor financial performance of the farm in the initial years of operation was due to problems in project implementation, particularly the absence at the start of the project of a breeding population of tilaplas of a species with proven growth potential in an intensive system. 2. The feeds being produced by 1985 were adequate to sustain good growth in tilapias. Feed trials had shown that there was no need to use a vitamin supplement in the feeds despite advice to the contrary from other authorities. 3. The farming system utilised was appropriate to Zambian conditions, despite being extremely intensive.

Graduation date: 1975

Thesis (M.S. - Biological Sciences)--University of Arizona. / Includes bibliographical references.

Thesis (M.S. - Wildlife Management)--University of Arizona. / Includes bibliographical references (leaves 120-124).

Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographic references (p. [175]-197).

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 200-221).

Thesis (doctoral)--Wageningen University, 2006. / "Propositions" ([1] leaf) inserted. Vita. Includes bibliographical references.