published_or_final_version / Zoology / Master / Master of Philosophy

Intensive methods for the mass production of Oreochromis niloticus (Chitralada strain) seed using concrete tanks, hapas within earthen ponds and earthen ponds were investigated. On the basis of these trials, the productivity and economic performance of various production strategies for hormonally sex-reversed Oreochromis fry (MT fry) were then compared and modelled for adoption in Central and Northeast Thailand. Regular disturbance and harvesting of seed after a short period of spawning opportunity (5-10 days) was found to increase seed production in concrete spawning tanks. Exchange of female broodfish increased synchrony of breeding. A change in conditioning and spawning environment had no effect on seed yield from spawning tanks and hapas (area =12.57 m2and 40m2 respectively). Seed wet weight, seed clutch size and weight was greater in female fish spawned in tanks than hapas. Females conditioned in hapas however produced heavier seed clutches of larger absolute and relative size than tank conditioned fish. Records of tagged females indicated considerable differences in the frequency of spawning; in hapas the distribution was normal wheras in tanks it was skewed. The evidence suggests that hierarchy is important in the control of reproduction and exerts it's strongest effect in clear water, densely stocked tanks. Selective female broodfish exchange optimised seed yield per unit weight of broodfish and seed production was not improved by conditioning females for periods longer than 10 days. Male broodfish exchange did not significantly improve (P > 0.05) seed yields. Early nutrition of broodfish raised under different supplemental feeding regimes in fertilised earthen ponds had a significant effect on later spawning frequency in concrete tanks. However, this effect was confined to broodfish maintained at densities lower or higher than optimal for seed production. Broodfish stocked over a range of densities for extended periods (201 days) showed greater variability of seed production in hapa than tank production systems. This was mainly due to periods of poor water quality in hapas; when water quality was high seed production was significantly higher in hapas than tanks over a range of broodfish densities. The optimal density of broodfish for seed production was exceeded in tanks but not hapas. The relationship between seed production and broodfish density over time suggested that both stocking biomass and number have an effect on fry output. Density of broodfish showed an inverse relationship to clutch size in both tanks and hapas and synchrony of spawning in tanks. Production of swim-up fry in large earthen ponds (area=1740m2) was not significantly different (P>0.05) at 2 levels of harvest intensity. The use of small broodfish however produced double the yield of hormone treatable fry than a similar biomass of larger broodfish of the same cohort. A commercial scale incubation system was devised and evaluated in order to allow tank and hapa systems harvesting unhatched seed to be compared with the production of swim-up fry obtained from earthen ponds. Seed removed from mouthbrooding females was roughly staged and incubated in batches of similar development to give information on survival to swim-up fry. A simple incubation system was designed with a capacity for hatching >100,000 eggs/set. A mean survival of 75% of all harvested seed to swim-up fry was obtained over several trials. A trend to intensification (fry/mVday) from ponds to hapas to tanks was evident when yields of swim-up fry are compared. Productivity exceeded any in the published literature for comparable systems, largely because of the intensity of broodstock management and early and efficient harvest of seed. Broodfish productivities (fry/kg female/month) were also higher across the range of systems tested often by a factor of 1.5-3. The best strategies were selected over a range of total investment cost using dominance analysis. Economic analysis suggested that for a start-up operation in Central Thailand fry production in earthen ponds can give the best return on levels of investment of less than Baht 0.8 million. Substitution of techniques into current carp fry production operations in Northeast Thailand indicated that more intensive methods (production in tanks and hapas) are more attractive over a range of investment levels. The break-even price of MT fry after hormone treatment in nylon hapas was approximately half the cost of treatment in a recirculated water concrete tank system. The break-even price in Central Thailand was lower than the Northeast by a factor of around 1.5 but the break-even price for both areas was lower than the current price of untreated Oreochromis fry.

Thesis (MComm (Business Management))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Numerous individuals daily partake in injurious consumption, such as excessive or unhealthy food choices. Individuals’ incorrect food choices can have a negative effect on their weight, health and general quality of life. Marketers could and should play a pivotal role in influencing consumers’ food choices, which will ultimately contribute to healthier individuals and societies as a whole. The purpose of this study was to investigate the relationships between self-concept and food choice, self-efficacy and food choice, emotional states and food choice, and weight perception and food choice, and to highlight implications for marketers based on these findings. These relationships were investigated in a Generation Y sample. A sample of 383 college-aged1 students of Generation Y completed a self-administered questionnaire that was designed based on previous studies. Respondents’ weight perception was also investigated as many students from Generation Y try to change their weight perceptions through their food choices. Respondents’ food choice was compared to the recommended food choice of the South African Department of Health (Department of Health, 2009). Based on this comparison, it was proposed that marketers of food products should promote a decrease in respondents’ meat consumption and an increase in milk, fruit, vegetable and starch consumption. Small yet significant relationships between respondents’ specific food choices and self-concept, self-efficacy, emotional states and weight perception were found. Marketers can incorporate these relationships into their advertising campaigns and brand slogans in order to positively influence Generation Y to make healthier food choices. Another significant finding was that male respondents indicated a higher ideal weight than their actual weight, while female respondents indicated a lower ideal weight than their actual weight. A relationship was also found between self-concept and weight perception for both men and women from Generation Y. The significance of this study lies in the expansion of knowledge regarding the food choice behaviour of a Generation Y sample and the recommendations made to marketers based on relationships found between food choice and the constructs at hand. These recommendations can ultimately improve consumers’ food choice. / AFRIKAANSE OPSOMMING: Verskeie individue neem daagliks deel aan nadelige verbruik, met inbegrip van oormatige of ongesonde voedselkeuses. Individue se foutiewe voedselkeuse kan hul gewig, gesondheid en lewensgehalte negatief beïnvloed. Bemarkers kan en behoort 'n belangrike rol te speel om individue te oortuig om gesonde voedselkeuses te maak. Die doel van hierdie navorsing was om die verhouding tussen self-konsep en voedselkeuse, selfekwiteit (‘self-efficacy’) en voedselkeuse, emosionele toestande en voedselkeuse en gewigspersepsie en voedselkeuse te ondersoek en om die implikasies hiervan gebaseer op hierdie bevindings aan bemarkers voor te lê. ʼn Steekproef van 383 lede van Generasie Y het ’n vraelys ingevul wat ontwerp is op grond van vorige navorsing. Respondente se gewigspersepsie is ook bestudeer aangesien verskeie studente (universiteitsouderdom) van Generasie Y poog om hul gewigspersepsie te verander deur middel van hul voedselkeuses. Respondente se voedselkeuses is vergelyk met die voedselkeuses wat aanbeveel word deur die Suid-Afrikaanse Departement van Gesondheid (Department of Health 2009). Op grond van die vergelyking is bevind dat bemarkers ʼn afname in individue se vleisinname, en ʼn toename in individue se melk-, vrugte-, groente- en styselinname behoort te bevorder. Die ondersoek het getoon dat daar klein, maar beduidende verhoudings aangetref is tussen respondente se spesifieke voedselkeuses en self-konsep, self-effektiwiteit, emosionele toestande en gewigspersepsie. Bemarkers kan hierdie verhoudings in hul bemarkingsveldtogte en handelsmerk-slagspreuke inkorporeer. Nog ʼn beduidende resultaat was dat die manlike respondente ʼn hoër ideale gewig as hul huidige gewig aangedui het, terwyl vroulike respondente ʼn laer ideale gewig as hul huidige gewig aangedui het. Die resultate toon ook dat daar vir beide mans en vroue van Generasie Y ʼn verhouding tussen self-konsep en gewigspersepsie is. Deur middel van hierdie studie is kennis rakende die voedselkeuses van ʼn steekproef van Generasie Y uitgebrei. Aan die hand van die verhoudings tussen voedselkeuse en respondente se self-konsep, self-effektiwiteit, emosionele toestande en gewigspersepsie, is daar aanbevelings vir bemarkers gemaak. Hierdie aanbevelings sal uiteindelik bydra tot die verbetering van Generasie Y se voedselkeuses.

[Truncated abstract] The role of fish consumption and omega-3 polyunsaturated fatty acids (PUFAs) in the prevention of disease has been the subject of much investigation in recent years. A clue that these factors might be of importance was the observation that populations consuming high levels of marine omega-3 PUFAs had lower rates of morbidity and mortality from cardiovascular disease. From there, research in this area has expanded to include a range of chronic diseases and their prevention. An area of particular interest is the role of fish consumption in the prevention of various cancers. In Australia, one in three men and one in four women are expected to be diagnosed with cancer by the age of 75. Identifying preventive factors that can be translated into constructive health promotional messages is of great importance in addressing this group of diseases that has such a large impact on the health and wellbeing of the population. ... Results and conclusions Analysis of the data from the population-based case-control study suggests a protective effect of preserved fish consumption, possibly due to the high oil content of these fish. The developed questionnaire is a valid and reliable tool for measuring fish and seafood consumption as determined by regression analysis with an independent biomarker and reliability analysis using intra-class correlation. Importantly, reliability can be maintained despite asking a high level of detail from participants. For ranking according to overall fish consumption, detailed questioning is probably not necessary, however inclusion of variables representing multiple categories of fish and seafood consumption in a regression model enables us to better account for variation in blood omega-3 PUFA levels than a single variable representing overall consumption. For the purpose of questionnaire validation, plasma phospholipid and erythrocyte membrane levels of EPA and DHA are equivalent biomarkers of fish and seafood consumption. The choice between them by future investigators will be based on more practical aspects such as convenience and the fasting state of subjects. The tangible product of this thesis is additional evidence to support a protective association between fish consumption and prostate and breast cancers, and a valid and reliable questionnaire v for measuring habitual consumption of fish and seafood in a West Australian population, that could also be applied to other populations after minor adjustment for local fish and seafood consumption patterns.

Diabetes and related complications are one of the leading causes of death for Mexican American women. Although dietary behavior is a critical component of diabetes management, research is lacking in relation to the interplay of food habits, culture, and diabetes among this population. The specific aims of this ethnographic study were to: (1) explore the relationships between culture, food habits, and type 2 diabetes as experienced by low income Mexican American women; (2) examine the role of food in the cultural identity of low-income Mexican American women; (3) examine how trying to adhere to the ADA dietary guidelines for people with diabetes impacts the relationship between food and culture of low income Mexican American women with type 2 diabetes. This sample consisted of 16 Mexican American women between the ages of 39 to 60 years. Twelve of the sixteen had experienced diabetes for at least 10 years, and were considered experts in the management of their illness. The remaining four had experienced diabetes for a shorter period of time and were considered novices. Individual interviews were conducted with each informant. All interviews were audiotaped with the exception of one. The interviews, observations, and field notes were analyzed for data. The analysis of data rendered 6 themes: (1) “la dieta,” (2) the location and fluidity of food (3) confidence-defiance self-management connection, (4) negotiating sociocultural and biomedical expectations, (5) eating for diabetes is a family affair, and (6) strategies for self-care. In addition, preliminary comparisons were conducted between experienced and more novice individuals with diabetes. / text