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A rationale is presented for a primary nursing strategy and an on-growing strategy for Clarias gariepinus (Burchell) culture in Africa, thus providing a potential model for the development of culture technology for the species. Existing information pertaining to the production strategies identified is reviewed, highlighting the attributes of African catfish for aquaculture. Some of the current deficiencies and inconsistencies in available information pertaining to controlled hatchery production are addressed. The early developmental stages of Clarias gariepinus are defined, in order to promote consistent use of terminology and help farmers better address the changing needs of their developing stock. The pattern of growth and survival of larvae and fry is investigated at higher stocking densities than those used experimentally to provide a database for planning full-scale commercial operations. Tank design and water flow rates appropriate for Clarias gariepinus in hatcheries are investigated and recommendations made. Finally, in order to promote maximal growth rates of hatchery stocks the maximum daily feed intake of larvae in relation to different feeding regimes is estimated based on rates of gastric evacuation and return of appetite. An overview of the controlled hatchery production of Clarias gariepinus is presented.

Mycobacterium spp. isolated from food and ornamental fish in Thailand (strains TB 1, TB40, TB267, TB268), and the type strains Mycobacterium marinum (NCIMB 1298), Mycobacterium fortuitum (NCIMB 1294), and Mycobacterium chelonae (NClMB 1474) were cultured in Long's medium, Eagle's minimum essential medium, Sauton's medium and modified Sauton's medium. The latter enabled excellent growth and production of extracellular products (ECP) from TB40, TB267, TB268 and M marinum in particular, whereas growth and production of ECP for all strains was limited in Long's medium. SDS-PAGE protein profiles of ECPs from 14 day culture supernatants showed major bands at 65, and <14 kDa. After 2 days culture at the higher temperature of 37°C (heat shock), the production of ECP from all mycobacteria strains except M marinum averaged approximately 4 to 10 fold higher than from strains cultured for 14 days at 28°C. The major fibronectin binding proteins from ECP of Mycobacterium spp. isolated from infected fish were identified at 21-25 kDa. Cross reactivity was detected between ECP from Mycobacterium spp. and MAb anti-heat shock protein (60 kDa) and MAb anti-M Tuberculosis. The 65 kDa antigen of TB267 is a strongly immunogenic protein eliciting antibodies in fish, rabbits and mice. Cross-reactivity was found between rabbit anti-65 kDa antibody and sonicated proteins from many other bacterial species. Therefore, the 65 kDa protein from Mycobacterium sp. isolated from snakehead fish may be a common protein in fish bacterial pathogens. Eighteen MAbs to TB 267 and M chelonae were produced. The epitopes to which the MAbs are against located on molecules susceptible to protease treatment. All MAbs recognized the 65 kDa protein. It is one of major proteins in the ECP, whole cell sonicates and lysates from Jv1ycobacterium spp. and is located in the peri plasmic space or cell wall, and is secreted in the medium during culture. A pnmary intraperitoneal (IP) immunisation of extracellular products (ECP) from Jv1ycobacterium spp., (strains TB40, TB267 or M marinum) mixed with Freund's incomplete adjuvant (FIA), followed by a secondary IP injection at 8 wks, resulted in the elevation of both the non-specific immune response (by measuring nitroblue tetrazolium, lysozyme and phagocytosis activity) and the specific immune responses of rainbow trout, Oncorhynchus mykiss (by measuring specific antibody levels). Nile tilapia were immunised by injecting extracellular products (ECP) of Jv1ycobacterium spp. (strain TB40, TB267 or the type strain M marinum) into their swimbladders and this resulted in the elevation of the non specific immune response. The cytological response of rainbow trout head kidney macrophages to ingested Mycobacterium spp was examined in vitro. The bacteria had previously been opsonised with either fresh rainbow trout serum (FS), or serum which had been heat-inactivated (IDS), or rainbow trout antiserum against the extracellular products (ECP) of Mycobacterium strains TB267 or M marinum. MAbs against the ECP were also used as opsonins. Opsonisation of the mycobacteria was found to greatly enhance the phagocytic and killing activity of the rainbow trout macrophage.

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The active synthetic constituent of oral contraceptives 17α- ethinylestradiol (EE2) and its natural steroidal estrogen analogues are being released into the aquatic environment mainly via wastewater treatment plants (WWTPs). Although steroidal estrogens have been frequently reported in very low concentrations in the environment, they have been placed at the top of the list of endocrine disrupting chemicals (EDCs) for their high estrogenic activity in non-target aquatic species like fish and frogs. Almost 30 years worth of intensive research has moved the problem of endocrine disruption in the aquatic environment from being a hypothesis to a well-known cause-and-effect story. However, the fate and effects of many pharmaceuticals, including EE2, remain poorly understood. Thus, the main objective of this thesis was to investigate EE2 bioaccumulation in fish by field and laboratory studies. An optimized sample preparation and analytical method protocol was achieved to detect EE2 in its biologically active form in whole fish tissue at trace levels (ng/g). Shorthead redhorse suckers (ShRHS) (Moxostoma macrolepidotum) collected in proximity to a WWTP in the St. Clair River have significantly accumulated EE2 with an average of 1.5 ng/g. EE2 bioaccumulation was limited to fish exhibiting intersex and with induced vitellogenin (VTG). EE2 was absent in fish from a reference site. Positive correlations between EE2 and lipid content as well as "15N supported the hypothesis of EE2 bioaccumulation in wild ShRHSs. A wider survey was carried out to explore patterns of EE2 bioaccumulation in the pelagic and benthic food-wed of the St. Clair IV River, Ontario. In the WWTP effluents and nearby surface waters, EE2 levels were extremely low and below our method detection limits. All of the seven sampled species from different trophic levels and the sediment samples collected from the impacted sites and the reference sites did not have any measurable EE2 concentrations. A laboratory controlled study where male goldfish (Carassius auratus) were exposed to EE2 via water versus food demonstrated that fish can rapidly accumulate EE2 by both routes of exposure. The uptake constant for water was 45 h-1 and the bioconcentration factor for EE2 in fish was 377. The fast uptake rate of EE2 via water coincided with a much slower elimination rate constant of 0.0786 h-1. The assimilation efficiency of 0.106 for EE2 by goldfish was determined by EE2 dietary exposure, which was used to predict EE2 accumulation under different exposure scenarios. The work presented here was the first demonstration of EE2 bioaccumulation in wild fish and the first to model EE2 bioaccumulation from water and dietary exposure in laboratory-exposed fish.

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Naphthenic acids (NAs), a group of compounds found in oil sands process-affected waters, have been implicated as a cause of the atypical odors which characterise fish taint. Sensory analyses were undertaken to clarify the role of NAs in fish taint. Triangle test and three-alternative forced choice (3-AFC) methods were used to estimate olfactory detection thresholds of NAs. Due to cognitive advantages, the 3-AFC method was found to be superior for the estimation of olfactory detection thresholds of NAs. 3-AFC analyses by trained panels of two commercial preparations and one oil sands extract of NAs, revealed that the odor detection thresholds and odor profiles of NAs differ markedly depending upon their source. Consumer preference panels revealed no evidence that the taste of fish collected from the Athabasca River was preferred less than the taste of fish from two other water basins in Alberta. / Food Science and Technology