The role of the lipid-soluble antioxidant α-tocopherol (vitamin E) in the nutrition of African catfish (Clarias gariepinus Burchell) has been investigated with respect to effects on growth, certain indices of health and prevention of tissue lipid peroxidation. Although juvenile C. gariepinus were not found to show an immediate dependency on vitamin E for growth, even during rapid growth stages, a minimum requirement of α-tocopherol based on the prevention of hepatic lipid peroxidation was established at 30-40 mg α-tocopherol per kg dry diet. This is in line with published values for numerous cultured fish species. Tissue α-tocopherol accretion was found to be dependent on dietary dose of the vitamin (supplied as all-rac-α-tocopheryl acetate) and, with the exception of blood-plasma, increased tissue tocopherol status resulted in increased stability against lipid peroxidation. Assessment of iron-ascorbate induced peroxidation (as TBARS) revealed that feeding catfish with diets containing a-tocopherol at several times the currently supplemented level, improved the stability of catfish muscle and this has fillet quality implications. Similarly, heightened fillet vitamin E content resulted in lower moisture exudation from previously frozen fillets, thus demonstrating the role of a-tocopherol in the maintenance of membrane integrity. Oxidation of dietary oils and elevated ingestion of iron were found to be antagonistic of tissue vitamin E concentration. Consumption of feed containing rancid oil had marked effects on tissue fatty acid composition and these effects were modulated by increased intake of α-tocopheryl acetate. In catfish fed diets containing similar amounts of ascorbate, a higher α-tocopherol supplement marginally improved ascorbate retention indicating a possible sparing of vitamin C by vitamin E. The present work will contribute significantly to the understanding of antioxidant nutrition in this poorly researched cultured species. Furthermore, these investigations have improved and strengthened the database of knowledge accumulated within the field of nutrition of finfish.

The oil and gas industry is of major economic importance to Australia. Offshore seismic surveys are an essential component of exploration for fossil fuel reserves. Offshore seismic surveys involve the use of arrays of air-guns that produce repetitive high energy, low frequency sound. There is increasing concern about the effect that the noise generated by a seismic survey has on the surrounding marine life. Various species of captive marine fish and one species of squid were exposed to the noise from a single Bolt PAR 600 B air-gun with a 20 cui firing chamber and a source level at 1 m of 203.6 dB re 1 μPa mean squared pressure. Ten trials were conducted in Jervoise Bay and two were carried out off the coast of Exmouth. A different noise regime was used in each trial, however most involved the use of approach-depart scenarios to simulate an actual seismic survey and a 10 second duty cycle. Noise levels received by the animals ranged between 128 - 192 dB re 1 μPa mean squared pressure. Behavioural observations of the fish and squid were made before, during and after air-gun noise exposure. The physiological stress response of the fish was monitored by measuring plasma cortisol and glucose levels before and after noise exposure. The sensory epithelium was removed from the ears of the fish prior to, immediately after and up to 86 days after air-gun noise exposure and examined using a scanning electron microscope. No statistically significant physiological stress response in fish was detected as a result of the air-gun noise exposure regimes used. Significant damage to the ciliary bundles of the sensory epithelium of the sacculus was observed in pink snapper (Pugrus auratus) that had been exposed to air-gun noise between 144 - 191 dB re 1 μPa for 1.71 hours. No regeneration of the hair bundles was observed 58 days after exposure to air-gun noise. / However, evidence of regeneration was observed between 58 and 86 days after noise exposure. Behavioural observations suggested that as air-gun noise levels increase, fish respond by swimming faster, in tighter groups and towards the bottom of the water column. Significant increases in alarm responses were observed in fish and squid to air-gun noise exceeding 158 - 163 dB re 1μPa. An increasing proportion of alarm responses were also observed as the noise level increased. A decrease in the frequency of alarm responses for repeated exposures was observed in squid and some fish. The implications of these findings are discussed with comparisons of noise levels measured from an actual 2678 cui seismic survey air-gun array.

The lipid composition of five species of marine finfish from temperate Australian waters was determined. Claims that the lipids of Australian fish contain high levels of omega-6 fatty acids and arachidonic acid (AA) were investigated. Individual fish were analysed from samples collected at three locations and two seasons, and they were found to have fatty acid compositions of similar nutritional value to those from northern hemisphere temperate waters. Levels of AA, eicosapentaenoic acid and docosahexaenoic acid were also found to be comparable. The variability in fatty acid compositions was greater between samples taken from different locations than from different seasons. Lipid contents and compositions were found to exhibit some species-characteristic nature, indicating a need for accurate species identification. A high-performance liquid chromatographic (HPLC) method for fish identification was developed, which was successful. The application of HPLC to processed fish was investigated and it was found to be suitable for gamma-irradiated and infrared dried fish, but not for those that had been smoked or microwave cooked. / Doctor of Philosophy (PhD)

Research into the polyculture of finfish and crayfish has been conducted in Western Australia for over a decade now. This research was instigated out of a need to increase revenues from freshwater crayfish farmers wishing to diversify their income base with a view to increasing profitability and reducing risk. It has become clear that several key variables dictate how the polyculture system (i.e. polysystem) will perform. These include biological factors like: size of participating species, relative densities, gender, planktonic turbidity, natural feeds; and abiotic factors like: light intensity, clay turbidity, floating cages for segregation, water quality, and habitat/shelter complexity. Many of these factors can be controlled / adjusted by the manager of the polysystem to maximise performance, production and profitability.While much of the research to date has focussed on the marron (Cherax tenuimanus) industry, it is also important to realise that an understanding of these factors can also assist other crayfish polysystems, like integrated agri-aquaculture systems containing yabbies (Cherax albidus). Some of the factors that influence how the system will perform may become more prevalent, like suspended clay turbidity and the associated role of light intensity in species interactions, or shelter complexity and the resulting choice of shelter material. But overall, they are the same basic variables and we must understand how they affect the particular multi-species system that we are dealing with. There is a lot to be learned from the literature on how these variables affect multi-species aquatic environments in the wild. Perhaps aquaculturists have not considered this enough in the past. Some farmers seem to believe that these variables are different JUST because it is a culture system. This is not true. / The variables will take on different levels in a culture system (i.e. a manager will stimulate turbidity, provide artificial feeds, stock different sizes, and supply particular types of shelter) BUT the actual variables themselves (e.g. food, density, light, shelter) are basic to ALL aquatic ecosystems. Other researchers have looked at important factors like density, gender, and light intensity / turbidity in crayfish polysystems - but the issue of habitat complexity and the role of shelter has not been adequately addressed. This thesis will investigate some basic questions about shelter and endeavour to apply them to crayfish polysystems, with the emphasis on marron (C. tenuimanus) and yabbies (C. albidus) because these are the two most commercially important species of crayfish in Western Australia. Importantly, it should be noted that due to the invasive nature of yabbies, and their apparent ability to displace native marron in the wild, findings will be related to yabby-marron competition / displacement where relevant. We need to know many things about shelter: what type is best in a multi-species system? Should the shelter size match the crayfish size? Do marron have different requirements for shelter than yabbies? Does it matter who gets first use of a shelter (i.e. prior residence effect)? Can we learn about crayfish shelter requirements by examining the behaviour / plasticity of crayfish species? If crayfish are stocked with finfish and they retreat into shelter as a predator-avoidance measure, is the complexity important given that their densities will be higher? If densities of crayfish inside shelters are higher in polysystems, will cannibalism be a concern, particularly when conditions are right for moulting? Does visual recognition and / or chemo-detection of a predator affect the shelter usage by marron or yabbies? / Does temperature affect shelter usage behaviour for a burrowing species like yabbies? Shelter is an important factor in the life history of a freshwater crayfish and an understanding of its influence on different species is important for maximising system performance. Crayfish are categorised depending on their ability to construct shelters (i.e. burrows). Yabbies have evolved in systems with fluctuating water quality and many predators and, as such, have learned to burrow (to escape drought and also to escape predators). Marron, on the other hand, are a non-burrowing native crayfish species that have existed with relatively few predators in the South-West. As a result, marron are less capable of modifying their behaviour when confronted with a predator (i.e. low behavioural plasticity). Species with high plasticity, like yabbies, are more capable of adapting to new environments, because they can change their behaviour to increase their chance of survival. Therefore we can expect yabbies and marron to utilize habitats differently and we should compare these behaviours as a basis to developing management strategies. This type of knowledge may also assist with managing the translocation and spread of yabbies in the wild and their displacement of native marron.Within multi-species systems, the physical structure of shelter plays an important role inprotecting crayfish and the perfect shelter would not only provide safety from co-stocked finfish, but also from conspecific cannibalism. Given the different life histories and behaviours, it is probable that both species of crayfish will have different refuge requirements.Over the course of this four-year investigation, trials were conducted in four culture systems (72L aquariums, 300L circular tanks, 80t mesocosm tank, and 720m2 earthen ponds) using marron and yabbies as the species of interest. / Silver perch and Murray cod were chosen as the finfish species of interest as they appear to have the highest aquaculture potential for native freshwater finfish in Australia at the present time. Further, both of these fish have been documented as potential predators of crayfish, resulting in a challenge to understand the role of shelter in minimising the negative effects of fish-crayfish interactions within a polysystem. This study has confirmed that shelter plays a critical role in multi-species system dynamics. In the case of polysystems, it will affect both interspecific and intra-specific interactions, ultimately governing production and profitability, along with the other, previously defined factors. This means that the manager of a polysystem can influenceproductivity by understanding: a) the behavioural characteristics and biology of the crayfish; b) the feeding biology of the finfish; and c) the system variables (both biotic and abiotic) that will affect the overall well being of the fish and crayfish. In the case ofshelter, the manager should understand the available shelter types, the appropriatedensities, the importance of matching complexity to the crayfish size, and the prior residence effect when choosing a timing strategy for stocking and harvesting. Prior residence increased resource holding potential for both marron and yabbies in the short term. In fact, prior residence was a stronger determinant of successful sheltering than crayfish gender or species. However, in longer-term trials the physical size of the crayfish (larger animals evicted smaller animals) and reproductive status (berried females were successful at evicting all other crayfish) were more important factors in determining successful shelter acquisition, although the temporal variations (i.e. growth and release of young) complicate the issue. / When stocking crayfish of different sizes, and in polysystems, the correct size of shelter becomes critical, as smaller individuals will be forced to leave over-sized shelter and locate a shelter commensurate with their own body size to avoid predators. This is relevant to crayfish nurseries where complex habitat is paramount for juvenile cohorts that display variation in sizes and gender. The expansion of crayfish polyculture holds considerable promise; however, furtherinvestigations are required into shelter complexity within floating fish cages, shelter types and arrangement of shelters within ponds (for increased production and ease-of-harvesting), potential of yabbies in polyculture (comparison of monosex and hybrid strains), and the impact of shelter on escape behaviour of marron in a polysystem.

Fish oil sparing and replacement is a major focus in the fields of aquaculture and aquaculture nutrition. Most of the commercial fish oil production is consumed by the aquafeed industry due to its highly digestible energy and elevated content of long-chain polyunsaturated fatty acids (LC-PUFAs; ARA – 20:4n-6, EPA – 20:5n-3, and DHA – 22:6n-3), being a valuable ingredient. Given the finite supply and the growing demand for fish oil its price has increased quite drastically, leading to the search for alternative lipid sources. Generally, vegetable- and terrestrial animal-origin alternatives lack LC-PUFAs, which are physiologically important nutrients for all fish, and considered essential fatty acids for carnivorous species. When fish oil is spared or replaced by alternative lipids fish survival, growth performance, and fish health are commonly impaired if adequate levels of essential fatty acids are not provided within feeds. Additionally, fish oil sparing typically distorts fillet fatty acid profile and associated nutritional value compared to a fish oil-based diet reflecting the composition of the alternative lipid used. It is clear that to address the fish oil bottleneck in aquafeed manufacturing, researchers must understand the essential fatty acid requirements of the key commercial fish species. Fatty acid essentiality in fish has been investigated, and there is preliminary evidence that not all LC-PUFAs may be equally required, with DHA being more important, and EPA being more expendable. Whereas ARA has not been investigated in the same extent as n-3 LC-PUFAs. Additionally, certain fatty acids groupings such as saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) may influence LC-PUFAs bioavailability, and in some cases maintain or enhance LC-PUFAs deposition. The current dissertation sought to provide new knowledge regarding LC-PUFA requirements of marine carnivorous fish (White Seabass Atractoscion nobilis, California Yellowtail Seriola lalandi and Florida Pompano Trachinotus carolinus) in the context of C18 PUFA-rich (i.e. polyunsaturated fatty acid with chain length of 18 carbon atoms) and SFA- and MUFA-rich alternative lipids. Determine if all LC-PUFAs (ARA, EPA, DHA) are equally important in meeting fatty acids requirements and also determine the effects of dietary SFA, MUFA, and C18 PUFA content in fish oil sparing and tissue deposition of LC-PUFAs. The overall findings highlighted that DHA and ARA appear to be the primary drivers of fatty acid essentiality, whereas EPA is likely required in minor amounts. It was also demonstrated that DHA/EPA ratio had little-to-no effect on fish performance. Additionally, LC-PUFA requirements seem to be more flexible than previously assumed being influenced by dietary fatty acid profile. LC-PUFAs in marine finfish are more bioavailable in the context of SFA-/MUFA-rich alternative lipids, thus, reducing the requirements for these nutrients and allowing the fish’s physiological demand to be met with dietary levels below the minimum levels recommended. Finally, these findings suggest that although marine fish accept a variety of alternative lipids, those rich in SFAs and/or MUFAs seem advantageous in terms of limiting the effects of fish oil sparing on tissue fatty acid profiles.

In aquaculture, biosecurity consists of policies, procedures and measures used to prevent or control the spread of fish disease. The focus of this research was the practice of biosecurity in the recirculation sector of finfish aquaculture in the United States and Canada. Specifically, this research: 1) identified and characterized finfish recirculation facilities in the United States and Canada; 2) assessed biosecurity utilization in these facilities; 3) examined the relationship between biosecurity utilization and fish culture variables; 4) examined the relationship between biosecurity utilization and socio-demographics of personnel operating these facilities; 5) described the attitudes, perceptions and beliefs about fish disease and biosecurity utilization of personnel, and 6) described the lived-experience of biosecurity practice of workers at these facilities. This research was comprised of two separate components using different methodologies. The first component was a self-administered, mail-back questionnaire sent to the managers of 152 finfish recirculation facilities in the United States and Canada in fall of 2001. The second component was a series of in-depth interviews conducted with 31 workers at 12 salmonid recirculation facilities in spring of 2002. Grounded theory methodology was used for the interview process and subsequent data analysis for the second component. An 86% response rate was achieved in the mail survey. Aquaculture activities using recirculation technologies were quite varied in purpose of operation, size of production, and life stages held. Four groups of fishes dominated the recirculation sector and constituted the primary production of over 45% of this sector of aquaculture. This sector was heavily reliant on ground water resources. Forty-one percent of finfish recirculation facilities did not have a secondary source of water supply. Biosecurity utilization is not homogenous within the recirculation sector. Frequency of biosecurity utilization was related to primary water source, type of fish grown, purpose of the operation and country of operation. Biosecurity was an important concern of facility operators, although among facility operators there were differences in perception of disease risk and benefits of biosecurity utilization. Analysis of results of this study resulted in formulation of the Practice of Biosecurity Theory (PBT). The theory describes a three-phase process in the practice of biosecurity: (1) orientation, when workers begin their initiation into the practice of biosecurity; (2) routine, when practice of biosecurity becomes a habitual behavior; and (3) thoughtful approach, where knowledge of fish health needs and biosecurity practices are integrated into a repertoire of biosecurity strategies that are situation- and site-specific. The practice of biosecurity was affected by three environmental conditions; personal biography, management's role, and peer pressure. This research gives educators, extension agents, researchers and government policy-makers a quantitative description of finfish recirculation aquaculture in the United States and Canada. It also provides baseline information on biosecurity utilization in recirculation aquaculture. This research provides insight into the human dimensions aspect of the practice of biosecurity and, therefore, may have application to other areas of agri-business. / Ph. D.

Achieving optimization of IMTA sites and modeling the efficiency of such a system requires knowledge of the spatiotemporal distribution and variability of TPM surrounding the finfish farms. The objective of this study was to quantify the impact of finfish farms on the surrounding particle field. Platforms equipped with transmissometers, fluorometers and CTD’s were towed around the sites while undulating through the water column in a high-resolution 3D spatial survey approach. In addition, combination turbidity and chlorophyll a sensors were moored at a variety of locations and depths. Surveys were conducted concurrently with the deployment of current meters. Farms surveyed were found to have little impact on the surrounding suspended particle field (mean effect < 1 mg L-1). Results provided evidence of minimal enhancement from fish farm wastes, primarily in surficial waters (0.5- 2 m depth) immediately adjacent to the cages, and evidence of predominantly tidal driven (M2) TPM dynamics.