Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: individual-based model, Oncorhyncus mykiss. Includes bibliographical references (p.73-75).

Assignment (MPhil)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains vi, 93 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Oregon’s fish hatchery system developed in the late 1800’s in response to salmon fishery losses. Salmon hatcheries consist of a number of built components. ‘Growing fish’ requires a variety of building types which support the hatchery process as well as constant input of resources. In addition to surveying and inventorying fish hatchery resources, this study will analyze the social, economic, cultural, and environmental conditions under which these fish hatcheries were organized and commissioned. Ultimately, this survey will not only serve as a baseline for future, more intensive-level surveys, but will also provide a foundation for a National Register Multiple Property Submission. The use of hatcheries to sustain native Oregon fish species constitutes a major aspect of Oregon’s fishing and environmental conservation efforts. Oregon’s heritage hatcheries stand as physical reminders of early conservation activity and while their preservation provides a more complete picture of Oregon’s relationship with natural resources

Adult fish that belong to the family Poeciliidae cannibalise juveniles, both in the wild and under captive conditions, but this behaviour has only been partly investigated in the Poeciliidae in some of the commercially valuable species. The objective of the research is to develop an understanding of intercohort cannibalism and parturition-associated behaviour in captive-bred swordtail (Xiphophorus helleri), with applications to industry and future research of other poeciliids. Experiments investigating the effect of adult stocking density and sex ratio on the production of juveniles were used to determine if cannibalism occurs under culture conditions. The average rate of intercohort cannibalism ranged from (5.5 to 53.9%), and was positively density dependent and independent of sex ratio, indicating that males and females were probably equally cannibalistic. The highest number of juveniles (1725.7±141.4) produced per tank over 70 days was obtained from two males and eight females. To develop a better understanding of adult and juvenile behaviour during parturition, fish were observed under controlled laboratory conditions using video and behaviours such as attack (burst of speed by an adult in the direction of a juvenile), escape (avoidance of cannibalism after attack) and cannibalism (predation of a live juvenile by an adult), for example, were identified. Under laboratory conditions most young escaped in downward direction after attack (49%) and most utilised the refuge made that was made available. Furthermore, most attacks (62-65%) and cannibalism (57-84%) occurred at the bottom. Since the presence of refuge significantly increased the rate of juvenile survival under culture conditions, it was hypothesised that the rate of cannibalism could be reduced under farming conditions if juveniles were protected when they escaped downwards. This hypothesis was accepted as it was found that refuge at the bottom of the water column or the inclusion of a false-bottom reduced the rate of cannibalism by 49% and 72%, respectively. Similarly, the hypothesise that the rate of cannibalism could be reduced if juveniles where given protection when escaping sideways (32% of juveniles escaped sideways in the laboratory) was also accepted when tested under farm-scale conditions because a false-side reduced the rate of cannibalism by an average of 45%. Since males and females were equally responsible for cannibalising juveniles in the laboratory, it was hypothesised that the rate of cannibalism would decrease proportionately with the removal of males (Le. 20% of the cannibals) from the population; the removal of males under farming conditions resulted in a 19.5% reduction in the rate of cannibalism. Since older juveniles were better able to escape cannibalism than neonates and since adults habituate to stimuli that previously resulted in attack behaviour, it was hypothesised that the rate of cannibalism would remain unaffected by the length of time that juveniles were exposed to adults in the breeding tanks. This hypothesis was also accepted when tested under farm conditions. However, some hypotheses based on laboratory observations were not accepted. For example, a constant low light intensity did not appear to decrease the rate of cannibalism under farm conditions; also, the occurrence of dead and deformed juveniles went unnoticed in the laboratory, and under farm conditions, where adults did not have access to the bottom of the tank, 10% of the harvest consisted of dead and deformed juveniles. It is concluded that technologies, such as bottom-refuge or a false-side, that increase the size of the liveharvest and allow for the removal of potentially less viable offspring are recommended for the commercial production of poeciliids. The overall similarity of X. helleri behaviour between the laboratory experiments and the farm-scale trials suggests that the post-partum behaviour of X. helleri remains consistent under these different conditions; thus, behaviour under one set of conditions may be used to predict behaviour under other conditions. The application and significance of extrapolations to industry and future research of X. helleri and possibly other poeciliids were discussed and the most applicable laboratory observations with the highest extrapolation capacity were proposed. Furthermore, techniques were developed to aid industry and future researchers in making predictions relating to behaviour of X. helleri under different conditions based on laboratory observations. The results were used to develop a model indicating that selection pressures against cannibalism are not likely to exist at the rate of cannibalism observed here since the potential genetic gain through kin survival and inclusive fitness was shown to be greater than any potential genetiC loss experienced by a victim of cannibalism. The model was successfully tested under a range of social conditions. Other possible explanations for cannibalism in poeciliids, such as parental manipulation, nutritional advantages, opportunistic predation and the recovery of energy are discussed. It is suggested that the most likely proximate cause of cannibalism under captive conditions is opportunistic predation. The theory that cannibalism ensures that only viable genes of the victim are expressed, through inclusive fitness, is a possible ultimate cause of cannibalism, which may have been inherited from feral ancestors of captive-bred X. helleri.

The Wilderness lakes system represents a segmented barrier lagoon and comprises three interconnected lakes; Rondevlei, Langvlei and Eilandvlei. The latter is further linked by the Serpentine channel to the Touw river and Wilderness lagoon. The role of these channels, as well as a sluice in the Serpentine, in structuring certain aspects of the ecology of the system was investigated. An analysis of the salt budget of the lakes suggests that the Serpentine dampens tidaI processes to such an extent that they play only a minor role in the overall budget. Furthermore, the channel between Eilandvlei and Langvlei prevents any tidal salt input to the upper lakes. Their estuarine environments are however maintained by salt inputs which occur when the mouth is closed. This unusual phenemenon means that the sluice may have a minimal effect on the salt budget of the system because it is only closed when the mouth of the lagoon is open. Environmental conditions in each of the lakes, the Touw river and Wilderness lagoon were compared in terms of their physico-chemical characteristics and submerged macrophyte communities. A principal components analysis suggests that the physico-chemical environment of each lake is similar. The Touw river however has a very different environment, whilst that of Wilderness lagoon has some similarities to both the lakes and the river. During the study macrophyte communities recovered from a major recession which occurred between 1979 and 1981 . Biomasses in excess of 1000g m⁻² were recorded in both Langvlei and Eilandvlei. In the latter however, macrophyte growth was less prolific than in the former, as some areas of the littoral supported no growth at all. Macrophyte encroachment in the channels is a major factor inhibiting water flow between the lakes. This encroachment is most severe in the Eilandvlei/Langvlei channel where macrophytes covered 80% of the channel's area.The dominant fish fauna throughout the system is composed of a marine/estuarine migratory component. In the lakes the Mugilidae and Sparidae are the most common families, whilst in the lagoon and Touw river predators such as Lichia amia and Argyrosomus hololepidotus also commonly occur. Eilandvlei serves as the initial nursery area for most migratory species. An estimated 52000 fish migrated up the Serpentine towards Eilandvlei during February 1984 . Most fish do not penetrate as far as Langvlei, and this can be related to macrophyte encroachment in the Eilandvlei/Langvlei channel. However, it is argued that should this channel be dredged and the macrophytes removed, the nursery potential of the system would not be greatly enhanced . This is because environmental heterogeneity, in association with an abundance of food in Eilandvlei, make this lake the most attractive nursery area to juvenile marine/estuarine fish.

The present study focused on using food wastes and feed supplements, e.g. enzymes (bromelain and papain), baker’s yeast and Traditional Chinese Medicines (TCMs) for rearing freshwater fish (grass carp and grey mullet) in Hong Kong. Different types of food wastes, e.g. meats, bones, cereals, fruits and vegetables were collected from local hotels, mixed in different ratios and processed into feed pellets for feeding trials. The cereal dominant food waste feed (FW A) was more suitable for grass carp and grey mullet, with the best growth performance (e.g. feed conversion ratio (FCR), specific growth rate (SGR)) and higher protein digestibility (in grass carp), compared to FW B and FW C which contained higher proportions of meat products. The NBT (Nitroblue Tetrazolium) activities in blood and plasma protein levels were decreased in the grass carp, cultured with food waste feeds without any supplements, compared to the commercial feed, Jinfeng®, 613 formulation (Control). Upgrading FW A by the addition of 1% and 2% mixtures of bromelain and papain significantly increased the feed protein solubility and subsequent to growth (SGR and relative weight gain (RWG)) and feed utilization (e.g. apparent net protein utilization (ANPU), protein efficiency ratio (PER)) in both fish species. The protein and feed utilizations by grass carp were also promoted by the yeast supplements with the optimal dose of 2.5% yeast (S. cerevisiae) added to FW A upgraded by enzymes. This showed that yeast could further enhance nutrient utilization contained in feeds after addition of bromelain and papain. The in vitro study on the grass carp’s plasma treated with TCM extracts also showed that TCM extracts could stimulate plasma bactericidal activity (on Aeromonas hydrophila), possibly through enhancing plasma complement activity. The formulation with Radix scutellaria, Rhizoma coptidis, Herba andrographis and Radix sophorae flavescentis in the ratio of 1:1:2:3 was more effective in enhancing plasma bactericidal activity than single TCM extracts. Besides, R. coptidis and R. scutellaria possessed the strongest antimicrobial activity (in vitro) on fish pathogens (such as A. hydrophila, Lactococcus garvieae and Vibrio cholerae) among the 17 tested TCMs. In addition, TCMs were less likely for developing drug resistant pathogens than antibiotics. Grass carp immunity (NBT activity in blood, plasma bactericidal activity and total immunoglobulin level) was boosted by the addition of TCM formulation and baker’s yeast (S. cerevisiae). The disease resistance to pathogen (A. hydrophila) was also enhanced, with significantly lower mortalities observed in groups feeding with TCM (1 and 2% for 21 to 28 days) and baker’s yeast (2.5 and 5% for 28-56 days). The uses of yeast and TCMs led to positive effects on growth, immunity and disease resistance to pathogens in fish, but the effects (grass carp) were less effectual when both were supplemented in feed. The combined use of both supplements may impair the effects of TCM formulation or yeast in the modulation of gut mircoflora, and upset the balance of beneficial microbial communities. The present study demonstrated the feasibility of using feed supplements (TCM and baker’s yeast) to enhance fish immunity and enzymes upgraded food waste feeds for rearing fish, for the development of a more sustainable aquaculture in Hong Kong.

Inadequate seed production has historically been a factor limiting the commercial culture of Clarias gariepinus. The need to determine the environmental requirements of larvae was identified, in order to facilitate their successful mass rearing in hatcheries. The effects of key environmental factors on the growth, survival and aspects of the behaviour of C. gariepinus larvae and juveniles were investigated under controlled conditions. A strong emphasis was placed on the interpretation of the observed responses in terms of the natural history of the animal. Larvae were obtained by artificially inducing and spawning feral adult broodfish. Larval growth rates were highest in the temperature range 26-33ºC, with a peak at 30ºC. Survival of larvae was high between 22 and 33ºC. The final temperature preferendum of juveniles, determined in a thermal gradient was 30ºC, and it was concluded that this temperature is probably optimal for most of the physiological processes of the animal. Larvae and juveniles displayed strong negative phototaxis. When reared under different photoperiod regimes, larval growth increased with longer dark periods, however a similar rate of mortality was recorded in all photoperiod treatments. The provision of cover was found to enhance larval growth under conditions of continual light (24L/OD), however under conditions of continual darkness (OL/24D) similar growth rates were recorded regardless of the presence or absence of cover. All growth rates in continual darkness (OL/24D) were higher than those in continual light (24L/OD), regardless of whether cover was provided or not. It was concluded that a OL/24D photoperiod is optimal for larval rearing. At salinities between 0 and 5% similar growth and mortality rates of larvae were recorded. At 7.5 % larval growth and survival rates were lower, and at 10 % all larvae died within 48 hours. The 96h-LCSO for unionised ammonia was found to be 2.3 mg/l. The cytological effects of unionised ammonia were evident as degenerative changes in the gill and liver tissues. In an investigation of tank hygiene, it was found that larval growth and survival rates were highest in tanks not cleaned at all. As the frequency of tank cleaning increased, the growth and survival rates of larvae decreased. When reared at densities ranging from 45-450/1, larval growth was found to be density dependent. A model of hatchery productivity (number larvae of standard size produced/time/vol.) was developed based on the density dependent nature of larval growth. The model predicts that maximum productivity, will be achieved at a rearing density of 1400/1. The high growth and survival rates obtained over a broad range of each environmental parameter investigated serve to explain how larvae survive and grow in their unstable floodplain habitat in nature. The broad environmental tolerances of C. gariepinus are of benefit with respect to the culture of larvae, as successful larval rearing is possible over a fairly wide range of environmental conditions.

Aquaculture plays an increasingly important role in food production as the catches of wild fish stocks continue to decline on a global scale through overfishing. However, the rapid development of intensive cage aquaculture in particular, which requires high inputs of energy, food and capital, can result in adverse effects on the environment. While spatial distribution and sediment loading models for particulate wastes from marine fish cages have been under development for more than 10 years, the models still contain numerous assumptions that limit their usefulness. These include the use of very limited data for fish feed and faecal pellets sinking rates that take no account of food manufacturer, type or size or environmental conditions. The present study provides information on a range of pellet types for three of the most important European farmed fish species (i.e. Atlantic salmon Salmo salar L., sea bream Sparus aurata, sea bass Dicentrachus labrax) that may be readily incorporated into models. Such data, combined with validation of predictions through in situ field investigations is designed to help improve the accuracy and usefulness of solid waste dispersal models. The studies comprise four main sections, i.e., quantifying food and faecal pellet characteristics, examining nutrient leaching rates from uneaten food and fish faeces, determining resuspension characteristics of uneaten food, modelling of solid wastes dispersion and thus the development of environmental tools. Existing literature relating to environmental impacts of cage aquaculture is reviewed and the key factors highlighted. Two preliminary studies provided information on the influence of gravity acceleration on settling velocity determination and appropriate techniques for monitoring the rate of nutrient leaching from faecal wastes. Settling velocities of Atlantic salmon diets were significantly greater at 20 psu salinity than at 33 psu and significantly higher for most pellet types at 10°C than, at 20°C. Settling velocities for unsoaked salmon diets were found to increase with pellet size, from a mean of 5.6 cm s-1 for the smallest pellet (2 mm) to 13.9cm s-1 for the 10 mm standard (20 to 24% fat) pellets. Settling velocities of extruded diets for sea bream and sea bass diets ranged from 3.9 to 10.6 cm s-1, broadly similar to those for salmonid diets. Settling velocities of salmon pellets were not significantly affected by immersion time (0 - 15 min). Given the water depths at fish cage sites and the settling times involved, it is concluded that it is unnecessary to take account of changes in food pellet settling velocity as a result of immersion. Freshly net-collected salmon faecal pellets appeared to consist of fine solid material approximately the size of the formulated diets. The range of salmon faecal settling velocities was 3.7 to 6.2 cm s-1 (mean = 5.3 cm s-1) at 15°C and 33 psu. There are no significant differences in nutrient leaching of carbon and nitrogen from all six salmon diets after 20 min immersion in sea water. However, a rapid loss of faecal nutrients occurred 2.5 to 10 min after immersion in sea water. Total C and total N were found to leach by as much as 22% and 26%, respectively, after 5 min immersion during one sampling occasion. Experiments conducted in a large-scale flume tank showed the critical resuspension velocities of a range of commercial fish feeds were between 8.63 cm s-1 and 9.53 cm s-1. Above the critical resuspension speed, pellets moved by saltation, i.e. traveling along the sediment by rolling, sliding or hopping on the bed. The velocities of pellet resettlement ranged between 0.79 cm s-1 and 3.98 cm s-1 under the critical resuspension speeds. Field trials, involving the deployment of sedimentation traps, showed a general relationship between sedimentation of material and distance from cages, i.e. more sedimented material was associated with sampling sites closest to the cages. The spatial changes in sedimentation rates in the first trial were between 15.4 and 31.7 g DW m-2 d-1 at 30 m and 10 m stations, respectively. Values in the second trial (38.5-65.5 g DW m-2 d-1) were twice those in the first trial, but followed the same pattern. The model presented in this thesis is a combination of a spreadsheet model (Microsoft Excel 6.0) and Surfer plot program (Golden Software Ltd., ver. 6.04). Excel is used to prepare basic mathematical operations behind the model, including a mass balance submodel and use of a formula for calculating dispersion of uneaten food and faeces on the sea bed developed by Gowen et al. (1989). The operation of the waste dispersion model for marine cages takes into account the various settling characteristics of waste particles. It was verified with a set of in situ sedimentation data obtained from the field trial described above. Results described the waste dispersal around the vicinity of the cage farm. For the future, it is intended that further validation and optimisation of the model will be carried forward by a combination of both increasing user involvement and incorporation of data from comprehensive studies as these become available. Together, these will contribute to reducing and remedying the environmental impacts of future development.

The primary objective of this study was to examine environmental parameters thought to affect cannibalism in certain fish species. It was found that environmental, behavioural, genetic and physiological factors all affect cannibalism in the species exhibiting the phenomenon. The diversity of factors nfluencing cannibalism served to illustrate the complexity of this behaviour pattern. Feeding to satiation was found to suppress cannibalism in catfish, trout and koi carp. High population densities were found to increase the rate of cannibalism, thereby acting as a population regulation mechanism for catfish, trout and the common and koi carps. Live food, as compared with dry pelletized feed was found to significantly suppress cannibalistic aggression. Catfish grown in total darkness, provided with refuges and living in turbid conditions were found to exhibit lowered cannibalistic and territorial aggression. Various lines of evidence suggested that cannibalism has a genetic basis, as was shown by the differences in cannibalistic behaviour of the two strains of Cyprinus carpio, viz. common and koi carp, with cannibalism being higher in the latter. This finding substantiates the hypothesis that cannibalism is genetically controlled and therefore open to evolutionary change. It is concluded that cannibalism is adaptive in times of food limitation, but that it is merely a by-product of normal feeding behaviour when food is abundant. Since cannibalism is advantageous and thus adaptive, the question arises ai to whether selection is occurring at the individual or the population level (or both). It was concluded that it is acting at the individual level, and that any benefits accruing at the population level iv were simply the effect of the initial cause, viz. individual selection. One of the aims of this study was to determine whether cannibalistic tendencies in fish are influenced by differing life history style trajectories. Based on the results of this study it is hypothesized that cannibalism is an r-selected trait. wi th the understanding gained from the knowl edge of the fundamental principles governing cannibalism, certain recommendations for its control in fish culture could be made. It is, however, imperative that further intensive studies be carried out to understand more fully this complex subject. General "rules" for regulating cannibalism could be helpful for any given cannibalistic species. However, in considering the differing life-history styles of each species, it becomes evident that species-specific guidelines need to be worked out. Until then, any suggestions for cannibalistic control offered to the aquaculturist can only serve as unrefined tools.