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A bacia hidrográfica do Mogi Guaçu é um importante sistema de sustento para diversas atividades econômicas regionalizadas. Em decorrência de atividades antrópicas como, uso e ocupação inadequada do solo, utilização de pesticidas e fertilizantes nas lavouras, lançamento de efluentes domésticos (in natura) e industriais, sem tratamento; dentre outras, verificou-se que o rio Mogi Guaçu é acometido por diferentes graus de degradação ao longo do seu curso; e, por conseguinte, as lagoas de piscicultura da área de drenagem. Este trabalho objetiva analisar a concentração de metais na água, sedimentos e rações de lagoas de pesque-pagues, no intuito de avaliar o nível de impacto dos metais sobre o ambiente. Foram feitas coletas de água e sedimentos, em quatro épocas diferentes, duas no período seco e duas no chuvoso, precisamente em dez pontos, distribuídos desde a nascente até a foz. As rações foram coletadas em cada um dos pesque-pagues. Análises das percentagens de matéria orgânica e inorgânica foram executadas, bem como análise granulométrica dos sedimentos. A análise quantitativa dos metais foi efetuada pela técnica espectroscópica de absorção atômica, tanto em água, sedimentos e ração. Os resultados demonstram que as percentagens de matéria orgânica são elevadas, ocorrendo em todos os períodos de amostragem. A elevada fração de argila e areia, na grande maioria dos pontos de amostragem, indica que os sedimentos têm mérito considerável na redistribuição dos metais na coluna d\'água. A concentração de metais em água excedeu os limites da resolução CONAMA 20/86 para águas de classe 2, com destaque para Cd (P1: Inconfidentes; 0,049 mg/kg), Cr (P9: Jacutinga; 0,190 mg/kg) e Fe (P8: Itapira; 9,60 mg/kg). Em sedimentos na totalidade dos pontos e, pelo menos, em um período, houve indicativo de contaminação. Para a análise das rações, segundo a IFOAM, níveis abaixo para Co, Cu, Cr, Fe, Mn e Zn, considerados metais essenciais. Portanto, as análises indicam ambientes impactados negativamente, com grau elevado de interferência antrópica. / The hydrographic basin of Mogi Guaçu is an important sustenance system for a lot of local economic activities. In result of human activities as use and inadequate occupation of the ground, pesticides and fertilizers in the farmings, launching of domestic and industrials effluent servants, without treatment; amongst others, it was verified that the Mogi Guaçu river must be submitted by different degrees of degradation to the long on its course; and, therefore, the fish culture on draining area. This work\'s purpose is to analyse the metal concentration in the water, sediments and rations on fish & pay lagoons, in intention to evaluate the level of impact of metals on the environment. There was water collect and sediments, at four different times, two in dry period and two in the rainy one, necessarily in ten points, distributed since the spring until the estuary. The rations had been collected in each one of fish & pay. Analyses of the percentages of organic and inorganic substance had been executed, as well as grain sized analyses of the sediments. The quantitative analysis of the metals was effected by atomic absorption spectroscopic technique, as much in water, sediments and ration. The results demonstrate that the percentages of organic substance are been raised, occurring in all the periods of sampling. The raised fraction of clay and sand, in the great majority of the sampling points, suggesting that the sediments have considerable importance in the redistribution of the metals in the water\'column. The metal concentration in water exceeded the limits of CONAMA, 20/86, with prominence to Cd (P1: Inconfidentes; 0.049 mg/kg), Cr (P9: Jacutinga; 0.190 mg/kg) and Fe (P8: Itapira; 9.60 mg/kg). In sediments on totality of the points, at least in a period, indicative contamination. For rations anylises, by IFOAM, low levels to Co, Cu, Cr, Fe, Mn and Zn, considered essential metals. Therefore, the analysis indicate negative environmental impacts, with high degree of human interference.

Steelhead populations support an economically valuable fishery in the Great Lakes region. Development of the region, resulting in land use changes and the introduction of hydropower, has affected the riverine habitat used by steelhead. I have developed an individual-based model of steelhead in the Manistee River, Michigan that simulates the long-term production of steelhead from the river. The model begins each year with a spawning population that produces redds for that year and then follows the offspring from each redd as individuals until they smolt one, two, or three years after spawning. Simulations run for ten-year periods. The simulated individuals are subjected to mortality from predation, starvation, and temperature extremes. Predation is a length-based mortality and is thereby affected by growth. Growth is determined by an individual's foraging success and bioenergetics. I conducted simulation experiments to examine the effect of changes in spawning numbers, temperature, and flow regime, on the number of individuals smolting in the river each year. Simulations reveal that the current flow regime and colder water temperatures are most beneficial for steelhead production and increasing the number of spawners does not increase steelhead production. The results also suggest that the young-of-the-year (YOY) stages have the greatest impact on steelhead production because the model showed no indication that steelhead life stages older than the YOY could compensate for density-related losses that occurred during the first year.

Thesis (M. A. (Aquaculture )) -- University of Limpopo, 2006 / Refer to document / NRF (National Research Foundation) and Canon Collins Educational Trust for Southern Africa (CCETSA)

Thesis (M.Sc. (Aquaculture)) -- University of Limpopo, 2012 / The feeding habits of a macrophagous fish, Tilapia rendalli, were investigated at an oligotrophic dam that has no macrophytes, Flag Boshielo Dam. This dam supports a significant population of the macrophagous, Tilapia rendalli. The diet of T. rendalli was investigated by examining the frequency of occurrence of different food items in the stomach of the fish over a period of twelve months. A size related dietary shift was evident. The diet of juvenile fish (<5 cm) was dominated by zooplankton and the diet of adult fish (>15 cm) was predominantly marginal vegetation, particularly Cyperus sexangulasris and Panicum schinzi. However, dietary overlaps between the different size groups were evident. The diversity of food items increased with fish size until the fish were 15 cm in length and thereafter declined as the fish predominately fed on marginal vegetation. Scales were used to determine the age of T. rendalli. Age at length data was fitted to the Von Bertalanffy growth model, which showed that males grew faster and attained a larger size than females. The growth of T. rendalli in Flag Boshielo Dam was comparable to those reported in other dams with macrophytes. It is inferred here that the absence of macrophytes is not a limiting factor in the growth of T. rendalli in lentic ecosystems. The ability of T. rendalli to achieve good growth rates when feeding on marginal vegetation prompted a subsequent study where its utilisation of readily available plant diets was evaluated under culture conditions. The culture of macrophagous fish that naturally feed on plant diets may be the solution to reduce the current dependence on fishmeal. Fishmeal is not only expensive, but its supply is not always guaranteed. This study focussed on the growth performance, gastric evacuation rate, gastric transit time and carcass composition of Tilapia rendalli fed fresh plants, to determine the extent to which T. rendalli can utilise fresh plants. Kikuyu grass (Pennisetum clandestinum), cabbage (Brassica oleracea), duckweed (Lemna minor), vallisneria (Vallisneria aethiopica) and fishmeal pellets (control) were offered ad libitum to duplicate groups of T. rendalli for 224 days. Specific growth rate (SGR), protein efficiency ratio (PER) and food conversion ratio (FCR) were used to determine the growth performance. Fish fed kikuyu grass attained a significantly (P<0.05) higher SGR and a better FCR than those fed on the other plant diets. Fish fed vallisneria lost weight. The serial slaughter method showed that vallisneria was vii evacuated significantly (P<0.05, ANCOVA) faster and was eaten in significantly (P<0.05) higher quantities than the other diets. Kikuyu grass was evacuated much more slowly and eaten in lesser amounts than the other plant diets. The low energy content (14.74 MJ/kg) of vallisneria may explain its faster evacuation and high consumption levels. Digestibility studies indicated that T. rendalli is capable of breaking down both cellulose and fibre. Fish fed kikuyu grass had higher protein levels, higher omega-3 fatty acids (25.13%) and higher mineral content than those fed on the other experimental diets. Fishmeal fed fish had the lowest content of the omega-3 fatty acids (2.52%). T. rendalli performed better when fed plant diets with higher protein and energy contents. The good growth performance and carcass quality of T. rendalli fed on kikuyu grass, led to another study where the use of kikuyu grass meal as a dietary protein replacement for fishmeal in practical diets for T. rendalli was evaluated. To determine the optimum substitution level, kikuyu grass meal was used to replace 20, 40, 60 and 80% of fishmeal in isonitrogenous (CP =16.70%) and isocaloric (GE =15.20 MJ/kg) diets. The test diets were fed to triplicate groups of fish held in 1 m3 fibre glass tanks at 10 (36 ± 2 g) fish per tank for 60 days. The best specific growth rate (1.60 g/day) and feed conversion ratio (1.86) were recorded for fish fed diets with 20% kikuyu grass meal. The lowest specific growth rate (1.29 g/day) and feed conversion ratio (2.56) were recorded for fish fed diets with 80% kikuyu grass meal. When the level of kikuyu grass meal was more than 20% in the diet, growth performance was reduced. However, there were no statistically significant differences in the growth performance indices measured across the tested diets. The observed reduction in growth for diets containing higher kikuyu grass meal is explained by the decreasing amino acids levels (particularly methionine and lysine) and increasing fibre content. The results from the growth trials suggest that kikuyu grass meal is a suitable protein replacement for the expensive fishmeal in T. rendalli practical diets when it constitutes up to 20% of the dietary protein.

This investigation explored the use of microcosms as a tool for studying the dynamics of tropical aquaculture ponds. The potential use of rabbit excreta as a pond fertilizer in integrated farming systems was also investigated. Twelve insulated fiber glass tanks were utilized as microcosms to simulate earthen ponds. Seven hand-sexed Nile Tilapia O. niloticus) were stocked per tank, and microcosm performance was observed for a 90- day experimental period. Three rabbit excreta loading rates corresponding to 50 and 75 kg/10,000 m³ /day, and a continuously adjusted manure loading rate were assessed. The fertilizer treatments were compared to a control treatment where fish were fed on a prepared food. Water quality variables and fish performance were regularly monitored. Nitrogen and phosphorous content of rabbit excreta were measured. The dynamics of the microcosms were similar to warm water earthen ponds with respect to physical and chemical characteristics. Statistical differences were detected between control and fertilized treatments in relation to dissolved oxygen levels, net primary productivity, total alkalinity, total ammonia and orthophosphate levels. Primary productivity was influenced more by light intensity and penetration than by nutrient limitation. Rabbit excreta overloading was observed in the 75 kg treatment. Fish growth was greatest in the control treatment, but it was not statistically different from the continuously adjusted fertilizer treatment (Pondclass) (0.0065 and 0.0056, respectively). Low daily fish gains were observed in the 50 and 75 kg treatments. Low dissolved oxygen and high total ammonia were concentrations resulted in low weight gains and condition indices of fish in the 50 and 75 kg treatments. Extrapolated fish yields corresponded to 6,205, 4,563, 3,686, 4,869 kg/ha/year for control, 50 kg, 75 kg and Pondclass treatments, respectively. The observed yields are comparable with field experiences in real ponds. The continuously adjusted treatment showed the lowest manure conversion ratio (3.85) in the fertilized treatments. The nitrogen content of rabbit excreta varied according to rabbit size, presence or absence of urine plus water waste, and food droppings. Urine plus water waste provided 28 % of the total nitrogen content in rabbit excreta, whereas food droppings provided 12 %. Rabbit urine may play an important role in aquacultural systems because it contains a large fraction of nitrogen in inorganic forms which are readily utilized for algal growth. Other rabbit excreta characteristics such as buoyancy may be advantageous in aquacultural systems. Rabbit excreta is a potentially rich source of fertilizer for use in fish ponds. / Graduation date: 1992

Diss. (sammanfattning) Arkitektkopia AB, Umeå : Sveriges lantbruksuniv., 2009. / Härtill 4 uppsatser.

Proliferative Kidney Disease (PKD) caused by the Malacosporean parasite Tetracapsuloides bryosalmonae, is presently the most economically damaging disease of British rainbow trout farming, costing the industry in excess of £2.5 million per annum in the UK alone. With no vaccine or prophylactic treatment available, and only management techniques currently adopted to minimise the stress and mortality associated with the disease, alternative approaches must now be considered. This document investigates if selective breeding for PKD resistance is possible by assessing the level of additive genetic variation, and calculating the subsequent estimates of heritability, for commercial strains of rainbow trout. During a PKD outbreak on a commercial farm, 1500 communally reared juvenile rainbow trout from two strains (Houghton Spring and Isle of Man) were sampled on a single day, their body weight and fork length measured, and severity of kidney swelling scored according to the scale of Clifton-Hadley et al. (1987). Fish were assigned to individual families using microsatellite parentage assignment. Significant additive genetic variation was observed in the population, and families were ranked according to estimated breeding values. A combined estimate of heritability (h2 = 0.19 ± 0.08) for kidney score suggests the population will respond well to selective breeding for kidney score, which may be deemed a measure of resistance, whilst the favourable genetic correlations between kidney score and the production traits measured suggest simultaneous selection for kidney score and growth traits should also be effective. In order to support the findings of the initial research, controlled challenge experiments were conducted. Using the family EBV information on kidney score from the IoM strain (due to its certification as a disease-free site), four females, two with high and two with low response to PKD, were each crossed with a randomly selected neomale to produce twenty two families for PKD challenge experiments. The PKD experimental challenges showed evidence of additive genetic variation to kidney score over an eleven week period, supporting initial findings. A low score was deemed as evidence of greater resistance to the parasite in this study. Although female EBV was taken into consideration in the statistical model, there was found to be no significant difference in resistance according to family. Immunohistochemistry stained kidney sections from each individual involved in the challenges proved kidney score correlated significantly to the number of parasites in the kidney, suggesting that the scale of Clifton-Hadley et al. (1987) is a sufficient and accurate basis on which to describe the severity of PKD, and infection level in rainbow trout. Having discovered evidence that furunculosis, causative agent Aeromonas salmonicida, plays a major role in the mortality of fish suffering from PKD in the field, the bacterial disease was investigated to assess the resistance of the same families used in the PKD challenges. Twenty one of the families were used to discover that additive genetic variation for resistance to furunculosis is apparent when assessed as both a binary and longitudinal trait, suggesting significant genetic improvement can be made to increase resistance to furunculosis in the IoM stock. No significant correlation was observed between kidney score, EBV, and resistance to this bacterium, but there was a positive phenotypic correlation found between furunculosis resistance and size, suggesting simultaneous selection for performance and resistance is possible within this population.

Disease outbreaks continue to be a major problem in the sustainable development of the aquaculture industry. Clinical outbreaks can negatively impact on the welfare of the fish and the economic gain derived from this industry. Jaundice observed as a yellow colouration in the abdominal skin, sclera of the eyes and fin bases is a significant health problem affecting the Vietnamese freshwater catfish industry. This study was designed to investigate jaundice of farmed catfish, Pangasianodon hypophthalmus using several complementary approaches. These included clinical investigations and identification of potential aetiological agents as well as epidemiological analyses to identify farm-based risk factors for this economically devastating condition occurring in the catfish farms of the Mekong Delta. The results of this survey demonstrated that the jaundice was not linked to a single geographical location as affected fish were found widely distributed throughout the five main production areas. Nor was any association found between any weight groupings, feed type or feeding regime applied in the affected farms. The highest prevalence occurred between June to October and fish mortalities ranged from 1 to 10% in the study sites. The duration of this condition was significantly correlated (P &lt; 0.05) to mortality but not to total farm area, depth of pond, stocking density, or amount of water exchanged. The number of fish ponds affected was not as high in the large-scale farms compared to the small-scale farms. The results from the clinical description study showed that the affected fish were suffering a form of jaundice or icterus. Histological examination revealed a number of serious pathologies in the affected fish. Spleenomegaly was associated with the loss of cell structure and connective tissue and the haematopoietic tissue had large areas of necrosis. In the liver, histological changes consisted of vasculitis and multifocal to diffuse hepatocellular necrosis. The presence of haemosiderin was observed in melano-macrophage centres in the spleen and kidney of jaundiced fish. No single pathogen was identified in the jaundiced fish. Myxosporean infection was found in both apparently normal fish and jaundiced fish. However, there was a definite tendency for jaundiced fish to be more heavily infected. Histopathological examination found several changes that could not be ascribed to specific aetiological factors and presume that both groups (jaundiced alone and myxosporean-affected jaundiced fish) have similar lesions. The results of this study would suggest that the parasite identified as M. pangasii was not a primary pathogen associated with the haemolytic jaundice. Neither were the gills myxosporeans associated with the haemolytic jaundice and they may be considered more as a nuisance rather than as primary pathogens in farmed P. hypophthalmus in the Mekong Delta, Vietnam. Univariate analysis of the whole dataset showed several variables were significantly associated with the haemolytic jaundice. However, none of the variables achieved lasting statistical relevance in multivariable models. In conclusion, this study identified a haemolytic jaundice condition affecting farmed P. hypophthalmus in Vietnam, but no single aetiological agent or farm based risk factor was identified with this condition. Several priority areas for further work were identified and include a prospective, longitudinal cohort study to identify further the risk factors associated with the clinical jaundice condition.

published_or_final_version / abstract / toc / Ecology and Biodiversity / Master / Master of Philosophy