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Dissertação mest., Aquacultura e Pescas, Universidade do Algarve, 2009 Os ácidos gordos (AG) essenciais presentes nas dietas são tidos como factores críticos no sucesso do cultivo larvar. Tem sido dado um maior destaque aos ácidos docosahexaenóico (DHA) e eicosapentaenóico (EPA) devido às suas funções na integridade celular membranar e predominância nos tecidos. A importância do ácido araquidónico (ARA) no crescimento, sobrevivência e resistência ao stress é também cada vez mais reconhecida. Realizou-se um estudo para determinar os efeitos que diferentes concentrações de ARA em microdietas causam no crescimento, sobrevivência e perfil de ácidos gordos das larvas de dourada. As larvas foram alimentadas durante 25 dias com microdietas, incluindo um período inicial de coalimentação com rotíferos enriquecidos. Foram testadas, em triplicado, quatro microdietas experimentais que diferiam nos níveis de ARA, variando entre 0,4% e 3,0% da matéria seca (ARA0,4/ ARA0,8/ ARA1,5/ ARA3,0). As microdietas apresentavam níveis de HUFA n-3 de 4,6% e um rácio DHA/EPA de 1,4. Mediu-se o crescimento com base no peso seco e taxa de crescimento relativo, e obteve-se a sobrevivência por contagem directa. O perfil em AG dos lípidos totais das larvas foi determinado por cromatografia em fase gasosa. Após 34 dias, não se registaram diferenças significativas no crescimento e sobrevivência, apesar de existir uma tendência nos tratamentos intermédios para um menor crescimento. A composição lipídica dos tecidos reflectiu o perfil de AG das dietas, particularmente quanto ao ARA. O DHA manteve-se constante, enquanto o EPA diminuiu com o aumento de ARA, mesmo com níveis semelhantes de EPA nas dietas, sugerindo uma competição entre estes AG para a incorporação nos tecidos. Até 1,5% nas dietas, o ARA mostrou ser preferencialmente depositado nos tecidos, sendo metabolizado em concentrações superiores (3,0%). O DHA e alguns AG saturados foram preferencialmente retidos enquanto que o EPA e os ácidos linoleico (LA), α- linolénico (ALA) e oleico (OA) foram metabolizados, provavelmente para fins energéticos. Nas condições testadas, as larvas de dourada mostraram uma boa tolerância à variação de ARA nas dietas, de 0,4% a 3,0%. No entanto, o crescimento não foi afectado nem se verificou uma melhoria da sobrevivência.

Dissertação mest., Aquacultura e Pescas, Universidade do Algarve, 2009 The general aim of this study was to understand the underlying factors responsible for the individual variation in growth of juvenile Senegalese sole (Solea senegalensis). Senegalese sole is a species of high commercial value and high interest for aquaculture in Europe, therefore it would be important to understand these individual variations. Understanding the causes for individual variation in growth in relation with the feed intake, metabolic rate and response to stress contributes to maximize the production efficiency by reducing food waste and improving water quality. In order to identify the possible factors responsible for the individual variation in sole growth, its relationship with metabolic rate, stress response and feed intake was determined. Twelve fish with 18.49 ± 2.94g of initial weight were kept in standard conditions and feed once a day, during a period of six months. Individual oxygen consumption measurements in Sole juveniles were determined by flow-through respirometry at standard conditions, after the fish were fed a single meal and after a stressful condition. Blood samples for plasma cortisol, were taken from all fish at the start of the experiment (control, indicative of basal levels) and after stress exposure. Quantification of individual feed intake was performed by incorporation with radio-opaque ballotinis glass beads in a dry feed, followed by radiography to quantify the amount of ingested pellets. Individual fish exhibited pronounced variation in growth (final weight ranging from 30.45 to 67.53g), oxygen consumption of fasted fish (108.0 to 447.4 μmol/g/h), oxygen consumption of fed fish (174.7 μmol/g/h to 813.5 μmol/g/h), oxygen consumption after emersion stress (186.8 μmol/g/h to 376.7 μmol/g/h), and plasma cortisol after emersion stress (4.81 ng/ml to 46.45 ng/ml). Individual differences in metabolic rate do not contribute to explain individual differences in growth. However, after emersion stress individual differences in stress response seem to play a role in explaining individual differences in growth, what may result from different copying styles. Sole feed intake as measured by X-ray does not seem to be a good indicator of growth rate. The oxygen consumption increases both when fish are fed and after an emersion stress, as result of additive costs of growth and stress to the cost of maintenance. All together, this study suggests that individual variation of growth in Solea senegalensis is essentially due to genetic variation, and its reduction may accomplished when genetic selection programs are adopted. Furthermore, a study with a larger number of fish and over a larger time period would be important to check some of the trends found in this thesis between growth potential, metabolic rate and coping styles of Senegalese sole.

Tese dout., Aquacultura, Universidade do Algarve, 2008 Diplodus sargus is a potential species for aquaculture. Constraints to its production are a high incidence of skeletal deformities and stagnation of the growth rate in juvenile stage, possibly caused by dietary imbalances. This thesis is focused on the amino acid (AA) requirements of Diplodus sargus larvae, on the formulation of diets with AA supplementation and also identifies larvae skeletal deformities patterns (Chapter 2). D. sargus AA requirements were estimated using the AA profiles from larval carcass. It was observed that the AA profiles were relatively constant during larval ontogeny, and dietary imbalances were identified in rotifers and Artemia (Chapter 3). Tyrosine, lysine, tryptophan and arginine supplementation was tested by tube feeding and lower gut absorptions efficiencies were observed for these AA. Also, these AA do not seem to be limiting D. sargus growth (Chapter 4 and 5). Based on the results from Chapter 3, a microencapsulated casein diet with a balanced AA profile was formulated and was compared to an unbalanced AA diet and to a live feed diet (control) (Chapter 6). Results showed lower ammonia excretion and less skeletal deformities in larvae fed a balanced diet. Tryptophan supplementation in the diet was tested because of its involvement in skeleton ossification (Chapter 7). However, a decrease on larval growth and no effect on skeletal deformities were observed. The effect of tyrosine and phenylalanine supplementation on D. sargus larvae was tested and a higher survival to a temperature stress test was observed in larvae fed a tyrosine supplementation (Chapter 8). Larvae given a phenylalanine supplementation had a decreased incidence on vertebral compressions. In conclusion, an AA balanced diet reduces skeletal deformities and improves nitrogen utilization. Skeletal deformities do not seem related to tryptophan deficiency. Supplementation of phenylalanine and tyrosine lead to a decrease on skeletal deformities and better resistance to a stress test, respectively. From the AA studied; tryptophan, lysine, phenylalanine, arginine and tyrosine; none seems to be limiting D. sargus larval growth Faculdade de Ciências e Tecnologia (FCT) Instituto de Investigação das Pescas e do Mar (IPIMAR)