Browsing by Issue Date, starting with "2020-11-24"
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- Nutritional bases of microdiet development for the early stages of two crustacean species: whiteleg shrimp (Penaeus vannamei) and European lobster (Homarus gammarus)Publication . Silva, Andreia Sofia Sardinha; Conceição, Luís Eugénio da Castanheira; Pinto, Wilson Gabriel Poseiro CoutinhoCrustaceans are an important source of aquatic food protein with a growing global demand leading to one of the fastest growing aquaculture sectors. Aquaculture of crustaceans is highly dependent on meeting their nutritional requirements and producing high quality stocks. However, knowledge on the nutrition, feeding ecology, body composition and nutrient requirements in crustacean larval culture is still limited. This thesis aimed at creating nutritional bases for the development of diets for two crustaceans species, whiteleg shrimp (Penaeus vannamei) and European lobster (Homarus gammarus), at their early development stages. A first feeding trial was conducted to study the dietary protein requirements of whiteleg shrimp postlarvae. For this trial, six experimental diets were formulated to include 34, 44, 49, 54, 58 and 63% protein levels, designated as treatments P34, P44, P49, P54, P58 and P63, respectively. In this trial, 3.18 mg initial mean body weight postlarvae were reared in triplicate groups for 21 days, being fed one of the experimental diets. Growth performance and survival of shrimp from different treatments were affected by the dietary protein levels, with shrimp fed diet P34 registering significantly lower results than the remaining treatments. Final weight, weight gain, RGR and survival of shrimp only increased until diet P44 and FCR decreased. Broken-line analysis of weight gain indicated that the optimal dietary level of crude protein is 47.1% for whiteleg shrimp postlarvae. This requirement level of protein is slightly higher than previous research on posterior stages of development. This can be due to higher growth rates in earlier stages of development. A second feeding trial was conducted to study the growth performance of European lobster juveniles fed on three different experimental diets. These diets were rich in protein, protein and calcium or in carbohydrates and calcium, designated as PROT, PROTCA and STASH, respectively. For this trial, 23 lobster juveniles were reared for 90 days fed one of the experimental diets with 8 replicates per diet, except diet PROT which had 7 replicates. Survival in this trial was 100%. Weight gain, FCR and RGR were not affected by the diet treatments. At the end of the trial, body weight and total body length showed to be significantly higher in juveniles fed PROTCA than in the remaining treatments. Cephalothorax length, colouration changes and molting were not affected by the diet treatments. This thesis concludes that a diet with a medium-high level of protein has shown good performance in shrimp postlarvae, with an optimal dietary level of crude protein estimated at 47.1%. Moreover, from the diets tested on European lobster juveniles, the diet rich in protein and calcium was considered the most suitable for early stages of development. This can be a result of this diet being the most related to the body composition of the lobster at the life stage studied.
- Temporal variability of physico-chemical parameters acquired in a real-time monitoring station in an inner area of Ria FormosaPublication . Tufoni, Paolo; Jacob, José; Cravo, AlexandraAs lagoas costeiras estão entre os ambientes mais produtivos da Terra, fornecendo múltiplos serviços ecossistémicos. No entanto, o aumento da pressão humanas, juntamente com as alterações climáticas, podem aumentar os perigos, resultando em alterações da sua dinâmica. Apesar do aumento do número de estudos de processos físicos, químicos e biológicos em lagoas costeiras, ainda é difícil obter conjuntos de dados de séries temporais longas. Neste trabalho, foi efectuada uma análise do conjunto de dados registados em tempo real ao longo de dois anos, por uma estação de monitorização fixa localizada na costa sul de Portugal, numa zona interior da Ria Formosa, onde a pressão humana é maior. O intervalo de amostragem de alta frequência 15 min) permitiu descrever a variabilidade temporal da temperatura, salinidade, oxigénio dissolvido (concentração e saturação), pH, clorofila a, e turbidez, a várias escalas temporais, desde a diurnae a semi-diurna, até à quinzenal e à sazonal. Os resultados da análise espectral revelaram que a variabilidade típica dos parâmetros estudados foi induzida principalmente por forças astronómicas, tais como as constituintes principal lunar semi-diurna M2 e lunisolar sinódica quinzenal MSF, mas também por outros factores relacionados com a configuração do sistema, tais como a constituinte lunar quarto-diurna M4 e o componente diurna associada aos efeitos da radiação solar. Além disso, os dados adquiridos permitiram a identificar processos marinhos, e eventos episódicos, desde o desenvolvimento de fitoplâncton, a ocorrências de mesoscala, tais como tempestades, afloramento costeiro e contracorrente costeira. Utilizando uma correlação cruzada entre os dados de vento de hora em hora e as séries temporais de temperatura quase em tempo real, foi possível identificar a alternância entre eventos de afloramento e de contracorrente, ambos suportados pela análise de imagens de satélite. Estes eventos de mesoscala tiveram um impacto importante nos parâmetros da água da Ria Formosa, o que reflectiu a influência das trocas de água através do sistema de múltiplas barras. A estação de monitorização fixa revelou ser uma equipamento eficaz em termos de variação da qualidade da água, permitindo ter uma imagem mais abrangente dos processos e eventos que ocorrem na área da Ria Formosa e que pode representar uma ferramenta muito útil numa perspectiva de gestão ambiental.
- Benefits of English camps for children in different countries and its´ impact on voluntourismPublication . Dobesová, Alzbeta; Almeida, ClaudiaMost people travel with purpose. Whether it's for fun, leisure, getting to know new cultures or new people, people go because they want to impact society by helping locals. Sometimes it's multi-purposed. Research has shown that voluntourism sometimes causes more harm than good. This work addresses the problem of the side effects of voluntourism, the positive and negative impact, as well as analyzing English summer camp in Slovakia, Ukraine, and Brazil and its effects on voluntourism. In this context, voluntourism is a form of tourism in which travelers participate in voluntary work, typically for a charity. At the core of voluntourism is the desire to help others. Based on a literature review on voluntourism (traveling with a purpose), a case study from Slovakia was applied, followed by a comparison of camps in Brazil and Ukraine. The empiric investigation analyzed the volunteers' motives for volunteering abroad. The results allow us to find an ideal approach to voluntourism and eliminate the negative sides to it. Even though altruism is necessary while volunteering abroad, the work project showed that while volunteers have individual skills to work in specific fields, self-promotion and internal well-being can still be the main motives of the volunteers.