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Efeito dos fertilizantes inorgânicos no desempenho zootécnica de alevinos de Tilapia Moçambicana (Oreochromis mossambicus - Peters, 1852) cultivados em tanques rede

Tue, 01 Apr 2025 00:00:00 GMT

Title: Efeito dos fertilizantes inorgânicos no desempenho zootécnica de alevinos de Tilapia Moçambicana (Oreochromis mossambicus - Peters, 1852) cultivados em tanques rede Authors: Conceição, Helton Fernando Dias da Abstract: O presente trabalho tem como objectivo avaliar a resposta zootécnica de alevinos de Tilapia Moçambicana (Oreochromis mossambicus) cultivados em tanques rede sob efeito de fertilizante inorgânico. O estudo foi realizado na unidade piscícola da Escola Superior de Ciências Marinhas e Costeiras, localizado no distrito de Quelimane, Província da Zambézia, por um período de 90 dias, compreendidos de 12 de Dezembro a 24 de Abril de 2016. Um total de 180 juvenis foram utilizados no ensaio, tendo um peso médio inicial de 3±1.04g, povoados em tanques rede (hapas) inseridas em dois tanques terra de 162m2, sendo um com aplicação de fertilizantes inorgânico (Tratamento 1) e outro sem fertilização e com alimentação a base de ração comercial da marca LFL (Tratamento 2). O estudo esteve assente em um tanque escavado com dois tratamentos e três repetições cada, perfazendo 6 unidades experimentais, povoadas com 30 peixes cada. Foram feitas biometrias quinzenais a 40% da amostra, sendo que o cultivo esteve acompanhado com o monitoramento diário de parâmetros de qualidade de água, medidos duas vezes ao dia (manhas e tardes) as 6:30h e 15:30h. Posteriormente, foram determinados os Índices de desempenho zootécnico de Crescimento Diário em Peso (CPD), Taxa Específica de Crescimento (TEC), Taxa de Sobrevivência Final (TSF), Factor de Conversão Alimentar (FCA) e Biomassa Total Produzida (BTP). Os resultados obtidos indicaram diferenças significativas (p <0.05) entre os tratamentos. As Tilápias alimentadas com a ração comercial obtiveram valores de peso medio (76.6±2g) superior em relação a biomassa dos peixes criados sobe efeito de fertilizantes inorgânicos (52.6±2.03g), sendo que o inverso foi observado para a taxa específica de crescimento diário (1.4±0.9%) contra e 1.2±0.8%. Conclui-se que a tilápia teve o melhor desempenho zootécnico quando alimentada com ração comercial, sendo que o T1 apresentou ganho de peso menor e, consequente menor peso final e ganho em biomassa também menor em relação ao T2 (ração comercial). Estes resultados sugerem que o uso de fertilizantes inorgânicos Apesar das diferenças estatísticas nos índices zootécnicos calculados este este método pode ser usado.

Impacto socioeconómico da produção aquícola em Moçambique: caso de estudo- Província da Zambézia

Tue, 08 Apr 2025 00:00:00 GMT

Title: Impacto socioeconómico da produção aquícola em Moçambique: caso de estudo- Província da Zambézia Authors: Ferreira, Lucinda Verónica Cuamba Abstract: Fish farming has become an excellent business and area of research, providing important economic and nutritional benefits for the population, where tilapia farming, in particular, has expanded significantly throughout the country, with an emphasis on Zambézia province. The aim of the study was to analyse the socio-economic impact of aquaculture production in Mozambique. 49 fish farmers were surveyed in the districts of Quelimane, Nicoadala, Pebane and Milange. The descriptive analysis showed that most of the fish farmers were men, aged between 35 and 55, with secondary education, living in medium-sized families where 1 or 2 people contribute to the monthly income. They produce in an area of less than 500 square metres, with one pond and use a semi-intensive system for tilapia production. Production is destined for commercialisation and is sold locally. Production aspects limit the development of fish farming and feed was identified as the main obstacle. Variables such as production area, number of ponds, construction cost, production cycles, cost of fry and revenue have a direct impact on productivity and profitability. Tilapia production is considered profitable, although fish farmers are unaware of the profits made at the end of each cycle. To do this, fish farmers need to know the production costs and understand cost accounting in order to be able to estimate the profits from the activity. They also need to undergo technical training in economic viability. Aspects such as the availability of inputs, technical training, extension services and access to finance must be taken into account in order to increase productivity and profitability

Efeito do ambiente e o método de cultivo sobre o crescimento da macroalga Eucheuma denticulatum na região norte de Moçambique

Fri, 02 Aug 2024 00:00:00 GMT

Title: Efeito do ambiente e o método de cultivo sobre o crescimento da macroalga Eucheuma denticulatum na região norte de Moçambique Authors: Madeira, Ana Domingos Abstract: Macroalgae cultivation plays an important role in several tropical and equatorial regions, contributing to local and global economic development. In Mozambique, the potential for the cultivation of macroalgae E. denticulatum and other species is estimated at around 10,600 hectares, but the record of large-scale production is low. In this context, this study aimed to evaluate the influence of the environment on the cultivation of the alga E. denticulatum in the northern region of Mozambique. Cultivation was carried out in the Palma and Mossuril regions for 9 months, using two cultivation techniques called "tie-tie" and tubular net. Samples were taken every two weeks to record the biomass, observe the quality of the vegetative parts and monitor the physico-chemical parameters at the site. The other environmental data parameters used to correlate with biomass as well as the relative growth rate (RGR) were obtained from My Ocean Copernicus. The generalized additive model (GAM) was applied to determine the influence of the environment on biomass accumulation and TCR throughout cultivation. The comparison between cultivation methods was made using the independent samples t-test. All statistical analyses were carried out using R software. The results indicated that there were no significant differences in biomass accumulation between the two cultivation techniques (t = -1.40, df = 392, p-value = 0.16), although the tubular net technique showed higher biomass values (12.16 ± 11.34 kg). Regarding to TCR, the tubular net method had a higher relative growth rate (16.44 ± 18.48 kg) compared to the tie-tie method (5.45 ± 7.48 kg), and these differences were confirmed by the test (t = -7.01, df = 179.45, p-value <0.05). The biomass model explained ~97% of the total variation, while the growth rate model explained ~90%, both with significant levels of the high selected variables (p-value < 0.001). The variables that most influenced the variation in biomass were tidal height (F-statistic ~175), pH (F-statistic ~125), sea surface temperature (SST, F-statistic ~44), dissolved inorganic carbon (DIC, F-statistic ~37) and nitrate (NO3-, F-statistic ~32). For growth rate variation, the most influential variables were nitrate (NO3-, F-statistic ~89), sea surface temperature (SST, F-statistic ~39) and wave energy (SWH, F-statistic ~12). These results highlight the importance of monitoring environmental variables during the cultivation of E. denticulatum in order to optimize production and can help guide the selection of sites for the establishment of macroalgae aquaculture enterprises for ecosystem recovery as well as for socio-economic purposes.

Dynamics of the Mozambique channel using surface drifters and satellite-derived geostrophic and Ekman currents

Thu, 06 Feb 2025 00:00:00 GMT

Title: Dynamics of the Mozambique channel using surface drifters and satellite-derived geostrophic and Ekman currents Authors: Sitoe, Nélio das Neves Olívio Abstract: This study examined the surface current dynamics around Madagascar and the Mozambique Channel. Dividing these regions into the Eastern Madagascar Coast, Northern, Central, and Southern Mozambique Channel subregions allowed for the assessment of the role of geostrophic-only and combined geostrophic and Ekman currents in the dynamics. Moreover, calculated virtual drifters were compared with 151 hourly Surface Velocity Program drifters (SVP drifters) from the Global Drifter Program spanning from 2000 to 2019. In addition, while some SVP drifters retained their drogues, others lost them; this status was considered in the analysis. The virtual drifter’s trajectories were calculated using the basic Lagrangian modelling equation, which requires velocity fields. The velocity fields employed are based on the CNES-CLS18 mean dynamic topography model, which comprises satellite altimeter observations, wind from numerical models and in-situ observations from SVP drifters. These velocity fields are compiled at four levels of processing by the European Union-Copernicus Marine Service. The virtual drifters from the two velocity fields were designated as Virtual Geostrophic Drifter (VGD) and Virtual Geostrophic-Ekman Drifter (VGED), while the SVP drifters were classified as real drifters. The results reveal substantial underestimations, averaging 29% with VGDs and improving to 21% when Ekman drift is incorporated in the VGEDs compared to real drifters. This shows improvement in the CNES-CLS18 mean dynamic topography model. The Eastern Madagascar Coast exhibited the highest velocity discrepancies due to the formed dipole in the southern tip of Madagascar, which prevented the movement of specific VGD to the channel. However, the Northern Mozambique Channel showed lower underestimation due to strong western boundary currents, local winds, and tropical cyclones, highlighting the region’s dominance of wind seasonality. Due to the eddy’s linearity and non-linearity, virtual drifters have substantial position errors in the Central and Southern Mozambique Channel. Moreover, virtual drifters failed to identify key submesoscale structures because the velocity field’s 25 km resolution was a significant issue. The dispersion of virtual drifters in the offshore Cabo Delgado coast of the Northern Mozambique Channel was predominantly influenced by seasonal Ekman-driven currents. This highlights the necessity of incorporating these dynamics into future simulations as winds modulate this region. A considerable part of these virtual drifters ran aground shortly after being released due to the strong winds from the south that influence the ocean surface, displacing them 45° to the left in relation to the wind’s direction. This phenomenon was observed predominantly in winter.