Aquaculture in Ghana : prospects, challenges, antidotes and future perspectives

Inland and marine capture fisheries productions in Ghana have more or less stabilised. Moreover, the increasing population is always putting pressure on the demand for fish which capture and marine productions alone are not able to meet. The national demand for fish is always greater than the country can supply and the gap is widening year after year. However, fish is the most important animal protein in Ghana accounting for about 82 % of protein consumption. Moreover, the relatively cheaper price of fish compared to the other animal proteins means that the year-after-year short-fall in fish production will affect the protein in-take of the poorer segments of the society in the near future if nothing is done about it. For example according to Tradezone, even though the national fish demand for 2007 was 913, 992 tonnes, the country was able to supply only 511, 836.The development of aquaculture has been seen to be one of the best solutions to the problem. The positive side is that the geo-ecological climate of the country is generally favourable for aquaculture development. These include the vast water surfaces of the dug-outs, dams, lagoons, the Volta Lake (the largest man-made lake in the world) and other water bodies. Nonetheless, this vast potential has not been tapped due to number of bottlenecks such as the availability of quality feed among others. Following the results of my studies and work, I therefore propose that; 1. The local agricultural products and by-products should be tested scientifically in order to formulate cheap feed for aquaculture development. 2. Integrated Agriculture-Aquaculture (IAA) should be promoted and developed since it is resource and ecologically efficient and at the same time economically beneficial to farmers. 3. The agricultural extension officers should be trained in fish farming techniques so that that they can help advice farmers more especially on issues of integrated agriculture-aquaculture. 4. Women should be encouraged and motivated to enter into aquaculture and 5. Finally, the Aquaculture Development Committee (ADC) should assist farmers in the acquisition of soft loans and land which have been major stumbling blocks to the development of aquaculture

Complementary tools for aquaculture management: remote sensing and in situ approaches for Sines

Tese de mestrado, Ciências do Mar, Universidade de Lisboa, Faculdade de Ciências, 2020O estado crítico dos recursos marinhos tem vindo a impulsionar o rápido desenvolvimento da aquacultura. De facto, a nível mundial, a produção aquícola regista atualmente um crescimento mais rápido que qualquer outro setor da indústria alimentar. No entanto, o aumento de práticas intensivas de aquacultura tem gerado preocupações, principalmente devido aos potenciais impactos ambientais associados. A presente dissertação teve como foco uma produção intensiva de robalo (Dicentrarchus labrax, L. 1758) localizada no sudoeste da Costa Ibérica (Sines, Portugal). Na área de produção, a qualidade da água e os possíveis impactos da atividade no meio envolvente foram avaliados. Para tal, seis campanhas de amostragem, realizadas entre junho de 2018 e julho de 2019, foram realizadas para recolha de dados de parâmetros físicos, químicos e biológicos ao longo das jaulas onde se encontram os peixes. Foram analisados dados de temperatura, salinidade, parâmetros de claridade da água, matéria particulada em suspensão, oxigénio dissolvido, pH, nutrientes e biomassa e composição fitoplanctónica. Parte dos dados foram adquiridos a partir de sondas multiparamétricas (e.g. temperatura, salinidade, oxigénio dissolvido e pH); as concentrações de matéria particulada em suspensão, nutrientes e biomassa fitoplanctónica foram determinadas analiticamente em laboratório. Os parâmetros de claridade da água foram obtidos através de dados de radiometria e da profundidade de Secchi. Os resultados dos parâmetros de qualidade da água foram comparados com as gamas consideradas como aceitáveis e ótimas para a aquacultura de peixes em ambientes marinhos, de acordo com a literatura internacional. Atualmente, a literatura científica disponível ainda fornece uma orientação direta limitada para a avaliação da qualidade da água nas águas costeiras portuguesas. Os resultados apresentaram valores dentro das gamas aceitáveis definidas na literatura (exceto um valor isolado de fosfatos obtido em outubro de 2018). Para avaliar o impacto desta produção de peixe no meio recetor, as médias e extremos dos parâmetros de qualidade da água passíveis de serem diretamente influenciados pela aquacultura foram comparados com os dados disponíveis para a região de Sines, anteriores ao início da produção de robalo na região. Neste caso, foram obtidas concentrações mais elevadas de azoto inorgânico dissolvido em comparação com os valores de referência para Sines. No geral, a claridade da água, oxigénio dissolvido, nutrientes e biomassa fitoplanctónica não sugeriram impactos negativos das unidades de produção na qualidade da água local. Não obstante, são necessárias mais análises para diferenciar os potenciais impactos da elevada industrialização em Sines, dos impactos da aquacultura. Os resultados do presente trabalho apontam como causas para o baixo stress ambiental diversos fatores: o regime hidrodinâmico, o baixo tempo de residência da água no sistema, a estratégia de alimentação e a dimensão das unidades de produção. As campanhas de amostragem in situ permitiram ainda verificar uma grande variabilidade dos parâmetros analisados na região, e a necessidade de utilizar métodos complementares para uma melhor caracterização espácio-temporal da área envolvente. Os produtos de deteção remota (DR) disponibilizam dados com grande resolução espácio-temporal, que podem complementar as abordagens amostragens in situ fornecendo informações relevantes os end users, neste caso, o aquacultor. Dados climatológicos da temperatura da água e da concentração de clorofila-a (indicador de biomassa fitoplanctônica) com os respetivos parâmetros estatísticos (desvio padrão e percentis 10 e 90) foram determinados para a região envolvente da aquacultura. Para verificar a coerência dos mesmos para a região, estes foram comparados com os dados in situ recolhidos durante as campanhas de amostragem. As médias semanais do percentil 90 (p90) da temperatura da superfície do mar (TSM) provaram ser adequados para alertar condições anómalas no local da aquacultura. Por outro lado, devido à alta variabilidade sazonal e interanual de clorofila-a (Chl-a) na região, a média do p90 mostrou ser mais fidedigna para a deteção de condições de alerta. O cálculo de anomalias diárias em comparação com dias anteriores (7 e 14 dias) também forneceu informações relevantes sobre a ocorrência de blooms na região. Atualmente, a disponibilização de dados de satélite quase em tempo real em várias bases de dados públicas, possibilita facultar ferramentas valiosas de baixo custo ao aquacultor. Para além da região envolvente, a área onde se encontram instaladas as jaulas de peixe foi também caracterizada utilizando dados de DR (TSM, Chl-a e turbidez) e comparada com os dados obtidos in situ. Para fins de monitorização, medições discretas de temperatura e turbidez indicam ser suficientes para representar a área devido à baixa variabilidade espacial. A alta variabilidade de Chl-a na região revelam a necessidade de recolher dados em várias estações ao longo da produção, ou complementar dados in situ mais escassos com produtos de DR de maior resolução. A adequabilidade de diversos produtos de DR considerados ao longo desta tese foi preliminarmente avaliada para a área da aquacultura em Sines. Para analisar a Chl-a, os novos sensores de alta resolução espacial da Agência Espacial Europeia, desenvolvidos no âmbito do Programa Copernicus da Comissão Europeia, como o Ocean and Land Color Instrument (OLCI) e o Multispectral Instrument (MSI) a bordo dos satélites Sentinel-3 e Sentinel-2, mostrou contribuições importantes para as áreas adjacentes ao litoral. Missões com dados históricos de Chl-a, como o Medium Resolution Imaging Spectrometer (MERIS) a bordo do Envisat e o produto que engloba múltiplos sensores da Ocean Colour Climate Change Initiative (OC-CCI), possibilitam uma melhor compreensão de variações intra-anuais. O produto de TSM do Group of High Resolution Sea Surface Temperature (GHRSST) revelou captar consistentemente o sinal de temperatura em Sines. Dada a intensa industrialização da zona de Sines e, neste caso, a presença de uma descarga de água quente proveniente da central termoelétrica de Sines a sul da produção, o uso deste último produto requer atenção na interpretação dos dados. Tal facto destaca a necessidade de aquisição de conhecimentos sólidos sobre a região de estudo para posteriores aplicações de produtos de DR, de modo a minimizar possíveis erros nas análises. Por fim, é salientada a necessidade da utilização de produtos de alta resolução espacial e temporal para monitorar as áreas costeiras, bem como a complementaridade da deteção remota com a recolha de dados in situ.The critical status of marine resources has provided impetus for rapid growth in aquaculture, which has become the fastest growing sector of the food industry worldwide. However, the increase of intensive aquaculture practices has been raising global concern mostly due to the associated potential environmental impacts. The present dissertation focused on an intense aquaculture in the SW Iberian Coast (Sines, Portugal) dedicated to the production of European sea bass (Dicentrarchus labrax, L. 1758). Water quality and potential impacts were assessed in the production area. Physical, chemical and biological parameters were collected along the cages in the course of six field campaigns, carried out between June 2018 and July 2019. These were temperature, salinity, water clarity parameters, suspended particulate matter, dissolved oxygen, pH, nutrients, and phytoplankton biomass and composition. The obtained water quality parameters were compared with threshold values for marine fish production, according to international literature. The scientific literature currently provides limited direct guidance for water quality assessment in Portuguese coastal waters. Results showed values within the acceptable for marine fish production (except an isolated value of phosphates obtained in October 2018). To assess the impact of this fish production in the receiving medium, the averages and extremes of water quality parameters that might be directly influenced by aquaculture were further compared with available data for Sines region, previous to the sea bass production in the area. A higher dissolved inorganic nitrogen signal was found in the collected data, compared to background nutrient levels for Sines. Overall, water clarity, dissolved oxygen, nutrients and phytoplankton biomass did not suggest any detrimental impacts of the production units on local water quality, although more research is needed. The findings point to the hydrodynamic regime, low water residence time in the system, feeding strategy and the dimension of production units as the reason for the lack of stress on the receiving waters. Typically, coastal aquaculture faces with high water quality variability. Given the capabilities of satellite remote sensing (RS) products to provide high spatio-temporal data, they have the potential to be used as complementary tools to support the activity, providing important knowledge for end users. Climatological water temperature and phytoplankton biomass (indexed as chlorophyll-a concentration) data with respective statistics were provided for the aquaculture region and compared with the in situ data collected to verify consistency. Sea surface temperature (SST) weekly 90th percentiles (p90) proved to be suitable to alert anomalous conditions in the aquaculture site. On the other hand, due to high chlorophyll-a (Chl-a) seasonal and interannual variability in the region, the mean p90 proved to be more reliable for the detection of alert conditions. The computation of daily anomalies compared to previous days (7-days and 14-days) also provided valuable information on the occurrence of blooms in the region. Currently, near real time satellite data can be accessed freely, providing users with valuable tools in a cost-effect way. The aquaculture site was also characterized using RS retrieved variables (SST, Chl-a and turbidity) and compared with the ground truth. For monitoring purposes, single discrete measures of SST and turbidity were found to be most likely sufficient to represent the area due to low spatial variability. High Chl-a variability in the region emphasized the need to collect several datapoints along the production or to complement scarcer in situ data with higher resolution RS products. In this thesis, several remote sensing products were considered, and their suitability for the aquaculture area in Sines was preliminarily assessed. To study the variability of Chl-a, novel high spatiotemporal resolution RS sensors, such as the Ocean and Land Colour Instrument on Sentinel-3 (OLCIS3) and the Multispectral Instrument on Sentinel-2 (MSI-S2), showed important contributions when focusing areas adjacent to the coast. Missions with available historical Chl-a data such as the Medium Resolution Imaging Spectrometer on-board Envisat, and the multi-sensor product from Ocean Colour Climate Change Initiative (OC-CCI), further enable understanding interannual features. The SST product from the Group of High Resolution Sea Surface Temperature (GHRSST) revealed to consistently capture the temperature signal in Sines area. For the aquaculture surroundings, given the high industrialization of the region and, in this case, the presence of a hot water discharge from a thermoelectric powerplant south of the production, the use of this product requires caution to not misinterpret data contamination. This highlights the need to have knowledge of the study region in order to minimize possible error inducers in analyzes with satellite products. The necessity of high spatial and temporal resolution products to monitor coastal areas is therefore underlined, as well as the complementarity of remote sensing and in situ approaches

Assessment of novel algal biomass sources as potential ingredients in diets for tilapia (Oreochromis niloticus)

The aquaculture sector is currently seeking alternative feed ingredients to ensure future socioeconomic and environmental sustainability; microalgae sources are seen to be a promising option. Two nutrition trials were conducted in order to assess substituting plant based protein sources in diets for juvenile Nile tilapia (Oreochromis niloticus), with a range of inclusion levels of two proprietary defatted microalgae samples (Nannochloropsis sp. and Chlorella sp.). The experimental algal ingredients utilised were by-products sourced from a pilot-scale biofuel operation. In both trials all experimental algal diets, along with their respective algal free controls, were isonitrogenous and isoenergetic. Fish growth performance, feed utilisation, biological indices, body composition, haematological parameters, histological appraisal of liver and the gastro-intestinal tract and assessment of epithelial skin colouration were evaluated. In trial 1, the final weight gain, specific growth rate, feed conversion ratio, biological indices and survival rate of fish were not affected by Nannochloropsis sp. supplementation (p>0.05). Carcass composition analysis indicated that fish Nannochloropsis (5%, 10% and 15%) had significantly lower body protein and lipid levels. Significantly elevated white blood cell counts, intestinal mucosal fold length and increased hepatocyte nuclei density were observed in fish fed the 15% inclusion. Using a novel photographic application method, 10% and 15% inclusion levels were observed to significantly modulate red spectrum pigmentation. In trial 2, all growth performance, feed utilisation and biological indices investigated showed significant differences at 60% inclusion of Chlorella sp. (p<0.05) with no significant differences in survival compared to control diets. Carcass composition revealed 60% inclusion significantly lowered fish body protein and lipid content, with ash increasing. Significantly elevated granulocyte counts were discovered at 30% and 60% Chlorella sp. inclusion. All algal supplemented diets (15%, 30% and 60%) indicated a significant increase in mid-intestine surface area. Significant increase of hepatocyte nuclei density was also observed in fish fed the 60% inclusion. No amplification of skin colouration was observed in this second trial. These studies indicate great potential for below 15% level inclusions of dried microalgae meal as a by-product from the biotechnology sector; particularly with regards to immunomodulation and promoting external pigmentation, applicable to commercial foodfish and ornamentals alike