On the Health Benefits vs. Risks of Seaweeds and Their Constituents: The Curious Case of the Polymer Paradigm.

To exploit the nutraceutical and biomedical potential of selected seaweed-derived polymers in an economically viable way, it is necessary to analyze and understand their quality and yield fluctuations throughout the seasons. In this study, the seasonal polysaccharide yield and respective quality were evaluated in three selected seaweeds, namely the agarophyte Gracilaria gracilis, the carrageenophyte Calliblepharis jubata (both red seaweeds) and the alginophyte Sargassum muticum (brown seaweed). It was found that the agar synthesis of G. gracilis did not significantly differ with the seasons (27.04% seaweed dry weight (DW)). In contrast, the carrageenan content in C. jubata varied seasonally, being synthesized in higher concentrations during the summer (18.73% DW). Meanwhile, the alginate synthesis of S. muticum exhibited a higher concentration (36.88% DW) during the winter. Therefore, there is a need to assess the threshold at which seaweed-derived polymers may have positive effects or negative impacts on human nutrition. Furthermore, this study highlights the three polymers, along with their known thresholds, at which they can have positive and/or negative health impacts. Such knowledge is key to recognizing the paradigm governing their successful deployment and related beneficial applications in humans.

Invasive Seaweeds in the Iberian Peninsula: A Contribution for Food Supply.

The introduction of exotic organisms in marine ecosystems can lead to economic and ecological losses. Globally, seaweeds represent a significant part of these non-indigenous species (NIS), with 407 introduced algal species. Furthermore, the presence of NIS seaweeds has been reported as a major concern worldwide since the patterns of their potential invasion mechanisms and vectors are not yet fully understood. Currently, in the Iberian Peninsula, around 50 NIS seaweeds have been recorded. Some of these are also considered invasive due to their overgrowth characteristic and competition with other species. However, invasive seaweeds are suitable for industrial applications due to their high feedstock. Hence, seaweeds' historical use in daily food diet, allied to research findings, showed that macroalgae are a source of nutrients and bioactive compounds with nutraceutical properties. The main goal of this review is to evaluate the records of NIS seaweeds in the Iberian Peninsula and critically analyze the potential of invasive seaweeds application in the food industry.

Performance of the nile tilapia with varying daily feeding amounts, using a commercial diet / Desempenho da Tilápia do Nilo com variação diária de alimentação, usando dietas comerciais

In order to evaluate the performance of Nile tilapia (Oreochromis niloticus), daily feeding amounts were varied in an experiment following a completely randomized design for 154 days and consisting of four treatments with three replications each, totaling 12 tanks with 3 m3 (3 x 1 x 1 m) of area each at densities of 5 fish m-3 (initial) and 3 fish m-3 until the end of the experiment. Throughout the experimental period, the daily amount of feed was varied and delimited for each feeding time (8h00, 11h00, 14h00 and 17h00) as: 25; 25; 25 and 25% in daily treatment 1 - T1; 20; 30; 30 and 20% in treatment 2 - T2; 30; 20; 20 and 30% in daily treatment 3 - T3; and 20; 30; 20 and 30% in treatment 4 - T4. Feed was offered six days a week, with extruded isocaloric (1,412 KJ) and isoproteic (32% crude protein) diets from 2 to 4 mm. Every two weeks, a sample containing 30% of stocked individuals was collected in each replication to monitor fish growth. Nile tilapia (O. niloticus) fed in daily amounts of 20; 30; 20 and 30% showed a better growth performance in the final of experiment, mainly on biomass, final average weight and feed conversion.

Para avaliar o desempenho da tilápia do Nilo (Oreochromis niloticus), as quantidades diárias de alimentação foram variadas em um experimento após um delineamento inteiramente casualizado de 154 dias e consistindo em quatro tratamentos com três repetições cada, totalizando 12 tanques com 3 m3 (3 x 1 x 1 m) de área cada uma em densidades de 5 peixes m-3 (inicial) e 3 peixes m-3 até o final do experimento. Ao longo do período experimental, a quantidade diária de alimentos foi variada e delimitada para cada tempo de alimentação (8h00, 11h00, 14h00 e 17h00) como: 25; 25; 25 e 25% no tratamento diário 1 - T1; 20; 30; 30 e 20% no tratamento 2 - T2; 30; 20; 20 e 30% no tratamento diário 3 - T3; e 20; 30; 20 e 30% no tratamento 4 - T4. O alimento foi oferecido seis dias por semana, com dietas isocalóricas extrudadas (1.412 KJ) e isoprotéicas (32% de proteínas brutas) de 2 a 4 mm. A cada duas semanas, uma amostra contendo 30% de indivíduos estocados foi coletada em cada replicação para monitorar o crescimento do peixe. Tilápias do Nilo (O. niloticus) alimentadas em quantidades diárias de 20; 30; 20 e 30% mostraram um melhor desempenho de crescimento no final do experimento, principalmente na biomassa, peso médio final e conversão alimentar.

Cultivo da tilápia do nilo em tanques-rede circulares e quadrangulares em duas densidades de estocagem / Culture of nile tilapia in circulars and squares net cages in two stocking densities

O presente experimento avaliou o efeito da densidade de estocagem no desempenho zootécnico da tilápia do Nilo, Oreochromis niloticus, cultivada em tanques-rede circulares, com volume de 3,14 m3 e quadrangulares de 3,00 m3 . Foram utilizadas densidades de estocagem de 100 e 150 peixes m-3 (p. m-3) em ambos os tipos de tanques-rede como diferentes tratamentos, cada um com cinco repetições, com peixes apresentando pesos e comprimentos médios iniciais de 80,00±2,56 g e 15,25±0,18 cm, respectivamente. Durante o experimento (112 dias), os animais foram alimentados seis dias por semana e quatro vezes ao dia com ração extrusada balanceada contendo 32% de proteína bruta, numa taxa de 5,5% da biomassa até o peso médio dos indivíduos atingir 300 g e, a partir desse momento, foi gradativamente reduzida até 2,0% da biomassa, em duas refeições diárias, no final do experimento. Também foi realizada uma análise econômica do cultivo, em cada tratamento, levando em consideração os custos com os peixes, a ração e mãode-obra. A análise do peso médio final mostrou um desempenho em tanques-rede circulares na densidade de 100 p. m-3. O ganho de peso médio diário, a eficiência alimentar e a conversão alimentar aparente foram significativamente melhores em tanques-rede circulares na densidade de 100 p. m-3. Com este trabalho, foi demonstrado um melhor desenvolvimento da tilápia do Nilo em tanques-rede circulares, utilizando uma baixa densidade de estocagem. Além disso, a receita líquida, por quilo de peixe produzido, também foi maior nos tanques-rede circulares na menor densidade.

The present experiment evaluated the effect of stocking density on the zootechnical performance of Nile tilapia (Oreochromis niloticus) cultured in 3.14 m3 round net cages and 3.00 m3 square net cages. Stocking densities of 100 and 150 fish m-3 (f. m-3) and both types of net cages were used as different treatments each one with five repetitions, with initial fish weights and lengths average of 80.00±2.56 g and 15.25±0.18 cm, respectively. During the experiment (112 days), fish were fed six days a week and four times a day with a commercial balanced floating 32% crude protein ration by a 5.5% biomass feed rate until individuals main weight reach 300 g, and gradually reduced and administered two times a day from this moment until a biomass feed rate of 2.0% at the end of the experiment. An economic analysis of each treatment cultures also was done using fish, ration and hand-men work costs. Fish final mean weight analyses showed an improvement in 100 f. m-3 circular net cages. The fish average daily gain, food efficiency and apparent food conversion were significantly better in 100 f. m-3 circular net cages. With this work, it was demonstrated a better development of Nile tilapia in a low stocking density in round net cages. In addition, net income per kilogram of produced fish also was the highest in circulars low density net cages.

Cultivo da tilápia do nilo em tanques-rede circulares em diferentes densidades de estocagem / Cultivation of nile tilapia at different stocking densities in round net cages

O presente experimento avaliou o efeito da densidade de estocagem no crescimento em peso da tilápia do Nilo (Oreochromis niloticus), cultivada em tanques-rede circulares com volume de 3,14 m3 durante 112 dias. Foram utilizadas as densidades de estocagem de 100, 150 e 200 peixes m-3 como diferentes tratamentos, cada um com cinco repetições. Durante o experimento, os animais foram alimentados seis dias por semana, com ração extrusada balanceada contendo 32% de proteína bruta, sendo ofertada quatro vezes ao dia, à 5,5% da biomassa até o peso médio dosindivíduos atingir 300 g e, a partir desse momento foi gradativamente reduzida até 2,0% da biomassa no final do experimento, sendo ofertada em duas refeições diárias. Os pesos médios e desvios padrões finais foram de 0,65±0,22; 0,53±0,36 e 0,45±0,21 kg, para as densidades de 100, 150 e 200 peixes m-3, respectivamente. A análise dos dados mostrou um crescimento em peso significativamente maior para a densidade de 100 peixes m-3 (F=68,232; p<0,01), o que demonstra o melhor desenvolvimento da tilápia do Nilo em tanques-rede circulares, utilizando-se baixas densidades de estocagem.

The present experiment evaluated the effect of stocking density on the weight growth of Nile tilapia (Oreochromis niloticus) cultured in 3.14 m3 round net cages. Stocking densities of 100, 150 and 200 fish m-3 were used as different treatments each one with five repetitions. During all the experiment, fish were fed six days a week with a commercial balanced floating 32% crude protein ration, which was administered four times a day by a 5.5% biomass feeding rate until individuals main weight reach 300 g, and gradually reduced and administered twice a day from this moment until a biomass feeding rate of 2.0% at the end of the experiment. Final mean weights and standards deviations were 0.65±0.22; 0.53±0.36 e 0.45±0.21 kg for densities of 100, 150 and 200 fish m-3, respectively. Data analyses showed a significantly higher weight growth for the density of 100 fish m-3 (p<0.01; F=68.232) which demonstrate a better development of Nile tilapia in circular net cages using low stocking densities.