Pilot scale field cultivation of the agar yielding red alga Gracilaria edulis was carried out at Vadakadu near Rameswaram from July, 2001 to July, 2002 involving the local fisher folk. The growth of plants during July, 2001 to January, 2002 was good and they reached harvestable size of 19.6 to 28.9 cm (mean length) after 60 to 80 days growth and harvests were made. The seed material introduced during March to July, 2002 degenerated due to turbid seawater, sedimentation and high seawater temperature. Data collected on environmental and hydrological parameters from the culture site at fortnightly intervals were correlated with the growth of cultured seaweed. The results obtained in this experiment revealed that commercial scale cultivation of G. edulis could be done successfully in the nearshore area of Vadakadu during the period July to January.
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The Plant Products in Aquafeed Working Group is an informal group of international experts working collaboratively to conduct research and develop support for research to optimize the use of plant feedstuffs in aquaculture diets.
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HIGHLIGHTS
1. Global aquaculture production continues to increase, whilst capture fisheries stagnate. Many wild fisheries have been overexploited. Cultivation, if managed sustainably, is a viable alternative.
2. The seaweed industry is undergoing a rapid global expansion and currently accounts for ~49% of the total mariculture production. Unabated exponential growth in the last 50 years has meant that the value of the industry reached US$6.4 billion in 2014, providing jobs, predominantly in developing and emerging economies.
3. There is increasing need to address new challenges imposed by trade and market demand. Case studies clearly show that
valuable lessons can be drawn from the major seaweed-producing nations and other aqua- and agriculture sectors.
4. Improving biosecurity, disease prevention and detection measures are critical, together with establishing policies and institutions. This will provide incentives and steer the long-term economic and environmental development of a sustainable seaweed aquaculture industry.
5. This policy brief highlights key issues that need to be addressed to create longterm sustainability of this emerging global industry, as it prepares itself for playing an important role in the ‘blue’ ocean economy agenda. -
Eulittoral seaweeds at different tidal elevations are exposed to various frequencies and durations of emergence. Their physiological activities (e.g. nutrient uptake) may be affected by water loss during emersion. We used three Porphyra species from different tidal elevations to test whether species at different vertical elevations on the shore respond differently to the increasingly non-marine environment, in terms of their physiological activities including nutrient uptake, tissue carbon, nitrogen and phycoerythrin contents. Simulated tidal cycles produced water losses of 0%, 40±10% and 90±5% tissue water. Emersion was stressful for all species regardless of their habitat. It was more stressful to nitrate and phosphate uptake for the sublittoral species P. yezoensis than eulittoral species, P. umbilicalis and P. leucosticta. Interestingly, tissue N for thalli that had been emerged and then re-submerged was significantly higher than those of continuously submerged individuals. During exposure, tissue N contents of all species declined but recovered quickly (e.g. within 30 min) after re-submergence. This result suggests that emersion-induced N release may constitute an undescribed biogeochemical pathway linking marine, terrestrial, and atmospheric N reservoirs.
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Seaweeds offer a natural source of antimicrobials that may help curb antibiotic resistance in livestock. The antibacterial activity of phlorotannin extracts isolated from two brown seaweeds Ascophyllum nodosum and Fucus serratus was tested. The mechanism of action of phlorotannin extracts against Escherichia coli O157, Salmonella agona, and Streptococcus suis was elucidated by observing cell membrane permeability and intracellular adenosine triphosphate (ATP). The two extracts were effective at killing three foodborne pathogens without negatively affecting the pig intestinal cells. A. nodosum minimum inhibitory concentration (MIC) range for the different pathogens was between 1.56 and 0.78 mg/mL, whereas F. serratus was 3.13 mg/ mL for all pathogens tested. A. nodosum was found to be much more potent compared to F. serratus. The difference in potency in the seaweeds may be a result of the phlorotannins’ structural linkages. The antimicrobial properties of the seaweed extracts tested may provide alternative and complementary treatments to antibiotics and zinc oxide in animal feeds. The seasonal screening was performed on both species to assess the availability of phenolics throughout the year using two quantification methods, the Folin− Ciocalteu (FC) assay and quantitative nuclear magnetic resonance (NMR). The variation between the methods highlights the challenges involved in the quantification of complex phenolic structures. However, both methods show that the phenolics are subject to seasonal variation, which may prove problematic to the animal feed industry.
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Background: Marine Enteromorpha polysaccharides (EPPs) have been reported to present various physiological and bioactivities based on their specific chemical structures, such as monosaccharide compositions and glycosidic linkages. Scope and approach: However, the structure-activity relationship of Enteromorpha polysaccharides is mostly unknown. This review aims to provide a brief summary of structural, functional, and chemical characteristics of Enteromorpha polysaccharides. Key findings and conclusions: Modified Enteromorpha polysaccharides have several powerful bioactive functions. Sulfated EPPs with lower molecular weights were found to exhibit excellent immune-relevant and antioxidant activities. Carboxymethylated, hydroxamated, phthaloyl, and acetylated derivatives also showed significantly enhanced antioxidant and antibacterial activities as well as moisture absorbing capacities. EPPs were considered as novel natural agents, exhibiting outstanding druggable effects compared with ordinary drugs. However, the structure-function relationships of them are yet to be clearly established. The purpose of this overview is focusing on the current advances in the structural characterization, biological activities and mechanisms of action of Enteromorpha polysaccharides.
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In this study the efficacy of using marine macroalgae as a source for polyunsaturated fatty acids, which are associated with the prevention of inflammation, cardiovascular diseases and mental disorders, was investigated. The fatty acid (FA) composition in lipids from seven sea weed species from the North Sea (Ulva lactuca, Chondrus crispus, Laminaria hyperborea, Fucus serratus, Undaria pinnatifida, Palmaria palmata, Ascophyllum nodosum) and two from tropical seas (Caulerpa taxifolia, Sargassum natans) was determined using GCMS. Four independent replicates were taken from each seaweed species. Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs), were in the concentration range of 2-14 mg/g dry matter (DM), while total lipid content ranged from 7-45 mg/g DM. The n-9 FAs of the selected seaweeds accounted for 3%-56% of total FAs, n-6 FAs for 3%-32% and n-3 FAs for 8%-63%. Red and brown seaweeds contain arachidonic (C20:4, n-6) and/or eicosapentaenoic acids (EPA, C20:5, n-3), the latter being an important "fish" FA, as major PUFAs while in green seaweeds these values are low and mainly C16 FAs were found. A unique observation is the presence of another typical "fish" fatty acid, docosahexaenoic acid (DHA, C22:6, n-3) at ≈ 1 mg/g DM in S. natans. The n-6: n-3 ratio is in the range of 0.05-2.75 and in most cases below 1.0. Environmental effects on lipid-bound FA composition in seaweed species are discussed. Marine macroalgae form a good, durable and virtually inexhaustible source for polyunsaturated fatty acids with an (n-6) FA: (n-3) FA ratio of about 1.0. This ratio is recommended by the World Health Organization to be less than 10 in order to prevent inflammatory, cardiovascular and nervous system disorders. Some marine macroalgal species, like P. palmata, contain high proportions of the "fish fatty acid" eicosapentaenoic acid (EPA, C20:5, n-3), while in S. natans also docosahexaenoic acid (DHA, C22:6, n-3) was detected.
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Gracilaria verrucosa was successfully cultivated in a pond based aquaculture system at Narakkal. Kerala. India. Daily growth rate of seaweed was found to be maximum (19.22%) during 60 days of introduction. The growth. pigment constituents and the yield of agar were influenced by the environmental parameters. Agar yield and photosynthetic pigments declined in the initial period up to 50 days due to acclimatization of the plants lo new environment which was collected from Chennai, India and introduced in the pond at 'Narakkal. After 60 days, the algae started establishing in the bottom of the pond and an initial harvest of 230.25 kg was harvested after 90 days of culture period. Further regular harvest was made at every 10 days interval yielding 1015 kg of Gverrucosa during the culture period. The agar content ranged between 7-14.8% and bottom sample exhibited better yield of. agar than the plants cultured in the floating raft.
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Sandfish (Holothuria scabra) is a high-value tropical sea cucumber widely distributed in the shallow waters of the Indo-Pacific. In New Caledonia, sandfish are locally called ‘gris’ and have been harvested since the 1840s. The WorldFish Center in New Caledonia grew cultured juvenile sandfish in earthen ponds to assess the potential for farming the species. In this paper, we report on pond culture grow-out of sandfish from small juveniles to market size in a 21-month trial. Sandfish in two ex-shrimp ponds reached mean weights of 390 and 441 g after 19 and 21 months, respectively. The overall average weight gains were estimated to be 0.60 g and 0.77 g per animal per day, and overall survival to be 69% and 41%, respectively. Some mortality occurred in ponds due to high water temperature and salinity. Beche-de-mer produced from the pond-grown sandfish had a darker skin colour and most was classified as grade-A, although cultured animals lost twice as much weight as the wild sandfish during processing. Positive features were the homogeneous sizes of pond-grown animals and the potential for reduced fluctuations in numbers. Recommendations for improving sandfish farming in ponds centre on the management of animal density and the practice of alternating earthen ponds.
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An assessment of the genetic diversity of marine populations is critical not only for the understanding and preservation of natural biodiversity but also for its economic potential. As commercial demand rises for marine resources, it is critical to generate baseline information for monitoring wild populations. Furthermore, anthropogenic stressors on the coastal environment, such as warming sea surface temperatures and overharvesting of wild populations, are leading to the destruction of keystone marine species such as kelps. In this study, we conducted a fine-scale genetic analysis using genome-wide high-density markers on Northwest Atlantic sugar kelp species, Saccharina latissima and putative species, Saccharina angustissima. The population structure for a total of 149 samples from the Gulf of Maine (GOM) and Southern New England (SNE) was investigated using AMOVA, Fst, admixture, and PCoA. Genome-wide association analyses were conducted for six morphological traits, and the extended Lewontin and Krakauer (FLK) test was used to detect selection signatures. Our results indicate that the GOM region is moderately more heterogeneous than SNE. While admixture was observed between regions, these results confirm that Cape Cod acts as a biogeographic barrier for sugar kelp gene flow. We detected one significant SNP (P-value=2.03x10-7) associated with stipe length, and 243 SNPs with higher-than-neutral differentiation. The findings of this study provide fundamental knowledge on sugar kelp population genetics for future monitoring, managing and potentially restoring wild populations, as well as assisting in selective breeding to improve desirable traits for cultivation and bioenergy production.
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Marine Agronomy Group, CAFNRM, UH-Hilo
200 W. Kawili st., HI 96720, USA
Contact: Marine.Agronomy.Group@gmail.com
Funding for this web portal is provided by the World Wildlife Fund and the University of Hawaii-Hilo.