Increasing biomass production yields is a critical challenge for macroalgae biorefineries. The continuous tumbling and mixing of free-floating algae through water or airflow has been shown to increase the productivity of algae in land-based cultivation systems. This approach has not been tested thoroughly in offshore cultivation. We report, here, a field feasibility study on the increase in green macroalga Ulva sp. growth rates in offshore cages, achieved by the combined effect of tumbling and mixing of the algae using influxes of water and air. The experimental system was tested in a shallow coastal area in central Israel, in the eastern Mediterranean Sea. A maximum daily growth rate of 19.2%, areal productivity of 33.72 g dry weight (DW) day−1 m−2, and volumetric yields of 37.78 g DW day−1 m−3, together with 38.47 ± 0.01% ash and 5.28% protein content on a dry matter basis were achieved in the cages with intensified cultivation in the first week of May 2017. Our study shows that cultivation with tumbling and mixing of biomass with air, and water exchange with the environment is a feasible method to increase Ulva sp. biomass productivity offshore.
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The Seaweed Consultant was hired by the FAO to assist the Ministry of Fisheries and Agriculture (MOFA) through the Oceanographic Society of Maldives (OSM) in introducing the Eucheuma (seaweed) farming technology at Gamu Island, Laamu atoll, Maldives.
Several prior attempts to introduce seaweed fanning in the Maldives had failed, mainly due to the problem of fish grazers. The farming technique used in the Philippines, Malaysia, Indonesia, and Tanzania (monoline system) could not be applied successfully in the Maldives due to the abundance of fish grazers which thrive in the lagoons.
When the consultant arrived in the Maldives in February 1996 for his first one-month technical assistance, he brought a sample of the net-bag propagule holders which he had devised in the Philippines to counter problems such as grazer attacks and losses due to turbulent weather. The floating net-bag technique is described in detail in the project field document No. 2. The new technique eliminated also the tedious process of tying every propagule to the monoline, thereby saving a lot of labour cost. When he visited the test station for the Eucheuma at Gamu island, he observed that the plants were almost consumed by the grazers since the propagules were cultured using the monoline system. The remaining plants were untied from the monoline and then brought to another site where the current was good and where the water motion was consistent. The five kilograms of cottonii which were salvaged were planted, placing them in 10 net-bags at the rate of 1/2 kilogram/bag. The propagule line containing the 10 net-bags was installed in the water in the selected area. After 15 days, the plants recovered and showed a good growth rate, which was computed to be 3-4% daily.
The seedlings in the net-bags were split continuously every month. Five hundred net-bags were procured to contain the rapidly increasing volume of seedstocks. By September, 1996, OSM reported that the seedling inventory was already 600 kilograms, requiring additional net-bags (35,000 pieces).
At this time the plant growth had increased to about 5-6% daily, which means that the biomass was doubling every 10-15 days.
In March, 1997, the Seaweed Consultant carried out his second one-month mission to evaluate the performance of the seaweed culture and to introduce the post-harvest technology to the project staff and workers.
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Since May this year, our once spotless beaches have undergone a virtual transformation in appearance, as considerable amounts of seaweed have taken over much of the seashore. The unattractive, though harmless, Sargassum seaweed has been washing upon our shores, especially the east coast, causing great concern across the island. Unsure about why the high proliferation is occurring or how long it is going to last, top professionals in the health, agricultural and ecological sectors have drawn on their vast expertise to see how to best deal with this natural phenomenon.
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Increasing consumer concern in greenhouse-gas (GHG) contributions from cattle is pushing the livestock industry to continue to improve their sustainability goals. As populations increase, particularly in low-income countries, the demand for animal-sourced foods will place further pressure to reduce emission intensity. Enteric methane (CH4) production contributes to most of the GHG from livestock; therefore, it is key to mitigating such emissions. Feed additives have primarily been used to increase animal productivity, but advances in understanding the rumen has resulted in their development to mitigate CH4 emissions. The present study reviewed some of the main feed additives with a potential to reduce enteric CH4 emissions, focusing on in vivo studies. Feed additives work by either inhibiting methanogenesis or modifying the rumen environment, such that CH4 production (g/day) is reduced. Feed additives that inhibit methanogenesis or compete with substrate for methanogens include 3-nitroxypropanol (3NOP), nitrates, and halogenated compounds containing organisms such as macroalgae. Although 3NOP and macroalgae affect methyl–coenzyme M reductase enzyme that is necessary in CH4 biosynthesis, the former is more specific to methanogens. In contrast, nitrates reduce CH4 emissions by competing with methanogens for hydrogen. However, nitrite could accumulate in blood and be toxic to ruminants. Rumen modifiers do not act directly on methanogens but rather on the conditions that promote methanogenesis. These feed additives include lipids, plant secondary compounds and essential oils. The efficacy of lipids has been studied extensively, and although supplementation with medium-chain and polyunsaturated fatty acids has shown substantial reduction in enteric CH4 production, the results have been variable. Similarly, secondary plant compounds and essential oils have shown inconsistent results, ranging from substantial reduction to modest increase in enteric CH4 emissions. Due to continued interest in this area, research is expected to accelerate in developing feed additives that can provide options in mitigating enteric CH4 emissions.
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Consequences of congeneric quantitative variation in secondary metabolites of seaweeds on diet specificity and host association in specialist marine her- bivores have received little attention. We investigated quantitative variation in caulerpenyne and oxytoxin 1 in 7 species of green seaweeds from the genus Caulerpa, along with the feeding preferences and host associations of 4 co-occurring sacoglossan molluscs. C. taxifolia and C. sertularioides contained high concen- trations of metabolites and were preferred least by all herbivores. Algae with intermediate metabolite con- centrations (C. racemosa, C. serrulata, and C. cupres- soides) were preferred by Elysia tomentosa and Lo- biger viridis. Oxynoe viridis and Stiliger smaragdinus had strong preferences for different low concentration Caulerpa species (C. racemosa var. laetevirens and C. lentillifera), suggesting not all feeding preferences are based exclusively on the major metabolites. In situ host associations of L. viridis and S. smaragdinus mirrored their feeding preferences, but this was not the case for E. tomentosa. Furthermore, those algal species with the highest and lowest metabolite concentrations had the lowest overall densities of sacoglossans. The results im- ply that the direct influence of quantitative variation in Caulerpa chemistry may only be limited to host associa- tions in some sacoglossans. However, feeding pressure from multiple herbivore species with unique prefer- ences could still contribute to variation in chemical defence amongst congeneric algae.
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In this Issue...
- Commercialization and Adoption of Snakehead Feed 1
- Strategies for Reducing Feed Costs in Small-Scale Aquaculture 2
- Goings On In the Pond 2
- Value Chain Analysis Helps Overcome Gender Barriers in Aquaculture 5
- AquaFish Student Corner: Graduate Student Profile 7
- AquaFish Alumni Corner: Where Are They Now? 9
- BMP Workshop, Tanzania 10
- SIRTD Award Closeout Meeting, Tanzania 11
- Chaza Cooperative Society, Tanzania 12
- PONDerings 13
- Notices of Publication 14
- Meetings and Events 18
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The President’s Global Hunger and Food Security Initiative, titled “Feed the Future (FTF)”, has the overarching goal of sustainably reducing global poverty and hunger (www.feedthefuture.gov). Providing sufficient food to the world’s growing population will require a 70 percent increase in agricultural production by 2050 (Bruinsma 2009). To meet this food security challenge under constraints of limited agricultural land availability and increased climatic variability, the world will need to support and develop scientific and technological innovations that increase agricultural productivity in an environmentally sound manner while improving the availability of nutritious foods.
The food price spikes of 2006-2008 and that are resurfacing today underscore the fragility of global food security, with recent estimates that nearly a billion people are food insecure (Shapouri 2010), affecting families in the United States and around the world. While the causes were many, the underlying challenges are clear: the world cannot achieve the Millennium Development Goals (http://www.un.org/millenniumgoals/) relating to hunger, poverty, health, gender and the environment when the growth of agricultural productivity and income stagnates or is otherwise insufficient. The global research portfolio, presented here, serves as an integral strategy within the broader Feed the Future Initiative.
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This report presents the latest thinking and new approaches to emerging and persistent challenges to achieve food security in the 21st century. It focuses on critical issues that have received less attention in the literature to date, such as: food waste, land acquisitions, gender aspects of agriculture, and early warning systems for agricultural emergencies. It also offers perspectives on how to better manage water and food linkages.
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The sea urchin, Mesocentrotus nudus, is widely distributed in North West Pacific regions. It has a substantial impact on macroalgal communities as a generalist herbivore. This study examined various aspects of its feeding ecology, including algal preference, foraging behaviors, and possible effects of past feeding history on its algal preference. We used six common algal species (Ulva australis, Undaria pinnatifida, Sargassum confusum, Dictyopteris divaricata, Grateloupia elliptica, and Grateloupia angusta) from the east coast of Korea as food choice in a series of indoor aquarium experiments. The first choice of starved M. nudus was exclusively U. pinnatifida, followed by G. elliptica and S. confusum. Unlike large urchins, small urchins equally preferred U. pinnatifida and G. elliptica. On the other hand, Undaria-fed urchins preferred to feed only G. elliptica, although its preference slightly differed over time. We then grouped sea urchins into three categories (starved, Undaria-fed, mixed species-fed) to observe 12-days feeding preference as well as early foraging movements. Foraging behaviors of the three groups were distinctively different, although they could not completely reflect the actual consumption. For example, U. australis was highly attractive, but rarely eaten. Undaria-fed urchins seemed to stay with only S. confusum and U. australis. This study demonstrates that M. nudus shows high flexibility in food preference depending on past feeding history and body size. Its foraging behaviors are also affected by past feeding conditions, exhibiting active chemoreceptive movements.
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We addressed the challenge for agriculture of doubling food production while halving the footprint in our 2010 Feeding the Future booklet. Aquaculture has an equivalent challenge, though providing a far smaller proportion of the food needed by nine billion people in 2050 it still can be an important contributor.
Seafood is widely appreciated as tasty and excellent nutrition. However, the ocean fi sheries cannot increase yields without destroying the fi sh stocks on which they depend. Aquaculture must bridge the gap between sustainable fi sheries and global demand. Having grown rapidly over the past four decades, aquaculture already provides a substantial proportion of the fi sh, crustaceans and molluscs we eat. As contributors to this booklet discuss, for continued growth we require greater sustainability.
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Marine Agronomy Group, CAFNRM, UH-Hilo
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