Digital library

  • Management of productivity, environmental effects and profitability of shellfish aquaculture — the Farm Aquaculture Resource Management (FARM) model

    This paper describes a model for assessment of coastal and offshore shellfish aquaculture at the farm-scale. The Farm Aquaculture Resource Management (FARM) model is directed both at the farmer and the regulator, and has three main uses:

    (i)prospective analyses of culture location and species selection; (ii) ecological and economic optimisation of culture practice, such as timing and sizes for seeding and harvesting, densities and spatial distributions (iii) environmental assessment of farm-related eutrophication effects (including mitigation).

    The modelling framework applies a combination of physical and biogeochemical models, bivalve growth models and screening models for determining shellfish production and for eutrophication assessment. FARM currently simulates the above interrelations for five bivalve species: the Pacific oyster Crassostrea gigas, the blue mussel Mytilus edulis, the Manila clam Tapes phillipinarum, the cockle Cerastoderma edule and the Chinese scallop Chlamys farreri. Shellfish species combinations (i.e. polyculture) may also be modelled. We present results of several case studies showing how farm location and practice may result in significant (up to 100%) differences in output (production).

    Changes in seed density clearly affect output, but (i) the average physical production decreases at higher densities and reduces profitability; and (ii) gains may additionally be offset by environmental costs, e.g. unacceptable reductions in dissolved oxygen. FARM was used for application of a Cobb–Douglas function in order to screen for economically optimal production: we show how marginal analysis can be used to determine stocking density.

    Our final case studies examine interactions between shellfish aquaculture and eutrophication, by applying a subset of the ASSETS methodology. We provide a tool for screening various water quality impacts, and examine the mass balance of nutrients within a 6000 m2 oyster farm. An integrated analysis of revenue sources indicates that about 100% extra income could be obtained by emissions trading, since shellfish farms are nutrient sinks. FARM thus provides a valuation methodology useful for integrated nutrient management in coastal regions.

     

    Author(s): J.G. Ferreira, A.J.S. Hawkins, S.B. Bricker

  • Maldives sea cucumber farming experience

    With recent technological developments and the increasingly intensive interest in tropical sea cucumber farming, it is an opportune time to review the existing strategies of the first successful commercial hatchery in the Republic of Maldives (the Maldives). This may help to understand the success of the hatchery and grow-out operations. This paper analyses the strategies used in the production and grow-out of the commercially important sea cucumber Holothuria scabra, and their effects on the local communities and the environment in the Maldives. Holothuria scabra has been cultured in the Maldives since 1996. Hatchery production techniques consistently produce high-quality juveniles. When the juveniles reach 2–3 cm in size, they are transferred to nearby company-owned atoll lagoons for further growth. The sea cucumber grow-out period varies between 12 and 18 months in these waters. In addition to the company’s own sea cucumber grow-out operation, considerable quantities of juveniles are grown, with similar grow-out periods, by contract growers and villagers from the nearby islands. When the sea cucumbers are fully grown (350–425 g), the local growers sell them back to the company and are paid a management fee according to the duration of care and quantity of the product. The participation of the local community and village groups is one of the reasons for the ongoing success of sea cucumber culture in the Maldives. Sea cucumber hatchery production is a profitable operation in the Maldives, even though the cost of production per juvenile is higher due to the remote location and associated higher energy and transportation costs.

    Author(s): Grisilda Ivy Walsalam, Beni G.D. Azari

  • Macroalgal germplasm banking for conservation, food security, and industry

    Ex situ seed banking was first conceptualized and implemented in the early 20th century to maintain and protect crop lines. Today, ex situ seed banking is important for the preservation of heirloom strains, biodiversity conservation and ecosystem restoration, and diverse research applications. However, these efforts primarily target microalgae and terrestrial plants. Although some collections include macroalgae (i.e., seaweeds), they are relatively few and have yet to be connected via any international, coordinated initiative. In this piece, we provide a brief introduction to macroalgal germplasm banking and its application to conservation, industry, and mariculture. We argue that concerted effort should be made globally in germline preservation of marine algal species via germplasm banking with an overview of the technical advances for feasibility and ensured success.

    Author(s): Yarish, Charles Filipe Alberto, Sergey Nuzhdin, Maddelyn Harden, Simona Augyte, Rachael Wade

  • Macroalgae for Functional Feed Development: Applications in Aquaculture, Ruminant and Swine Feed Industries

    Plant and animal derived products are the main ingredients currently used by the feed industry to produce concentrate feed. There is a need of novel feed ingredients to meet the demand of high quality products by the aquaculture, ruminant and swine production systems, together with the challenge of implementing new sustainable and environmentally friendly processes and ingredients demanded by the modern society. Macroalgae are a large and diverse group of marine organisms that are able to produce a wide range of compounds with unique biological properties. This chapter discusses the incorporation of macroalgae or macroalgal derived ingredients as a source of both macro-nutrients (i.e. proteins, polysaccharides and fatty acids) and micro-nutrients (i.e. minerals and pigments) for animal feed production. The biological health benefits of the macroalgal ingredients beyond basic nutrition for the development of functional feed in the aquaculture, the ruminant and the swine sectors are also discussed together with the industrial challenges of its application. 

    Author(s): Marta Miranda, Marta López-Alonso, Marco García-Vaquero

  • Macroalgae as a sustainable aquafeed ingredient

    Macroalgae, commonly known as seaweed, offer a novel and added-value dietary ingredient in formulated diets for fish. Production of biomass can be achieved without reliance on expensive arable land, as seaweed may be collected from coastal regions or farmed. There are three taxonomic groups represented by the term ‘macroalgae’: Rhodophyta (red), Chlorophyta (green), and Phaeophyta (brown). Like terrestrial plants, nutritional content in macroalgae can vary greatly among species, genera, divisions, seasons and locations. Aside from their basic nutritional value, seaweeds contain a number of pigments, defensive and storage compounds, and secondary metabolites that could have beneficial effects on farmed fish. This review appraises the beneficial qualities of these macroalgae compounds and their potential for exploitation in commercial finfish feeds. The current knowledge of the effects of macroalgae inclusion in finfish diets is also addressed. From these >50 fish feeding studies that were analysed, enhancing trends in fish growth, physiology, stress resistance, immune system, and fillet muscle quality were reported. However, only a small fraction of algal species have so far been investigated as potential components in finfish diets, and furthermore, this review has identified a number of knowledge gaps that current research has yet to address. To conclude, an appraisal is made of the possible technologies employed to exploit seaweeds to an industrial level through stabilising the algal meal, enhancing the digestibility and functional food properties. 

    Author(s): Alex H. L. Wan, Simon J Davies, Anna Soler-Vila, Richard Fitzgerald, Mark P Johnson

  • Macroalgae as a Source of Valuable Antimicrobial Compounds: Extraction and Applications

     In the last few decades, attention on new natural antimicrobial compounds has arisen due to a change in consumer preferences and the increase in the number of resistant microorganisms. Macroalgae play a special role in the pursuit of new active molecules as they have been traditionally consumed and are known for their chemical and nutritional composition and their biological properties, including antimicrobial activity. Among the bioactive molecules of algae, proteins and peptides, polysaccharides, polyphenols, polyunsaturated fatty acids and pigments can be highlighted. However, for the complete obtaining and incorporation of these molecules, it is essential to achieve easy, profitable and sustainable recovery of these compounds. For this purpose, novel liquid–liquid and solid–liquid extraction techniques have been studied, such as supercritical, ultrasound, microwave, enzymatic, high pressure, accelerated solvent and intensity pulsed electric fields extraction techniques. Moreover, different applications have been proposed for these compounds, such as preservatives in the food or cosmetic industries, as antibiotics in the pharmaceutical industry, as antibiofilm, antifouling, coating in active packaging, prebiotics or in nanoparticles. This review presents the main antimicrobial potential of macroalgae, their specific bioactive compounds and novel green extraction technologies to efficiently extract them, with emphasis on the antibacterial and antifungal data and their applications

    Author(s): Aurora Silva, Sofia A. Silva, M. Carpena, P. Garcia-Oliveira, P. Gullón, M. Fátima Barroso, J. Simal-Gandara, M.A. Prieto

  • Low algal diversity systems are a promising method for biodiesel production in wastewater fed open reactors

    Planktivorous fish which limit zooplankton grazing have been predicted to increase algal biodiesel production in wastewater fed open reactors. In addition, tanks with higher algal diversity have been predicted to be more stable, more productive, and to more fully remove nutrients from wastewater. To test these predictions, we conducted a 14-week experiment in Houston, TX using twelve 2,270-L open tanks continuously supplied with wastewater. Tanks received algal composition (monocultures or diverse assemblage) and trophic (fish or no fish) treatments in a full-factorial design. Monocultures produced more algal and fatty acid methyl ester (FAME) mass than diverse tanks. More than 80% of lipids were converted to FAME indicating potentially high production for conversion to biodiesel (up to 0.9 T ha-1 y-1). Prolific algal growth lowered temperature and levels of total dissolved solids in the tanks and increased pH and dissolved oxygen compared to supply water. Algae in the tanks removed 91% of nitrate-N and 53% of phosphorus from wastewater. Monocultures were not invaded by other algal species. Fish did not affect any variables. Our results indicated that algae can be grown in open tank bioreactors using wastewater as a nutrient source. The stable productivity of monocultures suggests that this may be a viable production method to procure algal biomass for biodiesel production.

    Author(s): Meenakshi Bhattacharjee, Evan Siemann

  • Little Fish, Big Impact

    Forage fish play a crucial role in marine food webs in many ecosystems (Box 1.1). These small and medium-sized pelagic species are the primary food source for many marine mammals, seabirds, and larger fish, transferring energy from plankton to larger predators. Forage fish are also important predators in marine ecosystems, feeding upon phytoplankton, zooplankton, and, in some cases, the early life stages of their predators.

    Forage fish play an intermediary role in many marine ecosystems, including estuaries, shelf seas, upwelling, and open ocean systems occurring from the tropics to the Earth’s poles. They constitute the majority of prey upon which some predators depend. Such highly dependent predators may be iconic or ecologically important, while others may be commercially or recreationally valuable fish species. In some cases, highly dependent predators may include threatened or endangered species. A reduction in available prey—because of fishing, environmental conditions, or a combination of both—can have direct and lasting impacts and can fundamentally change the structure and functioning of an ecosystem.

    Author(s): Ellen K. Pikitch, P. Dee Boersma, Ian L. Boyd, David O. Conover, Philippe Cury, Tim Essington, Selina S. Heppell, Edward D. Houde, Marc Mangel, Daniel Pauly, Éva Plagányi, Keith Sainsbury, Robert S. Steneck, Christine Santora

  • Life Cycle Assessment of Seaweed Cultivation Systems

    Life cycle assessment (LCA) is a holistic methodology that identifies the impacts of a production system on the environment. The results of an LCA are used to identify which processes can be improved to minimize impacts and optimize production.

    LCA is composed of four phases: (1) goal and scope definition, (2) life cycle inventory analysis, (3) life cycle impact assessment, and (4) interpretation.

    The goal and scope define the purpose of the analysis; describe the system and its function, establish a functional unit to collect data and present results, set the system boundaries, and explain the assumptions made and data quality requirements. Life cycle inventory analysis is the collection, processing and organization of data. Life cycle impact assessment associates the results from the inventory phase to one or multiple impacts on environment or human health. The interpretation evaluates the outcome of each phase of the analysis. In this phase the practitioner decides whether it is necessary to amend other phases, e.g., collection of more data or adjustments of goal of the analysis. In the interpretation, the practitioner draws conclusions, exposes the limitations, and provides recommendations to the readers.

    The quality of LCA of seaweed production and conversion is based on data availability and detail level. Performing an LCA at the initial stage of seaweed production in Europe is an advantage: the recommended design improvements can be implemented without significant economic investments. The quality of LCA will keep improving with the increase of scientific publications, data sharing, and public reports.

    Author(s): Michele Seghetta , Pietro Goglio

  • Life cycle assessment of seaweed biomethane, generated from seaweed sourced from integrated multi-trophic aquaculture in temperate oceanic climates

    Biomethane produced from seaweed is a third generation renewable gaseous fuel. The advantage of seaweed for biofuel is that it does not compete directly or indirectly for land with food, feed or fibre production. Furthermore, the integration of seaweed and salmon farming can increase the yield of seaweed per hectare, while reducing the eutrophication from fish farming. So far, full comprehensive life cycle assessment (LCA) studies of seaweed biofuel are scarce in the literature; current studies focus mainly on microalgal biofuels. The focus of this study is an assessment of the sustainability of seaweed biomethane, with seaweed sourced from an integrated seaweed and salmon farm in a north Atlantic island, namely Ireland. With this goal in mind, an attributional LCA principle was applied to analyse a seaweed biofuel system. The environmental impact categories assessed are: climate change, acidification, and marine, terrestrial and freshwater eutrophication. The seaweed Laminaria digitata is digested to produce biogas upgraded to natural gas standard, before being used as a transport biofuel. The baseline scenario shows high emissions in all impact categories. An optimal seaweed biomethane system can achieve 70% savings in GHG emissions as compared to gasoline with high yields per hectare, optimum seaweed composition and proper digestate management. Seaweed harvested in August proved to have higher methane yield. August seaweed biomethane delivers 22% lower impacts than biomethane from seaweed harvested in October. Seaweed characteristics are more significant for improvement of biomethane sustainability than an increase in seaweed yield per unit area.

    Author(s): Magdalena M. Czyrnek-Delêtre, Stefania Rocca, Alessandro Agostini, Jacopo Giuntoli, Jerry D. Murphy

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