World Aquaculture Magazine - March 2021

34 MARCH 2021 • WORLD AQUACULTURE • WWW.WA S .ORG a specific site has the greatest and most persistent effect on the overall success of the farm and on its surrounding environment. It should be made carefully, based on the best-available information and taking into account a wide range of considerations. Location criteria vary widely among farmed species and culture systems but, in general, the location should be well suited for the purpose and have the carrying capacity necessary to process the system’s wastes. Water supply and discharge are of paramount importance, as are the climate and the support infrastructure. Land-based projects require adequate soil structure and topography. Siting marine farms is a special case where proper location greatly affects waste disposal and assimilation. Ocean farm locations require a specific set of characteristics regarding water currents, depth, distance from the coast and absence of conflicting activities. Sophisticated siting tools that take these and other factors into account are available for ocean farm siting. When proper guidelines are followed, water quality and bottom impacts are avoided or greatly minimized (Nash et al . 2005, Phillips 2005). Many countries have identified, studied and pre-permitted small, well-defined geographic areas as appropriate for marine aquaculture and projects benefit from locating farms in these designated areas. Producers should establish an initial quantitative baseline of the main environmental variables of a proposed site and its surroundings and then design and implement a monitoring program to track variation. Aquaculture projects require taking market considerations into account for the site-selection process. Distance to market (and thereby transportation costs and carbon footprint) is a consideration of growing importance. 3. Use smart intensification to make the most efficient use of resources. In the past, low-intensity aquaculture was identified with environmental sustainability because of the association between extensive farming and natural productivity. Although non-fed extractive aquaculture is common practice and a sustainable way of producing aquatic species, this extensive approach makes sense until one considers and quantifies the use of finite resources by the different levels of intensification. Increasingly, more intensive systems are viewed as a sustainable alternative because of their lower footprint and more efficient use of resources. The type of farming system largely determines the environmental effects of the operation. Intensive systems make very efficient use of land and thus minimize habitat conversion. Intensification makes sense when the added resources of capital, feed and energy are amortized over the increased production in such a way that resource use per unit of product is lower than in more extensive systems. Intensive systems are akin to precision agriculture and can be friendlier to the environment due to their more efficient use of resources per unit weight (Boyd et al . 2017, Boyd et al . 2018). More efficient production represents a clear value proposition for producers; less land, water, energy, and/or feed per unit of production can result in higher profits (Engle et al . 2017). Stocking densities and feeding regimes should be such that they do not exceed the system’s capacity to process the resulting wastes. Adding mechanical aeration to aquaculture systems improves their carrying capacity by increasing oxygen and water circulation and is often the first and most effective means of intensification. By progressively increasing aeration, feeding and good management protocols, pond aquaculture systems can increase outputs by up to one order of magnitude. Central to the idea of smart intensification are water treatment and reuse technologies to minimize the use and discharge of water to the environment. Recirculating Aquaculture Systems (RAS) still involve high capital equipment and energy costs, but cheaper and energy-efficient systems continue to be developed and refined. These technologies incorporate enhanced control of the variables that affect production and make the culture environment more resilient and predictable. Although the cost of energy and the amortization of initial capital remain challenges, they may represent the future of sustainability in aquaculture. Biofloc aquaculture is another technology that allows intensification by promoting the development of bacterial flocs that assimilate nitrogenous wastes into bacterial biomass and thus detoxify the water while creating an additional food source. Bioflocs provide a cheaper alternative to RAS but can also create additional management challenges. 4. Use improved feeds and feeding techniques. Aquaculture feeds have improved significantly over the last two decades. Better formulation improves the feed’s nutrient content and digestibility while enhanced physicochemical properties decrease waste and improve the assimilation of those nutrients. Dependence of aquaculture feeds on finite resources such as wild- origin fishmeal and fish oil has long been recognized as a major sustainability issue and possible limitation to the growth of farming of highly valuable carnivorous species (Kristofferson and Anderson 2006). Research over the last decade has resulted in a reduction of the inclusion levels of fishmeal in aquafeeds for carnivorous species from >50 percent to as low as 15 percent (FAO 2012, Tacon 2018). Partial replacement or complete substitution of fishmeal and fish oil with renewable ingredients and by-products is one of the most active areas of research in aquaculture nutrition. Alternatives include soybean meal, cottonseed meal, by-products from corn and wheat, legumes, algae, by-products of fermentation and insect-based meals. Feed management is another area that deserves interest. It New farming systems strive for sustainability.