This chapter describes the application and optimization of the recirculating aquaculture systems (RAS) technology in the marine sector, in particular the development of urban recirculating mariculture for high-value marine fish. The system's performance and economic feasibility were tested in a pilot urban mariculture programme in the city of Baltimore (Maryland, USA), studying the Mediterranean gilthead seabream (Sparus aurata [Pagrus aurata]) as its candidate species. This fish, a non-native species in North America, commands a local retail price of up to US$20/kg. The Baltimore Urban Recirculating Mariculture System was designed to produce high-value marine fishes that cannot be farmed in net-pens or ponds, to use municipal pre-existing infrastructure and services, to have the ability to locate anywhere and to maximize the re-use of water. The life support system consisted of a particle removal microscreen drum filter, a moving bed nitrifying reactor, an ozone-based protein skimmer and a low head oxygenation unit. Conditioned artificial seawater was automatically delivered to provide the desired salinity and temperature. pH, ozone levels and photoperiod were continuously monitored and adjusted. Strict biosecurity was achieved by disinfecting all waste effluents before their discharge to the municipal sanitary sewer. Using this system, gilthead seabream of two strains were grown from 0.5 to 400 g commercial size in 268 days (first strain) and to 410 g in 232 days (second strain). Survival rates exceeded 90% and food conversion rates varied from 0.87 to 1.89, depending on fish growth. Growing densities ranged from 44 to 47 kg/m3 at 7-10% daily water exchange rates. Total ammonia and nitrite levels remained significantly below stressful concentrations. To increase the economic feasibility of the system, microbial communities associated with biofiltration were studied in an effort to improve nitrogen removal and thus maximize re-use of the saltwater. New bacterial-mediated nitrogen removal processes are described herein and addition of an anaerobic denitrification unit was also studied, both of which enhanced the ability to minimize saltwater discharge. The environmentally compatible recirculating mariculture pilot system described here can be scaled up to cost-effectively produce high-value marine fish in an urban setting.

The development and expansion of a viable marine shrimp-farming industry in the USA has been a goal of the US Marine Shrimp Farming Program research consortium for many years. Production research has focused on the development of systems for open pond culture, and a small but stable industry has developed based on these technologies. New advances have facilitated the intensification of production, reduction or elimination of water exchange, application of biosecurity protocols and stocking of high-health and genetically improved shrimp, all of which currently serve as the foundation for the US shrimp-farming industry. Based on these research advances, consortium scientists have shifted resources over the past few years to re-evaluate super-intensive raceway production technologies. At the Waddell Mariculture Center (WMC) in South Carolina, and the Oceanic Institute (OI) in Hawaii, prototype and pilot-scale systems have been operated over the past 3 years. In recent WMC trials, production of up to 3 kg/m2 was demonstrated with survival ranging from 55 to 71%, and harvest sizes from 14.6 to 17.1 g in 137 days. At harvest, production results for the latest trial based on the stocking of nursed 1 g juveniles were: survival=91%; mean weight=16.6 g; FCR=1.54; mean growth/week=1.44 g; and yield=4.50 kg/m2. At OI, three trials have been conducted with increasing stocking densities ranging from 100 to 300/m2. In the most recent 85-day trial, juvenile shrimp (∼2 g) grew to a harvest weight of 19.9 g with a mean growth rate of 1.47 g/week. Productivity of the system reached 5.2 kg/m2 and survival was 86.3%. All of these trials are based on high-output, minimal water usage, enclosed raceway designs that assure biosecurity and provide excellent potential for application in non-traditional, urban and/or contaminated environments. The demonstration trials described in this chapter, along with supporting research on breeding, microbial dynamics, feeds, engineering, financial feasibility and marketing, have brought these technologies to the point of commercialization. Urban and peri-urban application of these technologies in the USA could offer opportunities for the development of integrated marketing initiatives to improve the outlook for financial viability.

Informal reuse of waste water in aquaculture is widespread in parts of Asia, although there has been limited introduction of formally designed and engineered systems. As there is interest in assessing the contribution of wastewater-fed aquaculture to the development of sustainable cities, a multidisciplinary typology is presented of factors to consider (i.e. associated sanitation technology, aquaculture systems, disposal of produce and effluent, and institutional aspects). An overview is also presented of the global occurrence of waste water-fed aquaculture. Although most extant systems are threatened or in decline, waste water-fed aquaculture has potential, as indicated by the recent introduction of schemes in Bangladesh and India. Design criteria are presented for the maximum production of fish safe for human consumption with minimal treatment of waste water, and for the production of tilapia and duckweed as high-protein animal feed.

In the last 20 years K-12 aquaculture education has moved from its place as an extension of vocational agriculture in the United States to having solidified itself as an integral part of environmental, biological and research-related courses in classrooms across the USA. This attention to aquaculture in the classroom has been driven in large part through support by government agencies like the National Council for Agriculture Education, the US Department of Agriculture and the National Science Foundation, and other entities such as aquaculture industry, university outreach and education programmes, regional and state boards of education, and fishery management organizations. References give indications that aquaculture is an effective teaching tool (Caldwell, 1998) and students are highly motivated to learn in an environment that includes aquaculture (Wigenbach et al., 1999). This chapter presents an overview of the role of aquaculture in the education of our youth, and how technology has increased the quality of such an educational experience for students involved in research projects.

A working definition for urban aquaculture is presented that invokes concepts of land use planning, notions of urbanism, where trade links and markets, nucleated settlements, administrative organizations and specialist labour guilds are considered indicative of urban communities, and encompasses aquaculture closely linked with industrial activity. Early examples of 'proto-urban aquaculture' developed in association with Roman villas, monasteries, castles, manors and millponds are described, and important factors in the emergence of such practices, including technological advancement, demonstration of social status, declining or unreliable capture fisheries, growing market demand for aquaculture products and use of unexploited resources by entrepreneurs assessed. Pressures and events that contributed to the abandonment of these systems, notably the contraction and eventual fall of the Roman Empire, and economic decline and depopulation in the medieval period, are reviewed. Following this historical enquiry, pertinent accounts relating to contemporary urban aquaculture operations throughout Europe are presented, including production in intensively managed recirculation units, horizontally integrated marine aquaculture facilities and systems exploiting industrial by-products, in particular thermal effluents. This review suggests factors underlying the emergence of contemporary urban aquaculture are similar to those that gave rise to proto-urban systems. However, drawing on lessons learned regarding earlier declines, when considering prospects for contemporary urban aquaculture in Europe, it is recommended that a systems-based perspective is adopted.