Rising consumer demand for seafood, a plateau in harvest of fisheries products from the wild, and the development of enabling technologies have driven rapid growth of the aquaculture sector over the past five decades. Aquaculture now accounts for over 50% of global fish production. The growth of aquaculture production has promoted human nutrition, gainful employment and regional economic growth. However, the rapid growth of aquaculture had led to concerns regarding its ecological sustainability. Key issues include conversion of ecologically critical freshwater and coastal ecosystems to farms, pollution and eutrophication of aquatic and marine ecosystems, heightened transmission of parasites and pathogens, overutilization of scarce fish meal and oil in aquafeeds, introductions of non‐native species and interbreeding of escaped aquaculture stocks with locally adapted populations of wild relatives. Forward‐thinking aquaculturists seek to advance the sustainability of aquaculture, and promising contributions have been realized along a number of fronts.

Most current fish and shrimp production systems involve the application of feeds to a monoculture, and much of the nitrogen and phosphorus content ultimately becomes waste. Integrated aquaculture, involving polyculture of fish or shrimp with vegetables, microplankton, shellfish or seaweeds, can capture nutrients and particulate wastes into profitable products (Neori et al. 2004). Such systems can be realized in fresh or marine water. Greater use of integrated systems may contribute to the sustainability of world aquaculture.

Most high‐value aquaculture species are carnivores, and most traditional aquafeeds have high content of fish meal and oil. Aquaculture has been criticized for exacerbating existing shortages of fish meal and oil. Replacement of fish meals and oils with plant‐based feedstuffs has proven largely successful. Additionally, selective breeding of farmed types to effectively utilize such feed has shown promise.

While large sectors of aquaculture currently produce species – such as carps, tilapias and salmonids – not native to that region, we find ongoing efforts to domesticate and produce native species encouraging. Examples include pirarucu Arapaima gigas, tambaqui Colossoma macropomum and pacu Piaractus mesopotamicus in Brazil. The realization of sectors producing native species minimizes risk stemming from establishment of non‐native species and presents unique products to the marketplace.

Only ~10% of world aquaculture production comes from well‐managed selective breeding programmes, and most common farmed types are considered little removed from the ‘wild type’. Notable increases in production and resiliency of production systems can be achieved by development and use of genetically improved, more productive farmed types. Notable successes in genetic improvement of salmonids, Nile tilapia and ictalurid catfish can be replicated in other sectors. Particular benefit might be achieved from ongoing investments in genetic improvement of low‐value species, such as Chinese and Indian major carps, that are important to global aquaculture.

Interbreeding of escaped aquaculture organisms with wild relatives in the receiving ecosystem poses introgressive hybridization (as in the tilapias) and loss of local adaptation (Atlantic salmon). Reproductive confinement of farmed types has been approached by induction of triploidy and use of gene transfer or gene editing (Gratacap et al. 2019). While triploid Atlantic salmon show loss of productivity and gene technology‐based types are still in development, maturation of these technologies may contribute to ecological sustainability.

Interest in sustainability has driven development of certification programmes, such as the Aquaculture Stewardship Council, the Aquaculture Certification Council and the Global Agricultural Practices GlobalG.A.P. Sustainability certification is a market‐based system that sets standards for ecological and social compliance, audits compliance and authorizes labels to enterprises and products that meet the standards. Few readers of this column would argue with the intent of certification. Existing certification systems, however, include only a small proportion of world production and disenfranchise many stakeholders, including producers and consumers in developing countries (Bush et al. 2013). Certification systems might be redesigned to address the full range of ecological and other issues.

While these developments are all constructive, they are not in themselves sufficient to achieve sustainability. Two articles in this issue of Reviews in Aquaculture address other critical aspects of promotion of the ecological sustainability of aquaculture.

The rapid growth of the aquaculture industry inevitably raises concerns regarding consumption of renewable and non‐renewable resources. To achieve more efficient and ecologically sustainable production, emergy synthesis (ES), a sustainability assessment metric, has been employed to identify and quantify energy flows in defined aquaculture production systems. David et al. (2020) consider how ES can be applied to different production systems, ranging from small monocultures to large production systems, to establish indicators useful for assessing environmental performance. The main contributors to emergy performance of aquaculture systems are analysed in detail, and the unit emergy value (UEV) for water and feed input flows and the ecosystem service/disservice are identified. It is, however, a bit surprising that in published research concerning ES in aquaculture systems, water resources were labelled as either renewable or non‐renewable resources. David et al. considered that water UEV should be revisited in consideration of the advances in emergy analysis and water treatment technologies. Feed, which accounts for up to 70% production cost in intensive monoculture systems, may also need further studies and update, as the feed UEV used in published research reports may itself need update. It seems promising that polyculture, in which multiple species with complementary trophic niches are produced in a same culture unit, is considered sustainable, with the requirement of only natural foods. The review by David et al. may have important value as a reference for practising aquaculturists and for those designing aquaculture systems.

In China, more than 70% of fishery products are produced by the aquaculture sector, and more than 45% is produced by pond aquaculture. Pond aquaculture has been a traditional practice for fish production in China, especially culture of a few well‐known cyprinid species. Over the last ten or twenty years, several species of perciform fish, together with shrimps and even reptiles or species in other taxa, have been widely incorporated into pond culture systems in China. Chinese pond aquaculture is thus a successful and diversified polyculture system, as reviewed by Liu et al. (2020) regarding water quality parameters. Liu et al. review the efforts devoted to understanding ecological processes in these pond‐based polyculture systems, as well as the ecological engineering techniques which have been implemented in aquaculture practices for improving or maintaining water quality for sustainable aquaculture production. The possible environmental impact of pond aquaculture is analysed, although the ecosystem services/disservices are not approached. The aquaculture model and the aquatic ecological engineering techniques applied in the development of pond aquaculture in China reviewed by Liu et al. may have reference value for developing such aquaculture practices.

Realization of ecological sustainability in the aquaculture sector will require a concerted effort among aquaculturists, scientists, engineers and other stakeholders. We do not yet have in hand all the science that we will need. We trust that you will find these two articles in Reviews in Aquaculture provocative and useful as you consider promotion of aquaculture sustainability.