A recent journal article in Nature Ecology & Evolution about marine aquaculture hotpots has been generating some buzz in the aquaculture and science press. A research project to identify suitable areas for marine aquaculture was conducted by representatives of a partnership among The Nature Conservancy, the Wildlife Conservation Society and the National Center for Ecological Analysis and Synthesis at UC Santa Barbara, with new Ph.D. Rebecca Gentry as lead author.

The research team conducted a spatial analysis of the ocean surface to evaluate the potential for two kinds of aquaculture – finfish culture in cages and bivalve farming. They selected 120 fish species and 60 bivalve species and defined suitable habitat on the basis of average water temperature. Water depths greater than 200 m were considered unsuitable because they would be too deep to anchor gear. Areas dedicated to marine reserves, shipping lanes and areas with low dissolved oxygen concentration were also eliminated from consideration.

The potential suitable production area was 11.4 million km2 for marine finfish cage culture and 1.5 million km2 for bivalve culture. In this area, about 15 billion t could be produced annually, representing more than 100 times the current level of global seafood consumption. Said another way, the current level of seafood consumption of around 110 million t could be met by using a marine area about the size of Lake Michigan in the US. Every country with a coastline could meet its own seafood requirement with a small proportion (often <2 percent) of coastal water area dedicated to aquaculture.

The coastal areas with the greatest production potential were located in warm, tropical regions where temperatures are favorable for rapid growth of cultured organisms. Indonesia was singled out for having high production potential for marine finfish aquaculture. Other countries with high potential include Australia, India, Argentina, and Mexico.

The finding that space does not limit the potential for marine aquaculture is not surprising or new, but the Gentry paper provides solid evidence to support that claim. The authors rightly qualify their findings by saying that factors other than space will limit marine aquaculture development. The authors of the hotspot paper write “other factors, such as social, economic, political and/or regulatory constraints are limiting aquaculture development far more than biological constraints or conflicting uses.” Most of the high-potential areas identified are located in lesser developed countries with a low level of economic and infrastructure development, high rates of poverty and poor security and governance of marine resources – all important factors that limit the realization of production potential.

In an essay published in the same journal issue as the Gentry paper, Max Troell, of the Stockholm Resilience Centre, argues that the availability of aquafeeds, technology and favorable production economics are more limiting than space for the expansion of marine aquaculture. Aquaculture will need significant natural capital and ecosystem services from terrestrial and aquatic ecosystems and these are not uniformly distributed near areas with the greatest production potential.

The findings of the hotspot paper will be useful to guide and plan marine aquaculture development. The paper represents a first-cut, base-layer approach to defining suitable sites. The effect of temperature on the growth potential of suitable species is fundamental in aquaculture. Additional spatially explicit layers, each of which defines other important site selection criteria, can be added to the base layer defined by the Gentry article. In conjunction with consideration of the Ecosystem Approach to Aquaculture advocated by the FAO, the identification of marine aquaculture hotspots can be refined to designate the best production zones.

The idea of an ecological or biodiversity hotspot was first defined in the late 1980s as an area of species richness that is threatened with loss. Identification of biodiversity hotspots has served to focus conservation efforts. Similarly, the identification of marine aquaculture hotspots can focus development efforts by prioritizing specific areas for development.

At World Aquaculture 2017 in Cape Town, one of the better presentations of the conference was provided by Tom Hecht, emeritus professor from Rhodes University and former WAS Board member, who spoke about “Establishing aquaculture value chains.” He outlined the key factors that result in success in commercial aquaculture. At the top of the list was an attribute Tom called “natural strategic advantage,” which he defined as “matching environmental conditions with environmental requirements,” something that lies at the core of the hotspot paper as well.

The idea of natural strategic advantage is similar to the principle of comparative advantage from economics. With respect to aquaculture, by this principle, a country would produce more seafood if they have a comparative advantage of doing so. Comparative advantage can derive from resource endowments such as suitable land, water, or coastal space, or crop ingredients and animal protein resources to make aquafeeds. It can also come from the level of technological development, either through improved equipment or production technology, or by increased resource use efficiency, such as that obtained through the application of better practices. Some of the countries identified in the Gentry paper have the opportunity to press their comparative advantage with respect to marine aquaculture production.

The identification of marine aquaculture hotspots begs the question of where are the hottest of the hotspots. Where are the places where aquaculture can burn the brightest? What characterizes the hottest of the hot spots? There are numerous examples around the world to demonstrate that successful commercial aquaculture occurs where value chains are fully developed and where production is concentrated into regional clusters.

Other critical factors need to be considered to identify areas with the greatest production potential, and some of these are difficult to map in a spatially explicit way. Market structure, availability of skilled labor and other human resources, access to fingerlings and feeds, among other parts of the value chain, and an enabling regulatory environment are also critical determinants of successful commercial aquaculture development. —
John A. Hargreaves, Editor-in-Chief