If we started farming fish in all the suitable offshore habitat available globally, we could technically produce 100 times our current seafood needs, a new study reveals. Writing in Nature Ecology and Evolution, a group of researchers makes the case that this form of food production has the potential to solve some of our most pressing food security challenges, and to take the pressure off wild fisheries, too.
Fish and bivalve farming–called aquaculture–has gained attention in recent years as one possible way to secure enough protein for the planet’s burgeoning population. “Oceans represent an immense opportunity for food production, yet the open ocean environment is largely untapped as a farming resource,” the University of California, Santa Barbara-led researchers write in their paper. Theirs is the first study to put an estimate on that untapped potential.
To do so, first they selected 180 consumable species of finfish and bivalves like oysters and molluscs. Then they chose suitable aquaculture habitat based on the conditions those species require to thrive, such as depth and water temperature. Next, the researchers eliminated other types of unsuitable habitat for fish farming–like areas dedicated to marine reserves, high-traffic shipping zones, and waters deeper than 200 metres, where it would be too costly to anchor fish farms.
Through this process of elimination, the researchers were able to identify aquaculture ‘hotspots’ around the world–finding that there are almost 13 million square kilometres of suitable open-ocean habitat globally available for fish and bivalve farming. Together, these productive waters could produce about 15 billion tons of seafood each year, surpassing our current-day seafood needs 100-fold. The study also found that every coastal country on earth is capable of meeting its domestic seafood needs by using just a small percentage of its coastal waters to farm fish–which could ensure food security and also reduce the reliance on imports. If just one percent of the Indonesian coastline was reserved for aquaculture, for instance, it could produce 24 million tons of fish a year, more than enough to satisfy the national appetite for seafood.
Farming fish on this scale could also take the strain off wild fisheries, which are threatened by climate change–and are also the cause of stock declines through overfishing. Aquaculture isn’t necessarily a fault-free solution, however: fish farms have developed a negative reputation in recent decades for causing largescale nutrient pollution and the spread of diseases and parasites from farmed to wild fish. With this in mind, the researchers caution that aquaculture development would need to be closely aligned with policies and practices that protect the environment. Fish farming is now the fastest-growing food sector; it’s important to consider how to take its progress forward sustainably to limit the considerable environmental risks, they say.
Marine aquaculture presents an opportunity for increasing seafood production in the face of growing demand for marine protein and limited scope for expanding wild fishery harvests. However, the global capacity for increased aquaculture production from the ocean and the relative productivity potential across countries are unknown. Here, we map the biological production potential for marine aquaculture across the globe using an innovative approach that draws from physiology, allometry and growth theory. Even after applying substantial constraints based on existing ocean uses and limitations, we find vast areas in nearly every coastal country that are suitable for aquaculture. The development potential far exceeds the space required to meet foreseeable seafood demand; indeed, the current total landings of all wild-capture fisheries could be produced using less than 0.015% of the global ocean area. This analysis demonstrates that suitable space is unlikely to limit marine aquaculture development and highlights the role that other factors, such as economics and governance, play in shaping growth trajectories. We suggest that the vast amount of space suitable for marine aquaculture presents an opportunity for countries to develop aquaculture in a way that aligns with their economic, environmental and social objectives.
As the human population looks set to reach 10 billion people by 20501, our food systems will be under intense pressure to produce animal protein for an increasing population2. Faced with plateauing wild fishery catches3 and high impacts from land-based agriculture4,5, momentum is building to look towards marine aquaculture to meet the growing protein demand6,7. The relative sustainability of marine aquaculture compared with land-based meat production8 and the human health benefits of diets rich in fish9 make it even more pressing that we consider aquaculture’s potential. Oceans represent an immense opportunity for food production, yet the open ocean environment is largely untapped as a farming resource.
The majority of existing aquaculture takes place on land, in freshwater and in nearshore marine waters10. However, problems, such as high resource use, pollution and habitat destruction have created a generally negative reputation for aquaculture in several countries11,12 and pose challenges for continued expansion. Open-ocean aquaculture appears to have several advantages over the more traditional culturing methods, including fewer spatial conflicts and a higher nutrient assimilation capacity13,14, highlighting the opportunities for sustainable marine development. However, large-scale open-ocean farms are not yet common, making adaptive management and careful research an essential element of sustainable marine aquaculture expansion.
Despite the perception that marine aquaculture has high growth potential15,16, little is known about the extent, location and productivity of potential growing areas across the globe. Most of the research on marine aquaculture potential has focused on specific species17 and/or specific regions18,19, and there remains an important need to assess the more general growing potential across locations. To rectify this shortfall, we drew on physiology and growth theory coupled with environmental data to quantify and map the global potential for fish and bivalve aquaculture. These categories represent two major types of culture: fed aquaculture, where food is provided from an external source, and unfed aquaculture, where nutrition comes from the environment. We focused on quantifying a realistic biological baseline given the diversity of existing ocean uses, thus providing novel insight into the potential global aquaculture production and the role it might play in addressing future food security. Ultimately, the economic and social constraints of aquaculture may limit production, and their inclusion in future research will help further refine realistic production potential.
To characterize aquaculture’s potential, we used a three-step approach (see Methods). First, we analysed the relative productivity for each 0.042 degree2 patch of global ocean for both fish and bivalve aquaculture. To do this, we constrained the production potential for each of 180 marine aquaculture species (120 fish and 60 bivalves) to areas within their respective upper and lower thermal thresholds using 30 years of sea surface temperature data (Supplementary Fig. 1). We then calculated the average (multi-species) growth performance index (GPI) for each patch for all suitable fish and bivalve species, resulting in a spatially explicit assessment of the general growing potential for each aquaculture type (Supplementary Fig. 2). GPI is derived from the von Bertalanffy growth equation and uses species-specific parameters (growth rate and maximum length20) to create a single metric to describe the growth potential of a species21. GPI has been used frequently to assess growth suitability for culture and is particularly useful for fed species or those not subject to food limitations22,23,24. Locations with a high GPI are expected to have better growth conditions for a spectrum of aquaculture species and, thus, are well suited to development. Using a multi-species GPI average to assess growth potential provides a more general growth suitability metric than is possible when making detailed assessments for a single species. This approach is especially useful given the fast rate at which new species are being developed for aquaculture and the shift in focal species between nearshore and offshore cultures14,25,26. Moreover, using GPI averages across species provides a conservative assessment, since we are considering an average rather than the maximum growth potential.
Second, once the production potential was determined, we removed unsuitable areas with certain common environmental or human-use constraints. We excluded areas with unsuitable growing conditions due to low dissolved oxygen (fish only) and low phytoplanktonic food availability (bivalves only). We also eliminated areas at > 200 m depth because they are generally too deep (and thus expensive) to anchor farms, and areas already allocated to other uses, including marine protected areas, oil rigs and high-density shipping areas (Supplementary Fig. 5 and Supplementary Table 1). We acknowledge that advancing technology may alleviate some of these constraints through innovative farm designs that allow for deeper mooring and submerged farming structures. However, these constraints reflect the current common industry practice and provide a more conservative and economically realistic projection of potential. For the third and final step, we estimated the idealized potential production per unit area by converting the average (multi-species) GPI into biomass production, assuming a low stocking density is used and the farm design is uniform across space.
Results and discussion
We found that over 11,400,000 km2 are potentially suitable for fish and over 1,500,000 km2 could be developed for bivalves. Both fish and bivalve aquaculture showed expansive potential across the globe, including both tropical and temperate countries (Figs. 1 and 2 and Supplementary Table 3). However, as would be predicted by metabolic theory27, many of the areas with the highest GPI were located in warm, tropical regions. The total potential production is considerable: if all areas designated as suitable in this analysis were developed (assuming no further economic, environmental or social constraints), we estimate that approximately 15 billion tonnes of finfish could be grown every year—over 100 times the current global seafood consumption.