Why 95% of the World’s Fish Still Comes from Ponds and Cages – And What RAS Can’t Replace (Yet)

Recirculating Aquaculture Systems (RAS) are often hyped as the future of fish farming – yet land-based ponds and sea cages still produce ~95% of the world’s aquaculture output . This isn’t an attack on RAS, but a reality check on its current limits and why “traditional” systems remain the backbone of global seafood production. Let’s unpack the numbers and the lessons for a more sustainable aquaculture future:

Global Aquaculture: Traditional Systems Dominate

Global aquaculture hit record highs (over 120 million tonnes of farmed seafood annually in recent years), and the vast majority comes from conventional farms. Asia alone accounts for ~89% of world aquaculture production (with China leading the way) , mostly from ponds, open pens, and other land/cage-based methods. In fact, most of the 80+ million tons of farmed fish are raised in earthen ponds or floating net pens, while RAS contributes <5% of output today . Even for high-value species like salmon, which have seen major RAS investment, land-based RAS provides <1% of the global supply – over 99% of farmed salmon still come from ocean net pens . In short, traditional aquaculture systems currently feed the world, and by extension are crucial for food security.

Why Isn’t RAS Taking Over (Yet)?

RAS offers exciting benefits (e.g. recycling ~95% of water , and the potential for near-zero effluent and local production year-round), but scaling it up has proven difficult. Key challenges include:

• Biological Complexity: Fish are living animals with delicate environmental needs. Traditional ponds and cages harness natural processes (water exchange, microbial filtration, sunlight) that RAS must replicate artificially. Keeping water quality ideal 24/7 in a closed system is hard. If fish health and welfare needs aren’t fully met, performance suffers . For instance, issues like off-flavors, stress, or disease can pop up when you intensify fish culture in tanks – problems that require deep biological understanding to solve, not just engineering.

• High Capital & Energy Demands: Building a large RAS facility requires huge upfront investment (often tens or hundreds of millions of dollars), and operating it is energy-intensive (pumps, filters, heating/cooling systems running constantly). One industry analysis noted RAS expansion is being “severely hampered” by soaring construction costs, financing hurdles, and rising electricity prices . By contrast, a simple pond farm or coastal cage can rely on nature’s infrastructure (sunlight, gravity flow, natural water bodies) with far lower energy inputs.

• Operational Risk & Complexity: Closed-loop farming is technically demanding – you’re essentially managing a life-support system. A power outage, equipment failure or filter glitch can cause mass fish mortality in hours. Likewise, disease outbreaks in RAS can spread fast in the confined water loop. This means RAS farms need highly skilled staff and robust contingency systems, which are in short supply . It’s no wonder many investors perceive RAS as high-risk, given its capital intensity and the possibility that a single mishap (e.g. a pump failure or disease event) could wipe out a crop . Surveys of early RAS ventures have documented frequent redesigns and even failures, underscoring that this is far from plug-and-play farming.

(None of this is to say RAS can’t work – there are successful RAS hatcheries and a few grow-out operations – but it’s a tough nut to crack at commercial scale. As of now, dozens of ambitious RAS startups have struggled or stalled, while traditional farms keep churning out fish.)

Traditional Aquaculture = Food Security & Resilience

Why do ponds and cages still dominate? Simply put, they are proven, scalable, and essential for feeding billions. Traditional land- and water-based farms have expanded steadily for decades, providing affordable protein in regions that need it most. The majority of fish farmers worldwide are smallholders in Asia , tending ponds and cages that produce staples like carp, tilapia, and catfish. These low- to medium-tech farms form the bedrock of local food supply in many developing countries. They may not be high-tech, but they are accessible – requiring modest capital and utilizing local ecosystems and labor.

Critically, conventional systems currently out-produce RAS by orders of magnitude. Carp and other freshwater fish raised in ponds are among the most cultivated species globally , fueling domestic markets in Asia and Africa. Open-net pen farming in coastal waters (for species like salmon, seabass, bream) has likewise scaled up to millions of tons. Without these systems, we would simply not have the volume of fish needed to meet today’s seafood demand. In terms of climate resilience, traditional aquaculture has a broad base: millions of small farms that can adapt practices incrementally (e.g. improving pond management, moving cages deeper offshore, etc.), rather than betting on a few giant facilities. Moreover, innovations can and do improve these systems – from better feeds and selective breeding to multi-trophic farming that uses shellfish/algae to mitigate impacts. Focusing on such improvements can yield big gains in sustainability and output across that 95% of the sector.

Embrace Innovation – but Ground It in Science

The takeaway is not that we should abandon RAS or tech innovation. It’s that we must stay realistic and science-driven. RAS will likely play a bigger role in the future (some forecasts say up to 40% of fish farming by 2030 , though that may be optimistic), but it won’t magically solve all aquaculture challenges overnight. In the meantime, doubling down on biological and climate science is crucial. As one editorial put it, the industry’s rapid tech advances must be matched with equal attention to fish health, welfare, and environmental limits . We need to invest in breeding more robust, climate-tolerant strains, improving disease prevention, refining feeds, and understanding ecosystem carrying capacities. These fundamentals apply to all farming systems – whether a high-tech RAS facility or a rural fish pond.

Bottom line: Aquaculture’s future lies in smart integration of technology and biology. RAS and other innovations will find their place, but success will come from aligning our farming methods with the biology of the species and the realities of a changing climate, not just building expensive systems in isolation. By focusing on sound science, improving existing practices, and carefully scaling new ones, we can ensure aquaculture grows sustainably to meet global food needs – with both the hi-tech tanks and the humble ponds playing their part.

Sources: Data and insights drawn from FAO and industry reports, expert analyses, and academic studies on global aquaculture production and RAS performance , as well as commentary on the importance of biology and climate considerations in aquaculture innovation .