SINGAPORE – To have a hope of feeding Singapore at a time when global warming and overfishing are decimating fish stocks around the world, the authorities are looking to seafood farmed Singapore-style for a reliable protein source: high tech, high-yield, sustainable and climate-proof.

The Singapore Food Agency (SFA) told The Straits Times that a decline in wild-caught fish had propelled aquaculture into an important sector.

There are currently 123 fish farms in Singapore. They produced about 4,600 tonnes of fish last year, accounting for about 9 per cent of local fish consumption, said the agency.

While this may not seem like much, SFA pointed out that local production will help mitigate the nation’s reliance on imports and serve as a buffer during supply disruptions.

“We envisage farming to become more like manufacturing – where production takes place within a controlled environment with a defined input,” she said.

“The result is an assured and consistent output, and a predictable way to address the effects of climate change and extreme weather.”

Globally, the aquaculture sector is growing.

Professor Dean Jerry, deputy director for the centre for sustainable tropical fisheries and aquaculture at the Singapore campus of James Cook University, told The Straits Times that aquaculture production has surged over the last 30 years – from producing about 10 per cent of seafood protein globally to more than half currently.

Prof Jerry said land-scarce Singapore is also looking to aquaculture because it is the most efficient animal protein production sector globally.

“To produce the equivalent kilogram of protein requires substantially less land area, water usage, feed input, and often is less polluting in terms of production of climate change gases like carbon dioxide and methane, compared with beef production, for example,” he said.

For example, an aquaculture fish farm can produce up to 50 to 80 tonnes of product in one hectare, while a semi-intensive beef farm will produce about two tonnes of product per hectare, Prof Jerry said.

He believes that there is the potential to increase the amount of locally grown seafood to about 15 per cent if the industry can scale up production.

Seas under siege

Aquaculture has become a necessity because the pressures on the ocean are mounting.

The latest scientific report released by the United Nations on Wednesday (Sept 25) highlighted exactly how dire the situation underwater is likely to become, if global warming continues unabated.

The Intergovernmental Panel on Climate Change’s (IPCC) Special Report on the ocean and cryosphere – the frozen part of the planet – also highlighted how seafood might literally be swimming away.

The report, which referenced about 7,000 scientific papers and involved 100 authors from 36 countries, found that many marine species have shifted to different parts of the ocean in response to ocean warming, sea ice change and biogeochemical changes such as oxygen loss.

Ocean warming in the 20th century and beyond has also contributed to a decrease in maximum catch potential, the report noted.

As the oceans warm, marine food chains can be affected from the bottom-up.

“Warming in the ocean reduces mixing between water layers ,and therefore, limits the supply of oxygen and nutrients for marine life,” said Dr Hans-Otto Pörtner, co-chair for IPCC Working Group II, during a press conference on the latest report on Wednesday (Sept 25).

“Communities that depend highly on seafood may face risks to nutritional health and food security.”

Stratification – where warmer waters are less dense than cool waters, prevents the layers in the ocean from mixing, making it harder from nutrients at depth to reach the surface. 

Warmer upper ocean temperatures, for example, can reduce the delivery of nutrients needed by phytoplankton . 

As phytoplankton form the base of many marine food webs, their reduced numbers can have cascading effects on the organisms at the top of the food chain, which people eat.

The IPCC report noted that over the 21st century, the ocean is projected to transition to unprecedented conditions with increased temperatures and greater upper ocean stratification.

“In some marine ecosystems species are impacted by both the effects of fishing and climate changes,” it added.

Dr Jess Melbourne-Thomas, one of the authors for the IPCC report, said ocean and ice environments around the world are changing at an unprecedented rate, and that many of these changes will accelerate.

Added Dr Melbourne-Thomas, who is from the Commonwealth Scientific and Industrial Research Organisation: “Changes in these environments – which include sea level rise, ocean warming, melting ice and snow, and loss of oxygen in the surface ocean – have profound consequences for ecosystems and for human communities globally.”

No silver bullet

But fish farming is no panacea, the experts point out.

Many fish farms are still based in the open ocean, where they face the impact of climate change including as rising temperature and extreme events.

Prof Jerry pointed out that because aquaculture is essentially an outdoor food production sector, increased extreme environmental events such as cyclones, droughts and heat waves, could dramatically interfere with production systems.

Freshwater aquaculture in the Mekong Delta, for instance, could be affected by sea level rise as a result of climate change. This would lead to saltwater intrusion into areas where it previously has not existed, and wipe out the potential to culture a whole range of freshwater fishes like catfish and carps, he said.

On how rising temperatures could affect aquaculture, he pointed to salmon production as one example.

Salmon is a cold water fish which does not perform well when water temperatures get above about 18 deg C. In many countries, including Australia, salmon are currently farmed at their heat threshold. If water temperatures continue to rise, there will be less available areas for them to be farmed.

Rising temperatures can also speed up pathogen life cycles and increase the likelihood of bacterial outbreaks, Prof Jerry noted.

Already, about 40 per cent of current aquaculture production is lost to disease globally. This could rise with climate change.

“Warmer waters also will increase the likelihood of major microalgae events leading to red tides and the like which can lead to mortality events in the species cultured through oxygen depletion, or make the product inedible due to toxins exposing human health concerns.”

Technological solutions

Fish farmers in Singapore have been hit by algae blooms in recent years that wiped out tonnes of fish.

In 2015, coastal farms in Changi and Lim Chu Kang lost more than 500 tonnes of fish to plankton blooms.

The latest IPCC report noted that harmful algal blooms have increased in frequency and range expansion since the 1980s in response to due to climate change and other factors such as increased nutrient run-off from land.

“Harmful algal blooms have had negative impacts on food security, tourism, local economy, and human health,” said the report.

Fish farms in Singapore are now leveraging technology to overcome some of these challenges.

Singapore Aquaculture Technologies, for example, a fish farm located in the Johor Strait, has been using closed containment aquaculture systems.

These systems separate the water in the fish pens from the sea water, enabling fish production to be resilient to external environmental conditions, said the SFA.

Genetic improvement could also be another way to increase the productivity of a farmed species, said Prof Jerry, who is also the director for the Australian Research Council Research Hub for Advanced Prawn Breeding.

“We are looking at prawns as they are one of the major global aquaculture production industries which are highly efficient and… (have) high export value. So what we are doing is selectively breeding for faster growing, disease tolerant, good tasting black tiger prawns.”