A captive trout leaps to avoid capture at the Three Stream Smokehouse in Franschhoek. Picture: Tracey Adams

Durban - As South African farmers move to fill the growing demand for fish, the government has moved to control pollution and environmental damage from intensive fish- farming.

People around the world are now eating five times as much fish as they did 40 years ago, according to the Department of Environmental Affairs.

This created “vast new opportunities” for South African farmers to feed the growing demand for fish protein, the department said.

While fish farming could help to reduce the relentless pressure on wild fish in the sea, intensive fish-rearing schemes could also lead to significant environmental damage.

For example, the water in rivers, dams and the sea can be polluted by the high levels of excrement, leftover food nutrients, chemicals and drugs when thousands of fish are crammed into ponds and cages to fatten them up quickly and artificially.

The Environmental Impact Assessment (EIA) Guidelines for Aquaculture published for comment last week say the capture rate of wild fish from the oceans is levelling off in most parts of the world, but demand from populations continues to grow.

“This means that the shortfall in supply will have to come from aquaculture to maintain the global per capita consumption of fish.”

Aquaculture, which includes the intensive farming of fish, seaweeds and plants, supplied about 50 percent of world seafood consumption and was expected to continue growing rapidly.

Although South Africa has EIA laws in place, Environment Minister Edna Molewa says there are gaps in the regulations and it is essential to encourage an environmentally sustainable aquaculture industry.

The proposed guidelines say there are several fresh and saltwater species that are most likely to be farmed locally. They include indigenous fish such as cob, tilapia, mullet, yellowtail and catfish and exotic fish such as trout, Atlantic salmon and bass.

One of the main objectives of the guidelines is to limit the volume and extent of pollution in estuaries, rivers and dams.

“Ideally the quality of water that enters the aquaculture facility should be comparable with the quality that exits the operation,” the proposed guidelines say.

But where this was not possible, water should be treated to ensure that it complied with the minimum water quality standards, the proposed guidelines say.

Where possible, aquaculture farms should stock locally indigenous fish species to avoid the escape of exotic, hybrid or genetically modified fish that could cause significant ecological disturbances, including genetic pollution and the appearance of new fish diseases.

Fish farmers should also aim to reduce the potential contamination of the surrounding environment when using growth hormones as well as anaesthetics, disinfectants, pesticides and other chemicals.

According to Canadian marine ecologist Daniel Pauly, several fish farms “rob Peter to pay Paul” by feeding up salmon and other sea predators with smaller fish caught from the wild.

Writing in The New Republic magazine, Pauly noted that dolphins had become rare in parts of the Mediterranean Sea because aquaculture farmers were removing large volumes of small fish to fatten up blue fin tuna in sea pens.

The removal of top predators also disrupted the food chain and had led to massive increases in jellyfish populations in places once dominated by hake and sardines.

Anton Bok, the chairman of South Africa’s Marine Finfish Association, acknowledges that carnivorous species in sea fish farms eat more fish meat than they produce.

However, Bok noted that farmed fish were more efficient than wild fish at converting food into growth. - The Mercury