Will we have enough fish to feed the growing global population in twenty years? Not if that fish comes from wild fisheries, says Professor Johan Verreth. ‘The hundreds of millions of tonnes of extra fish we will need will have to come from fish farms.' The professor of Aquaculture and Fisheries will deliver his farewell lecture at Wageningen University & Research on Thursday 22 March.
Twenty years ago, fishing the world's oceans reached its peak of 90 million tonnes of fish per year, says Professor Verreth. 'Fisheries will continue to play an important role in the future. They provide us with an almost 100% organic fish product without the use of additional nutrients, antibiotics, fresh water or land. Fish farming, on the other hand, has to justify the use of these additional resources. The rearing of fish has to leave the smallest possible ecological footprint, which is a daunting task.'
Fish production via aquaculture is increasing worldwide. In 2015, the 70 million tonne yield was comparable to that of wild fisheries, but higher than that of beef production. 'It wouldn't surprise me if aquaculture exceeds chicken farming (90 million tonnes) and pig farming (100 million tonnes) in the near future. Half of all fish we consume on an annual basis comes from aquaculture. That makes fish our primary source of animal protein,' concludes Professor Verreth.
Tinned tuna: most popular fish product
Tinned tuna is the most popular fish product in Dutch households, followed by fish sticks, smoked salmon and natural salmon. Herring ranks fifth on the list. Tuna is also the most commonly caught fish worldwide. There are two types of tuna: yellowfin and skipjack tuna, more than 4.7 million tonnes of which are caught each year. Skipjack tuna is primarily found in the western and central Pacific and come from relatively healthy stocks.
Fish consumption on the rise
'It's important to bear in mind that our per capita fish consumption in on the rise,' says Professor Verreth. Since the 1970s, consumption figures have nearly doubled to more than 20 kilos per person per year. In the West, sea fish is more popular among older people. 'The population is stagnating in the West and most Westerners permit themselves the better, more expensive varieties, such as salmon,' he adds. Fish consumption is expected to increase by a few per cent over the years.
Fish for Africa
Things are different in Africa and Asia. The population is increasing considerably and consumption is expected to rise by several per cent until at least 2020. 'The key question is whether the required 100 million tonnes is feasible in the next twenty years,' says Professor Verreth. Nevertheless, he remains optimistic. 'I think is,' he says. 'But it would mean more than doubling the current figure! In rural Africa and Asia, extensive fish farming can take place in a large dammed river to keep input low. This will provide the poorer populations with affordable and essential fish proteins.'
Investing heavily in innovation is required in order to achieve 100 million tonnes of extra fish. 'This will call for fish breeding, which is a solution that is not being fully utilised at the moment. At the same time, we want to avoid rapid-growth fish known colloquially in Dutch as plofvis in order to ensure healthy animals that can process fish feed effectively. This cannot be fishmeal but should be plant-based in origin. Soya is not an option, as it requires too much arable land,' Professor Verreth concludes.
One point of improvement according to Professor Verreth is the conversion efficiency of feed protein into edible protein from meat or fish. According to his calculations this is 34% for salmon, which is higher than the efficiency for chicken listed in the literature. The efficiency of tilapia is between 13% and 22%, depending on which parts of the fish are eaten (which is often culturally determined).
The feed efficiency limit has not yet been reached. One way to ensure further optimisation is to develop an ecological production system, for which tilapia and prawns are particularly well-suited. The fish live in a river ecosystem where feed is low and production is high. The waste generated by the fish is reused for the production of fish feed. In such a system, bacteria and other microbial communities create flakes that can be consumed by the fish or prawns. This will rapidly increase protein efficiency without the need for large and costly input. A 'nutritious pond' concept like this has a positive effect on fish resilience and disease resistance.