Cleaner fish

10 February 2015

Posted by: Dr Anabella Williams

Category: Research & medical benefits

What’s more controversial and difficult to discuss than animal research? Food security and ethics around how we eat is one topic that brings its own set of heated arguments. So what about animal research about food security issues? Bella Williams looks at one reason why research is carried out on fish: to develop better aquaculture.

Of the 4.12 million procedures carried out on species protected under ASPA in 2013, 507,373 (12%) were carried out on fish, making them the second most commonly used species (after mice). The number of procedures carried out on fish has increased overall since 2003. While the vast majority of animal research is carried out in support of human health, research is carried out for other reasons, and each year many animals are used to research better aquaculture (fish farm) methods.

Generally, procedures carried out on Zebra fish are fundamental research to support medical research, for example looking at how zebra fish hearts are able to repair themselves, and whether it is possible to treat human patients with damaged hearts in a similar way. Many of the zebrafish used are involved only in the breeding of GM strains of fish for medical research studies.

Other fish are used for a variety of reasons, such as for environmental research, or to develop better aquaculture practices. People in the UK eat around 20kg of fish per year and half of that fish is farmed. The NHS guidelines recommend that everyone should eat at least one portion of oily fish per week, yet it is well-known that our seas are overfished, and that previously common fish are now critically endangered.  As with any farming practice controlling disease outbreak is critical. It allows animals to be kept successfully in captivity and prevents disease and pollutants from spreading to wild populations.

There has always been controversy over animal research, but there is far greater controversy over food security, and aquaculture is no exception. If we are to continue to eat fish despite their depleted wild populations, then farming them is a necessity, but it is accompanied by questions over how the animals are kept and the impact of aquaculture on the environment. Farmed salmon have been called the ‘battery hens of the sea’ by campaign groups, and while current practices may be imperfect, it is important that research is done to improve the health and welfare of captive animals. Creating healthier and more ethical food sources is a huge issue, and farming of any animal means taking steps to control the spread of disease, which tends to spread rapidly in captive populations.

Recent research at the University of Stirling, in partnership with Scottish Sea Farms, has led to the use of Ballan wrasse as a cleaner fish to prevent sea lice in farmed salmon through biological control, rather than through pesticides. Cleaner Wrasse are the best known cleaner fish, living symbiotically with other fish, grooming them and eating parasites. Although they are known to also eat healthy tissue, farmed fish provide them with plenty of food as sea lice tend to be rife in the cages used to hold captive salmon. The sea lice eat skin and blood from the salmon, causing infection, but with shoals of reddish-coloured Ballan wrasse introduced the lice are controlled, keeping the salmon healthy.   

Other research at Stirling looks at ways to prevent the spread of viral diseases between groups of fish in aquaculture tanks.

Fish farming is far from ideal, but it is increasingly seen as an alternative to depleting damaged fish stocks. As more and more of the fish we eat is reared in farms, it is vital that practices improve to provide an ethical and affordable alternative to wild-caught fish, and all this means research to understand how captive fish can be better cared for.

Bella Williams