Since the advent of industrialised fishing in the late 19th century, UK fish populations have drastically declined. Landings per unit of fishing power, a measure of fishing productivity and an indirect measure of population size, decreased by 94% between 1889 and 2007 for bottom-living fish such as cod and haddock. The true extent of the decline is unknown because data collection on landings only started after an 1885 government inquiry investigated claims industrialised fishing was damaging habitats and fish populations.
It is not only the UK where fish populations have declined: overfishing in Canada led to the collapse of the Newfoundland cod fishery in the 1990s for example.
Fishing negatively impacts the wider ecosystem with the most damaging form of bottom trawling, hydraulic dredging, killing 41% of seabed-dwelling organisms in a single pass. The seabed in actively fished regions is unlikely to recover, as it takes at least two undisturbed years to do so.
Farmed fish, in theory, impact less on the wider ecosystem and reduce the pressure on wild fish populations, however, this is not always the case. Wild fish are often used to feed farmed fish in the form of fishmeal and fish oil. The inputs are greater for farmed salmon and trout than the outputs: more wild fish is used as feed than farmed fish produced. In addition, farmed fish live at high densities which promotes disease transmission. Antibiotics are used to tackle this, which have the unintended consequence of encouraging the development of antibiotic resistant strains of bacteria. This poses risks if the resistance is transferred to bacteria that can infect humans.
Despite all these issues, it is difficult to stop eating fish because they provide omega-3 fatty acids, especially EPA and DHA. EPA and DHA can be synthesised in our bodies from the omega-3 fatty acid ALA, but at insufficient levels for optimum health. Both are important for brain health and have anti-inflammatory properties as well as other benefits. Hence EPA and DHA are vital dietary components, explaining why NHS guidelines recommend eating 2 portions of fish per week, one of them oily.
Fish obtain their EPA and DHA from consuming microalgae, which suggests an algal supplement is a potential alternative to eating fish. However, the evidence on the benefits of algal supplements is inconclusive, which prevents them from being recommended by dieticians and health services. Further research and innovation are needed in this sector to reduce prices and show that microalgae can be beneficial dietary supplements.
Although more research is needed, you can still take action now to tackle marine conservation while supporting your own health:
If you eat fish:
- Look for MSC or ASC certifications on packaging.
- Check the sustainability of different fish on the Good Fish Guide by the Marine Conservation Society.
- Choose smaller fish such as sardines or mackerel over larger ones.
- This reduces the number of steps in the food chain, increasing resource efficiency.
- Consider eating farmed shellfish, one of the most sustainable seafoods alongside seaweed.
- Regenerative ocean farmers such as GreenWave grow them for their ecosystem benefits; shellfish filter water, improving its quality.
- If you eat more than two portions of fish per week, consider reducing your intake and replacing it with plant-based sources of protein.
If you don’t eat fish:
- Eat plenty of foods high in the omega-3 ALA such as walnuts, chia seeds and tofu. Some of the ALA will then be converted to EPA and DHA by the body.
- Consider taking a microalgae supplement which contains both EPA and DHA. If it contains similar levels to a portion of oily fish such as mackerel (about 450mg) you’d only need two per week to meet the NHS dietary guidelines.