Reducing meat and dairy consumption is one way to improve your diet for the planet. But when it comes to sustainable seafood, buying sardines instead of salmon for your sandwiches and salads should be your first stop.
According to the Food and Agriculture Organization of the United Nations, a third of fish stocks are fished at rates that exceed what those populations can recover, and 90% are fished to their sustainable limit. One of the main causes of overfishing is, ironically, the demand for fish feed. More than a third of all fish caught in the world are fed by farmed animals rather than humans. Fish farming, or aquaculture, is the fastest growing food sector in the world. Most Atlantic salmon sold in supermarkets in the UK is farmed.
Raising these large predatory fish involves feeding them a diet rich in omega-3 fatty acids and protein, nutrients also essential to humans for brain development and nerve function. In a new study, my colleagues and I found that if people ate wild fish, such as sardines, which are usually destined for salmon farms, it would leave almost 4 million tonnes of fish in the sea and provide 6 million additional tons of seafood.
Feed people, not fish farms
The sea provides mankind with an abundance of nutrient-dense food, which we have enjoyed for thousands of years. Seafood is one of the most easily absorbed sources of key nutrients like omega-3s and vitamins D and A that humans need. It is thought that a diet that included seafood may have helped humans develop bigger brains. It is a global responsibility to use this resource sustainably, as more than 3.3 billion people depend on it as a source of animal protein.
Salmon raised on coastal farms off Scotland is the UK’s largest food export in terms of total annual economic value (followed by bread and pastries). Our research team carried out an in-depth assessment of the Scottish salmon industry, collecting data on the nutrient content of fish, the composition of fishmeal and fish oil and examining the transfer of micronutrients from fish food.
We found that by removing wild fish from salmon feed and using only fish by-products – such as trimmings and leftover fillets from farmed fish – 3.7 million tonnes of fish could be left in the sea and global annual seafood production could increase by 6.1 million tonnes. More than half of the essential dietary minerals and fatty acids available in wild fish are currently lost in the mouths of humans when these fish are fed to farmed salmon.
By comparing salmon to other options, our research has also highlighted the health and environmental benefits of eating more sustainably farmed seafood, such as mussels. Mussels belong to the class of bivalve molluscs which includes crustaceans like clams and oysters (but not shrimp, lobsters or crabs). Our research has shown that mussels are one of the most sustainable foods on the planet, more so than any other meat, fish, and most land crops like soybeans, wheat, and rice.
Mussels don’t need food, they just eat algae in the water. The reefs they create act as nurseries where young fish can grow to full size, helping to regenerate wild fish stocks. Bivalve farms do not use land or fresh water. They actually act as a carbon sink.
And if you like to eat salmon? The use of alternative feeds in salmon farms is growing, but some are better than others. Foods made from crops like soybeans and corn need a lot of land and water to produce, but those made from algae are higher in omega-3s and use up marine space (which it there are many) instead of the earth. We need more research and investment to produce nutritious seafood while reducing pressure on marine ecosystems.
If you’re ever unsure, there are two simple mnemonics to guide you on which fish you should buy:
ECOME – Eat clams, oysters and mussels everywhere
SMASH – Sardines, mackerel, anchovies, sprats and herring
So enjoy your mussels with fries and your sardines on the barbecue. Eat small oily fish and bivalve shellfish. Eating more of these tasty foods and forgoing canned salmon and tuna can make a real difference to the ocean.