YOU wouldn’t notice it by looking at the fish counter in a supermarket and not much is said about it, but just like vegetables and fruit different seafood is seasonal and should be eaten or avoided depending on the time of year.

Months without a ‘r’ is an old adage which often comes up when eating shellfish. The theory is that warmer waters means a greater chance of toxic algal blooms in the sea and being filter feeders, shellfish accumulate these toxins. In UK seas the blooms are less common and areas harvested for shellfish are carefully monitored for water quality, so if you’re buying them from a shop you don’t need to worry. In reality many shellfish species put their energy into breeding during the summer so the meat inside the shells shrink. As a result you should avoid them during the summer to get the best quality and ensure that the existing shellfish are able to breed and safeguard the stocks.

Native oysters, now considered a delicacy, used to be poor man’s food in the UK and in the beginning of the 19th century they were a common dish. Since then their stocks have declined due to overfishing, pollution, parasites and invasive species. Many UK stocks are now in severe decline or completely gone.

In an odd turn of events their fate may actually come down to higher demand for them, not less. At present most oysters sold are actually pacific oysters. These are hardier, grow quicker and are easier to produce in aquaculture than the native oysters.

To preserve the native oyster, some people say, we need to eat more, increase the demand and make it economically viable to grow them and boost their stocks.

Mussels is one of only two species (the other is arctic char) on the Marine Conservation Society’s Good Fish Guide that has the lowest and most sustainable rating. Farmed mussels are mostly grown on ropes using naturally settled mussels and as they are filter feeders do not require any feed input. In fact they actually purify the water as they feed.

To find out more about which seafood to avoid and when, you can have a look at the Good Fish Guide and their guide to Seasonal Fish.

Author Olle Akesson, marine officer at the Sussex Wildlife Trust