This is an article to help try and navigate these two key oyster related questions. We shall use the discussion to generate some rough 'rules of thumb' to help you on your own oyster quest!
Question 1: Can you eat oysters all year round?
Well, the answer to this question is it depends. There is an old adage, in the Northern Europe at least, that says:
‘Oysters should only be eaten when there is a letter r in the month'
This means that you should avoid eating oysters between May and August, or alternatively that the season for eating oysters is from September until April.
The basic reason for this is biology. With the lengthening of the days and the warming of the sea oysters start to move into breeding mode. All their energy is directed in to spawning and as a result they are not in the best condition to eat. They can be what is referred to as ‘spawny’ or ‘milky’. What is happening is that the oysters are converting their glycogen stores, what makes them taste good, into reproductive cells called gamete which can taste rather bitter.
However, it is important to note that this adage came about in reference to native species, i.e. the Native European Flat oyster.
As such, it is not directly applicable to non native species such as the Rock oyster and this is the oyster that is most commonly available in Europe.
Rough Rule of Thumb 1: For Native oyster species only eat them in season (i.e. September to April for Natives in Europe)
Question 2: So can you eat Rock oysters all year round?
Unfortunately, the answer to this question is that it also depends.
Despite the fact the Rock oyster is a non native species in many parts, its ability to breed depends upon environmental conditions and not where it comes from. If conditions are suitable, primarily defined by water temperature, they shall spawn. This can and does happen in England, France and other warmer parts of Europe for example.
Incidentally, this raises questions around non native species establishing themselves in the environment and the role climate change may have in this, but that is a topic for another day.
Therefore, if the Rock oysters are grown in areas with suitable breeding conditions Rough Rule of Thumb 1 should probably apply. Otherwise they can be eaten all year round, although even then you shall more than likely come upon the odd 'spawny' oyster during the warmer months. The reason for that is because despite the environmental limitations the Rock oysters shall still try to reproduce and some shall succeed, or partially succeed, in producing gamete.
Rough Rule of Thumb 2: You can eat Rock oysters all year round if they come from areas with cool summer water temperatures that prevent spawning (like our farm!)
Question 3: What is the best time of year to eat oysters?
Again, there is no easy answer to this question, as taste is subjective. The condition and taste profile of any individual farm’s oysters is in a constant state of flux and is heavily influenced by weather events such as rain.
However, for both Native and Rock oysters there is a general direction of travel. In the Northern hemisphere from September onwards, and as the autumn approaches, oysters start building their glycogen stores. In the depths of winter they shall start to use this glycogen as an energy source to see themselves through until the Spring algae bloom occurs.
It is glycogen that makes oysters taste good and so, personal preference aside, they are properly best when these stores are at their highest levels. That means oysters are probably best between September and December, with perhaps December being the best month of all. After that glycogen starts to become depleted and by April they can be in rather poor condition and termed ‘watery’.
Incidentally, glycogen is apparently tasteless and so can not itself add to the sweetness of an oyster. However, it is a starch which is a long chain sugar molecule made from glucose, the sugar we use in our own muscles. This means it is readily broken down by enzymes in our saliva and the molecules of glucose fit nicely onto our taste buds that detect sugar. Voilà, sweetness!
Rough Rule of Thumb 3: Oysters are probably best between September and December, with perhaps December being the best month of all.
Please keep in mind there are no right or wrong answers here because beauty, as they say, is in the eye of the beholder. These rules are as stated, rough rules of thumb, but hopeful they can give you some sort of frame of reference.