Fishing News is pleased to announce the launch of a new, monthly feature focused on answering scientific questions sent in by readers.

It will be run by researcher Hannah Fennell and will focus on the science of fish and the fishing industry.

If you have any questions about fish, shellfish, how stock models work, or anything else fishing related, please get in touch by emailing your questions to Hannah Fennell at

Hannah Fennell

Hannah Fennell

Question: Catching a bright blue lobster is supposed to be a one in a million chance. I have caught a number of them over the years. When I go back to take a picture, after I have finished hauling, the lobster has changed colour and isn’t as bright blue. What causes this, and are blue lobsters as rare as people say?

Explanation: The colour of lobsters, as with many other species, is due to a mix of genetic and environmental factors, including diet, temperature, and habitat. All crustaceans get their
colour from a type of reddish-orange pigment called carotenoid, which they obtain naturally from their diet. When it binds to the protein called crustacyanin (as it does in the shell of a lobster), it loses its red hue and produces another colour.

The colour produced depends on how the two molecules interact and can vary from one end of the visible colour spectrum to the other (including bright blue). Heating up these two molecules causes them to no longer interact, which is why when you boil a lobster it turns red.

When a lobster is taken from the sea, and a colour change occurs, it is likely that what you are seeing is the lobster equivalent of tanning. A study on American lobsters (Homarus americanus) found that lobsters got darker when they were exposed to UV light, in an attempt to protect themselves from UV damage that can harm DNA and proteins. Keeping lobsters in the dark may help keep their bright colour, but the study also found that in the absence of UV light lobsters would try and match the colour of their container.

The rarity of a bright blue lobster is still under debate: some place the odds as being one in a hundred thousand, while others think it’s closer to one in a million. However, it’s possible the reason for this confusion is because of the confusion between species. The American lobster is naturally muddy brown-green while the European lobster (Homarus gammarus) is naturally dark blue. Finding a bright blue American lobster is probably more unusual than finding a bright blue European one, and also easier to spot.

Either way, the colour of a lobster should not affect the flavour or the quality of the lobster, although brightly coloured lobsters may be valued more by customers for their novelty.