'Contrary to our assumption, the low-armour gene is not linked to a preference for fresh water, or low salinity,' said Barrett.

'Instead, we found a strong association between having the gene and the fish's inclination to move into different salinities -- a sort of wanderlust gene, if you will -- instead of staying put and acclimatising to the current salinity,' said Barrett.

'The new behavioural association we've identified may also shed light on why there's still a small but constant population of armour-less sticklebacks in the sea despite the high predation there. Sticklebacks with the mutant gene just like to go to new places.'

These findings were published in Biology Letters.