(Text by kind permission of Dr Cris Little)
The grey triggerfish (Balistes capriscus) is a warm-water species with a normal range in the tropical Atlantic and the Mediterranean. However, in the summer months when the seas are at their warmest they can be found in the waters around Britain and Ireland. Reports come mainly from the Southwest coast, but triggers have also been found in the North Sea. One individual reached as far north as Shetland!
Unfortunately, the triggerfish cannot survive the British winter and die off when the water temperature falls below about 12 Celsius. So where do they come from? The answer to this is not entirely certain. Triggerfish are rather feeble swimmers, so it seems more likely that they are brought in by the Gulf Stream from mid-Atlantic islands, such as the Azores, rather than travelling up from the Mediterranean against the currents.
With higher sea temperatures, the grey triggerfish looks set to become an increasingly common visitor to our coastal seas. So the chances of divers seeing this distinctive fish are better than ever. The wreck of the Royal Adelaide on Chesil Beach and Oxwich Bay on the Gower seem to be particularly regular haunts, but look out for them in any shallow rocky area or wrecks. It is also worth noting that the triggerfish may be a harbinger of other exotic warm-water species - so keep your eyes peeled when diving in the late summer!