Diving with British Marine Life: The Grey Triggerfish

Part 2 of a new series by blogger Georgie Bull…

Before starting University last September, I dove Chesil Cove in the hope that I could get a glimpse of a triggerfish on the Royal Adelaide wreck. Grey triggerfish (Balistes capriscus) are seasonal visitors to our waters and are known to congregate on the wreck at a similar time each year. They are often fished off or battered by storms fairly rapidly, so sightings are temporally confined too.

For anyone unfamiliar with Chesil, large pebble ridges create a wonderful pre and post dive work out for any diver keen enough to get in. Jon Bunker (Instagram: @jon_bunker) my Dorset dive buddy did a fantastic job of locating the wreck, and we had a very pleasant dive overall. Jon has invited me along on lots of his diving antics, and he’s the main reason I have so many photos to share.

On the dive we saw the likes of jewel anemones, congers, and a wonderful variety of wrasse. Without a trigger in sight, a couple of tompot blennies fighting one another became the main highlight. After the dive we spoke to a recreational angler on the beach, who mentioned he’d caught (and returned) a triggerfish while we were in the water. We were so close to a sighting!

Once I’d recovered from the pebble ridges and put my kit away, I accepted that I’d have to wait until next year.

Fast forward to a few weeks time, and the University of Plymouth’s Scuba Society were running their first shore club dive at Firestone Bay. I joined in, hoping to see a few different tunicates or echinoderms that I may not see so often in Lyme Bay. Instead, I was greeted with a large and relatively healthy triggerfish sat on the substrate. It turns out, I didn’t need to scale pebble ridges or use Jon’s impressive navigation skills to have an encounter with this species!

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Triggerfish have defensive spines on their dorsal which are used to avoid predation, but also wedge themselves into crevices outside of harms way. Like their namesake suggests, the erection of their largest spine is triggered by the depression of a smaller spine closer to their head. Triggerfish are also known for aggressive behaviour, as they are particularly territorial over their nests.

Grey triggerfish are a Southern European species, and are valued by anglers both commercially and recreationally. This value has resulted in them being categorised as ‘vulnerable’ by IUCN. They are also the only triggerfish encountered in UK waters, with the other 39 species of triggerfish found typically in warmer waters.

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In recent years, it’s been reported that grey triggerfish are becoming increasingly common in the UK. We have plenty of evidence to suggest that our oceans are warming, and we know from previous instances that migratory pelagic fish like the grey triggerfish are capable of shifting their distribution in response to environmental change.

In 1930, a grey triggerfish was recorded in St Malo, France; by the 1990s, they were being described as common in Jersey. In southern parts of the UK grey triggerfish sightings were unheard of too, up until the early 2000s. They are now regarded as common in some areas (like Chesil) at certain times of the year. It would be interesting to see this shift quantified more and understand if the increased catch rates may also be influenced by changing fishing methods and intensity.