The Cornish Blues
Updated: Jan 31
January can’t depart soon enough. Cold, dark and wet, not to mention the global pandemic. Like many folks I suspect, I’ve found myself pining for warmer weather and scheming what I’ll do when it eventually appears. Whilst things are bleak, I can at least fantasise about spring (nudibranchs, spider crab aggregations!) and a long summer of diving, hopefully made more social by a return to the rule of six -if we’re lucky.
I’ve certainly been thinking about a trip to see some of our most spectacular summer visitors again, namely Prionace glauca, the blue shark. Whilst climate change and other environmental factors are responsible for a raft of new or renewed voyagers from warmer seas, blue sharks have always been regular visitors to our shores. Indeed, I’m sadly old enough to remember when the SACGB had an office in Looe, and you’d see them coming in to the quayside with a dangling blue trussed up on the derrick like something out of Moby Dick or ‘Jaws’. Fortunately, times have moved on and to claim a British record, like the phenomenal specimen caught in 2017 (see link below), sharks must now be measured then returned alive. This is arguably progress, and certainly more useful for the scientists involved in studying these animals.
It’s only relatively recently, thanks to the pioneering efforts of divers and skippers like Charles Hood and Damian Brown, that the Great British public has had the opportunity to get nose to nose with these remarkable creatures. Whilst they are a truly pelagic shark, present in all temperate and tropical seas, the visiting blue sharks are (generally) more likely to be smaller females following the Gulf Stream over from the eastern coast of North America to appear in our waters between June and September.
Some other fun facts:
- Viviparous (births live young) with a litter size anything between 1-135 pups, typically around 35.
- Gestation of around 9-12 months, with pups born in the spring
- Males mature between four and six years, females between five and seven years.
- Like most sharks, females are known to have thicker skin to reduce damage when the male grips them with his jaws in order to mate.
- Believed to live for up to 20 years, growing up to 3.8m with unconfirmed reports of larger individuals.
- Lives on a diet of mackerel, smaller fishes, squid and cuttlefish.
- IUCN conservation status is ‘Near Threatened’ due to overfishing and the lingering trade in fins. In the UK it is listed as a ‘Priority Species’ under the Post-2010 Biodiversity Framework.
As I mentioned previously, I’ve been fortunate enough to participate in two of these trips now, the first in July of 2018 and then again in August of 2019. The day typically starts early, as to get out to the sharks you need to be a reasonable distance from shore, certainly with 50+ metres of water underneath you. The sharks come up on a trail of fish oil, blood and guts (blues are not averse to carrion) suspended in either a small mesh cage or net bag, before being lured to the surface by bait-bearing steel traces at various depths.
Once on the surface, and being tossed the occasional gobbet to keep them interested, the blues fall into a steady pattern of circling. At first I thought this was a ridiculous cliché’ before I got to see the behaviour for myself first hand. We weren’t allowed to enter the water until Damian our ‘shark wrangler’ (for want of a better expression) was happy the sharks were in a relaxed pattern. Barely containing my excitement, I was the first on that 2018 boat to try and slip into the water with a minimum of splashing.
This was not so as to avoid being engulfed by the jaws of the beasts, far from it. "They’re incredibly skittish." Damian explained. We were likewise advised to avoid sudden movements, splashing, and certainly diving down, for fear of them deserting the boat and having to start the whole lengthy process again. It was also the reason we were wearing snorkels rather than carrying bulky scuba cylinders. Imagine sharks being scared of bubbles!
Once in the water, but even at first sight if I’m honest, the most visually stunning thing about them is the colour, described variously as ‘metallic indigo’ and ‘intense deep blue’ to ‘rich ultramarine’. These all fall short of actually seeing it for yourself. It is almost impossible to delineate, being all at once a deep blue, iridescent shimmering silver and even gold in the sunlight. Being counter-shaded, the blue sheen fades to a silvery white belly, making it less of a target to potentially bigger predators below.
The next thing you notice is the elongated shape, I think I heard Mike deGruy say it best when he said it was like someone had took at typical shark and ‘stretched’ it out. Richard Ellis also observed that they are ‘a lithe, graceful animal, proportionally slimmer than any other Carcharhinidae’. They certainly circled the boat with graceful rhythm, sweeping round to the interesting metal box floating off the stern and occasionally coming in closer to bump our camera housings with their pointed snouts.
I never felt alarmed at any stage in the water with the blues. That’s not out of any sense of bravado (most people reading this know me after all) or to be blasé, but rather because a few minutes in the water with the blues is enough to make you realise all their attention was focused on the rear of the boat where the handouts were coming from. I mean, they weren’t completely disinterested, there was certainly some polite curiosity from the sharks but we were clearly neither food or competition so they seemed prepared to accept us.
The only time I saw one of the two blues (on my first trip) become even slightly agitated was when one of our number, Derek, got nipped on the bum. I won’t call it a bite, because it certainly wasn’t even that. He himself would be the first to admit he’d taken his eye off shark two in his rapt observation of shark one, and raising his legs to fin slightly he lifted the shark directly above said limbs toward the surface. I imagine it gave them both a fright (as well as a story for the grandkids) but it didn’t pierce any of neoprene of his wetsuit and the blue merely left a pale circle where it had gummed his arse in its panic.
Fundamentally, all of us entering the water with blues accepted that we are in their environment and for the most part everybody I’ve snorkelled with on these trips has reigned in the impulse to touch a fin or brush their back. Fingers, as we were expertly advised, stay covered in gloves and balled into fists if not clutching housings. There is minimal risk, but a little healthy respect is certainly necessary if you’d like to take part in such an encounter:
‘The blue shark is not considered dangerous, but it has the size and the equipment to be taken seriously.’ -Ellis
You must also resign yourself to chance. My 2018 trip was a day of blazing sunshine, excellent water visibility, and the sharks were up the trail in two hours and lingered with us for at least three or four hours on the surface before we had to head home. In 2019, it took us near all day to attract a solitary female to the surface, possibly because she was wary of a larger blue that we sighted beneath that didn’t come up. It was no less a magical experience, but certainly one that tested everybody’s patience. As with all wildlife encounters of this sort, nothing is guaranteed and you often need to manage your own expectations -but by god, it is worth it!
'Exceptional' British record shark caught off Cornwall, BBC News, 2nd August 2017
The Book of Sharks, Ellis 1983, Alfred A. Knopf Ltd. pp127-128
Shark Watcher’s Handbook, Carwardine, Watterson 2002, BBC Worldwide Ltd. pp132-133
Wild and Temperate Seas: 50 Favourite UK Dives, Appleyard et al. 2020, Dived Up Publications pp52-53
Field Guide to Sharks, Rays and Chimaeras of Europe and the Mediterranean, Ebert & Dando 2020 Wild Nature Press (PUP) p343