Baffling jellies, a little shark and a possible giant – A day in the Cornish Rock Pools

Sometimes everything’s just meant to be. This is one of those times.

It’s a random get-together; my Twitter friend Nanny Pat from Bosinver Farm Cottages has suggested we meet with her family and friends to explore a special beach that her son loves. Sounds good to me!

The view towards Falmouth, Cornish Rock Pools
The view towards Falmouth

The sun is struggling through the clouds as we all descend from Mawnan towards the glittering shore. We are nine adults, six children, one dog, some huge buckets and a promisingly enormous picnic bag that Nanny Pat has packed for us.

We waste no time and strike out across the slippery rocks. These are serious rock poolers. I am, as other half puts it, “among my people”.

Just one more rock... exploring the Cornish rock pools
Just one more rock… exploring the Cornish rock pools

We set to and the finds flood in. There are fish eggs everywhere, some are just starting to develop like these clingfish eggs.

Cornish clingfish eggs are a distinctive yellow colour
Cornish clingfish eggs are a distinctive yellow colour

Others are nearly ready to swim away, eyes jammed against their transparent egg cases, tails squished around them.

Ever feel like you're being watched? Fish eggs in a rock pool.
Ever feel like you’re being watched? Fish eggs in a rock pool.

Best of all, I’m baffled by some of the creatures we find.

The medusa (jelly) stage of a hydroid or sea fir - possibly clytia hemisphaerica or similar
The medusa (jelly) stage of a hydroid or sea fir – possibly clytia hemisphaerica or similar

First there’s a transparent disk of jelly a centimetre across. I scoop it up in a tub and peer at it until I go cross-eyed. It shows no sign of life, but I’m sure it is an animal. All around its rim are mauve dots and a thin purple cross hangs across its centre.

The underside of the medusa
The underside of the medusa

I rule out all the UK jellyfish and it’s the wrong shape for a sea gooseberry. When I take a photo of it in the water, my camera shows some short tentacles, invisible to the naked eye.

Having since consulted the experts, it looks to be the medusa (jelly) stage in the lifecycle of some sort of hydroid or sea fir.

Swimming free - the side view with tentacles showing.
Swimming free – the side view with tentacles showing.

I’m distracted from my observations by some excited shouts and squeals. “Quick, we’ve found a shark!” one of the adults calls.

The children are gathering around the edge of a pool and there in some shallow seaweed, a dogfish (small spotted catshark – scyliorhinus canicula) lies stranded.

Scyliorhinus canicula - small spotted catshark or dogfish stranded in a Cornish rock pool
Scyliorhinus canicula – small spotted catshark, also known as dogfish – stranded in a Cornish rock pool

The animal is calm despite being out of the water and surrounded by eager kids. We take a minute to take photos. Some of the children tentatively touch its sandpaper-rough skin and Cornish Rock Pools junior sluices it with water in an effort to keep it happy.

Close up you can see the rough skin (that used to get used as sandpaper) and the cat-like eyes
Close up you can see the rough skin (dogfish skin used to be used as sandpaper) and the cat-like eyes

The dads rush in for the privilege of relocating our shark to a deeper pool, where it lurks as we carry on our rockpooling.

The 'rehomed' catshark waiting for the tide to come in. It was so well camouflaged it was hard to spot among the seaweed.
The ‘rehomed’ catshark waiting for the tide to come in. It’s so well camouflaged it’s tricky to spot among the seaweed.

One of the finds, a little fish catches my eye. When I first see its red body and dark head, I think it could be a black-faced blenny. The shape doesn’t seem right though. After much staring, I conclude it’s probably a scorpion fish. In my photos the spines on its face can be seen more clearly, confirming that it’s the smallest specimen of this species I’ve ever seen.

A juvenile scorpion fish - the smallest I've ever seen
A juvenile scorpion fish – the smallest I’ve ever seen.

The picnic is perfect in every way. Some of the children huddle together with their sandwiches on top of a tall rock. The smaller kids play in the sand and shower some into the olives, but no one cares.

The tide has moved in but there’s still time for some last-ditch rock pooling to the east of the beach. One of the boys is desperate to find and eel and his determination pays off. He locates a good-sized common eel under a rock, but it slithers into a crevice, evading capture.

Love is in the air! Berthella plumula sea slugs under a rock.
Love is in the air! Berthella plumula sea slugs under a rock.

There is no shortage of crabs here and we find pairs of lemon-yellow berthella plumula sea slugs clinging to the underside of the rocks. I’m told there are giant gobies around and it’s not long before one of the dads sends up a triumphant cry. “It’s a giant.”

It's a whopper, but is it a giant? Goby found in a mid-shore pool
It’s a whopper, but is it a giant? Goby found in a mid-shore pool

We all look closely. I’ve seen some big rock gobies and I know they can be hard to tell apart from the rarer giant goby. This one looks like it could be the real thing. It’s large, at least 17cm, and has the fat-lipped face and salt and pepper colouring of a giant goby.

The goby's face showing the super-thick lips.
The goby’s face showing the super-thick lips.

I take photos of the sucker fin on its belly and hope we’ll be able to get a definitive answer from the experts. The giant goby has a detatched lobe at the front of its sucker fin which the rock goby doesn’t have…apparently.

The pelvic sucker fin of the goby
The pelvic sucker fin of the goby

As we release the goby into the pool where we found it, the children spot their granddad walking onto the beach. He’s arrived just as the tide overtakes the last pools and he invites the kids to join him for a spot of skimming.

It’s the first time I’ve been to this beach. I think I’ll be back.  Some things are indeed meant to be.

Brittle star
Brittle star

 

A good sized three-bearded rockling
A good sized three-bearded rockling
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