autumn | Cornish Rock Pools

As you may have noticed, blog writing has been relegated to my ‘to do dreckly’ list for a couple of months now. In September, I unexpectedly started a job that I didn’t know I’d applied for and my photos of rock pooling trips, including this day at Prisk Cove, have been piling up ever since. It’s time for a catch-up!

A swimming variegated scallop was one of the highlights of this short video I put together at Prisk Cove this autumn.

For once, the gales and mizzle held off for our visit to Prisk Cove, making it an ideal day for sitting by the pools and staring. The longer I looked the more I discovered.

This Aeolidiella alderi sea slug had recently munched its way through a Daisy anemone, turning the cerata on its back from white to a deep, speckled brown. It is sometimes called the ‘white-ruffed’ slug due to the paler cerata that form a smart collar behind its head.

Aeolidiella alderi – the white-ruffed sea slug

Finding a nudibranch sea slug made an auspicious start to the day, and there were plenty more discoveries in store. Many of the tunicate sea squirts I find on the shore are dull brown, but this Ascidia mentula was an explosion of colour.

Up close, the Ascidia mentula sea squirt looks like a riotous display of tiny red fireworks

Nearby, a chiton nestled among the barnacles, moving very slightly as I watched. These unassuming little molluscs have changed very little since the Devonian period. You have to look closely to appreciate their varied patterns. There are several species commonly found on our shores and some – like this one – have clusters of bristles fringing their armoured plates.

Flatworms are far more exciting to watch than chitons. They are speedy for their size, flowing seamlessly over rock and engulfing any obstacles they meet.

This remarkably bright flatworm is a Cycloporus papillosus. I mostly see them in shades of star-studded blue, but this one has other ideas. They vary in colour to match their equally resplendent prey, the star ascidian sea squirt.

Caught crossing the rock in search of new food supplies, this flatworm was easy to spot. Once it is on a sea squirt, it will become almost invisible.

Cycloporus paplillosus flatworm, normally found on star ascidian sea squirts.

The colourful Cycloporus papillosus flatworm lives on star ascidian sea squirts like these.

Rocky overhangs are my happy place. They’re a kind of lucky dip with fascinating creatures hiding in every single one. I wouldn’t advise putting a hand in an overhang as there’s almost always a crab lurking at the back, but it’s worth going through the contortions required to obtain a good view of what lies within. This spiny starfish, however, wouldn’t win any games of hide-and-seek.

Always watch your fingers when there are velvet swimming crabs about. This one had especially blue claws.

Unlike the starfish, my next find was a master of disguise, hugging the rock and changing colour to match it. Only the googly eyes and a tiny fluttering fin gave this topknot flatfish away.

Pressed against the rock, the topknot is almost invisible.

Among boulders encrusted in colourful sponges, I was delighted to find my favourite slug: “Discodoris” – the Geitodoris planata. This one was busy tucking into the sponges and sported plenty of acid glands to ward off any would-be predators, visible as white patches on the slug’s back.

Geitodoris planata enjoying a feast of sponges.

Tortoiseshell limpets can go unnoticed due to their diminutive size, but they have one of the prettiest shells on our shores. This one, nestling among the pink seaweeds, was a perfect burst of pink and blue.

I always tell people that they should go slowly and look closely to see and appreciate wildlife. It works every time and is good advice for life in general, yet it’s advice I sometimes forget myself. In my haste to find the next thing, I can easily miss what is in front of me.

This quiet, meandering day at Prisk Cove, was a rare chance to truly stop and look, to watch animals doing their own thing. From the mysid prawns flocking around the snakelocks anemones to the way the green shore urchins had arranged their shelters of seaweed, pebbles and shells, there were endless insights into rockpool life. If the tide hadn’t come in, I would happily have stayed for many hours, staring into those perfect pools.

Nadelik lowen! Merry Christmas! Wishing you a happy and restful time.

Mysid prawn hovering over a snakelocks anemone

“The urchin’s got his hat on…” – Green shore urchin using a limpet shell for shelter.

Whatever the weather, always stay safe in the rock pools. Follow my rockpooling tips to look after yourself and the wildlife on the shore.

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I’m not a fan of winter. Even though I go rock pooling all year round and love the way the wildlife varies with the seasons, the November to February period is a challenge for me. The thought of sticking my hands in icy-cold water makes me want to hibernate. Right on cue, a fierce northerly wind blows in for the spring tides. I layer up and wear my fluffiest, most comforting jumper to bring you this week’s blog post.

Obelia geniculata - a hydroid known as 'sea fir'. — Obelia geniculata – a hydroid known as ‘Kelp fir’. Recognisable by its zig-zag ‘stems’.

I’m trying to photograph hydroids at the moment. These relatives of the jellyfish and anemones are generally translucent and no more than a few centimetres long, making them hard to spot. At this time of year when the seaweeds die back and the waves roll in, it’s especially tricky. My camera doesn’t like focussing on them and they won’t stay still in the current, but their nodding tentacles and curious structures are mesmerising.

Another hydroid - Coryne pusilla. This one can't retract its tentacles into little cups. It has a ringed stem (visible in the bottom-left of the photo). — Another hydroid – Coryne pusilla. This one can’t retract its tentacles into little cups. It has a ringed stem (visible in the bottom-left of the photo).

As always there are strange creatures galore. This Sea gherkin is unusually large and gnarled.

A Sea gherkin (Pawsonia saxicola) - this is a type of sea cucumber and clings onto the rock with its tentacle feet. — A Sea gherkin (Pawsonia saxicola) – this is a type of sea cucumber and clings onto the rock with its tentacle feet.

Among the sponges and brittle stars I come across this invasive species from the South Pacific, the Orange-tipped sea squirt, Corella eumyota.

The twisted gut is very prominent in this species and you can see the orange colouration at the top. It’s thought this species may compete with native squirts and other invertebrates, but we will only find out by monitoring its spread. This is the first one I’ve recorded here.

Nearby I find the native sea squirt Ascidia mentula with lovely red flecks in its almost transparent test.

Ascidia mentula - a tunicate sea squirt. The red streaks reminded me of fireworks. — Ascidia mentula – a tunicate sea squirt. The red streaks reminded me of fireworks.

This sponge also catches my eye. It’s hard to identify many sponges with any certainty without examining their spicules under a microscope, but this one has the appearance of Myxilla rosacea.

A striking sponge with its fine structures and deep pores. Possibly Myxilla rosacea. — A striking pink sponge with fine structures and deep pores. Possibly Myxilla rosacea.

On the next tide we make a successful return visit to the beach where Cornish Rock Pools Junior achieved finding a world record haul of stalked jellyfish last year. We come close to matching the numbers we found last time. I lose count at 25 because Junior makes it clear he doesn’t want his record broken.

Many of the stalked jellyfish are juveniles, only a few millimetres long and it tests my eyes to pick them out among the swirling seaweed. Then I spot this 1mm pinprick of a jelly blob and take a photo in case it turns out to be a stalked jelly.

My eyes must still be good - a 1mm baby stalked jellyfish. It's not possible to say for sure what species. — My eyes must still be good – a 1mm baby stalked jellyfish. It’s not possible to say for sure what species.

On my screen at home its column is clearly visible although the tentacles are either retracted or haven’t yet grown. Little is known about the very early stages of development of these creatures and how to separate the species by sight, but David Fenwick who runs the amazing Stauromedusae UK website confirms that it is definitely a stalked jelly.

It’s great to be able to show a friend from Natural England how abundant these species are in the Looe and Whitsand Bay Marine Conservation Zone, which aims to give them protection from developments and disturbance.

Haliclystus octoradiatus - the blobs between the arms are primary tentacles, which easily identify this species from most others we see. — Haliclystus octoradiatus – the blobs between the arms are primary tentacles, which easily identify this species from most others we see.

One of her sons does an impressive job of finding stalked jellies and even finds one that is in the middle of eating an amphipod. The current is too strong to get a great photo, but you can clearly see the unfortunate creature’s head sticking out of the stalked jellyfish’s mouth here.

A stalked jellyfish (Haliclystus octoradiatus) eating an amphipod.

I’ll be submitting all my stalked jellyfish records to help reinforce the evidence that will hopefully keep these protected species from harm.

A juvenile Calvadosia cruxmelitensis stalked jellyfish. We found 3 species of stalked jellyfish on the site.

I can’t help taking a look at some other things while I’m here. But before long the cold is hurting my fingers and chilling my insides in the sort of way that can only be fixed by a steaming mug of hot chocolate.

That’s the bit of winter I look forward to!