Category Archives: Crabs, prawns and lobsters

From Cornwall to Cornouailles – a dabble in the Breton rock pools

Once the busy summer season of rock pooling events is over, we like to jump on the ferry and get away for a few weeks. We have friends to visit and lots to do, but somehow we always end up on the beach. It’s fascinating to discover the difference it makes to be a few hundred kilometres further south.

Although there are plenty of familiar species here, there are some that are around their northern limit here in Brittany, but might put in appearance in Cornwall one day, especially as the seas warm up.

On a sheltered shore in the lee of the Quiberon peninsula, the beach where our friend Mylene spent her childhood holidays, I find a Pachygrapsus marmoratus crab, a species I saw nearby last year when I didn’t have my camera.

Pachygrapsus marmoratus crab
Pachygrapsus marmoratus crab

The rippled pattern on its carapace and the wide flat edge between its eyes make it unlike any of our native crabs. Originally found further south on the Atlantic coast, it has been working its way northwards in recent years and seems to be firmly established in Brittany now.

The three teeth along each side of the carapace distinguish this species from other rock crabs
The three teeth along each side of the carapace distinguish this species from other rock crabs

Something I didn’t notice last year is how fabulously green its knee joints are, matching its emerald eyes. It’s not afraid to use those leg-joints, scuttling away at high speed at every opportunity to hide among the dense aggregations of the invasive Pacific oyster. I nearly lose it several times before it decides to settle in the corner of a pool, allowing me photograph those hairy legs and green knees.

The fabulous green knees of Pachygrapsus marmoratus!
The wonderful green knees of Pachygrapsus marmoratus!

Junior calls out that he’s found a slug. He thinks. He’s not sure. There are so many living blobs on the shore that it can be hard to tell.

The blob is a plump yellow thing, perhaps four or five centimetres long and from the speed it’s crawling across the rock, it is most definitely a slug. Initially, I assume it’s a sea lemon, but it doesn’t quite look right. It has a more squidgy, unicoloured look and instead of the citrussy bumps of the sea lemon’s skin, this slug has rounded protrusions of varying sizes all over its back. I can’t place it so we call it a ‘Doris might be a sea lemon, species’ and I take plenty of photos to help identify it for sure later.

Doris verrucosa - the 'warty Doris' - exploring a bed of Pacific oysters
Doris verrucosa – the ‘warty Doris’ – exploring a bed of Pacific oysters

It’s over a month after we return from holiday that I remember the photos and transfer them to my computer. On screen it’s obvious that this Doris slug looks nothing like any sea lemon I’ve ever seen. With the help of some extremely geeky books, websites and a forum of fellow nudibranch aficionados, I manage to confirm that it is a Doris verrucosa. The “warty Doris”… not the most charming name, but Junior is rightly thrilled that he found it. This isn’t a species we’ve ever seen in the UK.

Each rhinophore on the slug's head is framed by two pairs of prominent protrusions and the gills are framed by a crown of tall protrusions.
Each rhinophore on the slug’s head is framed by two pairs of prominent protrusions and the gills are framed by a crown of tall protrusions.

We revisit a beach that is the polar opposite of the sheltered shore of Quiberon. Ste Anne de Palud is a west-facing windswept expanse of muddy sand framed by a north-facing rocky headland and pools, which provide an incredible habitat for all sorts of clam shells and colourful anemones as well as a perfect set of conditions for the honeycomb reef worm, which builds its huge beehive-like structures all around the rocks.

A honeycomb worm reef overhanging a pool at Ste Anne la Palud, Brittany
A honeycomb worm reef overhanging a pool at Ste Anne la Palud, Brittany

The anemones are fabulous, but so well tucked under steep overhangs of rock or so well buried in sediment that they are tricky to see, let alone identify.

Sagartia elegans anemone, Ste Anne la Palud
Sagartia elegans anemone, Ste Anne la Palud
Strawberry amemone showing its blue beadlet fighting tentacles
Strawberry amemone showing its blue beadlet fighting tentacles
Another colour variation of Sagartia elegans
Another colour variation of Sagartia elegans

Junior is digging holes in the sand and discovers just how packed with life the sand is as he uncovers dozens of thin tellin shells, which burrow their way back down as he watches. The tideline is strewn with evidence of the diversity of life beneath our feet, with spiny cockles, sea potato urchins, the delicate tubes of the worm Pectinaria belgica and necklace shells.

Spiny cockles and their relatives are common here
Spiny cockles and their relatives are common here
Pectinaria belgica worm tube
Pectinaria belgica worm tube
Necklace shell. Euspina catena
Necklace shell. Euspina catena

There’s a good chance that some of the less familiar animals we’ve seen will show up on the Cornish coast at some point. The St Piran’s hermit crab has already successfully made the crossing and I saw them first here.

A trip to Brittany feels like the perfect way to familiarise myself with creatures that I might need to identify in future. It’s also a good excuse to eat lots of pancakes and put my feet up. Both make me happy!

The vast, rich sands of Ste Anne la Palud
The vast, rich sands of Ste Anne la Palud
A juvenile sea hare
A juvenile sea hare

Rock Pooling at Coverack with Wildlife Watch

The sun breaks through the cloud as the first children arrive. It’s a perfect day for a Wildlife Watch expedition and although I don’t know the beach at Coverack well, a quick paddle in the rippling shallows has already yielded sand eels, an attractive pink thin tellin shell and plenty of shore crabs so it’s shaping up well.

Lesser sand eel - being dark on top and light underneath makes it harder for predators to spot them in the water.
Lesser sand eel – being dark on top and light underneath makes it harder for predators to spot them in the water.

I always look forward to meeting my Wildlife Watch groups and this one doesn’t disappoint. My assistant, Vicky, does a fabulous job of welcoming everyone and helping set up and the children are enthusiastic and curious, raring to get stuck in. It’s especially good to see how well the kids care for the animals, making sure they have enough water in their tubs, replacing any stones and seaweed they move and not detaching animals that might get damaged like anemones and limpets.

One lad is particularly adventurous and knowledgeable, so we have fun investigating a gully between two huge rocks. We find the inner face of one rock is covered in a massive sheet of breadcrumb sponge and there are especially large strawberry anemones in the pool beneath. My new friend stays there trying to catch an elusive fish while I help others identify creatures.

Soon, the finds are coming in to our makeshift shore laboratory. Glittering sand eels, a feisty velvet swimming crab with devilish red eyes, a whole troop of hermit crabs and colourful brittle stars which we watch walking on their long arms.

A lovely baby hermit crab with green eyes (Pagurus bernhardus) has a go at pinching my fingers.
A lovely baby hermit crab with green eyes (Pagurus bernhardus) has a go at pinching my fingers.

My new friend comes over with a shore crab. He’s learned that they keep their eggs under their tails and is excited to find one he thinks is in berry. He seems disappointed when I reveal that, although she has something under there, it’s not eggs. But this is something far more exciting. It’s a parasitic barnacle, Sacculina carcini, which I’ve been searching for and never seen. The yellow mass under the crab’s tail is the barnacle’s fruiting body, the barnacle’s eggs – not the crab’s.

This green shore crab has a yellow lump under her tail - the parasitic barnacle Sacculina carcini
This green shore crab has a yellow lump under her tail – the parasitic barnacle Sacculina carcini

Unfortunately for the crab, once it is infected it can no longer moult and grow or lay eggs. The barnacle will take a lot of energy from the crab as it spreads through its body. It can even trick male crabs into behaving like females to ensure that they will successfully release the barnacle’s young when the eggs are ready to hatch. It’s amazing to see, even if it’s not good news for the crab.

The yellow lump under the tail contains the eggs of the parasitic barnacle which has infested the crab.
The yellow lump under the tail contains the eggs of the parasitic barnacle which has infested the crab.

As always, I get more than a little distracted doing my own rock pooling. I can’t help myself. I briefly feel guilty that I’m not available enough to the children while I’m crawling about among the slippery boulders, but then I spot a miniscule thing moving on the rock and it has my entire attention.

The thing looks like a tiny lobster. I scramble to grab a suitable pot and when I look back at the rock I can’t see it any more. I stare at the area where I saw it but it’s just not there. I look all around the surface of the rock in vain, gently tip a little sea water down it to see if anything moves but I’m scared I might wash it off accidentally.

When I finally relocate my mini crustacean, it is nearly at the edge. With a lot of care and determination, I succeed in catching it in my pot. It’s only about 5mm long, but seems to be a tiny squat lobster, the smallest I’ve ever seen.

Tiny squat lobster about 5mm long (Galathea sp.) at Coverack, Lizard
Tiny squat lobster about 5mm long (Galathea sp.) at Coverack, Lizard

Back at the trays, we all gather round to take a close look at all the animals and learn about their lives and strange habits. We have a fabulous diversity of creatures to watch before they’re returned to the shore.

I slip my baby squat lobster into a petri dish to take some photos. It looks a bit strange, as though something has got caught on its back legs. When I look a couple of minutes later, the thing that’s stuck to it has grown. It’s hard to see as the whole animal is only a few millimetres long, but when the ‘thing’ comes away I’m in no doubt. The squat lobster is growing and has just shed its old skin.

Moult of the squat lobster - the animal has moved out of its old shell so that it can grow.
Moult of the squat lobster – the animal has moved out of its old shell so that it can grow.

The old carapace is an exact replica of the animal, only colourless and transparent. As the new, soft shell of the squat lobster begins to harden it seems to grow before our eyes.

The freshly moulted squat lobster (Galathea sp.) showing off some very hairy claws. Coverack, Cornwall.
The freshly moulted squat lobster (Galathea sp.) showing off some very hairy claws. Coverack, Cornwall.

It’s something I’ve never seen before. It’s what’s so special about events like this. Even though I’m here to help others learn and see new things, I’ve seen something new myself.

If you’d like to come to a Wildlife Watch event with the Cornwall Wildlife Trust this summer, you’ll need to book quickly as they are filling up. Find the whole list on the Cornwall Wildlife Trust’s website. Maybe I’ll see you there?

A beautiful live thin tellin shell - one of many lovely finds at Coverack
A beautiful live thin tellin shell – one of many lovely finds at Coverack
Necklace shell at Coverack, found by my Wildlife Watch group.
Necklace shell at Coverack, found by my Wildlife Watch group.

Wrasse and wrack

The Cornish summers are anything but predictable. One day I’m sweltering in shorts and beach shoes and the next I’m shivering in waders and a thick jumper. Although the showers are back with a vengeance, there’s always something to be found if I can make it across the rocks without breaking an ankle.

Painted top shell, East Looe
Painted top shell, East Looe

My first outing is to the rocks beyond East Looe beach and I’m pleased to come across a new colony of St Piran’s hermit crabs on the mid-shore.

A St Piran's hermit crab starting to emerge from its shell.
A St Piran’s hermit crab starting to emerge from its shell.

They’re becoming a familiar sight around Cornwall and I’m starting to recognise them from the tips of their red legs, before their chequerboard eyes and equal-sized claws emerge from their shells. Continue reading Wrasse and wrack

A Window to the Underwater World

The pools sparkle as the sun finally shoulders its way through the February murk. Beneath the surface, the seaweeds are sprouting up, the first sign of spring in the rock pools, and with them come the sea slugs. Many of these minute molluscs choose to spawn in the shallow waters around the shore, where their favourite foods such as sponges, sea squirts and seaweeds are abundant.

A baby sea hare, Aplysia punctata, grazing on seaweed.
A baby sea hare, Aplysia punctata, grazing on seaweed.

How they travel such distances to find mates and lay their eggs here is something of a mystery to me. They are delicate, squishy little things at best, and mere blobs of jelly out of the water. Once in the water, though, they reveal their colours and shapes, and most rockpoolers delight in finding them. Today, I see mostly pale, blobby ones rather than their spectacular cousins, but they are intriguing nonetheless. Continue reading A Window to the Underwater World

50 Years on from the Torrey Canyon – A fragile recovery

Next month, 50 years will have passed since the Torrey Canyon tanker ran aground off the Isles of Scilly, releasing a 700 square km oil slick. On the last day of 2016, I visited Porth Mear to learn how a long-term survey has revealed the secrets of the beach’s fragile recovery, and to see if the St Piran’s hermit crab (Clibanarius erythropus)has managed to make more than a temporary comeback.

Clibanarius erythropus - A red legged hermit crab making a comeback in the Cornish rock pools this year.
Clibanarius erythropus – A red legged hermit crab making a comeback in the Cornish rock pools this year.

When the Torrey Canyon hit rocks in February 1967, its cargo of oil ended up on the Cornish, Breton and nearby coasts. The oil, along with huge quantities of solvent emulsifying chemicals used in an attempt to disperse it, decimated seabird populations and marine wildlife.

Concerned by the impact on his local beach, biology teacher, Richard Pearce, decided to monitor the wildlife on the shore three times a year. He’s been doing his survey without fail ever since.

I wasn’t born when Richard first marked out his quadrats on Porth Mear beach, but I grew up hearing stories of the horror people felt at the sight of the thick black tide, the pervasive smell of the oil, and the woefully unprepared volunteers attempting to shift the cloying oil with garden tools. Decades later, lumps of tar were still washing onto our beaches after every storm.

I’ve always wondered what the process of recovery looked like, so I jumped at the chance to join Richard at Porth Mear for survey number 150.

Survey 150…

It’s clear, after many surveys, that Richard knows the beach well. So well, in fact, that even when the gouged crosses and splodges of green paint that mark the survey quadrats have worn away or been covered up by seaweed, he still knows exactly where they are.

Richard examines a quadrat while Chris notes the data
Richard examines a quadrat while Chris notes the data

As he shows me his method, calling out the presence and coverage of seaweeds, barnacles and molluscs to his partner, Richard tells me how after the Torrey Canyon disaster the green seaweeds were the first to flourish. With many of the grazing molluscs wiped out by the oil and the chemicals used to disperse it, the seaweeds soon took over. After this other animals gradually returned.

Crosses in the rock and paint marks show the quadrat boundaries - now on his 150th survey Richard knows just where they all are!
Crosses in the rock and paint marks show the quadrat boundaries – now on his 150th survey Richard knows just where they all are!

Over the years, Richard has seen many changes. Some are seasonal or weather related, others are harder to explain but may be due to warming seas. Why one pool that was once crammed with mussels now has almost none and why limpets are doing particularly well this season is hard to say, but the data he is collecting reveals changes that would otherwise go unnoticed.

 

Not for the faint-hearted - Richard has to scrabble down steep rocks and wade knee-deep to reach some of his quadrats.
Not for the faint-hearted – Richard has to scrabble down steep rocks and wade knee-deep to reach some of his quadrats.

The tide drops and, while Richard is knee-deep examining a quadrat alongside a long deep pool, I explore the lower shore pools, determined to find out whether the St Piran’s crab is still here. After an absence of more than 30 years, this equal-clawed hermit crab started to reappear around Cornwall in 2016 and we had one record on this beach in the spring. Although past records are too patchy to be sure, it’s thought that pollution from the Torrey Canyon played a role in the loss of this species, so 50 years on it would be lovely to find it re-establishing.

Every time I see a shell move, I leap on it, looking for the red legs and spotty eyes, but every one is a common hermit crab (Pagurus bernhardus).

The disappointment mounts... I find lots of common hermit crabs (Pagurus bernhardus) - the right claw is much chunkier than the left with lots of raised bumps on it.
The disappointment mounts… I find lots of common hermit crabs (Pagurus bernhardus) – the right claw is much chunkier than the left with lots of raised bumps on top.

Rooting around in the pools always reveals some unexpected treasures. I make my first record of a stalked jellyfish (Calvadosia cruxmelitensis) at this site.

Stalked jellyfish - Calvadosia cruxmelitensis - at Porth Mear
Stalked jellyfish – Calvadosia cruxmelitensis – at Porth Mear

This is always a good beach for finding Cornish clingfish, and the rocks of the lower shores don’t disappoint. In one small area I find a dozen of these stunning little duck-faced fish, some with iridescent blue spots on their heads.

Cornish clingfish at Porth Mear
Cornish clingfish at Porth Mear

 

And another Cornish clingfish...
And another Cornish clingfish…

As I follow a gully across the shore I find several scorpion fish lurking among the rocks. Brittle stars lurch away into the seaweed and Xantho pilipes crabs close up, pretending to be pebbles.

My other half and Junior join me, hunting for crabs and fish. Every thirty seconds I remind them that we need to look for little hermit crabs and they ignore me as they should. They’re used to me and my missions.

Not a hermit crab... a feisty male edible crab at Porth Mear.
Not a hermit crab… a feisty male edible crab at Porth Mear.

Junior at least keeps pointing out suitable pools. He knows they like the ones with pink coralline seaweed and there are lots here. I barely have time to glance at one before he’s trying to drag me to the next.

And then it happens. A shell moves and as soon as I pick it up I know. The legs are red, the shape’s wrong for the common hermit crab.  When the crab extends its claws there can be no doubt, they’re hairy and pretty much equal sized. This is a St Piran’s crab.

When I see the red legs and equal-sized claws I know - a St Piran's hermit crab at Porth Mear
When I see the red legs and equal-sized claws I know – a St Piran’s hermit crab at Porth Mear

I yell like I’ve won a golden ticket. Under my camera it’s easy to see the black and white spotty eyes of the crab. We all gather to look and as I take an underwater photo, I see other shells moving.

The long eye-stalks with black and white-spotted eyes are distinctive too - a St Piran's crab at Porth Mear
The long eye-stalks with black and white-spotted eyes are distinctive too – a St Piran’s crab at Porth Mear

Sure enough, this next shell has a St Piran’s crab in it, and the next, and the next. While I’m taking photos in the pool, Richard is examining shells on the rock by a small overhang. “There are nine more here,” he says. Soon we’ve counted at least fourteen. They’re all larger than the one found here earlier in 2016.

A St Piran's hermit crab in the pool at Porth Mear
A St Piran’s hermit crab in the pool at Porth Mear

Whether there are other groups of St Piran’s crabs on this beach is hard to say. The tide is surging in now so we’ve run out of time to search.

A St Piran's crab foraging in the pool at Porth Mear
A St Piran’s crab foraging in the pool at Porth Mear

The existence of the St Piran’s crab is a fragile one; storms, temperature change, pollution and disturbance threaten our shore wildlife now more than ever. Richard’s survey provides an incredible conservation tool with its wealth of data about what’s here and how it changes.

50 years on from the Torrey Canyon disaster, the confirmation of the St Piran’s crab’s comeback is an uplifting way to complete this survey (and the year).

A Scorpion fish at Porth Mear
A Scorpion fish at Porth Mear
A rock goby
A rock goby
A brittle star on the move at Porth Mear.
A brittle star on the move at Porth Mear.
Xantho pilipes crab pretending to be a pebble at Porth Mear
Xantho pilipes crab pretending to be a pebble at Porth Mear
As the last tide of 2016 rushed in, I had to say aurevoir to this little St Piran's hermit crab. Hopefully they'll be sticking around in 2017.
As the last tide of 2016 rushed in, I had to say au revoir to this little St Piran’s hermit crab. Hopefully they’ll be sticking around in 2017. Happy New Year!

 

 

Home from Home: Quiberon in Brittany

Things have been quiet on this page the last couple of months. Cornish Rock Pools Junior, Other Half and I took an extended holiday to visit the towns and beaches of Brittany. As always our travels had a bit of a marine theme…

Est-ce que c’est un anémone?” the eager child in the dark-rimmed spectacles asks. We explain what a ‘stalked jellyfish’ is to the class of seven-year-olds. “Jellyfish!” they chant.

 

Stalked jellyfish - a Lucernariopsis cruxmelitensis.
Stalked jellyfish – a Lucernariopsis cruxmelitensis.

Between fascinating excursions to the fire station and the sardine factory, we are giving impromptu English lessons to a class of primary school students during our twinning visit to Quiberon in Brittany.

 

We have covered the words goby, crab, jellyfish and shark so far and there’s still a sea of raised hands. The children seem desperate to tell us about their finds around the shores of Quiberon. Continue reading Home from Home: Quiberon in Brittany

Summer Lazing in Cornwall’s Rock Pools

It’s funny how the summer days float by. The house has been practically bursting with people for weeks now and I haven’t found the space to write about our many beach trips, but August still feels like a lazy month.

It reminds me of my childhood summers; a jumble of paddling, swimming, rockpooling and finds. Only I’ve just turned 40 and now I’m the one remembering hats and towels, preparing picnics and being called on constantly to help build dams or identify creatures. Every few days I realise that I’ve failed to take many photos and still haven’t blogged anything I’ve found. It’s just the way August goes.

Compass jellyfish. Also known as sea nettles as they pack quite a little sting, these jellyfish have beautiful markings.
Compass jellyfish. Also known as sea nettles as they pack quite a little sting, these jellyfish have beautiful markings.

The warm waters are drawing in all sorts of creatures at the moment. The north coast especially is teeming with jellyfish. Harmless Moon jellyfish have washed up in their thousands. These transparent little jellies have four mauve circles in their centre in a pattern that reminds me of cucumber slices (OK, that’s probably just me). 

One of many moon jellyfish washed up by the strong swell. This species is harmless.
One of many moon jellyfish washed up by the strong swell. This species is harmless.

Other jellyfish that have mild stings, like the compass jellyfish are also washing in and I think my thigh met with one of the many blue jellies in the water at Mawgan Porth a couple of weeks ago from the unattractive rash I developed! On the plus side, some friends found a spiny starfish in a pool at the top of the mid-shore pools, which looked like it might be feeding on the stranded jellies. Continue reading Summer Lazing in Cornwall’s Rock Pools