Green shore crab with a clutch of yellow eggs in a Cornish rock pool.

Egg hunting in the Cornish Rock Pools

It may seem too early in the year for rock pooling, but this is an exciting time of year on the shore. Spring has arrived in the Cornish rock pools and the huge clutch of eggs under the tail of a female green shore crab proves it.

Eggs come in all sorts of forms in the rock pools. Why not get out for your own ‘egg hunt’ on the shore this Easter?

Here’s my quick guide to some of the common types of egg you might see.

Dog whelk

Dog whelk eggs at Mawgan Porth
Dog whelk eggs at Mawgan Porth

I’m often asked to identify these eggs. The distinctive yellow or pink-tinged capsules of the dog whelk are common on mid-low shore rocks, often in crevices and overhangs in the rock.

 Netted dog whelk

Netted dog whelk eggs at Plaidy, nr Looe
Netted dog whelk eggs at Plaidy, nr Looe

These eggs are unmistakable. Look for these strings of transparent discs with eggs inside attached to seaweed in mid-lower shore pools.


Cornish rock pools junior holding a one-clawed green shore crab with eggs (Hannafore, Looe)
Cornish rock pools junior holding a one-clawed green shore crab with eggs (Hannafore, Looe)

Female crabs carry their clutches of eggs under their wide tails. They look like a big spongy mass, but on close inspection you can see the individual eggs. In the summer, some crabs become infected with a parasitic barnacle, which can sometimes be mistaken for eggs.

 Fish Eggs

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.

Many species of fish come into the shore to lay their eggs. The males of several species, such as the blennies, stick around to guard the eggs until they hatch. Clingfish and gobies often lay their eggs on the underside of rocks.

A male worm pipefish with eggs
A male worm pipefish with eggs

 The male worm pipefish (relatives of the seahorse) carries eggs on a special slit on his belly.


Shark egg case (Scyliorhinus stellaris)
Shark egg case (Scyliorhinus stellaris). The live fish hatches after around 7-9 months in this case.

On the lowest tides look out for the ‘mermaid’s purses’ – the egg cases of the lesser spotted and greater spotted cat shark – among kelp and seaweed on the lower shore.

 Sea slug spawn

A coil of sea slug spawn from the 'sheep slug' aka 'Grey slug' (Aeolidia papillosa)
A coil of sea slug spawn from the ‘sheep slug’ aka ‘Grey slug’ (Aeolidia papillosa)

Many sea slugs lay coils of eggs, often found under rocks.

The eggs of the sea hare (Aplysia punctata) look like pink silly string.
The eggs of the sea hare (Aplysia punctata) look like pink silly string.

Sea hares lay strings of pink or yellow eggs, which are hard to the touch and look like silly-string.

 Snot-worm Eggs

'Snot worm' eggs
‘Snot worm’ eggs

Look out for green blobs that look like balls of snot. These are the eggs of the Green leaf worm and family.

Happy egg hunting! Let me know what you find.



8 thoughts on “Egg hunting in the Cornish Rock Pools”

  1. Wow! All these eggs are amazing and weird. It is amazing what you can find. The photo of the fish eggs with all those eyes staring at you is rather amusing lol Easter came early to the Cornish coast I see.


  2. Thanks Sean. The fish eggs are special. I love the sea hare eggs too, it really does look like pink silly string all over the rocks! Great tides next week so I’m looking forward to seeing what’s in the pools.


  3. Brilliant, just brilliant. A great themed article, and I ashamed to say that as a trained marine biologist, there were several examples that I have never seen before. Thank you.


    1. Thank you – so pleased you enjoyed it. Marine biology is a massive subject so it’s reasonable not to have met every species or seen their eggs. I see new things all the time. I often think about how I only really know a tiny community of creatures on the edge of a massive ocean – even when you’re diving you can only access the shallowest waters. I haven’t done a degree in marine biology, but I get the impression most degree students don’t get to spend a huge amount of time on the intertidal zone or on taxonomy, which is a bit of a shame as it’s so accessible and utterly fabulous (I would say that).


      1. I have the degree, and you are right. I spent many holidays with my grandparents in Flushing and know the foreshore from Kiln Quay to Trefusis point intimately. That is where I became a marine biologist, not at University.


    1. Thank you. I love finding mermaid’s purses too – and it’s generally easy to identify what species of shark or ray laid them thanks to the Shark Trust’s guide – If you find live catshark eggs attached to seaweed and look closely, you can often see the developing embryo moving inside which is just magical. There are some fantastic rockpooling and diving spots around Dorset, I must get up there some time.


      1. Thanks i looked on the sharktrust and i think the ones i found were lesser spotted dogfish egg cases i will have to look out for the live ones as it sounds brilliant.


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