Mermaid’s Purses

Autumn storms can be very unpleasant, but they can also give us clues to what is living in the waters off our shore. One aftermath of a storm is the collection of marine material washed up to the strand line at the peak of the waves crashing onto the beach.

In Sidmouth, we usually find the fronds and lumpy holdfasts of the various kelps that grow on the seafloor a few hundred metres from the Esplanade. If you poke about in the stranded material, occasionally you will find small squarish pouches with curly tendrils at each corner. These are called mermaid’s purses, they are the egg pouches of a group of fish that includes sharks.

Sharks, skates and rays are members of the class of Chondrichthyes, cartilaginous fish. Many of them give birth to live young, but some lay their eggs protected in a rubbery pouch. The pouches have tendrils at the corners to help keep them in place where they were laid. Sometimes they are torn away by storms but usually the tendrils start to break down and release the pouch when the young fish has hatched, these are the ones you tend to find on the beach.

The different fish groups have distinctive pouches or purses. The one I found recently is elongated and has long curly tendrils, this is characteristic of two members of the shark family, the nursehound or bull-huss and the lesser spotted dogfish, alternatively and confusingly named the small-spotted catshark, both of which are caught from the beach by local fishermen.

From its size, the purse in the picture which was picked up on the Jacob’s Ladder beach is probably a bull-huss which will interest marine scientists. If bull-huss are breeding in Lyme Bay that will be an extension of the recorded UK breeding ground which is from Falmouth to Wembury.

The fish come together to breed in spring and early summer, always at night apparently. The eggs develop inside the mother and are then laid two at a time over the summer and autumn. The purse tendrils catch on seaweed, sugar kelp beds are a favourite site and we do have sugar kelp off Chit Rocks. The embryos take about 12 months to develop and hatch, the young fish pushes through a slit at the end of the purse. While they are developing, the embryos wriggle and flick their tails to circulate water and bring oxygen in through the slit.

Bull huss can grow to one and half metres (5ft) and weigh up to 11kg (25lbs). There is a picture in Tindall’s 1929 beach diary of former fisherman Scrummer Smith holding one about that size that had been caught in his herring net. They feed on small fish, crabs, marine worms and shellfish. Being in the shark family, they are covered in rough denticles and the skin used to be used as sandpaper. They are a popular food fish on the continent and this has led to over fishing. Hopefully the local population can find a safe home in our sugar kelp.

Ed Dolphin