by Jim Hall
with additions by Andy Horton
are likely to have come across 'Mermaid's Purses',
containing the eggs or young of the Lesser-spotted Dogfish,
canicula, lying amongst the debris on the tideline.
These egg capsules that have been dislodged after being laid by the adult
female dogfish are doomed to perish. Some, if not most, of the capsules
are empty. However, on many occasions I have found a live embryo inside,
some of them nearly ready to break free from the capsule.
Empty Dogfish egg case washed up on Shoreham Beach, Sussex
My early attempts at hatching these embryos were largely unsuccessful*. On one early occasion, the young dogfish seemed unable to free itself, so I cut off the end of the purse and released the fish. Unfortunately, after reeling around helplessly for five days, the young fish eventually perished. I did not know why this happened, but one problem was to get the fish to feed itself orally after many months living on the egg yolk.
Early in May 1993, I had my first success. When the dogfish hatched out in a tank set aside specially for young fish, it just lay quietly or moved around very gently. At the time, I was feeding newly hatched brine shrimp to a baby Lumpsucker, Cyclopterus lumpus, in the same tank, and some live mysids to other young fish. This dogfish lived and grew rapidly.
Eight weeks later, another small dogfish was born, very pink at first like a baby child, then it darkened slightly after three days. This one was quiet like the previous success, and when it was transferred to my main 50 gallon (227 litre) tank and it reached 8 cm long in two months and thrived.
Young Dogfish just released from the purse. It is helpless at first and just lies around on the floor of the aquarium.
During early August 1993,
I travelled to the Isles of Scilly and when I returned I found one of the
nine developing egg capsules in my tank empty. I had assume the dogfish
had managed to extract itself from the purse and had been attacked. The
newly hatched dogfish are very soft and vulnerable for a day or two.
I decided to transfer the remaining eight purses to a separate tank set aside for the purpose of rearing young fry. I also decided to expel one of the embryos a little early to see if it would survive. The baby dogfish lay quietly for a couple of hours, and then moved around normally with a tiny egg yolk still attached. The fish was healthy, so encouraged by this success, I released a further two dogfish that were 'very close' and they lived as well.
These fish did not look for food, as they were still feeding from their yolk, but I felt that they would harden up sooner and be more used to their surroundings by the time they were ready to attempt oral feeding.
The other six purses were all within two weeks of expected birth and over the following weeks I took the risk of expelling them all early. They were all bombarded with newly hatched brine shrimp and small mysids and they all survived and after five weeks were transferred to the main tank with the bigger fish. In the large tank the ten hatchlings all thrived, with the first born reaching 18 cm, the second 13 cm and the remaining eight at 10 cm by September 1994.
The egg yolk when viewed
through the purse needs to be reduced to the size of a 'match head' before
expulsion is attempted. If the yolk sac is any larger than this, death
is probable because the egg yolk will almost certainly rupture on the aquarium
gravel. The yolk sac needs to be small enough to allow the baby dogfish
to swim around comfortably. When the dogfish emerges it is always sluggish
and will most likely to lie on the bottom looking decidedly ill. After
a few hours it is likely to perk up.
The egg capsule is about 6 cm long by 2 cm wide. The baby dogfish are about 8 cm at birth.
The female dogfish will lay
about 10 eggs per month during the breeding season from November to July.
They are laid about two at a time in areas of quite strong currents with
the capsules carefully attached by long elastic threads to seaweeds or
It is possible to find 'Mermaid's Purse's that have come adrift just after laying and to keep the purses in the aquarium through the whole of their development. It begins as a tiny yolk in the purse and after about one month a tiny dogfish can be distinguished. After about seven months the dogfish has almost absorbed the yolk and completely fills the purse.
Raising the Dogfish
From February to October
1994, I expelled eleven embryos of which nine survived to 13 cm, and seven
of these were distributed to various aquaria. In my six foot (2 metre)
tank I have two specimens that reached 20 cm by November 1995.
The dogfish will eat all the normal food of mussel and white fish consumed by the other fish in an aquarium without crabs or sea anemones.
In late 1994 and 1995, 'Mermaid's Purses' were not so easily found on the south Wales coast with only three brought home from the strandline, with minute embryos just visible. Most of the purses were found on Swansea beach after a period of bad weather. However, this beach is now cleaned by specially adapted tractors which clear the debris on the strandline.
The Dogfish is a common small
shark in the shallow waters all around the British Isles, although not
so prevalent off the east Scottish coast. It is also found in more southerly
seas and throughout the Mediterranean. It lives on or near the bottom and
its back is a sandy brown colour with small dark brown spots. Adults reach
about 65 cm in length.
Lesser Spotted Dogfish
Its natural food consists
of small crustaceans especially hermit crabs
off Sussex, but it will eat worms and molluscs.
# The larger egg cases of the Greater Spotted Dogfish, Scyliorhinus stellaris, and the cases of the Thornback Ray Raja clavata, Undulate Ray Raja undulata, the Skate, Raja batis, or any of the rarer true skates and rays of the family Rajidae could conceivably be discovered. When laid they are a translucent olive-brown and the developing embryo can be seen. If they are washed up for a long time on the strandline they turn black. The dogfish purposes should have at least some of the thin tendrils that were originally used to secure the purse. However, the broader skate's purses have a long curved spike at each of its four corners.
At the beginning of 1996, a week before the Sea Empress oil spill on 15 February, I was lucky enough to obtain two purses of the Greater Spotted Dogfish from Mike Batt (Tenby Aquarium) who found them washed up on the shore at Lydstep, near Tenby in south Wales. At the same time young newly hatched fish were also found on the shore. These two purses remain alive in my aquarium and are expected to hatch around Christmas.
I was also able to obtain an egg case of the Greater Spotted Dogfish from Weston-super-Mare Sea Life Centre. This purse was 12 cm long by 4 cm wide, excluding the tendrils, and the dogfish successfully hatched from the purse in October at a size of about 13 cm and is thriving on diet of mysids and white fish.
The Greater Spotted Dogfish is also known as the Bull Huss and the Nursehound.
* the Dogfish would squirm around inside the purse, but was unable to break free.
Egg Capsules of Rays & Sharks
Purse and Sea
Photograph by Chris Roberts
trying not to damage any of the gorgeous pink seafans and a Lesser-spotted
comes along and ties it egg cases on to one."
Egg cases of the now rare and endangered Flapper Skate, Dipturus intermedia, (=Diptrus batis*) were discovered washed ashore on Baleshare Beach, an island west of North Uist, Outer Hebrides.
Shark Trust Eggcase ID Key
November 2014 - March 2015
Cases of the Flapper Skate
Photographs by Penny Martin
Over four thousand egg cases of the now rare and endangered Flapper Skate, Dipturus intermedia, (=Diptrus batis*) were discovered washed ashore on just three beaches in the Orkney Isles. They were found on the remote shores of Skaill Beach, Bay of Birsay and Aikerness Beach, on West Mainland.
There about 250 Spotted Ray cases, 120 Thornback Ray, 3 Cuckoo Ray, 13 Blonde Ray and 65 Lesser Spotted Dogfish cases collected.
They egg cases had horns but they are concealed within the fibrous case .. you can see the outline in the photo above.
The smallest and largest .... 300 x 145 mm and 180 x 100 mm
Red List Entry
Orkney Skate Trust
2009, research showed what was formerly listed
as a single species, Dipturus batis, should be instead classified
as two separate species, Dipturus flossada, and the Flapper
Skate, Dipturus intermedia.
A group of Little Grebes wre seen diving under the surface of Widewater Lagoon. On the strandline, the amount of seaweed was less than stormy years, but included at least one clump of Mermaid's Purses, the eggcases of the Lesser-spotted Dogfish, Scyliorhinus canicula.
In the aftermouth of the near gales, thousands of empty Undulate Ray, Raja undulata, egg cases (=Mermaid's Purses) were thrown ashore on the strandline of Shoreham and Lancing beaches. One typical egg case was measured in its dried out state at 65 x 50 mm (at its widest part), with the curved horns at up to 50 mm each (giving an overall length of 160 mm).
8 September 2014
A large amount of weed had become snagged on the Worthing Pier supports and wound around the weed was a couple of Mermaid's Purses, and one contained a live embryo of a baby Lesser Spotted Dogfish Scyliorhinus canicula. The baby shark was released from its Mermaid's Purse and placed in a small aquarium.
Lesser Spotted Dogfish washed ashore against the metal supports of Worthing Pier
The small shark will feed on the yolk-sac
Alas the embryonic shark only lived for two days out of its purse. It measured 75 mm long and the yolk-sac diameter was 10 mm. (It may have been attacked and killed by a Long-legged Spider Crab, Macropedia? but it was breathing rapidly before its demise. Tip: keep it in an aquarium with absolutely no other inmates.) The purse was estimated to be about 65 mm long, larger than the more typical size of 55 mm.
10 January 2011
6 June 2009
These egg cases were washed ashore on the beach at Newport, Pembrokeshire, south-west Wales.
Click on each case for their identification.
Razorbill Ribs Gallery
17 March 2008
Egg Cases of the Lesser Spotted Dogfish (top) and Undulate Ray
One Undulate Ray eggcase looked in good condition from Shoreham Beach, Sussex, and was placed in an aquarium in case the embryo was still alive.
This large eggcase was discovered on my local beach (Waterville, Co. Kerry, Ireland).. The size can be discerned from the tennis ball. It is large enough to be the eggcase of the endangered Skate, Dipturus (=Raja) batis,
Report by Rosemary Hill
usual debris was on the Shoreham Beach strandline
including a Ray's, Raja
eggcase illustrated above.
It measured 67 mm long and this was probably the eggcase of an Undulate Ray, Raja undulata. It width was 48 mm.
The horns were 40 mm and 45 mm long.
Egg Cases on Constantine Bay beach, north Cornwall
Photograph by Amanda Bertuchi
16-17 January 2006
Twenty four egg cases of the endangered Skate, Dipturus (=Raja) batis, were discovered on the Sandside shore near the Dounreay nuclear power plant, Caithness, west of Thurso and Scrabster Harbour and John o'Groats on the northernmost coast of mainland Scotland, the first records reported to the Shark Trust and the first records on the mainland Scotland since these egg case occurrences have been recorded.
Egg Cases of the Common Skate
egg cases were estimated at between 23 to 28 cm long and 13 to 16 cm wide
in a dried state.
Egg Capsules of Rays & Sharks (Link to the Web Pages)
BMLSS Mermaid's Purses
January 2005 Report
Egg Capsules of Rays & Sharks (Link to the Web Pages)
Photograph by Richard Land
These large egg case washed up on the shores of the Orkney Isles, north of mainland Scotland.
The large size of these egg cases means they are almost certainly* the cases of the endangered# Skate, Dipturus (=Raja) batis.
The width of the purse on the right seems to be about 127 mm.
Over a hundred egg cases were washed up.
These egg cases are washed up every year. The local school children collected twenty in 2004. The photograph shows the much smaller ray egg cases for comparison.
The lengths (wet when discovered) varied between 270 - 300 mm in length with a width of between 140 mm and 160 mm.
These egg cases lacked the external horns present on ray egg cases and these ones appear to be internal. Divers report the egg cases resting on the bottom at between 7 and 20 metres in depth over sand or sand and gravel bottoms. These are scallop grounds. When lifted the egg cases falls to the bottom and stays there. Large adult Common Skate are observed by divers on these grounds, but no juvenile skates have been spotted.
There is a problem inamuch
that these egg cases do not match a known photographed egg case of the
Common Skate. This is being investigated. It is possible that the original
photograph is incorrect and these "hornless" egg cases are correct for
Common Skate? Or, more likely, the horns have broken off?
Information provided by Richard Land
thought to be either the egg cases of the Norwegian (or Black) Skate,
nidarosiensis, or the Long-nosed Skate, Dipturus
Common Skate is now absent from most of the seas around the British Isles.
There is a small population caught off Mull (SW Scotland, islands) but
the Orkneys remain a stronghold for an unimportant commercial catch of
mixed Skate (Common and Black Skate).
Egg Capsules of Rays & Sharks (Link to the Web Pages)
Case Identity Sheets (Shark Trust)
undulata egg case (by Andy Horton)
Identification by Peter Bor (Egg Capsules of Rays & Sharks)
|Species||Length mm||Width mm||Horns|
|Lesser Spotted Dogfish
On 25 March 2005, a damaged ray eggcase from the coast at Shoreham measured 40* mm long, 34 mm wide (dry size) with one "horn" measuring 50 mm at the longest attachment point or 40 mm when measured to the length of the purse. These small purses are often washed up on the Sussex coast. It looks like a small specimen of Raja undulata, the Undulate Ray eggcase which are sometimes, 80 x 50 mm. The Thornback Ray egg purses, Raja clavata, seem to have shorter horns, but this needs confirmation. The size only matches the Thornback though. (*Damage meant it could possibly be longer.) There is a possibility of a smaller Spotted Ray, Raja montagui, eggcase?
* NB: When the egg cases are placed in water they expand in size (John Knight). It is these larger sizes that are measured as they correspond to the size when they are submerged.
What does an eggcase look like? (Shark Trust link)
for ID (Bucket Science)
Original report on: http://www.thisiscornwall.co.uk
More information on:
Vince Smith's One-List/Cornish Wildlife
Send a message to the list at: CornishWildlife@onelist.com
EMail for the BMLSS
(by Len Nevell)
Egg Capsules of Rays & Sharks
BMLSS Shark Page
International Marine News
TAXONOMIC INDEX TO BRITISH MARINE WILDLIFE
Use these links if your are familiar with the scientific classifications of marine life