Look out for mermaids’ purses

Cuckoo ray egg cases. Photo by Paul Chambers and Mar Biol Section. 2016

From the Société Jersiaise Marine Biology Section

Nursehound egg case. Photo by Paul Chambers

Nursehound egg case. Photo by Paul Chambers

Since December 2012 the Marine Biology Section of the Société Jersiaise has been coordinating a citizen science project with mermaids’ purses (eggcases from rays and catsharks). In the autumn and winter empty mermaids’ purses wash up on our coasts in large numbers and can be identified back to the ray or catshark species that laid them. The Shark Trust have been running an eggcase project for several years and it was this that inspired the Société Jersiaise to start its own project (all our data goes to the Shark Trust but we are also looking for local trends).

undulate ray

Undulate ray Raja undulata (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

Since starting the project we have collected and identified nearly 6,500 eggcases. The aim is to get five years’ data before running a full analysis but some basic trends can already be discerned. For example, Jersey’s commonest eggcases (44%) come from the undulate ray, a species which is rare elsewhere and listed as threatened in the EU, but is common here. Almost as common is the blonde ray (39%) with other species being much rarer: small spotted catshark (10%); thornback ray (3%); small-eyed ray (2%); and nursehound and spotted ray (both >1%). The below chart shows the situation as at end of February 2016.

Mermaid purse results 2012-2016

Mermaid purse results 2012-2016

We have also noted a seasonal trend in some of the eggcases – e.g. the gap between undulate and blonde ray numbers in the autumn (between weeks 39 and 46 on the chart below) seems to be an annual thing but we’re purposefully not looking at trends in detail until the five years are up.

Blonde and undulate ray eggcase appearance in Jersey 2015.

Blonde and undulate ray eggcase appearance in Jersey 2015.

Now, we’ve been doing this for over three years and in that time we’ve consistently had the same seven species handed in. Then, in 2016, we’ve suddenly had four eggcases from a cuckoo ray handed in, three of which are in perfect condition. This is unexpected because there has never been a single record of cuckoo ray in Channel Island waters – nor are there any commercial or amateur fishing records (we’ve checked with Marine Resources and the JFA and there are no angling records). It does not appear in historical lists by Joseph Sinel or Ronnie Le Sueur although, before the 1980s, there was a model of a cuckoo ray in the old Jersey Museum but it was not thought to be local.

Cuckoo ray egg case. Photo by Paul Chambers

Cuckoo ray egg case. Photo by Paul Chambers

Three of the cuckoo ray cases were collected by Sabina Danzer on the west coast and they are perfectly preserved. The other one was more battered and collected by Geoff Walker in Grouville. The appearances are probably not a coincidence but whether it means that this species (which normally prefers deeper waters than ours but which can stray into shallower seas) has entered our waters is not known. It may simply be that the eggcases have been swept in from the central English Channel but, if so, then why haven’t we had them previously? All very mysterious.

Cuckoo ray eggcases are distinctive as they have very long ‘horns’ that overlap one another. Most of our eggcases are collected by dog walkers and beach cleaners and so if anyone spots a cuckoo ray or fancies participating in the eggcase research, please contact the Marine Biology Section on marinebiology@societe-jersiaise.org

Small spotted catshark

Small spotted catshark Scyliorhinus canicula. Photo by H. Zell (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

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