While walking the beaches of Plettenberg Bay and Natures Valley one can regularly find the egg cases of the twineyed skate Raja mireletus. The twineyed skate is a small medium-brown skate with close-set small dark brown spots on the upper surface, and is white underneath. Its name comes from two blue eyespots on the pectoral fins. This species reaches a total length of 50 cm in South Africa, while it can grow up to 60 cm in the Mediterranean. In southern Africa the twineyed skate is found from Angola to southern Namibia, with a gap in distribution between the Orange River and the Cape Town and False Bay area where it reappears and is found along the north east coast to KwaZulu-Natal, Mozambique, and Kenya. They are usually found in water shallower than 50 m, but have also been caught in trawl nets at a depth down to 200 m. Prey is primarily small crustaceans but includes fish, cephalopods, and shrimp. In South African waters this skate is caught by trawlers and anglers, but is not heavily persecuted as there are untrawlable reef refuges where they are able to thrive. Twineyed skates reach maturity at 2-3 years of age, and can live up to 10 years. The egg case of this skate has a central pouch with horns extending from each of the four corners. These egg cases are deposited onto the seabed where fibres on the pouch’s surface aid in anchoring it to the ground, and hatches after 5 months. A single female can lay 40-72 eggs in a year.
Keep an eye out the next time you take a stroll on one of Plettenberg Bay’s magnificent beaches for one of these egg cases. You can report your finding on www.elmoafrica.org.
Written by: Minke Witteveen
For further reading:
- Chembian, A.J. 2010. Description of spawning ground and egg capsules of the batoid Raja miraletus Linnaeus, 1758 in the Wadge Bank, along the south-west coast of India. Indian Journal of Fisheries 57: 13-16.
- Compagno, L.J.V. and Ebert, D.A. 2007. Southern African skate biodiversity and distribution. Environmental Biology of Fishes 80: 125-145.
- Smale, M.J. and Cowley, P.D. 1992. The feeding ecology of skates (Batoidea: Rajidae) off the Cape south coast, South Africa. South African Journal of Marine Science. 12: 823-834.
Smale, M.J., Ungaro, N., Serena, F., Dulvy, N., Tinti, F., Bertozzi, M., Mancusi, C. and Noarbartolo di Sciara, G. 2009. Raja miraletus. The IUCN Red List of Threatened Species. Accessed: 14-03-2016. URL: http://www.iucnredlist.org/details/161599/0