The hermaphroditic skinheads of the sea
While doing some research on fish occurring in local waters, I came across a most fascinating and odd looking species that I had to know more! The poenskop Cymatoceps nasutus looks like it could play the role of a gnome or troll in a movie as it does not age well! Poenskop is the Afrikaans common name for this fish, meaning ‘skin head’, while others may know it as the black musselcracker. This is a large and robust fish, which has four prominent canines in the upper jaw and six in the lower jaw. It has a rounded snout, which becomes white and fleshy as it ages, giving the appearance of a large bulbous nose! Adults are greyish black in colour, while juveniles vary greatly in colouration but are mostly greenish brown with white blotches. Poenskop do not only have an interesting appearance but also an interesting biology. This species is endemic to South Africa, and ranges from Cape Agulhas to St. Lucia, found in waters to a depth of 100 m. On the rocky reefs they inhabit the adults are territorial benthic predators, feeding on molluscs, crustaceans, and echinoderms. These fish can live up to 45 years old, 1.1 m long, and 40 kg in size. Poenskop reach maturity at an age of 10 years (roughly 55 cm in length) and spawn in winter. This fish is a hermaphrodite, and starts off its life as a female, and at a size of roughly 70 cm and 18 years old changes to a male. Due to this species high residency, slow growth, late maturity, longevity, and hermaphroditism, it is very vulnerable to overexploitation. It is currently rated as Vulnerable by the IUCN, with a decreasing population. Poenskop is also on the SASSI list rated as red – don’t buy this fish! Marine Protected Areas are invaluable for the recovery of this species, poenskop in no-take MPAs are more abundant, and are of a larger size than poenskop in other areas.
Written by: Minke Witteveen
For further reading:
- Branch, G.M., Griffiths, C.L., Branch, M.L. and Beckley, L.E. 2010. Two Oceans: A guide to the marine life of southern Africa. Pp. 290. Random House Struik Publishers, Cape Town.
- Mann, B.Q., Buxton, C.D. and Carpenter, K.E. 2014. Cymatoceps nasutus. The IUCN Red List of Threatened Species 2014. Accessed: 2016-07-30. URL: http://www.iucnredlist.org/details/170204/0