There were Somalis, who traded in the slave trade, and had standing contracts with their Arab counterparts on the coasts, and I am yet to come across a verifiable historical documentation, or registration, i.e. ship manifesto, of listed Somalis being enslaved, for example in the British museum, where such records would have most likely been found, however, it does not mean, it had not happened, for it would have been possible for Somalis, particularly minorities being swept, and added unto shipments, as happened in West Africa, sub continent in Asia, and Southern Europe.
Slavery is a complex trade, and there are people under enslavement to this date in North Africa.