A recent PBS television offering depicted the horrors of the collection of captive African negroes at ports/beaches, where captives were sold to ship captains and hauled out to anchored ships in small boats/canoes; men, women, husbands wives and children as likely to be forcefully separated as not.
And who had carried out the raids on African villages and captured these unfortunate people? Most likely members of other tribes and Muslim Arabs, would be my guess.
Very few black slaves were sold directly to Europeans by Muslims. This is because throughout the period of the trans-Atlantic slave trade the coast in question was controlled by powerful black pagan kingdoms, who maintained a monopoly on the profitable trade.
Muslims throughout this period, and today, for that matter, are mostly found some hundreds of miles inland, in the sahel and desert, not the coastal jungles.
Until well into the 19th century Europeans did not venture inland at all, so they did not capture slaves themselves. This was because the diseases were so virulent they wiped out European expeditions within weeks. A relatively minor exception was the Portugese, who had some success. This was because the Portugese had imported so many black slaves during medieval period and interbred with them that they acquired some of their genetic immunity.
Some of those sold to Europeans were no doubt captured originally by Muslims, then sold tthrough intermediaries to the coast. But most were captured by other pagan tribes and nations, or were criminals or undesirables sold by their own lords.