What effects did the portuguese mariners have in west africa?

The primary impact did the Portuguese Mariners have in West Africa is it extended African slave exchange. 
The transoceanic slave exchange started in the fifteenth century after the Portuguese began investigating the shore of West Africa. At initially, the quantity of subjugated Africans taken was little. In around 1650, in any case, with the improvement of estates on the recently colonized Caribbean islands and American territory, the exchange developed.