the coastal population changed from 'tawny' Sanhaja Berbers to 'black' Wolofs. Tristão is believed to have reached as far as the Ponta da Berberia (Langue de Barbarie), just short of the entrance to the Senegal River. Bad weather prevented his entering the river or landing there, so he set sail back. On the way home, Tristão stopped by the Arguin banks and took another 21 Berbers captive. Nuno Tristão arrived in Portugal declaring he had finally discovered sub-Saharan Africa, or in the nomenclature of the time, the "Land of the Blacks" (Terra dos Guineus, or simply Guinea). Portuguese slave raiders immediately descended on the Senegalese coast, but finding alert and better-armed natives on that coast, the slave raids were not nearly as easy nor as profitable as they had hoped. Fourth voyage In 1446 (or perhaps 1445 or 1447, date uncertain), Nuno Tristão set out on his fourth (and final) trip down the West African coast. Somewhere south of Cap Vert, Tristão came across the mouth of a large river. Tristão took 22 sailors with him on a launch upriver, to search for a settlement to raid. But the launch was ambushed by thirteen native canoes with some 80 armed men. Quickly surrounded, Nuno Tristão, along with most of his crew, was killed on the spot by poisoned arrows (two might have escaped). Tristão's caravel, reduced to a crew composed of clerk Aires Tinoco and four grumetes ('ship boys'), immediately set sail back to Portugal. (However, the account of Diogo Gomes differs here; he asserts the caravel never made it back—that the native canoes overpowered and seized it, and then dragged the caravel and dismantled it upriver.) It is uncertain how far Nuno Tristão actually sailed and where he died. Up until the 1940s, Portuguese tradition asserted Tristão died at Rio do Nuno (Nunez River, modern Guinea), or that he fell just short of it, and died at Rio Grande (Geba River, Guinea-Bissau). As a result, Nuno Tristão was traditionally credited as the 'discoverer' of Portuguese Guinea (modern Guinea-Bissau), and even said to have been the first European to set foot on the landmass of what is now the modern city of Bissau. If true, then Nuno Tristão's last journey was an enormous leap beyond the previous Portuguese milestone (Cabo dos Mastos, Cape Naze, Senegal). However, modern historians, drawing from larger evidence (including the accounts of Diogo Gomes and Cadamosto),