In July 1830 he commissioned the Curlew for service on the west coast of Africa, where he was for the most part senior officer, the commander-in-chief remaining at the Cape of Good Hope.
In May 1833, at Prince's Island in the Gulf of Guinea, he had intelligence of an act of piracy committed on an American brig, the Mexican,[1] the previous September, by a large schooner identified as the Panda, a Spanish slaver from Havana, and then on the coast.
Against the Esperanza there was no legal evidence; her owners instituted a prosecution against Trotter, and Lord Palmerston, then foreign secretary, agreed that the schooner should be returned to Lisbon.
At Plymouth, however, the captains of the ships there sent parties of men who completed her refit free of cost to Trotter; and the Admiralty promoted him to post rank on 16 September 1835.
In 1840 he was appointed captain of the Albert steamer, commander of the Niger expedition of 1841, and chief of the commission authorised to conclude treaties of commerce with the local rulers.
Trotter in the Albert struggled on as far as Egga, where, on 3 October, he was prostrated by the fever; and, as the greater part of his ship's company was also down with it, he was obliged to turn back.