Of course, cruising the open ocean looking for slavers was a waste of time, the patrols were off the African and Brazilian coasts. Technically Brazil had banned the trade in slaves, but as this article by Commader Foote R.N. in the United Services Journal of 1845 shows, that wasn't quite the case.
A slave market in Rio
A FEW REMARKS ON THE SLAVE-TRADE IN THE BRAZILS.
When we see slave-vessels fitting out in every port of the empire of Brazils, from Para to St. Catherine's, openly protected by the authorities; when we see slaves landed and sold within a few miles of the Emperor's palace at Rio de Janeiro, and the vessel, after discharging her cargo, fearlessly enters the harbour, triumphing in her success; whilst the authorities refuse, and British cruisers are unable to interfere, being once within three miles of their coast, it will be perceived how utterly useless it is to trust to the good faith or co-operation of the Brazilians in such a matter.
Not more than two or three years ago, a boat belonging to H.M.S. Clio ( a brig sloop carrying 71 men and 18 guns).was attacked on the coast of the province of Esperito Santo, when in possession of a slave-vessel, having more than three hundred Africans on board, by a great number of large boats and canoes full of men, who re-captured and burnt the vessel, having landed all the Negroes.
This attack was made in the presence, if not by the direction, of the Juiz de Paz of the district. The boat, obliged to retreat, in want of water, and unable to reach the Clio, put into the port of Campos (about forty miles distant); she went in with her ensign and pendant flying, and the officer (a Lieutenant) proceeded on shore, with his side arms, to purchase refreshments, when, to his surprise, he and the whole of his crew, consisting of a Midshipman and thirteen men, were seized, and thrust into one common prison, where they could with great difficulty procure the common necessaries of life. The authorities then caused the English colours to be hauled down on board the boat, and took possession of her. The officers and crew remained several days in prison, until the Clio arrived off the port, where, being unable to enter, from the shallowness of the water, she threatened a blockade; and they were released.
A boat, belonging to H.M.S. Rose (18-gun sloop), having captured a vessel with 280 Africans on board, and sent her to Rio Janeiro, again resumed her cruising ground. The officer and crew landed one morning to cook their breakfast on the rocks, when they found themselves suddenly surrounded by a great number of men on horseback, all armed, who made them prisoners (the boat's crew having, by order, left their arms in their boat), and conducted them on foot to the town of Campos, a distance of about fifteen miles, where they were, in a similar manner to the Clio's boat's crew, lodged in prison. The cause for this sudden and unwarrantable behaviour was the appearance of a slaver in the offing, and the Rose's boat was actually employed by the slave-dealers in embarking the Negroes from this newly-arrived vessel, which being accomplished, she ran into Campos, whither also the boat was conducted. The Commander of the Rose having become acquainted with the fate of his boat and crew, detained several coasting vessels at the mouth of the Campos river, and sent an officer to demand the immediate restoration of his men; they were in consequence given up. No satisfaction whatever has been offered for this outrage. The Juiz de Paz still retains his office, still continues to receive the usual bribes for the disembarkation of Negroes, and still continues to animate the ignorant country people by whom he is surrounded against the English pirates!
The slave-dealers, secretly applauded by the Government, and encouraged by these successful attempts to insult the British flag, now armed themselves at the different slave stations, and came to the determination of firing into any boat which took refuge in their ports or creeks, or even approached the coast within musket-shot. An opportunity soon presented itself. A boat, belonging to H.M.'s sloop Fantome (16-gun Acorn-class brig-sloop) anchored one evening in a little creek at the Ilha Grande, for protection from the wind and sea; a few men came down to the rocks, and asked if they were English. The officer in charge of the boat answered in the affirmative, and pointed to the colours which were flying. At peep of day on the following morning they were awakened by a volley of small arms, and several balls passed through the hull of the boat; but as the men were fortunately lying down at the time, two only were wounded, one receiving a shot through his hand, and the side of another being grazed. One of the same men who came down to the rocks on the previous evening was distinctly recognised, with about twenty or thirty others (mulattoes and blacks), all armed with muskets. The officer s first impulse was to slip the cable and dash at them, and the men in the boat were most eager to do so, as the people on shore were concealed behind the rocks, and were firing whenever they could get their old broken-down muskets to go off; but he (the officer) had received positive orders not to land on any account whatever; and he consequently retired, trusting that a proper representation of the case would be sufficient to procure instant redress; but the only satisfaction the British Minister ever received was the empty assurance of the Brazilian Government that they had caused an inquiry to be instituted, and that the man who had authorised and headed the attack had fled from the island, and could not be found, although he was seen and recognised by the same officer not six weeks after the occurrence.
At Santos, a seaport in the province of St. Paul's, the slave-trade is carried on with greater vigour and less secrecy than in any other part of the Brazils. It was in this port that Captain Willis, of the Frolic, and his officers, were waylaid, and nearly murdered, and slave-vessels are here fitted out with every necessary equipment, which is taken on board in the open day; they sail with no cargo, with the exception of slave-provisions and water, and it is so arranged that they shall not wait more than six hours on the coast of Africa, the slaves having been previously collected and prepared for instant embarkation.
One of the most notorious and iniquitous traffickers in human flesh the world ever produced, is named Jose Bernardino de Sa; this wretch has carried on the slave-trade for a number of years, and has risen from a bankrupt petty coffee-merchant to immense wealth, and is decorated with orders. Vessels of every size and rig are employed in his service, on either side of the coast of Africa, in prosecution of this revolting traffic; and it is calculated that within the three years ending in 1843, he has imported no less than sixteen thousand Africans into the Brazils; yet this "Knight of the Order of Christ" promenades the salons of St. Christovao, mingles with the Ministers of the Sovereigns of civilized Europe, and possesses such influence over the Ministers of his own country, that none dare oppose him in his loathsome undertakings.
Jose Bernardino de Sa as well as owning a fleet of ships also owned a slave trading post at Cape Lopes in Africa. He died in 1855, with the title of Visconde da Vila Nova do Minho.