There's an interesting section on the canoe houses in Falola and Heaton's A History of Nigeria:
"In the Ijo-speaking communities of the eastern Niger delta, the canoe house became the organisational unit responsible for conducting the slave trade with Europeans. A canoe house was a branch of a lineage that had developed enough wealth, most likely through the trade in slaves, to equip a war canoe of fifty soldiers that could be put at the disposal of the state in times of peril. The ability to equip a war canoe served two functions. First, it illustrated the power of the house - and, by extension, the house head - in the community, thereby establishing the house as an important actor in local affairs. Second, the war canoe could itself be used for the procurement of more slaves. Slaves could then be sold for more wealth or incorporated into the house. Those slaves incorporated into the house would help in the procurement of more slaves. Over time, slaves became assimilated into their new house, and through marriage, or bravery in battle or slave raiding, could become fully integrated into the house, even to the point of becoming the house head. House systems such as these had emerged in both Bonny and Elem Kalabari by the end of the seventeenth century."
This accommodating approach to household slavery is of course the story of what happened to King Jaja of Opobo, as mentioned in my earlier post below.
The text goes on to discuss the was in which the Ekpe secret cult was used as a system of rules to control the slave trade in the Bight of Biafra (a little similar to how the masons controlled business in medieval times), and how the Aro Confederacy adopted Ekpe in order to assert its authority, via the oracle at Arochukwu. There is a fascinating passage a couple of pages further on which brings to mind present day evangelical pastors:
"While surrounding groups stood in awe of the oracle at Arochukwu, the Aro themselves did not hold the oracle in such high regard. Rather, they manipulated the oracle to achieve commercial dominance in the region. According to Opoko and Obi-Ani, "In the town of Arochukwu itself... the indigenes did not disguise the fact that the oracle was a fraud manipulated by some selfish, though entrepreneurial, individuals in their midst in order to exploit outsiders and hold them in perpetual awe." Nevertheless, the Aro managed to keep the secret of the oracle to themselves, while simultaneously invoking the oracle to enhance their own authority and bring a sense of overarching law and order throughout a region known for its decentralised political institutions and high level of internal strife... The ploy worked, and the Aro applied the religious authority of the oracle to maintain a stranglehold on the slave market in the interior of the Bight of Biafra throughout the eighteenth and nineteenth centuries."