I found something similar in the book 'Mongo Culture' (Issued on occasion of an exhibition held in Belgium, Sint-Niklaas, from 26 August until 21 October 1984).
The picture is not very clear, but the two items shown have a resemblance with your piece. They consist of a long wooden stick with an iron point attached on one side. I don't know if you can see it on my pics, but I believe there are also some 'rings' added to the shafts.
The length of these pieces is : 2m14 and 1m97.
This is what is written in the catalogue (my translation from dutch) :
A long, narrow iron point (86 cm) attached to a wooden shaft. This is called a 'BOSIKI'. The bosiki was used to 'stab' fish or kopal in the water (river). Copal is an amber coloured and odourless type of resin which is used to produce varnish.
