They are from Suriname and French Guiana, Rio Maroni, Saramacca River and Suriname River (all eastern Suriname).
The fishes in your post I think are undoubtedly G. abalios.
The reason everything is labelled surinamensis is because at the time of their description and until 1989, the species was widespread in SA. It has since been restricted greatly (by Kullander in 1989) to only those three rivers and the other fishes have been described as different species, abalios, dicrozoster, winemilleri for example.
The fishes in your post I think are undoubtedly G. abalios.
The reason everything is labelled surinamensis is because at the time of their description and until 1989, the species was widespread in SA. It has since been restricted greatly (by Kullander in 1989) to only those three rivers and the other fishes have been described as different species, abalios, dicrozoster, winemilleri for example.