“cf." is used with a specimen that the author (writer/ichthyologist,describer, etc.) wants to compare with the following cited species, but hebelieves that it is different, probably new to science
"aff."is used a specimen that has similar characters (morphology) asthe following cited species, but he is not (yet) sure that it is a differentspecies.
"sp." is used in the case that an author (writer, ichthyologist,etc.)can not say any of the above mentioned, but he is sure of the fact that thespecies he is talking about (writing, or showing a photo of) belongs to thereferred genus (eg. Rasbora sp.), but does not know at all if new, or whichspecies it might be.