Yeah, this has been a controversy for a while and I don't have 100% definitive answers, instead only my personal take.
[1] The photographed "capapretum" from Malon-monsters vendor for $90 are the same "Peru piraiba" as Rodrigo of Predatory Fins was selling too (for about $65 on sale), which I saw in person, and both Malone and Rod, it appears, are "forced" by the community at large to label them capapretum. Or maybe they do sincerely think so too. IDK. Why? From Rod's words to me this is because peers, their buyers believe / say that "Peru piraiba" don't exceed 3ft or a bit over (some things like this we hear from our SE Asian peers too
GiantFishKeeper101
) and hence cannot be true piraiba, aka filamentosum, such as those from Suriname (maybe other places too? Brazil? Guyana? IDK) which easily and relatively quickly grow to 4'-5' and more.
[2] Our experience confirms this growth rate and/or size disparity as our two "Peru piraiba" have been stuck at the same size for years and grow very, very slowly and are still well under 3 ft, maybe around 2.5ft, after 5 years, while our 7 yo Suriname is around 5 ft and keeps growing; it was 4 ft at 5 years old.
[3] From the photographs on our MFK threads, capapretum babies and juvies look distinctly different from filamentosum and with my present limited knowledge I identify Malon's and Rod's fish as filamentosum, not capapretum.
Maybe there are more than 2 species? Capa was split from fila only in 2005...
That's the controversy as far as I can tell, in my mind.
***Bottom superficial line is that if Malone and Rod sold them as filamentosum and priced them accordingly higher, their buyers wouldn't buy or probably would feel cheated by being sold "a sub par growing filamentosum". No vendor wants that.
***Bottom taxonomic line: there is a mystery to me at least, why Peru filamentosum are so slow and/or small growing, on par with capapretum which grow to 3'-4' even in the wild.
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