Ahhh gents, sorry to join the conversation late. I've been exceptionally busy with work. I don't know where to find it as I don't read Chinese either but if you do and you search on Chinese search engines such as baidu they discuss about true Congo goliaths vs normal goliaths. They have distinct body differences being broader top down compared to the skinnier profile. They also have different snout shapes. There may be even more than these two as there's usually one or two of the cryptic black goliaths mixed into a batch of 500-1000 juvies when the come in. Little is shown about it in captivity because most don't make it alive to adult or subadult sized. I can attest from first hand experience keeping so many ATFs now. Sometimes they are just mixed into batches that you have to eyeball and spot. I got my brasiliensis dorado out of a school of Frankie's. took almost half an hour or selective net out lol. All this talk sure makes me miss my old monster...
Ok that makes sense. I have noticed the exact same thing about the shape of the gatfs we get in the hobby as well. I got all excited because I thought something scientific was published that escaped my attention and I wanted to gobble it up.
Most interestingly of all is this. While genetically there is only one species of Hydrocynus goliath, there are three unique haplotypes. Haplotypes- a set of genetic data that tends to be passed on to descendants- can be distinct, but are far less than a subspecies, think of them like breeds of dog.
There may be something to this. The article from which that image came stated that based on genetic evidence, Hydrocynus goliath has undergone a population explosion in geologically recent times. This could be the very earliest parts of sympatric speciation, even though at this point they're definitely all still gatfs.
Should we, as a community, start thinking of them as morphs? As I prepare to rewrite the sticky, that's a particularly relevant question.
