Different head form between B. Filamentosum and B. Capapretum

[Marcus_H]

Hello,

so far i've only read about 2 ways to distinguish B. Filamentosum and B. Capapretum :

1. colour pattern (filamentosum having bigger spots when young, capa those rainbow-colourlines when subadult)

2. Size. (true filamentosum reaching over 2 meters)

But after looking at several pictures and videos (sadly never seen one in real life) it seems to me, that b. capapretum has a somewhat round, heavier looking head and a shorter lower jaw compared to the upper jaw.

Is that correct?

Greetings

 

[thebiggerthebetter]

I hope when Fugupuff comes back from South America end of Oct, he will weigh in.

I'd add growth rate, of course. The lack of spots low on the body on fila, mostly on and near the top. I used to think what you said about the heavier built head on capa but since the horopgedrik posts, I am not sure anymore.

 

[Marcus_H]

Yeah i guess growth rate and final size are definetly related, at least within this genus.

Outside it is not always the case, for example i kept Pangasion Catfish in an aquarium and a silurus glanis in my pond, but even tho the silurus has the far bigger end size, his growth rate was way slower.

 

[Chicxulub]

I've noticed a difference in the head of a capa as well. It's actually the most obvious thing to me, but I've never found a way to clearly articulate the difference. At adult sizes, the difference apparently isn't obvious and the only way to tell (other than the extreme size of large filas) is in the dental morphology.

When they're babies though, the difference is incredibly easy to tell from the spots. In a capa, they're larger than the eye, in a fila, they're the same size or smaller.

 

[MikebNJ]

This is my Capapretum that I originally thought was a Paraiba. Big spots

 

[horopgedrik]

I think I have both B. filamentosum and B. capapretum now. Before it happened, I kept looking to all kind of piraiba-supposed fishes on the market, and take some specimens, just to satisfy my curiosity about this fish.
IME, my conclusion about difference between B. filamentosum and B. capapretum when juvenile:

1. Barbel length: less reliable as a clue, because it can be vary due to condition of the fish itself. But, let's say when in undamaged shape, B. filamentosum at size 4'' has very much longer barble, than B. capapretum at same size. My B. filamentosum has 8'' barbel lenght at size 2.5'' and it keeps growing until now, I think its barble now around 12". My B. caparetum just has barble as long as its body TL at time when I bought it (4'' fish, undamaged shape), and now it seems it doesn't grow more longer.

2. Black spots: less reliable as a clue, because B. capapretum can also has small size of spots, when it feels comfort. My B. capapretum, suddenly changed its appearance after I took home, got lighter base color, and smaller spots than in previous condition (my current tank pH 5,5-6, water temp 31-32 celsius) . But, when it get stressed, my B. capapretum will suddenly came back to "big spot appearance". In B. filamentosum, you won't experience such events, B. filamentosum's is stable fish anyway, never change in appearance due to its mood, no matter how bad it get stressed, the size of spots and the body color won't change. Also just like Wes said, yes it's true that B. filamentosum isn't skittish, the opposite (most) of B. capapretum.

3. Mouth shape: reliable clue as a distinction, when you look at the mouth (front angle), you can see it clearly, both of lower jaw and upper jaw in B. capapretum (also smiling W-shape mouth), but in B. filamentosum you can only see its upper jaw (straight-horizontally upper jaw).

4. Head shape? I'd say it less reliable also, because I have one B. capapretum that its head shape similiar to B. filamentosum.

5. My own version, another clue that can easily spot as distinction when juvenile, is the pectoral and dorsal fin color, my juvenile B. filamentosum has very dark (even black) pectoral and dorsal fin color, and never change since 2.5'' size. The opposite of B. capapretum that has white/light grey pectoral and dorsal fin color.

Here some pic of my B. filamentosum, maybe you can notice my conclusion on it:





(notice that pbass growth and piraiba spots distribution, all above are pics of the same fishes that taken at different time, my conclusion is, no matter how fast piraiba grows, it still can't outgrows C. temensis and C. kelberi LOL)

And here there are my B. capapretum(s):

 

[Marcus_H]

Thank you very much for this abstract! I always tought the W-shape of the mouth had more to do with simple damage than anything else! How bis is the difference in growing so far?

TBH at least on these pictures, the capas with their brighter colour and the "puppy-mouth" look more likable to me.

 

[horopgedrik]

Thank you very much for this abstract! I always tought the W-shape of the mouth had more to do with simple damage than anything else! How bis is the difference in growing so far?

TBH at least on these pictures, the capas with their brighter colour and the "puppy-mouth" look more likable to me.

IME, all of my 3 fishes show different growth rate:
- My fila, only took 3 weeks to grow from 3" to 6", let's say it was 4'' per month (still don't know whether it was the max or not)
- My "puppy-mouth" capa, as you said, about 3" per month
- My smallest capa, has slowest growth rate from all, about 2" per month

About "puppy-mouth" capa, yeah me too, it's my first piraiba-supposed fish by the way, very different looking capa to me. Unfortunately, got dorsal fin damaged.
Remember this picture, that taken by Enrico Richter?

For me, both 2 fishes in that pic are salton catfish, neither both of them are truly piraba B. filamentosum, the lighter fish on the background just very similiar to my capa fish, the one that you called it "puppy-mouth" capa. And the fish at the front, just very clearly looks like ordinary adult/sub-adult B. capapretum.

 

[Marcus_H]

Yeah i know this pic, but i always wondered weather or not the fish in the front is actually a capa or fila or something else. The head is just so different. And i don't think it's just damaged, its just way bulkier in so many ways, much wider, higher etc. But this might be because of the angle the pic was taken.

 

[Chicxulub]

Yeah i know this pic, but i always wondered weather or not the fish in the front is actually a capa or fila or something else. The head is just so different. And i don't think it's just damaged, its just way bulkier in so many ways, much wider, higher etc. But this might be because of the angle the pic was taken.

It looks like a capa to me. I suspect that the bulkiness is from the damage. I've seen several instances where Brachys with that damage buckle their frontal bones in their face, causing them to bow out and give a bulkier appearance. That's exactly what I see with the above fish.