What's this next to P. typus?

[Tanganyikafreak]

I was just searching the internet for some pics of Lophiobagrus brevispinis and I stumbled into this pic.
Does anybody have an idea of what kind of fish is beside the P. typus?
I'm guessing it's an Azian catfish, but which one......???

[Marc van Arc]

If I'm not mistaken, this is Polynemus borneensis. No catfish, but very interesting!

[Tanganyikafreak]

Indeed it seems to be a Polynemus species, thanks!!
Nice fish indeed ;)

[Richard B]

Doesn't Polynemus borneensis come from peaty acidic conditions?

Not the sort od mix i'd thought would go.....

[Carp37]

Is it definitely borneensis? Most Polynemus species are marine/brackish/anadromous aren't they? (which would still be a pretty awful mix).

Fishbase doesn't recognise borneensis as a species (doesn't mean Fishbase is right- just an observation), but goes straight to P. melanochir melanochir, which is apparently freshwater/brackish but looks the wrong shape IF they've got the right photo.

[Tanganyikafreak]

According to Wikipedia:

Threadfins are silvery grey perciform marine fish of the family Polynemidae. Found in tropical to subtropical waters throughout the world, the threadfin family contains nine genera and 33 species. An unrelated species sometimes known by the name threadfin, Alectis indicus, is properly known as the Indian threadfish (family Carangidae).

Ranging in length from 20 centimetres in the black-finned threadfin (Polydactylus nigripinnis) to 200 centimetres in fourfinger threadfins (Eleutheronema tetradactylum) and giant African threadfins (Polydactylus quadrifilis), threadfins are both important to commercial fisheries as a food fish, and popular among anglers. Their habit of forming large schools makes the threadfins a reliable and economic catch.
Their bodies are elongate and fusiform, with spinous and soft dorsal fins widely separate. Their tail fins are large and deeply forked; this is an indication of their speed and agility. The mouth is large and inferior; a blunt snout projects far ahead. The jaws and palate possess bands of villiform (fibrous) teeth. The most distinguishing feature of the threadfins are their pectoral fins: they are composed of two distinct sections, the lower of which consisting of between 3-7 long, thread-like independent rays. In Polynemus species there may be up to 15 of these modified rays.


Sixfinger threadfins, Polydactylus sexfilisIn some species, such as the royal threadfin (Pentanemus quinquarius), the thread-like rays may extent well past the tail fin. This feature explains both the common name threadfin and the family name Polynemidae, from the Greek poly meaning "many" and nema meaning "filament." Similar species, such as the mullets (family Mugilidae) and milkfish (family Chanidae) can be easily distinguished from threadfins by their lack of filamentous pectoral rays.

Threadfins frequent open, shallow water in areas with muddy, sandy or silty bottoms; they are rarely glimpsed at reefs. Their filamentous pectoral rays are thought to serve as tactile structures, helping the fish to find prey within the sediments. Noted for being euryhaline, threadfins are able to tolerate a wide range of salinity levels. This attribute allows threadfins to enter estuaries and even rivers. They feed primarily on crustaceans and smaller fish.

Presumed to be pelagic spawners, threadfins probably release many tiny buoyant eggs into the water column which then become part of the plankton. The eggs float freely with the currents until hatching. In Hawaii, sixfinger threadfins (Polydactylus sexfilis) are the subject of commercial open-ocean cage aquaculture.

[Tanganyikafreak]

Looking at the species in the tank I'm guessing there might be a little salt in this tank:
Tanganyika Mastacembelus, L. brevispinnis, P. typus, N. brevis (Tanganyiak shelldweller), Stiphodon(gobies), Mudskipper, a small frog and some other , for me unknown, goby species.
Altough the frog being there gives me lots of doubt about added salt in the tank

[Marc van Arc]

Is it definitely borneensis?

I got the info from Mergus 5, which was published in 1997. The species name may well have changed in 12 years.

[Richard B]

salt is not really good with Tanganyikans - they need certain dissolved minerals to obtain hard water, but not the sort of marine aquarium salts to create brackish water

[Tanganyikafreak]

I know and I totally agree with you my friend ;)
But it was mearly a guess of mine ;)

[jimoo]

There are pure freshwater Polynemus species. I have no idea about this one, but there is at least one that occurs in the Mekong.

[Silurus]

I think the fish in question is likely to be either P. dubius or P. aquilonaris, both of which are known to be generally restricted to freshwater.

[sidguppy]

Looking at the species in the tank I'm guessing there might be a little salt in this tank:
Tanganyika Mastacembelus, L. brevispinnis, P. typus, N. brevis (Tanganyiak shelldweller), Stiphodon(gobies), Mudskipper, a small frog and some other , for me unknown, goby species.
Altough the frog being there gives me lots of doubt about added salt in the tank

this is all in 1 tank?
there are several waterparameter conflicts.....

the Tanganyikans need hard, alcalic water. the mudskipper needs fairly brackish salty water and both the stiphodon and the frog (i assume Hymenochirus; African Dwarf clawed frog) need neutral to slightly acidic, soft water.

not a good combination.