Pearl Danio seen at Bukit Brown

[Trichopsis]

I was at Bukit Brown Cemetery earlier today, and found a small drain that I think flows behind the private houses along Andrew Road. I followed it for some distance (plenty of beautiful dragonflies & damselflies), and saw plenty of wild-type guppies, with others probably being mosquitofish. Other larger fishes in the deeper parts turned out to be some sort of barb; not sure if they were the native Systomus banksi or the introduced Systomus rhombeus / Puntius sophore.

Further upstream, the drain was replaced by a more natural-looking stream, overgrown with vegetation along the banks, and some sparse strands of Hydrilla and other aquatic plants rooted at the bottom. By dragging a couple of aquarium nets through the water, I managed to catch quite a few pearl danio (Danio albolineatus). According to this paper documenting the presence of this non-native in our freshwaters, the streams at Lorong Asrama in Mandai were listed as the locality. So this might mean that pearl danio are actually more widespread in and around the Central Catchment Area in Singapore.

This species isn't very common in the trade, unlike other Danio species (certainly much less commonly seen than Danio rerio or choprae). Not to mention that the entire site will being seeing quite a fair bit of disturbance and development as some of the graves are exhumed and road construction begins. Don't know if this will directly affect the stream though.

[Trichopsis]

Update: Turns out that the pearl danio is a lot more widespread than initially reported!

There is a small waterway that starts out as a concrete drain flowing beneath a road in Tampines, before it turns into a stream with vegetated banks and a muddy/sandy substrate. I explored this stream today, and found schools of pearl danio. Here's a photo of one that I caught.



Besides pearl danio, other non-native fishes in this stream include large numbers of guppies (Poecilia reticulata) and mosquitofish (Gambusia affinis), cichlids like tilapia (Oreochromis sp.) and flowerhorn. The only native fishes I saw were croaking gourami (Trichopsis vittata) and common snakehead (Channa striata).

It's really puzzling how this fish has colonised streams in scrubland, when it's not that common in the aquarium trade in the first place; I would have expected the zebra danio to become established, rather than the pearl danio. How is the pearl danio being introduced into these streams?

[weng0202]

I think probably released by fish hobbyist. They are pretty tough fish and should survive well in our waters.

[misa]

wow bro, do you often go on such interesting fieldtrips?

[Trichopsis]

misa: Not very often, but I do sometimes explore streams and small drains here and there just to see what fishes can be found living inside. Most of the time, these waterways are dominated by guppies and tilapia, but there's always the chance of finding interesting stuff. Sometimes it's all about splashing around a bit with a net to see what turns up. I stay out of the nature reserves and military training areas though.