Sunday, 28 August 2016

Archerfish, family Toxotidae

Thanks to Bruce Hansen for his help with the rare archerfish species.

There are seven known species of archerfish, of which only three are commonly traded, Toxotes chatareusToxotes jaculatrix, and Toxotes microlepis. Generally, retailers make no attempt to separate these species, though sometimes Toxotes microlepis may be offered specifically as a ‘freshwater archerfish’.

The other archerfish, all freshwater species, have not yet been traded in significant numbers. The so-called primitive archerfish Toxotes lorentziis a strictly freshwater species but is rare and not commercially traded. It is confined to Australia and New Guinea, and is very unusual in appearance, being greenish-brown and bearing only the vaguest pattern of vertical bands. Toxotes oligolepis looks much like Toxotes jaculatrix, but is rare and apparently confined to the Molucca Islands, Indonesia. It is unlikely to be offered for sale. Its peculiar characteristic is that the third spine in the dorsal fin is the tallest and thickest, instead of the fourth or fifth spines, as is the case with the other archerfish species. Toxotes blythi is a Burmese species distinguished by having horizontal, instead of vertical, banding. It is an exceptionally attractive species and unlikely to be confused with anything else. Finally, Toxotes kimberleyensis is a newly described species from Australia, found in the Fitzroy River. It resembles Toxotes jaculatrix, though it tends to have rather dark dorsal and anal fins when compared with that species.

All archerfish share the same basic requirements. They are relatively big fish, and aquarists should expect Toxotes chatareusand Toxotes jaculatrix to easily reach 20 cm in captivity. Toxotes microlepis is a little smaller, at 12-15 cm, but still needs plenty of space. They are also hearty feeders, and combine that with their preference for being kept in large groups, and you have fish that demand a big tank with excellent filtration. All archerfish are predatory and will eat very small tankmates such as small livebearers, but otherwise make good community fish. Finally, archerfish are excellent jumpers and will leap out of uncovered tanks.

In the wild archers are schooling fishes, but in captivity they can be difficult fish to keep in groups and many aquarists find keeping a single specimen to be easiest. Single specimens do tend to be rather shy and nervous though, and serious aquarists should consider keeping them in groups if they have the space. Less than six specimens tends to be risky, and almost always the largest specimen bullies the other fish. Stressed archers turn dark and are easy to spot. It would certainly be very unwise to keep archerfish of substantially different size together.

Archerfish are famous for their ability to spit water up to 150 cm to knock down insects and other small prey from overhanging leaves and branches. They will also leap (like salmon) to catch their food. In captivity they can be ’trained’ to spit at dead or processed food items quite easily. Begin by setting the tank up so that about 10 to 15 cm (4 to 6 inches) of glass is above the waterline. Once the fishes have settled in, feed them on small crushed prawn chunks. They will happily take these midwater. Then stick them to the glass at the waterline. The archers will pick them off. Gradually place the food a little higher each time. Eventually the fish will jump against the glass to get the food. Once the food reaches a certain height they give up jumping and start spitting. Enjoy!

Distinguishing the common species of Toxotes

Toxotes chatareus is quite commonly sold, often alongside Toxotes jaculatrix, where both will be simply labelled as ‘archerfish’. It normally has 5 spines in the dorsal fin and a series (typically 6-7) alternating short bands and spots. Many, but not all, specimens have an overall sooty cast that helps distinguish them from the other species, which tend to be silvery. This is a brackish water species (SG 1.005-1.010) that can be expected to reach a length of 
around 20 cm in captivity (up to 40 cm in the wild). There is a freshwater population of this species found in Australia, but European and American aquarists are unlikely to be offered these fish.

Toxotes jaculatrix is the species most often mentioned in aquarium books, but it is by no means the only species traded. This species usually has only 4 spines in the dorsal fin and a series (typically 4-5) vertical, wedge-shaped bands on the flanks. There may be smaller spots between them, but not in the ordered way typical of T. chatareus. The last two bands usually run onto the dorsal fin, something that can be contrasted with the two discrete spots of typical of T. microlepis. This is a brackish water species (SG 1.005-1.010) that can be expected to reach a length of around 20 cm in captivity (up to 30 cm in the wild).

Toxotes microlepis is said by some aquarists (e.g., Frank Schaefer, author of the Aqualog brackish water aquarium book) to be the most commonly traded species. It is easily confused with T. jaculatrix. It shares with that species 4-5 wedge-shaped bars on the flanks, but usually has smaller spots in between at least some of them. The last two bars do not cross onto the dorsal fin, as they do with T. jaculatrix, leaving the two dark spots on the dorsal fin as quite separate entities. As its Latin name suggests, this species also has smaller scales that those found on other archerfish, though this characteristic can be difficult to notice on live fish. This is a fresh and brackish water species (SG 1.000 to 1.005) that can be expected to reach a length of around 12 cm in captivity (up to 15 cm in the wild).

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