The Forktail Blue-eye - Pseudomugil furcatus
by Paul McFarlane
From the Monthly Bulletin of the Hamilton and District Aquarium Society, October 2001
Aquarticles
In 1942, during WW2, the tiny village of Popondetta in the southeast of Papua New
Guinea was near the terminus of the Kokoda Trail, a jungle track leading across the
mid-peninsula mountains to Port Moseby. In an effort to capture this major centre, the
Japanese had launched a surprise offensive down the Kokoda Trail. After months of jungle
fighting, Australian troops, along with some Americans, repulsed the offensive. The
Japanese efforts ended with vicious fighting that resulted in the capture of their
beachheads on the east coast at Gona, Buna and Sanananda - only a few kilometres from
Popondetta.
Only 11 years later, 1953, in the same general area near Pumani Village, collectors
searching small streams first discovered a two inch, bright yellow fish unknown to
science. In 1955 the fish was named Pseudomugil furcatus (Nichols). In its
natural habitat, this species inhabits small, fast flowing, freshwater jungle streams
having significant vegetation. Temperatures range from 24 to 27C and the pH range is 7 to
8.
This has been a fish with an identity crisis. In 1982, Allen removed it from the genus Pseudomugil
and created another, resulting in the name Popondetta furcata (named after
the village at the end of the Kokoda Trail). Since the fish was first introduced into the
hobby, in Australia, in 1981, and from there to the rest of the world, Popondetta
furcata was the name which hobbyists came to know it by. Unfortunately, someone
discovered that the name Popondetta was already in use as the name of a genus of
beetles. This meant that it couldn't be used for a fish and Allen renamed them, in 1987,
as Popondichthys furcatus. One would think that would be it, but in 1989 a review
of the entire group of blue-eyes resulted in this fish's name being returned to its
original - Pseudomugil furcatus. At least it hasn't been changed since then!
Furcatus first appeared on the North American hobby scene only about 12 to 15 years ago
- at least that's when I first obtained them. At about two inches in length they are a
fish that can be maintained comfortably in as little as a five gallon tank although a
group in a larger, planted tank, displaying their brilliant yellow and black colouration,
makes a striking display. An added advantage is that water parameters of medium hard water
and a pH a little above 7 - which describes the water many of us have in this part of the
world - suits them just fine.
I have found, over the years, that furcatus are somewhat susceptible to velvet disease
(oodinium). This is usually brought on by allowing their water to get a little
"old" and thereby permitting nitrates to build up past their level of tolerance.
The problem is easily prevented by doing some regular partial water changes and not
allowing sponge filters to go too long without rinsing.
These fish make excellent community tank inhabitants providing that their tankmates are
not too large or aggressive. They should do well with smaller Tetras, Rasboras, Danios,
etc. Occasionally, especially when kept by themselves, in pairs, in smaller tanks, a male
may be aggressive with a female, sometimes to the point of harming her. Although this
isn't common, plants for the female to hide in will prevent it entirely. Keeping them in
groups, preferably with extra females, also helps.
Like most Rainbowfish, this one is not difficult to breed. Those that most people think
of, the Melanotaenia, produce large numbers of small eggs. Pseudomugil,
on the other hand, lay only a few eggs at a time but they are larger. A P. furcatus
female will lay perhaps 5 to 10 eggs per day.
These fish will lay their eggs in bushy plants or on a sand or gravel tank bottom if
left to their own devices but few if any youngsters are likely to be saved. My own
preference is to use a floating spawning mop of the type used for killifish. The eggs are
adhesive and are deposited in the mop. They can be picked every day or two.
The picked eggs can be placed in water in a small container to which some fungicide is
added. Hatching takes a week to ten days. After hatching, the fry can be transferred to a
small tank with a few inches of water; a sponge filter is the ideal filtering device. A
wide-mouthed eyedropper is useful in moving the fry. I have found that no matter what I
do, no more than about 75% of the eggs are fertile, and even this will lessen considerably
if the adults are not well fed.
The fry are best fed vinegar eels, microworms or something like APR for 2 or 3 days
before starting with live baby brine shrimp. Unlike larger Rainbows, these fish grow
fairly rapidly - with good food and water changes - and should be sexable and of spawning
size in 3 or 4 months.
Another very similar species, Pseudomugil conniae, is found in the vicinity of
the village of Popondetta. Although it was originally thought to be furcatus, it differs
from that species in some colouration. In particular, it lacks black edging on the caudal
lobes.So far, to the best of my knowledge, P. conniae has not been available in
our area.
Reference: Rainbowfishes - In Nature and in the Aquarium, Dr. Gerald R.
Allen, Tetra Press, 1995
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