Characodon audax and the Goodeid Factory
By Randy Carey
Some species are worth preserving. Some because they are attractive. Others because they are rare. Characodon audax is a species worthy on both counts.
One problem with livebearers is that many species eat their young. An added problem of Goodeids and Halfbeaks are that female produce few young. The averages of many are only in the teens per female. For Characodon audax it is 10 to 20.
Recently I have developed a technique for mass harvesting livebearers, specifically Goodeids and Halfbeaks. This technique takes advantage of them being viviparous rather than ovoviviparous.
As you may recall, being ovoviviparous, a female Poeciliid can give birth to several successive broods from a single insemination. In contrast, females of the Goodeids and Halfbeaks (two vivaparous families) require insemination for each brood. Add the fact that livebearer males are always eager to fertilize and that the femalesí gestation periods are rather regular, one can target the time of births by placing the female with a male at a certain time and then let nature take its course. Characodon audax
This is a very attractive livebearer, but unfortunately an uncommon one. The body is a metallic silver and the unpaired fins on the males are jet-black. A couple of years ago Aquarium Fish Magazine published an article on rare livebearers. The large, eye-catching photo which opened the article was of Characodon audax.
As I recall, the article mentioned that this species was threatened in the wild. Even in the hobby some aquarists have had a difficult time propagating the species. Livebearer expert Mike Schadle told me that typically a hobbyist who would obtain the species would seldom get more than one generation before the whole colony would die. He added that he knew of only two other aquarists in the country who are maintaining this species. When I purchased my original specimens at an MAS meeting over two years ago, they were the only four Jim Mathis had to BAP. However, for some reason I had successive luck with the fish right from the start. My third generation of audax is now giving way to the fourth.
A few difficulties have been claimed about successfully breeding Characodon audax
One peculiar characteristic of this fish has set me back on several occasions. When I harvest livebearers, I place the female in a small tank by herself. I stuff the container (usually a one gallon bowl) with plants (live and/or plastic) but still leave ample room for the female to swim. This allows the fry to take safe haven among the clutter of plants. This technique worked fine for my audax, but the problem arose when I would transfer the fry from the bowl to a larger container such as a ten gallon tank. Typically when the fry would encounter new water, either by transferring them to a larger tank or by adding/changing water to their container, I would loose half or more. Eventually the fry grow out of this sensitivity, but it has been a real problem for the first couple of weeksóespecially when I was unaware of this sensitivity.
Since I donít want to leave over a dozen fry in a bowl of unchanged water for two or three weeks, I need to harvest the fry in the larger grow-out tank. But this seems to suggest that I set up a 10 gallon tank for each female whose fry I want to harvest. If I want to harvest from several females, I will need several tanks. The Goodeid Factory
I want to harvest audax from multiple females. Necessity is often the mother of invention, and in this case it was. I could not justify several fry tanks with a dozen or so fry per tank. The solution was to harvest all of the fry in the same tank. Any audax male left with the birthing females will surely reduce the number of fry. (The same is true of all Halfbeaks which I have had.) So the birthing tank should contain only the required females. For a time I thought the females would also cannibalize, but evidence suggests they donít if I provide ample cover for the new born.
As another goal, I want the fry in the grow out tank to be roughly the same size. I feel this gives each young fish an even opportunity at feeding time.
So my solution is to coordinate the females to all give birth about the same time and in the same tank. Fortunately, this can be done for Goodeids and Halfbeaks. You may recall that the gestation time for each livebearer species is quite regular. This maternity period usually ranges from four to six weeks depending on the species. So if you know when a female is inseminated, you can predict the time of birth usually to the day.
Females of the Goodeids and Halfbeaks require insemination for each brood, so the breeder has some control of when a gestation period begins. Since the Poeciliid females will produce several broods from a single encounter with a male, keeping multiple females on the same cycle will be difficult.
Armed with these two facts about Goodeids (and Halfbeaks), I developed a schedule in which I could predictably harvest the young from many females at a time. The technique requires that I introduce all females into the same tank and time the births to all happen about the same time. If I can coordinate all of the females to be on the same schedule, I can accomplish several goals:  reduce the risk of cannibalism,  keep the fry sizes about the same for multiple broods,  be able to keep all the fry in one tank instead of several (without forcing the fry to undergo a change in water during their first weeks),  track only one date of expected birthing rather than a date for each female (while trying to remember which female is due next).
The ever repeating schedule follows these steps:
Females who have yet to be with a male since they last delivered are all introduced into a tank of males at the same time. Male livebearers are typically eager to mate, so I will assume that all females will be fertilized within the first day or two.
The females are withdrawn after a week to a females-only tank. By limiting the mating opportunity to a week , this will prevent the possibility that female will be fertilized weeks later. If this breeding cycle is to be repeated, the system cannot tolerate staggered gestation periods. Either all of the females must wait for the one or two late females or the late females need to skip the next cycle. I would rather have an unfertilized female wait out the current cycle and the get back on schedule rather than have it deliver unpredictable late and miss or delay the next cycle.
Prepare the spawning/rearing tank just days before the earliest possible births. Preparation includes fresh water, lots of plants as refuge for the fry, and the introduction of the females. Since Characodon audax has a six-week gestation, the first fry could come six weeks from the day they were introduced with the males. I prepare the spawning tank two days before that target date.
As females become noticeable thinner, I remove them to the female tank. This will reduce the chances of cannibalism.
The females are given a time of rest and are fed well. By giving the females a two-week rest, I have noticed larger broods. Presumably the females are developing more eggs during this time. They are also garnering needed rest. If I want more fish, I will use more females. If I want healthier fry, I will give the females a resting period.
[repeat the cycle]
I have applied this approach to Characodon audax with good success. One attempt yielded seventy-some fry from five females and one birthing tank. I have also applied the technique to the Halfbeak Nomorhamphus ebrardti, a species which eager hunts down its young.
Perhaps the trickiest part is being disciplined enough to get started. The breeder must be willing to hold out all females from the male tank until all breeding females have delivered. The aquarist needs to be sure that all females which begin the cycle have not been fertilized. In the case of a six month gestation species like Characodon audax, the first harvest from the technique might be as long as three months after the breeder starts the program! Species Maintenance
My Goodeid factory accommodates an important principle in species maintenance: Produce offspring in breadth, not depth. In other words, produce the fry you need from one generation as long as you can before you start producing from the next.
Each time the offspring of a species are bred together (or even with a parent), this line is taking another step toward inbreeding. For species which can be obtained repeatedly from the wild (such as most of our common fish), an inbred line can be discarded in favor of wild caught stock. However, when species such as Characodon audax are rare and seldom if ever imported, the keeper of that species should work to slow the rate of inbreeding--an important aspect of species maintenance.
So an important tactic of maintaining a species is to keep a generation going as long as it can before breeding is passed on to the next generation. When the breeding colony starts to die or becomes unproductive, replace the breeders with the best specimens from the most recent broods. When we must replace a breeding colony, the younger specimens we use as replacements, the longer that generation will continue and the amount of inbreeding is less through time.
Without adding new blood into our colony, the affects of inbreeding will increase with each generation. Some aquarists refrain from introducing new specimens into the breeding colony because they want to keep the stain (or even the location) pure. Unless the strains are quite different, I believe in mixing new blood to strengthen the genetic diversity. Fortunately for me, I was able to pick up two females from one of the other two hobbyists who are keeping Characodon audax. I added the fish to my breeding colony. So . . .
Most aquarists do not aim to breed their livebearers in large numbers. The occasional birthing of a single female may provide more fry than there is demand. Characodon audax, however, is quite attractive and thus will be in demand from even the amateur aquarist. Furthermore, its threatened status and rarity in the hobby add to the importance of maintaining this species. But who is talking about just maintaining it? Perhaps it can enjoy a resurgence in the hobby. Keep the factory rolling.