Breeding The Red-Belly Piranha

Serrasalmus (= Pygocentrus) species

By Dr. Herbert R. Axelrod

From the "breeding aquarium fishes Book 4, 1976 TFH Publications, Inc





A pair of spawning piranhas just seconds before they released masses of eggs into their spawning "nest." Photo by Hiroshi Azuma


Three-inch long tank-raised piranhas. These fish must be well fed or they will start to chew each other up! Photo by Hiroshi Azuma.




For several years I served as chairman of the Exotic Fishes Committee of the American Fisheries Society, and while in that post I had the responsibility for making recommendations to the Congress about the best means of protecting American Waters from such menaces as the piranha from South America, the walking catfish from southeast Asia and Tilapia from Africa. The fear with which American conservationists viewed the piranha is amazing, and even though I argued that prohibiting the importation of piranhas would not stop their availability since they are so easy to breed, they still proposed laws which made importation illegal except under certain very special circumstances.



Throughout the jungles of South America, children play and splash. Among the piranhas without any fear of these ferocious fishes. Piranhas are dangerous only when they are starving or in an unnatural situation. 

Photo by Harald Schultz


I’m frequently asked why piranhas are so feared if I go swimming with them in every river of Brazil, without the slightest hesitation. I’m not that brave…but I’m not stupid either. After spending so much time with Brazilian Indians, I’ve learned to do what they do. They know that piranhas never attack humans in rivers or lakes in which the fish have enough food. They are dangerous only when they are starving, such as in artificial situations (new reservoir, aquaria) or in pools that are drying out and have been isolated from the main body of water (intermittent ponds). How then did this fish get such a terrible reputation? It goes back to the days of our great president Theodore Roosevelt. He is, by the way, the American president I respect so much that I wish he were around to lead us now.






These pictures show the piranha in their pre-spawning display, immediately prior to spawning. Photos by Hiroshi Azuma.




Anyway, Teddy Roosevelt planned an expedition to the innermost reaches of Brazil; he hoped to find new animals, fishes and geographical landmarks. Naturally he was an honored guest in Brazil; he was the first North American notable to visit the country’s jungle and all the details of his journey were prepared by the host country. Since he wanted to find something significant, his hosts led him to a huge river which he "discovered" and which eventually bore the name Rio Theodore Roosevelt, named in his honor. It is a branch of the Rio Aripuana. Being a knowing politician, Teddy had a fairly large entourage of reporters who detailed every momentous happening for the American press. The Brazilian hosts were always thinking up spectaculars for the trip, and the famous Brazilian ichthyologist Miranda-Ribeiro got the brilliant idea of taking a small segment of the Rio Theodore Roosevelt and isolating it from the rest of the river by hanging two huge nets across the river a few hundred yards apart. Then scores of local fishermen began catching piranhas with hook and line. Every one that was caught was thrown into the isolated area until several thousand piranhas had been accumulated in this netted-off section of the river.


It was then that Teddy Roosevelt was brought to this part of the river and told about the fierce man-eating fishes to be found there. "No one must dare go near the water," for the fish would certainly eat a man down to his skeleton!!! Of course the reporters…and Teddy… were a bit skeptical about this sort of thing, but their skepticism played right into Miranda-Ribeiro’s hands. "Can you prove this claim? How do we know these piranhas are such fierce and devastating fishes as you say?" the reporters asked. So the Brazilian host took a sick old cow, which was in season, at the moment and whose main feature was that she had a heavy, bloody discharge, and they drove her into the water.





This top view and the front and back views on the facing page Indicate some of the frenzied spawning antics of this most feared freshwater fish. Their actions are so intense that heavy stones are utilized to hold down the spawning mat. Photos by Hiroshi Azuma.



Rio Theodore Roosevelt


Almost immediately the starving, crazed piranhas attacked the cow, and in short order her legs were so badly bitten she fell sideways into the water where her screams and thrashing brought more piranhas onto the scene. The river was bloodied and the piranhas were so excited that they leaped out of the water onto the cow’s body to grasp a mouthful of flesh. The reporters stared in disbelief, for within a few moments the cow was brutally torn apart and devoured by thousands of these starving ten-inch long fish. The newspapers were filled with tales which, though far from being exaggerated, were lacking in the particular detail which would have made the story more honest. Teddy himself was impressed, so he took a fishing rod and caught a few piranhas using a chunk of raw meat as bait. He brought the fish back, and they were scientifically described, naturally, as Serrasalmus roosevelti, in honor of their discoverer.


Many years later, in the 1960’s, a documentary television film was made of the same sort of thing. Willi Schwartz of Manaus, Brazil set up a huge wooden aquarium about 20 feet square and about five feet deep. The tank was filled with about 100 large piranhas…and they were kept so starved that they started to eat each other. Then an animal was thrown into the tank and cameras photographed the scene through glass portholes built into the side of the wooden aquarium. When the film was shown on nationwide network TV in the United States the producers failed to mention the unnatural circumstances under which the film was made…and further stature was added to the big "lie" about piranhas.


This is being written in 1976, while the film "Jaws" is finishing up its fantastically successful run throughout the country. It is a film about a huge white shark which terrorizes a community, beginning by eating a skinny-dipping girl. The film goes so far as to have the shark attack a large wooden board, chewing off the stern and sliding a passenger into his mouth.





The piranhas’ eggs are large and sticky. They adhere to the spawning grass. The lower photo shows a close up of some of the eggs. Photos by Hiroshi Azuma.


If the reports can be believed, the film has grossed more money than any other film in the history of show business. To a scientist it is horrifying in its inaccuracy. The shark itself, by the way, is mechanical!


To follow "Jaws" is supposed to be a film about piranhas. I received a few telephone inquiries about it from "Hollywood" promoters, but I wouldn’t have anything to do with further bad-mouthing of the magnificent piranha; should the film actually be made, I would actively work to preserve the truth as far as piranhas are concerned.


In 25 years of travel and fishing in almost every river system in South America, nearly all of which had schools of piranha, I NEVER was bitten, nor did I ever meet anyone who was bitten…nor did I ever meet anyone who even knew anyone who was bitten by a piranha…and these are mostly Indians who live on the river and swim in it every day. But this does not mean that you can’t be bitten if you stick your hand in your aquarium or grab one in a net! So be careful, but not frightened.


Now that we have dismissed the myth surrounding the magnificent piranha, let’s take a look at how we can breed them, because there is every possibility that our illogical conservationists might well make importation of these animals illegal. (Some states…and several countries…already have laws which makes possession and importation of piranhas illegal.)


When young (under five or size inches) red-belly piranhas all look the same. Males are indistinguishable from females. But once they reach sexual maturity, changes which make sexing fairly simple begin to occur. The females begin to develop fatter bellies with their bellies swelling to a girth 50% greater than the bellies of the males; at the same time their bodies become suffused with a purple hue. The males darken at this time, turning almost a blue-black. Since they are such large fish, you must put them into as spacious a tank as possible. A 50-gallon tank would be the smallest that would be suitable. Larger tanks are even better…and kiddie pools are best, since they have no sharp corners and are large enough to handle the thousands of babies which might result from a spawning.


While piranha are tropical, they do not require very high temperatures to spawn. Certainly 75-80º F. is a proper range. As long as the water is clean, the pH and hardness are inconsequential. Soft, acid water is probably best, though there are reports of their spawning having occurred in almost every kind of water suitable for maintaining the fish alive. If they live and grow in your water, they will spawn in the same kind of water.


Piranhas are basically scavengers. They eat meat, fish and just about anything that is bulky. Don’t offer them flake food when they are five inches long! But perhaps they can take fish pellets which will enable you to flush the tank in which the fish are kept, all the better, for then you can offer white mice or large goldfish. As the mice struggle in the water, the piranha makes a swift dive at the mouse and neatly cuts it in two! This sort of diet makes for good fish conditioning but might be frowned upon by people who are not accustomed to feeding animals. Snakes in most zoos, by the way, are fed white mice as their staple diet!


When the fish are highly colored and the female is plump, separate them for a few days…or a week… and put the female into the large tank in which they will spawn. The female needs the extra time to become accustomed to her surroundings. The large tank should be set up with a mass of fine-leafed plants in the center, perhaps even held down with some large stones. The female thoroughly investigates the tank for the first day or two and then is ready for her mate. Keep a few large goldfish in with the fish so that have a snack. You don’t want the piranhas hungry at this stage of the game. As a matter of fact, you never want your piranhas hungry or they will attack anything swimming in their tank! When they are well fed they are safe with other fishes their own size.


The male is added to the tank after two or three days at the minimum. He slowly circles the female and begins to show much heightened coloration, turning almost black except for his highly iridescent scales, which contrast so much more during this period of time.

As the male chases the female, she quite easily avoids his advances, especially if the tank is large enough. Finally she does not move away from the male but stands her ground, usually over the plants. The male then comes alongside her, with his anal fin continuously flicking, and pushes hard against her, trying to enfold her with his body. They swim upwards and a squirt of eggs falls onto the plants.



Perhaps as many as 30 eggs are shed at each embrace. The eggs adhere to the plants, since they seem to be very sticky. This act is repeated constantly, time and time again, for hours, until the eggs are in a huge mass covering the plants. It takes about 20 eggs, laid next to each other, to measure one inch. The eggs are a lovely orange and are quite a contrast to the deep green plants.


You would expect that the piranhas would leave the eggs…or start to eat them…the way other characins would behave. No!

The piranhas carefully inspect the eggs, eating a few which probably were not  fertilized, and doing housekeeping chores to insure the eggs won’t be smothered or covered with debris. Actually they act more like cichlids (substrate spawners) than they do characins. The parents guard the eggs and viciously attack anything that comes near them. (I poked in a stick and they cut it in two…it was the thickness of a pencil…a chopstick.) In 56 hours the eggs have hatched and the young are still kept in the same area and guarded.





In Venezuela, I caught this piranha and cut in down the middle. I was amazed at the size of the cavity which houses the internal organs. Piranhas are eaten by many of the native peoples. The dark organ in the middle of the viscera is an ovary filled with eggs. Photo by author (H. R. Axelrod).


Myleus and Colossoma are two genera closely related to the piranha, but the fish are almost strictly vegetarian. Photo by author (H.R. Axelrod).

In about a week after spawning, the fry are free-swimming. The parents can be removed at any stage after spawning, but they usually don’t devour their spawn until they are at least free-swimming.


The fry can be fed newly hatched brine shrimp as soon as they are free-swimming. If you feed them sufficiently well, they will be an inch long in a month and capable of eating a dozen baby guppies a day.


The problem then becomes one of food. If you had a big spawn, you might well have had 7,500 eggs, and it is very conceivable to get 6,000 of them into the free-swimming stage. But what kind of live foods can you have for such a swarm? It would take a gallon of brine shrimp eggs to feed them the first week, then you would need larger shrimp or larger other live foods…and finally some baby guppies…or baby anything that swims and is smaller than they. After a month they can be weaned to beef heart (shaved, frozen and scraped), but don’t let them get hungry or they will immediately start to chew each other up. As a matter of fact that’s they way they usually grow, eating up their smaller brethren until perhaps a hundred or fewer are left, and most of them have torn tails and anal fins. Some piranha breeders have noted that the young piranhas have a great tendency to attack each other’s eyes, though their fins are attacked first.


The advantage of the kiddy swimming pool is obvious now, since you’ll need some place to store the piranhas until you’ve been able to sell them. Whatever you do, don’t throw them into your local river or lake! If you must dispose of them, be sure they are dead. Then put them into a plastic bag and burn them. I heard a story about one that jumped out of a tank. It was immediately seized by the family cat almost as soon as it hit the rug. The fish got the last bite and neatly took off the cat’s nose. Be careful!


Page 96



Dissections made by Hiroshi Azuma show the tremendous quantities of orange eggs found inside normal females. Breeding piranhas can be very profitable! Photos by Hiroshi Azuma.


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