Researchers Domesticating Amazonian Fish for Conservation

April 17, 2008

Editor's Note: Photos are available. Contact Candace Pollock at (614) 292-3799 or pollock.58@cfaes.osu.edu.

COLUMBUS, Ohio -- Aquarium enthusiasts, drawn to the unique and unusual nature of South American fish, may eventually be able to supply their hobby with species bred and reared in North America, rather than turning to imports. The move supports the conservation of tropical species being overexploited not only as ornamentals, but also for consumption.

Ohio State University aquaculturists are striving to breed and rear the silver arowana and the pacu, two Amazonian fish species highly valued in the United States and in other countries as ornamental fish and popular in their native regions as food. The goal of the research is to perfect the technology needed to sustain domestication and provide new opportunities for U.S. breeders to raise the breeds either as ornamentals or as food fish.

"Culture of tropical fish has the potential to become a fast-growing industry in North America because of the high level of know-how required by the professionals and extremely high value of the product," said Konrad Dabrowski, an aquaculturist with the Ohio Agricultural Research and Development Center. "At present, wholesalers in the U.S. offer juvenile arowana at $20-$60 per fish. By comparison, the current price for live exotic tilapia is $4-$6 per pound. Ohio and other Midwest producers of exotic tilapia can transition to production of ornamental fish and receive a much higher unit price per live fish."

Dabrowski and his colleagues are coming off the success of breeding and rearing the first wild Amazonian catfish in North America (Pseudoplatystoma faciatum) -- a species being overexploited for food in various South American countries because of its high quality meat and minimal bones. Their work on fish development, reproductive physiology and nutritional requirements was published in the April issue of Journal of the World Aquaculture Society. Hatchlings spawned three years ago at Ohio State's tropical aquaculture laboratory now weigh 15 pounds, and they keep growing.

"These catfish have a huge growth potential. They can weigh up to 80 pounds. What we've achieved in growth rate with the catfish in six months would take yellow perch to reach in five years, by comparison. That's why they are so highly prized," said Dabrowski, a professor in the School of Environment and Natural Resources. "We are hoping that U.S. born South American catfish can become the stamp for conserving this species, as well as other threatened tropical fish."

The silver arowana is one such threatened fish, an endangered species in several countries. Arowanas belong to the Osteoglossiformes family, an ancient fish species whose origins date back 200 million years. Arowanas are native to Asia, Africa, Australia and South America and are highly sought after because of their unusual characteristics, such as a bony tongue, and their symbolism for good luck in many cultures.

"Arowanas are endangered because of the nature of their collection from the wild. The males, which carry the babies in their mouth, are the ones that are targeted. The young are collected and the adult fish is either eaten for food or simply discarded. It has no value," said Dabrowski.

Dabrowski and his colleagues have successfully raised larvae and juveniles of the South American silver arowana (Osteoglossum bicirrhosum). The fishes, which are in their second year of growth, have the potential to live up to 25 years. Currently researchers are addressing the nutritional requirements of the silver arowana, specifically how the nutrients from the yolk sak are transferred to body tissues, and how that transition plays into acceptance of external feed.

Researchers are also attempting to breed the South American pacu (Piaractus mesopotamicus) -- a species native to the rain forests of Brazil. The pacu is a relative of the piranha, but are herbivores and generally non-aggressive. The pacu is a popular food fish in its native regions, but makes an ideal aquarium species for North American breeding because of its unusual food preferences.

"The pacu has a peculiar feeding habit. It eats nuts and fruits from the Amazon rain forest. In the lab, we've had success in feeding pacu apples, oranges, bananas, even the banana skins," said Dabrowski. "The potential is there to raise this type of fish for food production because of its eating habits and access to cheap feed."

The pacu, like the Amazonian catfish, can also grow quickly within a short period of time, and live for as long as 40 years.

"This fish can grow 10-20 pounds in two years. The trout, by comparison, would only grow to about one-tenth of that size within the same time period," said Dabrowski.

For now, researchers have been unable to induce reproduction in the pacu.

"It may require a more elaborate environmental regime manipulation involving light, pH, temperature and the simulation of migratory behavior, such as forced swimming," said Dabrowski. "One of the major challenges is to maintain the proper temperature. Exposing the pacu, or any of these South American fish, to temperatures, say 55 degrees or lower, for even a short period of time can be lethal."

The researchers have found success in breeding and sustaining the Amazonian catfish with a recirculating aquarium system. They hope to use the system, or elements of it, in their work with the silver arowana and the pacu.

The Ohio State University research was funded by the U.S. Agency for International Development Aquaculture Collaborative Research Support Program and the Peruvian Science Foundation. The research has been a collaborative effort with The Sao Paulo State University in Jaboticabal, Brazil, and The University of San Marcos in Lima, Peru.

Author(s): 
Candace Pollock
Source(s): 
Konrad Dabrowski