By Bill Hauser
My first job working with fish was 50 years ago this summer. I have worked with fish ever since and am retired from formal fish work, but I am still learning more about fish almost daily. Just recently, I learned more about a Fish Talk topic from about a year ago. Below is the article I wrote and below that is some new information.
I was fortunate last fall to take a trip to South America that included a five day trip near Manaus, Brazil on the middle Amazon and Rio Negro Rivers. Then, I felt even more fortunate to come home with a truly unusual souvenir. It is a fish scale. (You know, of course, that I am a bit of a fish nerd.) But this is not just an ordinary fish scale. This scale is from a representative of a species that is one of the largest freshwater fishes in the world. The scale is nearly 3 inches long and 2¼ inches wide. The fish it came from was estimated to be about six feet long and weigh more than 300 pounds. A modest size for this fish.
The fish is an Arapaima; sometimes called pirarucu or paiche. It inhabits rainforest rivers and associated lakes and swamps in the Amazon Basin. The Arapaima has relatives in both Africa and Australia. Large individuals may be 6 ½ feet long and occasionally more than eight feet in length and weigh 440 pounds, though few longer than 6 feet are caught today. Maximum reported length is nearly 15 feet. By comparison, the white sturgeon, the largest fish caught in North America was caught in the Frazer River in British Columbia and it was 12 feet, 4 inches long and weighed an estimated 1,100 pounds.
Arapaima and their relatives exhibit features that are considered primitive and these species have been around for at least 135 million years. These fishes belong to a larger group of fishes labeled “bonytongues” because of the unusual bone structure in their tongues and the tongues have teeth that mesh with bones on the base of their skull.
Arapaima are popular as a food fish for both commercial and subsistence consumption. The flesh is fine, white, and tasty. Unfortunately, they have been heavily harvested and commercial fishing has been banned in Brazil.
There is something very special about the Arapaima. It is one of few species worldwide that can utilize atmospheric air. It does have gills, but it also has lung-like tissue loaded with blood vessels (called a labyrinth organ) in an enlarged swim bladder that allows this fish to extract oxygen from air (recall that gills extract oxygen from water). This ability allows the Arapaima to survive seasonal conditions in water with low dissolved oxygen but the fish must surface every 5 to 20 minutes to take a gulp of air which produces a distinct coughing sound.
Stop a moment and think about this. Here is a very large, tasty fish that comes to the surface every 10 minutes or so and announces its presence. What happens next? They provide a very easy and lucrative target for a spearfisher. One catch may yield 150 or more pounds of succulent white meat. By the early 1900s, Arapaima were severely overfished. Approximately 7,000 tons per year were harvested. (Do keep in mind that at about this time this region was occupied by thousands of non-natives harvesting the worldwide supply of latex for rubber.)
The Arapaima feeds on fish, invertebrates, and occasional small land animals and birds. It does have an unfair advantage. It is large and it functions easily in the low oxygen waters while other fishes become lethargic and more vulnerable under these conditions.
Spawning by the Arapaima is influenced by the seasonal flooding of the Amazon drainage. (The extent of seasonal flooding in this area is not unlike the 30-foot tidal swings in upper Cook Inlet but the changes in water surface elevation take months instead of hours.) Eggs are laid when the water is low or beginning to rise in February to April. About 47,000 eggs are laid in a nest about 20 inches wide and 6 inches deep, usually in mud bottoms. As the water rises, the larval fish hatch and take advantage of the flood season – from May to August - to develop. Eggs and fry are guarded by the parents and the male protects the young by brooding them in his mouth while the female circles nearby. Anecdotal reports describe a white substance secreted from a gland on the head of the female that is used as food by the fry.
Today, although commercial fishing for Arapaima is not allowed, this fine tasting fish is raised successfully in fish farms for sale as a food fish.
Other interesting tidbits about the Arapaima include: the exposed portion of the scale is rough and, when dried, is quite abrasive and used by indigenous people as a small file. The scales are also used to make jewelry.
Actually, you may have seen an Arapaima. I have. But outside of its native habitat. They make great aquarium fish. You just need a large aquarium.
Some South Americans believe the tongue has medicinal qualities. It is dried, mixed with guarana bark, grated, blended with water, and ingested to kill intestinal parasites. Although some people eat the tongue, it may also be dried and used as a scraper.
Clearly, we will never see Arapaima in Alaska, but it is always fun to learn more about fish.
I had help from Mr. Google, Dr. Wikipedia, and Encyclopedia of Fishes, edited by J. Paxton and W. Eschmeyer, 1994.
The recent information I found was from the BBC, Aug 13, 2014 and was based on a report of a study led by a professor from Virginia Tech in the scientific journal, Aquatic Conservation: Freshwater and Marine Ecosystems. The team interviewed 182 fishermen from 81 communities that spanned 400 sq. miles. They found that 57% of the arapaima populations were depleted, 19% were locally extinct, and 17% were over-fished. Not only this, but about 25% of fishermen continue to fish for arapaima regardless of depleted populations. When large individuals are removed, they target smaller fish and other species. Unfortunately, there is no other economic alternatives.
Sadly, these gentle giants are being removed from the Amazonia environments.
For an impressive view of the size and power of arapaima, go to: www.bbc.co.uk/nature/life/Arapaima#p00mkbxp
Find more information about Amazonia and South America at www.billhauserbooks.com
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