Arapaima Gigas
Short answer: Arapaima gigas (pirarucu) is one of the largest freshwater fish in the world, native to the Amazon basin. FishBase gives a common length of about 2 m and maximum reports of 4.5 m and 200 kg.
Very large historical records are poorly documented. It's an obligate air-breather. It uses a lung-like swim bladder and has to surface roughly every 5-15 minutes, which is a big part of why it has been easy to overfish. Its large overlapping scales have a hard mineralized outer layer over flexible layers of collagen fibers. Studies by Marc Meyers and colleagues found piranha teeth can't easily penetrate them. It feeds mainly on fish by suction, and birds or small animals are occasional prey. Taxonomy is unsettled. The genus Arapaima was long treated as a single species, but work by Donald Stewart (2013) revived and described additional species, such as A. leptosoma, so 'arapaima' doesn't always mean A. gigas. The IUCN lists A. gigas as Data Deficient.
What should you know about Arapaima Gigas?
Quick facts. Each one stands alone and has a stable ID you can cite.
The arapaima must surface to breathe air roughly every 5-15 minutes.
FishBase lists maximum reports of 4.5 m and 200 kg.
Video transcript: Arapaima Gigas: Armor That Beats Piranhas
DID YOU KNOW? The arapaima is one of the largest freshwater fish on earth, native to the Amazon and its surrounding river systems, where it can grow over 10 ft long and weigh more than 400 lbs. Its body is armored with tough, mosaic-like scales that provide protection from predators such as piranhas, and it hunts with sudden powerful suction that can pull prey, including fish, birds, and even small mammals straight into its mouth. NOW YOU KNOW!
Burned-in captions, read frame by frame (see transcript.md) · 21.9s Reel ·
The write-up
Armor that beats piranhas. The Amazon's giant air-breathing fish.
- Exhibit A
Giant of the Amazon
FishBase lists a common length of about 2 m, with maximum reports of 4.5 m and 200 kg. Very large historical records are poorly documented.
- Exhibit B
It breathes air
The arapaima is an obligate air-breather. It uses a modified, lung-like swim bladder and surfaces roughly every 5-15 minutes.
- Exhibit C
Piranha-proof scales
Its scales combine a hard, mineralized outer layer with flexible layers of collagen fibers underneath. Research by Meyers and colleagues found piranha teeth can't easily bite through.
- Exhibit D
Suction hunter
It feeds mainly on fish, opening its mouth fast to suck prey in. Birds and other small animals are occasional prey.
- Exhibit E
How many species?
The genus was long treated as one species. Stewart (2013) described or revived additional species, such as A. leptosoma, and A. gigas is assessed by the IUCN as Data Deficient.
Questions people ask about Arapaima Gigas
How does the arapaima get most of its oxygen?
It's an obligate air-breather.
Source: Write-up · Exhibit B (It breathes air) · FishBase: Arapaima gigas (Schinz, 1822); Wikipedia: Arapaima gigas
About how often must an arapaima surface?
Roughly every 5-15 minutes.
Source: Write-up · Exhibit B (It breathes air) · FishBase: Arapaima gigas (Schinz, 1822); Wikipedia: Arapaima gigas
Which predator's teeth struggle to bite through arapaima scales?
Piranha.
Source: Write-up · Exhibit C (Piranha-proof scales) · Wikipedia: Arapaima gigas
What does the arapaima mostly eat?
Mainly fish.
Source: Write-up · Exhibit D (Suction hunter) · FishBase: Arapaima gigas (Schinz, 1822); Wikipedia: Arapaima gigas
What is the IUCN status of Arapaima gigas?
Data Deficient.
Source: Write-up · Exhibit E (How many species?) · Stewart (2013), A new species of Arapaima from the Solimões River, Amazonas State, Brazil, Copeia; Neotropical Ichthyology: Integrative taxonomy data are reconciled around Arapaima gigas for the Brazilian Amazon; FishBase: Arapaima gigas (Schinz, 1822)
Test Your Knowledge
All quizzes →5 questions, all from this case file. Answers are revealed instantly.
How does the arapaima get most of its oxygen?
- By breathing air at the surface
- Through its gills only
- Through its skin
- From plants
Show the answer
Answer: A. By breathing air at the surface It's an obligate air-breather. Source: Write-up · Exhibit B (It breathes air) · FishBase: Arapaima gigas (Schinz, 1822); Wikipedia: Arapaima gigas
About how often must an arapaima surface?
- Every 5-15 minutes
- Every day
- Every hour
- Never
Show the answer
Answer: A. Every 5-15 minutes Roughly every 5-15 minutes. Source: Write-up · Exhibit B (It breathes air) · FishBase: Arapaima gigas (Schinz, 1822); Wikipedia: Arapaima gigas
Which predator's teeth struggle to bite through arapaima scales?
- Piranha
- Shark
- Crocodile
- Otter
Show the answer
Answer: A. Piranha Piranha. Source: Write-up · Exhibit C (Piranha-proof scales) · Wikipedia: Arapaima gigas
What does the arapaima mostly eat?
- Fish
- Fruit
- Algae
- Insects only
Show the answer
Answer: A. Fish Mainly fish. Source: Write-up · Exhibit D (Suction hunter) · FishBase: Arapaima gigas (Schinz, 1822); Wikipedia: Arapaima gigas
What is the IUCN status of Arapaima gigas?
- Data Deficient
- Extinct
- Least Concern
- Critically Endangered
Show the answer
Answer: A. Data Deficient Data Deficient. Source: Write-up · Exhibit E (How many species?) · Stewart (2013), A new species of Arapaima from the Solimões River, Amazonas State, Brazil, Copeia; Neotropical Ichthyology: Integrative taxonomy data are reconciled around Arapaima gigas for the Brazilian Amazon; FishBase: Arapaima gigas (Schinz, 1822)
Cite this case file
Easterling, Marcus. "Arapaima Gigas." The Detail Department (DetailEnjoyer), case file DD-684, last updated Dec 26, 2025. https://detailenjoyer.com/case/arapaima-gigas/
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