The green spotted pufferfish (Tetraodon fluviatilis) inhabits freshwater and brackish water habitats. Brackish water has a lower salt content than the ocean and is found in rivers or estuaries where freshwater is mixing with seawater.

The green spotted pufferfish is a member of the Tetraodontidae family of fish, famous for their natural defense mechanism of inflating their stomachs when threatened to appear larger. Many species of pufferfish, including the green spotted puffer, are toxic to most predators, including humans. There are at least 191 unique species in this family of fish found in many tropical areas around the world. They are less common in temperate regions.

This species of fish has been known to occur in coastal freshwater and brackish water areas near South and Southeast Asia, including mangroves.

There are no known major threats to this species, although they are commonly caught in the wild to be sold for use in aquariums.

Scientists have been studying the genome of the green spotted pufferfish because it has the same number of genes as humans but compressed into a much more compact genome structure. This has led scientists towards better understanding the human genome and the role that certain types of genes play.


  1. What is the purpose of the pufferfish behavior of inflating their stomachs with water to appear larger than they are?      

    • Answer

      The behavior of inflating the stomach with water (or air, when removed from the water) to appear larger than they are is a natural defense mechanism of the pufferfish to help intimidate predators.  

  2. In a healthy state, brackish water is teeming with aquatic life that is specially suited to the salinity levels found where freshwater mixes with seawater. What importance are brackish water ecosystems to wildlife that live most of their lives outside of the water?

    • Answer

      Many species of birds live their lives along the shores of estuaries and brackish water rivers. They consume mollusks, crabs, and other plants and animals that thrive in brackish water environments. Humans also consume wildlife found in brackish water environments, as do other animals.

  3. Is the collection of aquatic species for use in private aquariums damaging to aquatic ecosystems?

    • Answer

      Although there are species of fish that can be harvested sustainably for use in aquariums, many aquatic ecosystems are under threat from the harvesting of fish for the aquarium trade.

brackish water

salty water, usually a mixture of seawater and freshwater.

defense mechanism

adaptation of an organism to defend itself against predators.


mouth of a river where the river's current meets the sea's tide.


having to do with a habitat or ecosystem of a lake, river, or spring.


set of genes, or chromosomes, that hold all the inherited characteristics of an organism.


type of tree or shrub with long, thick roots that grows in salty water.




existing in the tropics, the latitudes between the Tropic of Cancer in the north and the Tropic of Capricorn in the south.