Porcupinefish are always a fun sight on dives. They are sometimes called blowfish.
The porcupinefish gets its name from the many long spines located all over the head and body. They are members of the pufferfish family, but should not be confused with pufferfish. The porcupinefish's spines are visible even when they lay flat, whereas they are not usually visible on a pufferfish.
When threatened, the porcupinefish can inhale air or water to inflate its body to over twice the normal size. Additionally, this causes the spines to stand up, making the porcupinefish edible only by large predators.
You are not likely to see an inflated porcupinefish, even if you attempt to chase one. I have heard if you manage to grab one by the tail they will inflate, but we all know that's not a good idea, don't we? I have also heard that inflating is stressful and has an effect on the fish's lifespan.
Porcupinefish are a grayish tan color, with white on the underbelly. They are usually covered with small black spots or splotches.
They can reach up to 36 inches (91 cm) in length. They have large heads which taper off towards the caudal fin. They are also distinguished by their large, round eyes which appear to watch you when swimming by. They also have oval-shaped mouths which are usually open.
Geography and habitat
Porcupinefish are found worldwide in tropical, and sometime temperate, regions.
They live in holes on reefs at pretty much all depths. Usually you will encounter them swimming out above reefs, though.
They tend to be solitary, but occasionally you will see them in small groups. They also tend to move very slowly, although they still swim faster than most scuba divers.
Porcupinefish are known to produce toxins in their organs and on their skin. Nevertheless, they are known to be eaten in some areas. My guess is that the toxin is mild enough to only be dangerous to smaller predators.