We’ve all seen images of an adorably puffed-up pufferfish, but in reality, divers and divemasters do real harm when they cause these fish to puff up.

Pufferfish are some of the easiest fish for scuba divers to identify. They include porcupinefish, globefish, and any other fish within the family Tetraodontidae and Diodontidae that enlarge their bodies by puffing them up as a defense mechanism. Unfortunately, while puffing up can successfully discouraging predators, it also can be quite harmful for the pufferfish, sometimes leading to death. Here we’ll explain why it’s time for divers and divemasters to leave pufferfish alone. Observe or photograph them only from a respectful distance — and under no circumstance should you ever artificially puff one up.

What makes pufferfish expand?

Pufferfish can instinctually inflate their bodies whenever they feel threatened as soon as they hatch. This helps them appear more intimidating to potential predators. When the pufferfish matures it can use this defense mechanism to full effect, allowing the fish to puff up to three times its original size. This can take as little as 15 seconds.

How does it puff up?

Until researchers at James Cook University proved the mechanism a few years ago, scientists did not know how a pufferfish expands. Marine biologists at James Cook studied the behavior and found that the pufferfish forces its body to puff by unhinging its jaw to widen its mouth. While unhinging the jaw, the fish gulps large amounts of water, quickly expanding its entire body. This expansion makes the pufferfish look much more intimidating than usual, with the goal of scaring off predators.

Why is puffing bad for a pufferfish?

As you can imagine, gulping lots of water stretches out the fish’s stomach as well as its skin. Swimming becomes very difficult for pufferfish when they’re blown up to three times their normal size. Already not the most streamlined swimmers — which is why they have this defensive tactic in the first place —the puffed-up fish has lost even more mobility. A puffed-up puffer will basically drift along until it returns to normal size.

How does a pufferfish return to its normal state?

The pufferfish expels water from its stomach the way it entered, but at a much slower rate. Studies have shown that it can take an average of 5.6 hours before the fish returns to a typical metabolic level. During this time, the fish is vulnerable because of its size and immobility. The pufferfish is also typically exhausted from the exertion of puffing up. Because of these factors, divers and guides should view and appreciate this oddly formed fish from a distance, and tell other divers to do the same. Just as with all other marine life: keep your hands to yourself when it comes to pufferfish.

By guest author Liz Maynor

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