The Tanzania Marine Research team has recently observed an unusual phenomenon on the reefs of Mafia Island: a sudden explosion in numbers of the Sharpnose puffer fish, commonly known as tobies. Usually occurring in much fewer numbers, the population boom observed during the last phase has sparked our interest into studying their biology and social organization.
Tobies are found in reefs throughout the Pacific and Indian Oceans. They are among the most popular of the so called balloonfish or blowfish, which belong to the Tetraodontidae family. Puffers are so called because of their ability to inflate their extremely elastic stomachs to twice their original size through ingestion of water or air. This behaviour is exhibited by the fish as a defence mechanism during stress or to protect itself from potential predators.
There is a single genus of Sharpnose puffer, Canthigaster, and its members are readily identified by their elongated, pointed snouts. Sharpnose puffer fish feed mainly on filamentous green and red algae, tunicates, and occasionally on corals, bryozoans, polychaetes, echinoderms, and molluscs. Males are territorial and are often seen fighting, they are even known to sometimes nip the fins of other fish. They are territorial and haremic and spawn with a different female each day. Most of them are poisonous, due to a powerful neurotoxin present in their internal organs, which makes them possibly lethal for any potential predatory fish.
The fact that they were recently observed in great numbers suggests that they might be particularly well adapted to these reefs. It will be important to monitor these populations as Sharpnose puffer fish are known to often damage delicate corals while searching for food.