Globe Fish
Diodon nicthemerus
The Globe Fish is easily recognised with a grey back, black blotches on the sides, a white belly and yellow spines, which are formed from modified scales. As members of the Order Tetradontiformes (along with other pufferfish, toadfish and boxfish) their skin contains the poison tetrodotoxin. They have large prominent eyes and the teeth of the species are totally fused into beak-like jaws, allowing the fish to break off branches of corals and grind small mollusc and crustacean shells on which they are feeding. Their large soft-rayed paddle-like rounded fins attribute to their slow swimming ability. When threatened, the fish inflates its body to five times its normal size with air or water, radiating its spines outward, proving an effective defensive strategy against predators. This potentially can cause the swallowed fish to become lodged in the throat of predators, preventing them from being swallowed.
This species occurs on sheltered to moderately exposed reefs from depths of 0 to 50 metres along the southern Australian coast from Dongara, WA to Seal Rocks, NSW. Juveniles are pelagic and benthic as adults. Globe fish tend to shelter in caves during the day or hover above the substrate in schools, then emerge and become most active at night, where they will feed on a variety of invertebrates, particularly hard-shelled crabs. They grow to a maximum length of 28 cm.
Other common names include Slender-spined porcupine fish.
Occurrence at the Busselton Jetty
Globe fish are particularly prevalent under the jetty and are seen from the underwater observatory on a daily basis, often solitary. They are most often seen feeding and hiding in amongst the invertebrates covering the jetty piles, and inconspicuously taking up refuge under ledges surrounding the observatory. Occasionally, curious individuals will come toward the observatory windows and remain very close for a time.
Image by: O. Rynvis
