Diodon nicthemerus—the spot‑fin porcupinefish (also called slender‑spined porcupinefish)—belongs to the family Diodontidae. Like other porcupinefishes it can inflate by gulping water/air when threatened, erecting itsslender, normally recumbent spines for defence. It crushes hard‑shelled invertebrates with fused upper and lowerbeak‑like dental plates and frequents temperate coastal reefs and seagrass beds.
Ecology & Biology
Diet: molluscs, echinoids, crustaceans and polychaetes—benthic, hard‑shelled prey crushed by the dental plates.
Behaviour: solitary or in small groups; retreats to crevices or inflates when disturbed.
Reproduction: pelagic broadcast spawner; pelagic eggs/larvae drift before recruiting back to coastal habitats.
Identification
Pattern: mixed stripes and spots over the flanks; fins typically show fine spotting, giving the common name.
Spines: slender and flexible, usually recumbent when relaxed, erect when inflated.
Mouth: two fused beak‑like plates (upper/lower) typical of diodontids.
Size & Longevity
Length: commonly 15–25 cm, maximum around ~30 cm.
Life: roughly 6–10 years (estimates vary).
Range & Habitat
Temperate southern–southeastern Australia (including Tasmania) and adjacent waters, inhabiting rocky reefs, kelp beds and seagrass meadows from about 2–60 m.
Conservation & People
Threats: coastal habitat degradation, incidental capture and pollution; overall fishing pressure is modest.
Food safety: some diodontids may carry tetrodotoxin/ciguatera risks; follow local advisories.
IUCN: Least Concern (LC) (subject to latest assessment).
