Distribution, body size and biology of the megamouth shark Megachasma pelagios

We compiled historical reports of megamouth sharks Megachasma pelagios (mostly fishery by-catch and strandings) from 1976 to 2018 (n = 117) and found that they are distributed globally (highest latitude, 36 degrees) with three hotspots: Japan, Taiwan and the Philippines. Despite possible biases due to variability in fishing effort, more individuals were reported at higher latitudes in the summer, suggesting seasonal, latitudinal migrations. Sex ratios were female-biased in Japan, but more even in Taiwan and the Philippines, suggesting some sexual segregation. Females (total length, L-T = 3.41-7.10 m) were larger than males (L-T = 1.77-5.39 m) and matured at a larger L-T (5.17 m) than males (4.26 m). Also, we reviewed the systematics, feeding ecology and swimming behaviour of Megachasma pelagios based on the literature. Our review shows that, compared with their morphology, anatomy and genetics, behavioural ecology of this species remains largely unknown and electronic tagging studies are warranted.