Sicklefin lemon shark

What it is

This robust shark features a short, broad head and a stocky body. Its colour ranges from yellowish-brown on top to lighter shades below, with yellow-tinted fins. The species is named for its highly falcate, or sickle-shaped, dorsal and pectoral fins. It grows up to 3.8 metres long, though most adults remain smaller. Small nostrils have triangular skin flaps, and the mouth corners show short furrows. Teeth are serrated in larger individuals, with upper teeth angled towards the jaw corners.

Where it lives

Its distribution spans the tropical Indo-Pacific, from South Africa and the Red Sea east to French Polynesia. Populations exist around Madagascar, India, Southeast Asia, northern Australia, and many Pacific islands. It inhabits coastal continental and insular shelves, favouring murky bays, estuaries, and lagoons. Individuals live from the intertidal zone down to 92 metres. Juveniles often occupy shallow nursery areas like mangrove flats, sometimes in water so shallow their dorsal fins break the surface.

How it lives

A sluggish predator, it cruises near the sea bottom or rests there, capable of pumping water over its gills while stationary. It rarely travels far, with many sharks staying within a few kilometres of their tagging site. Diet consists mainly of bottom-dwelling bony fish like mullets and porgies. Older sharks may eat stingrays. They occasionally visit cleaning stations where wrasses remove parasites. Larger sharks may prey on them. Young sharks are more inquisitive than cautious adults.

Breeding and life cycle

Females give birth to one to thirteen pups every other year after a ten to eleven-month gestation. Embryos develop a placental connection from depleted yolk sacs. Births occur in shallow nursery grounds, timed to regional seasons such as October in Madagascar. Newborns measure 45 to 80 centimetres. Juveniles grow slowly, adding roughly 12 to 15 centimetres annually. Both sexes reach sexual maturity at lengths between 2.2 and 2.4 metres. Evidence for returning to birth sites to breed is scant.

Fish and people

Regarded as potentially dangerous, it can react vigorously if provoked, though it is usually shy. It is harvested for meat, fins for soup, and liver oil for vitamins. Unregulated fishing has severely depleted stocks in Southeast Asia and India. Habitat loss from mangrove deforestation and reef damage adds pressure. The species adapts well to captivity and appears in public aquariums. In places like Moorea, it supports ecotourism through feeding dives. It is listed as Least Concern in Australia but Endangered globally.

Status and threats

The IUCN assesses this species as Endangered worldwide. Low reproductive rates and limited movement make recovery from depletion slow. Populations have been extirpated in parts of India and Thailand. Unmonitored fisheries using gillnets and longlines drive declines in Southeast Asia. Pollution and blast fishing further threaten survival in coral reef and mangrove habitats. Australian populations remain more stable, facing only minor bycatch threats.

Questions people ask about Sicklefin lemon shark

Good reading and sources

• Sicklefin lemon shark on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data