Lemon Shark

Negaprion brevirostris

The lemon shark is easily recognized for its two, equal-size dorsal fins and its yellow-brown to olive color, ideal camouflage against sandy in-shore areas they prefer to forage in. Although these sharks average between 8 and 10 feet long, they are not considered a high threat to humans. They are social animals that prefer group-living and a defined home range. They feed at night, so contact with humans is limited.

Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Negaprion
Species: brevirostris

Common Names

The lemon shark gets its name because of its pale yellow brown coloring. It is also known as requin citron (France), tiburon galano (Spain), squalo limone (Italy), zitronenhai (Germany) cacao-limao (Brazil), ceq (Senegal),citroenhaii (Netherlands), galano (Cuba), limon (Mexico), requium shark (UK), tiburon amarillo (Ecuador) and tubarao-limao (Portugal).

Importance to Humans

The lemon shark is targeted by commercial and recreational fishermen along the US Atlantic Ocean, Caribbean, and in the eastern Pacific Ocean. The US bottom longline fishery commonly targets this species and it is also caught as by-catch in both pelagic and gillnet fisheries. Their fins are highly prized and exported to Asia for shark fin soup. Their skin may be used for leather and their meat can also be consumed, all of which make this shark very marketable. There is some concern that populations in the western north Atlantic and eastern Pacific Ocean are declining due to over-fishing.

Danger to Humans

These sharks represent a small threat to humans. According to the International Shark Attack File, there have been only 10 unprovoked attacks by lemon sharks, all occurring in Florida and the Caribbean. There have been no fatal attacks attributed to this species. The lemon shark does inhabit coastal waters which swimmers, surfers and divers commonly utilize. The low number of attacks by this species indicates that it is a minimal threat to humans.

Conservation

The Highly Migratory Species Division of the National Marine Fisheries Service currently manages the lemon shark in US Atlantic waters. This species is part of an aggregate of sharks, which are managed as a single group called large coastal sharks. Currently they are monitored through a quota and seasonal based management plan. The World Conservation Union/Species Survival Commission (IUCN/SSC) rates this species as "Near Threatened". It is close to being classified as vulnerable, but does not meet criteria to be considered endangered or vulnerable at this time. This status is based on their current population size and the effects current fishing practices will have on their future population.

> Check the status of the lemonshark at the IUCN website.

The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.

Geographical Distribution

This species inhabits coastal inshore waters from New Jersey (US) to Southern Brazil, Gulf of Mexico and Caribbean in the northwestern Atlantic Ocean and along Senegal and the Ivory Coast of Africa in the eastern Atlantic. There is some evidence that two separate populations exist within the western Atlantic Ocean; one in the Caribbean and one in the Gulf of Mexico. In the North Pacific the lemon shark ranges from the Gulf of California and Baja California south to Ecuador.

Habitat

The lemon shark is commonly found in subtropical shallow water to depths of 300 feet (90 m) and inhabits coral reefs, mangroves, enclosed bays, sounds and river mouths. However, this species will not penetrate deep into freshwater systems. Lemon sharks can be found in oceanic water during migration but tend to stay along the continental and insular shelves. The lemon shark is also known to form loose aggregations based on size and sex and have been seen congregating near docks and fishing piers during the night, returning to deep water during the day.

Distinguishing Characteristics

1. First and second dorsal fins are triangular and close to the same size

2. Snout is blunt and shorter than the width of the mouth

3. The first dorsal fin originates behind the pectoral fins

Biology

Distinctive Features

The lemon shark is a large stocky, blunt nosed shark with two dorsal fins of similar size. The first dorsal fin is low and positioned posterior to the pectoral fins, the second dorsal is of similar shape and size and positioned anterior to the origin of the anal fin. The pelvic fin has weakly concave rear margins and the pectoral fin outer margin is slightly convex and both fins are weakly falcate. The snout is round and shorter than the width of the mouth. There is no mid-dorsal ridge present on this species.

Coloration
The lemon shark has a yellow/brown or olive gray coloration on the dorsal surface and a lighter yellowish color on the undersides. There are no conspicuous markings.

Dentition
The upper teeth are narrow and broad with triangular smooth-edged cusps and finely serrated bases. These teeth get more oblique as they get closer to the corner of the mouth. The lower teeth are narrow and triangular with smooth-edged cusps.

Size, Age, and Growth
Lemon sharks are one of the larger species of sharks, commonly obtaining lengths between 95-120 inches (240-300 cm). and have a growth rate of .21 inches/year (.54 cm/year). The maximum length that can be reached by this species is between 125-135 inches (318-343 cm). Females and males reach sexual maturity around 6-7 years of age and at 95 inches (240 cm) and 88 inches (224 cm) respectively. Pups are between 24-26 inches (60-65 cm) at birth.

Food Habits
The lemon shark is commonly found over sandy or muddy bottoms and eats a diet consisting mainly of bony fish and crustaceans. Catfish, mullet, jacks, croakers, porcupine fish, cowfish, guitarfish, stingrays, eagle rays, crabs and crayfish make up the majority of their diet. In addition, this species will eat sea birds and smaller sharks. Lemon sharks will eat until full with the rate of digestion is dependent on the amount of food consumed at a single time.

Reproduction
Development in the lemon shark is viviparous, resulting in the birth of live free swimming pups. Mating occurs in shallow water during the spring months and is followed by a 10-12 month gestation period. Gravid females return to shallow nursery grounds during April to September to give birth. The young remain in these nursery grounds for several years. Litters range from 4-17 and from 24-26 inches at birth. Subsequent to birth, females are thought to take a year off before reproducing again.

Predators
Larger sharks prey upon juvenile lemon sharks, but adult animals have few if any predators.

Parasites
Dermophithirius nigrelli is a parasite known to cause skin lesions on lemon sharks. In addition Nemesis pilosus, Paralebion elongatus, Alebion carchariae, Perissopus dentatus, Nesippus orientalis, and Kroyeria spatulata are all copepods that are parasitic on lemon sharks.

Taxonomy

Poey first described the lemon shark in 1868 and named it Hypoprion brevirostris, later renaming it Negaprion brevirostris. The lemon shark has also appeared in literature as Negaprion fronto and Carcharias fronto Jordan and Gilbert, 1882, Carcharias brevirostris Gunther 1870, and Carcharhinus brevirostris Henshall 1891.

Prepared by: Alexia Morgan