Negaprion brevirostris

The lemon shark (Negaprion brevirostris) is a species of shark from the family Carcharhinidae. Lemon sharks can grow to 3.4 metres (11 ft) in length. They are often found in shallow subtropical waters and are known to inhabit and return to specific nursery sites for breeding. Often feeding at night, these sharks use electroreceptors to find their main source of prey: fish. Lemon sharks enjoy the many benefits of group living such as enhanced communication, courtship, predatory behavior, and protection. This species of shark gives birth to live young, and the females are polyandrous and have a biennial reproductive cycle. Lemon sharks are not thought to be a large threat to humans. The lemon shark was first named and described in 1868 by Felipe Poey. He originally named it Hypoprion brevirostris, but later renamed 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). The shark's yellow colouring serves as a perfect camouflage when swimming over the sandy seafloor in its coastal habitat. The lemon shark commonly attains a length of 2.4 to 3.1 m (7.9 to 10.2 ft) and a weight up to 90 kg (200 lb) by adulthood, although sexual maturity is attained at 2.24 m (7.3 ft) in males and 2.4 m (7.9 ft) in females. The maximum recorded length and weight is 3.43 m (11.3 ft) and 183.7 kg (405 lb), respectively. It has a flattened head with a short, broad snout, and the second dorsal fin is almost as large as the first. Lemon sharks have electroreceptors concentrated in their heads, called the ampullae of Lorenzini. These receptors detect electrical pulses emitted by potential prey and allow these nocturnal feeders to sense their prey in the dark. Lemon sharks are found from New Jersey to southern Brazil in the tropical western Atlantic Ocean. They also live off the coast of west Africa in the southeastern Atlantic. In addition, lemon sharks have been found in the eastern Pacific, from southern Baja California to Ecuador. This species of shark often occupies the subtropical shallow waters of coral reefs, mangroves, enclosed bays, and river mouths; however, lemon sharks have also been found in the open ocean down to depths of 92 meters (301 feet.) Although lemon sharks do swim up rivers, they never seem to travel very far into fresh water. They are found in open water primarily during migrations, and tend to stay along the continental and insular shelves for most of their lives. Information about activity patterns and the use of space is important in understanding a species’ behavioral ecology. Animals often make decisions about habitat use by evaluating their environment’s abiotic conditions that serve as valuable indicators of good foraging sites or predator-safe locations. Lemon sharks select habitats in warm and shallow water with a rocky or sandy bottom. The environmental temperature influences an individual’s body temperature, which ultimately affects physiological processes such as growth and metabolism. Lemon sharks, therefore, select warm-water habitats to maintain optimal metabolic levels. They are believed to avoid areas with thick sea grasses because they make finding prey more difficult. Lemon sharks tend to live in or near shallow-water mangroves, which are often the nursery areas of several species of fish. One theory is that lemon sharks select mangrove habitats due to the abundance of prey that resides there, while another theory posits that mangroves provide a safe haven from adult lemon sharks that occasionally feed on juvenile sharks and are unable to enter the shallow waters. Ontogenetic niche shifts, or changes in an animal’s niche breadth or position, to deeper waters are known to occur in relation to a lemon shark’s size. These changes occur due to the dramatic decrease in the risk of predation as body size increases. Habitat selection clearly depends on a variety of biological and environmental variables. The mangrove areas that lemon sharks inhabit are often referred to as their nursery sites. A nursery site is best defined as the most common area sharks are encountered, the location sharks tend to remain at after birth or frequently return to, and the habitat used by shark groups repeatedly for several years. The nursery ground concept has been known and studied for at least a century. In addition, fossil evidence from 320 million years ago suggests the use of shallow, coastal areas as pupping grounds is primitive. Lemon sharks have proven to be an ideal model species to challenge the belief that all sharks are asynchronous opportunistic predators due to their tendency to use nursery areas for an extended period of time. Lemon shark feeding behaviors are easy to determine because their well-defined home ranges are conducive to accurate calculations of both the amount and types of prey in the environment and diet of a lemon shark.