Lemon Shark
Scientific Classification: Negaprion brevirostris
Overview
Lemon sharks get their name from the yellowish lemon-like tint on their skin. These colors help them camouflage in the sandy ocean floors of the Atlantic and Pacific Oceans where they hunt for food, mainly consisting of bony fish, crustaceans, and mollusks. With a large, stocky body, rounded nose, and two dorsal fins, lemon sharks are well-adapted to life in shallow marine ecosystems such as coral reefs, mangrove fringes, and enclosed bays.
These sharks are quite social. From a young age, they congregate in groups and frequently form close bonds with specific individuals. This behavior is particularly evident in juvenile lemon sharks, who often group together based on familial ties or the advantages of social living, such as enhanced protection from predators. Lemon sharks are frequently exhibited in aquariums, making them a familiar sight to many.
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Negaprion
Species: N. brevirostris
Diet
Mainly bony fish, but also crustaceans like prawns, crabs, and lobsters and cephalopods like squids and octopus.
Size
Up to 12 feet in length. Weighing up to 550 pounds.
Lifespan
40+ years
Conservation
Vulnerable
Features
Lemon-like Coloration
Lemon sharks are named for their yellow-brown or olive-tinted skin, which helps them blend into the sandy, tropical waters they inhabit. The dorsal (upper) side is darker with yellowish-brown coloration, while the ventral (lower) side is lighter yellow.
This coloration makes them hard to distinguish from their surroundings against the backdrop of shallow coastal waters, providing them with excellent camouflage, and aiding in their ability to ambush prey and avoid predators.
Visual Streak
The eyes of lemon sharks feature a visual streak of densely concentrated photoreceptors, including both rods and cones, along the horizontal meridian of the retina. This configuration of densely packed photoreceptor cells helps discern fine detail and color underwater, which are crucial for detecting movements and shapes in the broad, flat landscapes typical of their environments.
This adaptation is particularly beneficial for animals like lemon sharks that live in relatively shallow, clear waters.
Distribution
Did you know?
Although lemon sharks are primarily saltwater species, these sharks can occasionally swim into freshwater areas. They do not typically travel far upstream and are usually limited to the lower stretches of rivers or estuaries.
Lemon sharks thrive in the shallow, subtropical waters of the Atlantic and East Pacific Oceans. You can find them along the coasts from New Jersey to southern Brazil, which includes the Gulf of Mexico and the Caribbean Sea. They also live near Senegal and the Ivory Coast in the eastern Atlantic, and from the Gulf of California down to Ecuador in the North Pacific.
These sharks, especially the juveniles, often spend time in mangrove forests where the thick roots provide excellent cover from predators and sources of food. Lemon sharks also frequent other shallow water environments like coral reefs, saline creeks, enclosed bays, and river mouths, typically over sand or mud bottoms. While they mostly stick to shallower depths, they also venture to deeper ocean waters up to 300 feet in depth during migrations as a result of seasonal variations in water temperature.
Diet
Lemon sharks are primarily nocturnal and piscivorous, mainly feeding on fish, while also hunting crustaceans and cephalopods such as squid and octopus. These sharks typically patrol the sandy or muddy seafloors in search of their next meal. Their diet includes a variety of fish such as catfish, cowfish, croakers, jacks, mojarras mullets, parrotfish, porcupinefish, guitarfish, and stingrays. Lemon sharks sometimes engage in cannibalism, eating their younger counterparts as well as occasional sea birds.
Instead of hunting indiscriminately, lemon sharks show strong preferences for certain sizes and species of prey. They often choose prey that is plentiful and easier to catch depending on the habitat, favoring slower-moving species. For example, researchers have shown that juvenile lemon sharks observed in Bimini prefer parrotfish above others like mojarras, toadfish, filefish, grunts, and barracuda.
Reproduction
A “shiver” of sharks
A group of lemon sharks is referred to as a “shiver,” which can include as many as 20 individuals. Less commonly, a group of sharks may also be called a “school of fish,” since sharks are technically fish.
Lemon sharks reach sexual maturity between the ages of 11-13, measuring about 7.4-7.9 feet in length. These sharks are viviparous, meaning they give birth to live young. Females follow a biennial reproduction cycle – giving birth to 4-18 pups every other year. This cycle involves a year of gestation followed by a year dedicated to egg development and nutrient provision for future offspring. Mating typically occurs in the spring and summer, with the gestation period lasting 10-12 months.
Each pup is about 1.6 to 2.1 feet long at birth. The young sharks stay in nurseries, such as seagrass flats, creeks, and mangroves, for the first 2 to 3 years of their lives. These nurseries provide safety from predators and easy access to food along the shoreline. As they age, they gradually move into deeper waters as they grow and expand their range.
Behaviors
Resting on the seafloor
Lemon sharks are frequently spotted lying on the ocean floor, however, they rarely rest – doing so only 4.3% of the time. Resting actually consumes more oxygen than actively swimming. These sharks usually breathe by swimming which allows oxygen-rich water to flow over their gills. However, when they pause on the seabed, they have to work harder to pump the water over their gills to breathe.
Many shark species, including lemon sharks, are known for their social behaviors, often living in loose aggregations that can number up to 20 individuals. They typically associate with others of similar age and size. Studies show that they have a level of social intelligence, with abilities to learn from each other, cooperate, and even form stable relationships and social hierarchies.
Living together offers lemon sharks several benefits, such as enhanced protection from predators, communication, and courtship.
However, group living isn’t without its challenges. It increases the likelihood of spreading diseases and parasites. In the case of competition over food and space, smaller sharks generally yield to larger ones.
Social
Feeding
Sharks typically hunt by stalking or ambushing their prey, but lemon sharks have developed unique strategies tailored to their size and environment. Juvenile lemon sharks, usually under 6.6 feet long, often explore crevices and holes along rocky and reef bottoms. As they grow, young lemon sharks learn and develop senses to effectively search for and capture prey.
As lemon sharks grow larger, those over 6.6 feet adopt a different approach, targeting schools of fish in the surf zone. Interestingly, these larger sharks coordinate with each other to not only chase the fish but also herd them against the shoreline to trap them effectively. This tactic allows lemon sharks to efficiently approach schools of sardines in murky, turbulent waters, especially during low-light conditions when fish move between shallow and deeper areas.
Importance to Humans
Danger to Humans
Lemon sharks are generally not aggressive and pose little threat to humans. They prefer shallow coral reefs, which are often popular with swimmers and divers. It’s wise to maintain a safe distance to avoid startling these sharks. The International Shark Attack File reports just 10 unprovoked attacks by lemon sharks, none of which were fatal.
Aquariums
Although lemon sharks do well and are sometimes kept in captivity in public aquariums, they are not as frequently displayed especially compared to species like nurse sharks or reef sharks.
When lemon sharks are kept in captivity, it is typically for research purposes or educational displays in larger, well-equipped aquariums that can meet their needs effectively. These facilities aim to educate the public about shark conservation and the ecological roles of sharks like the lemon shark.
Trade
Lemon sharks are caught by fisheries and sport fishing intentionally or as bycatch. Catch-and-release practices are common in recreational fishing, but the impact on individual sharks can vary depending on how the catch is handled.
Meat and Fins
Like many shark species, lemon sharks can be targeted for their meat and fins. Shark fins are highly valued in some cultures for use in shark fin soup, a delicacy in parts of Asia. The meat is sometimes sold in local markets as fresh, salted, or frozen products.
Skin
The skin of lemon sharks can be used as leather, known as shagreen. It’s known for its rough texture due to the embedded dermal denticles, which give it a unique and durable quality. This type of leather has been used in decorative arts, bookbinding, and even on sword handles for its grip-enhancing properties.
Ecological Interactions
Predators
Adult lemon sharks have very few predators because of their large size. However, juveniles face predation from larger shark species. The most significant threats to adult lemon sharks stem from human activities such as fishing and habitat destruction rather than natural predation.
Parasites
Lemon sharks are often plagued by various parasites, including copepods, flukes, and tapeworms. Among these, the microbothriid monogeneans such as Dermopthirius and Dermopthiriodes are notable.
A specific parasite, Dermophithirius nigrelli, is known to cause skin lesions on lemon sharks. These parasites use a structure called a haptor to secrete a sticky substance, helping them adhere to the shark’s skin. In aquarium settings, lemon sharks may show signs of distress by rubbing against rocks and walls. They may also display irregular grey patches, a dark band of bruised skin around the mouth, and lesions around the eyes and on top of the head.
Furthermore, several types of copepods like Nemesis pilosus, Paralebion elongatus, Alebion carchariae, Perissopus dentatus, Nesippus orientalis, and Kroyeria spatulata also parasitize lemon sharks.
Associations
Remoras (Echeneis naucrates), also known as suckerfish, engage in a primarily commensalistic relationship with lemon sharks by using a modified dorsal fin that acts like a suction cup to attach themselves to the sharks.
This attachment allows remoras to feed on scraps from the shark’s meals, parasites, and dead skin, effectively keeping the shark clean while nourishing themselves. Additionally, being close to a large predator like a lemon shark offers remoras protection from other potential threats, as well as an energy efficient way of transportation.
Conservation
The lemon shark is commonly caught both intentionally and as bycatch in small-scale and commercial longline and gillnet fisheries, as well as hook and line by recreational fishers. These fisheries are largely unregulated and widespread.
In 2018, commercial fishers in the United States landed about 8,910 lemon sharks, totaling 37,593 pounds of dressed weight – the weight of an animal after it has been cleaned and prepared for sale or cooking. Additionally, the mangrove habitats that Lemon sharks use as nurseries are being destroyed due to the expansion of shrimp farming. This habitat loss is a significant threat to their populations.
You May Also Like
- Beharry K. 2012. Negaprion brevirostris (Lemon Shark). The Online Guide to the Animals of Trinidad and Tobago.
- Bouyoucos I., Suski C., Mandelman J., Brooks E. 2017. In situ swimming behaviors and oxygen consumption rates of juvenile lemon sharks (Negaprion brevirostris). Environ Biol Fish 101: 761-773. https://doi.org/10.1007/s10641-018-0736-0
- Compagno L., Dando M., Fowler S. 2005. A Field Guide to the Sharks of the World. London: Harper Collins Publishers Ltd.
- International Shark Attack File. 2022. Species Implicated in Attacks. Florida Museum.
- Newman S., Handy R., Gruber S. 2010. Diet and prey preference of juvenile lemon sharks Negaprion brevirostris. Marine Ecology-progress Series – MAR ECOL-PROGR SER. 398. 221-234. doi: 10.3354/meps08334.
- Poynton S., Palm H., Campbell T. 1996. Pathogenic monogeneans on captive lemon sharks Negaprion brevirostris: A new pathogen, a new treatment. Veterinary Information Network, Inc.
- Reyier E., Franks B., Chapman D., Scheidt D., Stolen E., Gruber S. 2014. Regional-scale migrations and habitat use of juvenile lemon sharks (Negaprion brevirostris) in the US South Atlantic. PloS one, 9(2), e88470. https://doi.org/10.1371/journal.pone.0088470
- Schwab I., Heidermann D. 2021. Vertical pupil in a lemon shark. Pictures & Phylogeny 128(2): 316. https://doi.org/10.1016/j.ophtha.2020.09.016
- Sundström L. Negaprion brevirostris The IUCN Red List of Threatened Species. 2015. Available from: http://www.iucnredlist.org/details/39380/0
- Tyrrell L., Moore B., Loftis C., Fernández-Juricic E. 2013. Looking above the prairie: localized and upward acute vision in a native grassland bird. Sci Rep 3, 3231. https://doi.org/10.1038/srep03231