Lemon sharks (Scientific name: Negaprion brevirostris) are found mostly in tropical waters the eastern Pacific and the western and eastern Atlantic Oceans. Also known as galano and galano de ley, they are found around reefs and in shallow waters and can survive in brackish water in areas with low oxygen and feeds mainly on bony fishes, guitarfish and stingrays and may also eat crustaceans, mollusks and seabirds.
Lemon sharks are one of the most studied sharks because they adapts better to captivity than other sharks and they are found in waters off the United States and the Bahamas where scientists are studying sharks. Lemon sharks have a powerful bite and may attack humans if provoked. In 1993 in Monroe County was off Key West a snorkeler was bit by a lemon shark. According to e International Shark Attack Files of Florida Museum of Natural History, Lemon sharks have accounted for 10 non-fatal unprovoked attacks and zero fatal attacks for of total of 10 attacks. [Source: International Shark Attack Files, Florida Museum of Natural History, 2023]
Lemon sharks reach a lengths of 3.4 meter and a weight of 185 kilograms. They are yellowish or light brown in color and have large fins and an abrupt snout. While adult lemon sharks may occasionally eat juveniles, there are no known predators of adult lemon sharks. The longest recorded lifespan for the lemon shark in captivity is 25 years. Using size and growth rate information, individuals caught in the wild have been estimated at over 30 years old. [Source: Alexander Lister, Animal Diversity Web (ADW) /=]
The International Union for Conservation of Nature (IUCN) Red List lists lemon shark as “Near Threatened”; They have no special status according to the Convention on the International Trade in Endangered Species (CITES). Humans utilize lemon sharks for food, drug research and education. Their body parts are sources of valuable materials and sources of medicine. Lemon shark meat is sold fresh, salted or frozen and their fins ate prized for making shark-fin soup. Liver oil from lemon sharks has been used for its vitamin content and the shark’s hide has been used as leather.
Websites and Resources: Shark Foundation shark.swiss ; International Shark Attack Files, Florida Museum of Natural History, University of Florida floridamuseum.ufl.edu/shark-attacks ; Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems
Lemon Shark Habitat and Where They Are Found
Lemon sharks live in tropical, saltwater, marine environments and are found in reefs, coastal areas, sea bottoms, the open ocean and brackish water typically at depths of zero to 90 meters (295 feet). Their habitats include coral reefs, mangrove areas and enclosed bays. They also show up where humans are found and sometimes father around docks. [Source: Alexander Lister, Animal Diversity Web (ADW) /=]
Lemon sharks are not strangers to freshwater water. They have been observed in river mouths and brackish water sounds, though they do not typically go very deep into these areas. Lemon sharks can adapt to low oxygen and shallow water environments and may be found resting on ocean bottoms. Lemon sharks are migratory. Efforts are being made to learn more about their migrations through tagging and tracking. They are most commonly found in the open ocean during migrations.
Lemon sharks inhabit the Western Atlantic Ocean, from the coast of New Jersey to southern Brazil, the Caribbean Sea, and the Gulf of Mexico. They have have been spotted in the eastern Atlantic Ocean along the coasts of Senegal and the Ivory Coast in Africa. They live in the eastern Pacific Ocean, from Baja California to Ecuador.
Lemon Shark Characteristics
Lemon sharks reach weight of 184 kilograms (405 pounds) and range in length from 2.4 to 3.7 meters (8 to 12 feet). Females are larger than males, averaging 2.4 meters compared to 2.25 meters for males. They vary in color from dark olive to yellowish brown on their backside, with a lighter yellow underside, and have no conspicuous markings. Their coloration appears to be an anti-predator adaptation in which the darker-colored dorsal (top) side blends in with the surface of the oceans if looking from the sky and lighter-colored ventral (bottom) side blends in with the sky light if looking from underwater. These colors do not change by sex or age.
According to Animal Diversity Web: These sharks are large and stocky, with blunt snouts that are shorter than the width of their mouths. The bottom teeth are triangular and narrow with smooth-edged cusps, while the upper teeth are more broad and have smooth cusps and serrated bases. Teeth become more oblique as they near the corners of the mouth. They have two dorsal fins, with the posterior fin being shorter than the anterior, and paired pectoral and pelvic fins.. [Source: Alexander Lister, Animal Diversity Web (ADW) /=]
Lemon sharks communicate with vision and touch and sense using vision, sound, electric signals and chemicals that can be sensed by smelling. They have very acute vision. Their retinas have specialized horizontal bands known as "visual streaks" that are extremely rich in cones, which discern color and visual detail. As with all sharks, lemon sharks have ampullary receptors (Ampullae of Lorenzini) concentrated on their heads, which sense electric charges and serve to help them hone in on prey items. These sharks also have a homing sense, enabling females to return to the same areas each time they give birth and juveniles to return to safe nursery waters.
Lemon Shark Behavior and Feeding
They are diurnal (active during the daytime), nocturnal (active at night), crepuscular (active at dawn and dusk), motile (move around as opposed to being stationary) and migratory (make seasonal movements between regions, such as between breeding and wintering grounds). They are usually solitary, but they been found in groups of up to 20 individuals based on sex and size, often around fishing docks. They are most active at dusk and dawn. Adults are most active at night. Juveniles are most active in the day. [Source: Alexander Lister, Animal Diversity Web (ADW) /=]
Lemon sharks feed on molluscs, crustaceans, and bony fish, including cowfish, flathead mullets, spot-fin porcupinefish, Atlantic guitarfish, spotted eagle rays, brown crabs, red swamp crayfish and southern stingrays. Giant tiger prawns and shore crabs are important sources of food for juveniles. Lemon sharks are hosts to a variety of parasites. Remoras and sharksuckers feed on scraps from feeding lemon sharks and help ride the sharks of parasites. [Source: Alexander Lister, Animal Diversity Web (ADW) /=]
Vision is very important for lemon shark to capture prey as demonstrated in an experiment conducted at the Lerner Marine Laboratory, which found that temporarily blinded lemon sharks were not able to detect a 113 kilogram chunk of blue marlin while unimpaired lemons sharks easily located it. Lemon sharks also have an acute sense of smell. Another experiment at the same laboratory found that lemon sharks were able to detect of tuna juice in concentrations of one part per 25 million in sea water.
Lemon Shark Mating and Reproduction
Lemon sharks are viviparous (they give birth to live young that developed in the body of the mother) and are iteroparous (offspring are produced in groups such as litters). They engage in internal reproduction in which sperm from the male fertilizes the egg within the female and employ sperm-storing (producing young from sperm that has been stored, allowing it be used for fertilization at some time after mating). [Source: Alexander Lister, Animal Diversity Web (ADW) /=]
Lemon sharks breed once a year during spring and summer months. The gestation period ranges from 10 to 12 months. After producing a litter, females take a year off before mating again The number of offspring ranges from four to 17. Females and males reach sexual or reproductive maturity at six to seven years.
Lemon sharks practices polyandry. Each breeding season, the female mates with several males. Each sexual encounter often involves a lot of biting and blood. Sharks have only been observed mating a handful of times. At first it was though they copulated stomach to stomach, but in 1959 a scientist watched a pair of lemon sharks mating side by side, moving in synch, as if they were a "single monster with two heads."
Females likely store sperm from multiple mates to allow sperm competition, A study in 2011 revealed that many lemon shark litters exhibit multiple paternity, indicating the sharks are are polyandrous (with females mating with several males during one mating season. Mating generally begins with male biting a female on the pectoral fin and inserting his clasper (sexual organ) into her cloaca (sexual organ)
Lemon Shark Offspring and Development
Lemon sharks usually give birth to live young in litters of 4-17 pups. Parental care is provided by females. During the pre-fertilization and pre-birth stages provisioning and protecting are done by females. Young are typically 60-65 centimeters (around two feet) long at birth and independent and able to take care of themselves from the start. They grow throughout their lifetimes, at an average rate of a half a centimeter a year. Adult lemon sharks sometimes eat juveniles.
Each time they give birth, female lemon sharks return to the same nursery areas. Juveniles remain in shallow waters of the nursery area, likely to avoid predators and have easy access to coastal prey, for two to three years. They do not typically leave these safe areas until they have reached at least 90 centimeters (three feet) in length and are less vulnerable.
Lemon sharks take 12 to 15 years to reach maturity, at which time they may weigh 100 kilograms (220 pounds) and be 2.8 meters (9.2 feet) in length. According to Animal Diversity Web: Young sharks spend their first year around mangrove swamps, feeding on small fish and crustaceans and staying shallow waters were there are less vulnerable to attacks from larger fish, especially other sharks. In the Bahamas there are large numbers of youngsters living in mangrove swamps which offer them a plentiful supply of food and few dangers than in the open sea and around reefs. Juvenile lemon sharks stay in the nursery areas in which they were birthed until they are large enough to be able to survive in deeper waters. Their activity areas are typically just a few square kilometers, whereas adults may range within several hundred square kilometers.
Sicklefin Lemon Sharks
Sicklefin lemon sharks (Negaprion acutidens) are a species of requiem shark widely distributed in the tropical waters of the Indo-Pacific. Also known as sharptooth lemon sharks and broadfin sharks, they are closely related to lemon sharks. The two species are almost identical in appearance. [Source: Wikipedia]
Sicklefin lemon sharks live in tropical, saltwater, marine environments and you can typically find them in reefs, atoll lagoons, other shallow coastal areas and intertidal (littoral) zones at depths of zero to 92 meters (302 feet). Lemon sharks utilize sandy plateaus near coral intertidal areas as nurseries. As they grow, they do not tend to stray far from these areas. [Source: Elizabeth Lee, Animal Diversity Web (ADW) /=]
Sicklefin lemon sharks found mainly in the western and eastern parts of the Indian Ocean, and the western central, eastern central, and northwest parts of the Pacific Ocean. Historically, these lemon sharks were found in areas around India and Thailand but are less numerous there now. Sicklefin lemon sharks tend to swim along the substrate of the sea floor. Their daily movements follow tide changes. They move into the shallow flats at high tide and into the deep lagoons at low tide. Both sexes of lemon sharks move further away from shore during winter months. /=\
Sicklefin lemon sharks mainly feed on bottom-dwelling fish such as stingrays porcupine fishes and other fishes. They occasionally hunt birds that land in the water and other, smaller sharks of any species that is small enough to eat. They also consume squid and other cephalopods and bottom-dwelling aquatic crustaceans such as crab and lobster.
Sicklefin Lemon Shark Physical Characteristics
Sicklefin lemon sharks range in length from 2.2 to 3.4 meters (7 to 11 feet). Both sexes are roughly equal in size and look similar but males are slightly larger and have slightly different shapes. Male lemon sharks reach maturity at about 2.4 meters (8 feet) in length, and females at about 2.2 meters (7 feet). Males have a pair of claspers (sex organs) on their abdomens. Sicklefin lemon sharks size can help determine sex because males are larger than females. This size comparison is typically done using the fork and total length measurements. Female lemon sharks can sometimes be sexed by indicators of current or past pregnancy like presenting an extended abdomen or possessing postpartum scars. [Source: Elizabeth Lee, Animal Diversity Web (ADW) /=]
Sicklefin lemon sharks are short-nosed and stoutly built and have a total vertebral count of 224 to 227. Their identifying feature is their titular fin shape — the trailing edge of their pectoral fins are sickle shaped. According to Animal Diversity Web: They have two prominent dorsal fins, two pectoral fins, two pelvic fins, one small anal fin, and one hypocercal caudal fin. Lemon sharks are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature), , as their body temperatures match the temperature of the surrounding water. /=\
Lemon sharks have 27 to 33 rows of teeth on both their upper and lower jaws. Their upper anteroposterior teeth are erect and slim, with slender cusps and no cusplets. Their lower teeth do not have cusplets, but are erect and long with slightly curved cusps. The lower teeth have no serrations, and the upper teeth have serrations that are confined to the crown of the tooth. Sicklefin lemon sharks share all of these features with lemon sharks (Negaprion brevirostris).
Sicklefin Lemon Shark Behavior
Sicklefin lemon sharks are nocturnal (active at night), crepuscular (active at dawn and dusk), motile (move around as opposed to being stationary), migratory (make seasonal movements between regions, such as between breeding and wintering grounds), solitary and have dominance hierarchies (ranking systems or pecking orders among members of a long-term social group, where dominance status affects access to resources or mates). [Source: Elizabeth Lee, Animal Diversity Web (ADW) /=]
Sicklefin lemon sharks have an average core home range of 1.7 square kilometers and stay within 10 square kilometer of this area for months at a time. Females tend to shift their core home ranges about 0.45 kilometers further offshore into deeper areas during winter months. Both sexes do not defend a territory, which may overlap with other sharks.
According to Animal Diversity Web: Sicklefin lemon sharks typically only interact with other lemon sharks for mating, foraging, and defense. Young lemon sharks interact with each other as juveniles in their nurseries, as they are left by their mothers to grow and mature on their own. Although they are solitary, they demonstrate a dominance hierarchy by using social information about other sharks, like size and sex, to increase their chance to feed. Sharks lack eyelids and do not fully sleep. Instead, they exhibit resting phases in daylight hours, still able to be cognizant of threats around them. Sharks are nocturnal (active at night), and crepuscular (active at dawn and dusk),, as they do most of their feeding and active swimming at dusk, overnight, and at dawn. /=\
Sicklefin lemon sharks are migratory animals. In late July to September, they move directionally south, to warmer areas that are as far as 140 kilometers away within one to two days. Lemon sharks return north typically from March-April. Males typically begin this move 1-2 months earlier than females. The females' migration periods vary annually due to breeding; on years where they give birth, they leave at the later end of the migration period. /=\
Sicklefin lemon sharks communicate with vision, touch, sound, chemicals usually detected by smelling and electric signals. They also use vibrations to communicate and sense using vision, sound, touch, electric signals and vibrations. Sharks communicate with each other by arching their backs and remaining non-confrontational. Male lemon sharks bite the females when attempting to find a mate and bite them during the act of mating to remain stable.
Sicklefin Lemon Shark Mating and Reproduction
Sicklefin lemon sharks are viviparous (they give birth to live young that developed in the body of the mother) and iteroparous (offspring are produced in groups such as litters). They engage in internal reproduction in which sperm from the male fertilizes the egg within the female and employ sperm-storing (producing young from sperm that has been stored, allowing it be used for fertilization at some time after mating). Males breed every year. Females breed every two years. The breeding season is from late January to April. The number of offspring ranges from six to 12, with the average number of offspring being 9.3. The gestation period ranges from 10 to 11 months, with females giving birth to live young between October and early January. Females and males reach sexual or reproductive maturity at 12 to 16 years.[Source: Elizabeth Lee, Animal Diversity Web (ADW) /=]
Sicklefin lemon sharks are polygynandrous (promiscuous), with both males and females having multiple partners throughout their lives. According to Animal Diversity Web: Female sharks emit pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species) that signal to male sharks in the area that they are ready to mate. This is necessary as sharks are solitary, so these pheromones lead the males to the females. Male sharks are known to bite female sharks that are potential mates, as well as biting the females during the act of mating to remain stable. Male sharks use organs called claspers to transfer their sperm into the oviduct of the female sharks. The male sharks will bite on or around the females' pectoral fin and use this to stabilize themselves to insert one of their claspers into the female. Some females are found with multiple bite marks at a time, leading to the conclusion that multiple males will mate with one female during one mating period. The existence of litters with multiple paternities also lends credence to this theory.
Sicklefin Lemon Shark Development
Sicklefin lemon sharks are 45 to 80 centimeters (1.5 to 2.5 feet) long at birth and grow about 12 to 15 centimeters (3.5 to 4.5 inches) a year. Parental care is provided by females. During the pre-fertilization and pre-birth provisioning stages provisioning and protecting is done by females. The average litter size for lemon sharks is 9.3 pups. Female lemon sharks have been observed returning to the same nursery site each time they give birth. Males are not parentally involved other than mating.[Source: Elizabeth Lee, Animal Diversity Web (ADW)]
Young are born independent. After giving birth, female sharks leave their young in nurseries where the juveniles grow with other juvenile sharks. The sharks stay in these shallow-water intertidal nurseries until they reach about 90 centimeters (3 feet) in length, but sometimes they stay in and around their nurseries for additional years.
According to Animal Diversity Web: Neonatal lemon sharks are identified by the presence of an open or healing umbilical scar. The umbilical scar heals shortly after birth, so those without the presence of this scar were identified by size. They grow 28.2 centimeters (about 1 foot) in their first year of life.
Humans, Sicklefin Lemon Shark and Conservation
Sicklefin lemon are utilize by humans for food, medicine, drug research and education. Their body parts are sources of valuable materials. Tourists like to check them out at reefs and aquariums. Sicklefin lemon sharks rarely attack and injure humans without provocation. There are no reported fatal attacks on humans by these sharks. Individual, changes in lemon shark behavior has been directly linked to humans who feed them for fishing and tourism. Consequently, these sharks have become more aggressive to other sharks and humans, leading to more shark attacks and aggressive interactions with humans. It also has caused more inbreeding amongst lemon sharks because it decreases shark mobility.[Source: Elizabeth Lee, Animal Diversity Web (ADW)]
Sicklefin lemon sharks' meat is consumed fresh, dried, salted, frozen, or smoked. Lemon sharks' fins are cut off and used for shark-fin soup bases. Lemon sharks' hides are used for leather and their liver is used to extract vitamin oil which is used in modern medicine to help boost the human body's immune system. In the Western and Central Pacific, sicklefin lemon sharks are sought out by divers and with tourists. In one shark feeding ecotourism operation in French Polynesia, sicklefin lemon sharks have been estimated to generate about US$5.4 million a year.
The International Union for Conservation of Nature (IUCN) Red List lists sicklefin lemon sharks as “Endangered”; They have no special status according to the Convention on the International Trade in Endangered Species (CITES). Sicklefin lemon sharks are heavily fished in some places leading to declines in their numbers there. In Australia, and some island nations in the Western Pacific, and the Indian Ocean, their populations appear stable. However, in Asia, Africa, parts of the Pacific, Indonesia, the Philippines, Thailand, the Red Sea and the Arabian Sea regions populations have decline. By some estimates across their range, the number of sicklefin lemon sharks decreased 50-79 percent from 1971 to 2021. /=\
Sicklefin lemon sharks are commonly caught and killed in longlines, gillnets, trawls, and handlines both intentionally and accidentally. Those that live in and around coral reefs are negatively affected by coral bleaching. Coastal development impacts their mangroves nurseries. Measured aimed to help coral reefs and regulating fishing help sicklefin lemon sharks.
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated March 2023