A highly social and intelligent shark
The Lemon shark (Negaprion brevirostris) is a species of shark from the family Carcharhinidae. Lemon sharks can grow to 11 feet in length. They are often found in shallow subtropical waters and are known to inhabit and return to specific nursery sites for breeding. Lemon sharks are highly socially driven, and we see these traits with our resident Lemon sharks here in Jupiter, Fl.
Family: Carcharhinidae – Requiem sharks
Common Name– Ground Sharks
Common Name– Requiem Sharks
Status: IUCN Red List NEAR THREATENED
Average Size and Length: The Lemon shark grows to a length of 7.9 to 10.2 feet long. The longest recorded Lemon shark is 11.3 feet. Males reach sexual maturity at 7.3 feet and females at 7.9 feet.
Average Weight: The Average weight of a Lemon shark is 200 pounds and the largest recorded was 405 pounds.
Current Rare Mythical Sightings: Here in Jupiter, we see Lemon sharks daily.
Teeth and Jaw: The upper teeth of the Lemon shark are narrow and broad with triangular smooth-edged cusps and finely serrated bases. The teeth become more oblique toward the corner of the mouth. The lower teeth are narrow and triangular with smooth-edged cusps.
Head: Its head is flat, with a short, broad snout.
Denticles: Lemon shark dermal denticles are large and overlapping with 3 to 5 ridges. The median ridge is high, sharp and separated by deep furrows, and the posterior margins are opposite the primary ridges.
Demographic, Distribution, Habitat, Environment and Range: Lemon sharks are found from New Jersey to southern Brazil in the tropical western Atlantic Ocean. In the southeastern Atlantic, they live off the coast of west Africa. They have also been found in the eastern Pacific from Ecuador to southern Baja California.
Lemon sharks prefer subtropical waters that are shallow, such as coral reefs, enclosed bays, mangroves (typical nursery areas) and river mouths. They typically choose areas with rocky, or sandy bottoms. However, they are also found down to depths of about 300 feet in the open ocean. Here in Jupiter, they are often found at depths greater than 100 feet at some of our frequent locations. There does seem to be a correlation between the size of the shark and deeper depths.
Lemon sharks are known to swim up rivers, but 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.
Diet: Lemon sharks tend to prey and feed at night but are active both day and night. They are believed to avoid areas with thick seagrasses because they make finding prey more difficult.
They typically eat fish, and on occasion will eat crustaceans and other benthic organisms. Rather than feeding randomly, lemon sharks display a high degree of preference for certain species and size of prey when environmental conditions are favorable. Catfish, mullet, jacks, croakers, porcupine fish, cowfish, guitarfish, stingrays, eagle rays, crabs and crayfish make up most of their diet. Lemon sharks only eat until they are full.
Larger sharks are known to eat juvenile Lemon sharks and also sea birds.
The general trend in the foraging behavior of Lemon sharks imitates to the optimal foraging theory, which suggests a positive relationship between prey selectivity and availability (Cortés, Enric; Samuel H. Grube (March 1990). “Diet, Feeding Habits and Estimates of Daily Ration of Young Lemon Sharks, Negaprion brevirostris (Poey)“).
They are known to frenzy. The sounds and vibrations of struggling prey along with bodily fluids and blood attract Lemon sharks. Lemon sharks engage in group feeding, and also group scavenging.
Ram-Suction Index: Ram. Lemon sharks charge their prey.
Aesthetic Identification: The Lemon shark has a yellow/brown or olive gray coloration on the dorsal surface and a counter-shaded pale yellowish-white color on the underside.
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. Both the pelvic and pectoral fins are weakly falcate. There is no mid-dorsal ridge.
Biology and Reproduction: Lemon sharks are viviparous. Females engage with many different partners, and store sperm inside them for several months. Mating occurs in shallow water during the spring and summer months and is followed by a 10-12-month gestation period. Gravid females are philopatric and return to shallow nursery grounds to give birth and the young remain in these nursery grounds for several years. Litters range from 4-17 (maximum recorded was 18) individuals and from 50-60 cm in length at birth. Lemon sharks reach sexual maturity around 12–16 years.
Studies of the respiratory physiology of Lemon sharks suggest that they are adapted to being active in environments with a low oxygen level, such as the waters around mangrove bays which have high temperatures and high organic content. They have circulatory and respiratory mechanisms, such as blood with an unusually high affinity for oxygen, that enhances oxygen uptake. Lemon sharks are quite capable of resting on the bottom but use up more energy at rest than when swimming at a normal rate; probably because of increased effort in pumping their gills when resting and from decreased efficiency of oxygen uptake with lower intake velocity of water through their gills. Comparative data on oxygen consumption show that this tropical shark operates at a metabolic level some 2+ times greater than the temperate Piked dogfish.
Behavioral Traits, Sensing and Intelligence: Lemon sharks are social and do live in loose aggregations, as we do see here in Jupiter. Group living starts after there are born. The young Lemon pups remain in a group in the mangrove nurseries for several years together, learning together. Lemon sharks that are older than a year old, tend to stay in similar sized groups.
Lemon sharks are extremely social in nature and are driven by this need. The brain of a Lemon shark, being comparable in relative mass to that of a mammal or bird, suggests they have the ability to learn from social interactions, cooperate with other individuals, and have the potential to establish dominance hierarchies and stable social bonds (Guttridge, T (August 2009). “Social preferences of juvenile lemon sharks, Negaprion brevirostris“. Animal Behaviour. 78 (2): 543–548).
Lemon sharks are also known to congregate for reproduction at known mating grounds.
They are active during both day and night, but most active during dawn and dusk.
Here in Jupiter, we can confirm from diving with them for so many years, and based on their known intelligence and social behavior, Lemon sharks do undergo behavioral changes based on external factors. We have watched several resident Lemon sharks develop learned feeding behaviors, and social interactions with humans, Nurse sharks, and Goliath Groupers.
Speed: According to Gruber, S.H. the average speed of a Lemon shark is 1.5 kph, but during dawn and dusk will reach speeds of 2.5 kph.
Lemon Shark Future and Conservation: The Lemon shark is threatened because it is targeted by commercial and recreational fishermen along the U.S. Atlantic Ocean, Caribbean, and in the eastern Pacific Ocean due to its prized meat, fins, and skin. Lemon shark skin may be used for leather and its meat can be consumed and is believed to be a delicacy in many cultures. Concern exists that over-fishing has led the Lemon shark populations in the western north Atlantic and eastern Pacific Ocean to decline. In addition, Dr. Gruber has confirmed that Lemon sharks are threatened due to environmental and habitat degradation.
Mentioned in my paper Environmental Changes Impact Shark Behavior: Local Impacts, Causes and Customized Unmanned Systems Used in Solutions, are the negative chain results of a harmful red algal (Karenia brevis) bloom on our ecosystem all the way up the food chain impacting the behavior of sharks. Most recently we have teamed up with Hannah Medd-Rutzen, founder of American Shark Conservancy, and her team. Hannah has confirmed poor water quality here in Jupiter, Florida has impacted the skin of Lemon sharks in a negative way. Noticeably the color of their skin has changed. Keep checking out our site for current and up to date research, data, and findings on this project.