These sharks have a streamlined and slim body. As adults, they can reach 3. These sharks love the warm, tropical waters all over the world. But often times, they are seen near the surface as well.
The desired water temperature is 20 to 30 degrees Celsius 60 to 86 degrees Fahrenheit. They primarily inhabit continental and insular shelves, but have also been found over deep water reefs and in open ocean, slope, and shallow, coastal water habitats.
This species has been found at depths of up to m, and records show that they have been seen in waters as shallow as 18 meters. It has been noted that this species has a wider latitudinal distribution along continental shelves compared to the open ocean or along insular shelves.
During various stages of the life cycle, silky sharks transition between different habitats. For the first few years of life, juveniles live in nursery grounds and lead a demersal or semi-pelagic lifestyle. As they grow older and reach an average young adult length of about cm, they migrate offshore to deeper waters. At this stage, they often join and travel with large schools of pelagic fish such as tuna, ensuring a constant food supply. Adult silky sharks return seasonally to continental and insular shelf areas in order to feed and reproduce.
However, they tend to spend most of their time in deeper waters. Unlike most members of the genus Carcharhinus , the pectoral fins of this species are sickle-shaped. The first dorsal fin is relatively small, with a rounded apex, which originates behind the pectoral fins. The second dorsal fin is also very small, with a long trailing tip that almost reaches the precaudal pit, which is a notch on the dorsal side of the shark that is located where the caudal fin, or tail fin, begins.
Silky sharks are the largest members of their genus, reaching up to kg in mass and 3. Females grow to be much larger than males. Upon reaching maturity, female silky sharks range from 2.
Silky sharks get their name from the silky feel of their hide. Their skin, as in other shark species, is covered with dermal denticles. However, the unusually dense packing of these structures in this species makes their skin feel much softer to the touch than the rougher skin that is commonly associated with sharks.
Another distinctive feature of silky sharks is the shape of their teeth. They have between 14 to 17 teeth on each side their upper jaws, and these teeth are notched or serrated rather than concave, which is the condition in most other species of sharks. Garrick, et al. The dorsal coloration of this species can vary greatly, from a dark brown to a blue-grey color. The ventral surface is generally white, but in some individuals the ventral surface of the pelvic and pectoral fins can have darkly colored tips.
Silky sharks give birth to live young, providing placentally derived nutrition throughout the developmental process. In females, the oviducts are modified to form uteri, with only the right ovary being functional. The embryos develop in longitudinally oriented individual chambers, with their heads pointing anteriorly in the uterus. When silky sharks are born, they range in length from 70 to 75 cm. Juveniles rapidly grow an additional 25 to 35 cm by their first winter, which is thought to enhance their survival.
Gilbert and Schlernitzauer, ; Joung, et al. Male silky sharks release pheromones; however, it is uncertain as to whether or not the pheromones are used to attract mates, ward off competition, mark territory, or some combination of the three.
Additionally, studies have shown that no sexual segregation exists within silky shark populations. Pheromones do not play a role in determining social structure, meaning that silky sharks do not travel together solely for mating purposes. Rather, size appears to be the determing factor in social structure, with co-travelling generally being of the same size class. Gilbert and Schlernitzauer, ; Knickle, ; MarineBio. Mating rituals of silky sharks, if they exist, are unknown.
During the mating process, the male inserts his claspers into the female's cloaca, releasing sperm. Males mate with multiple females during a breeding season. In tropical waters, silky sharks do not have a set breeding season and mate year-round. Silky sharks located in the warm temperate waters of the Gulf of Mexico have a set breeding period during the summer months of June, July, and August.
Carrier, et al. Reproductive maturity is reached at 7 to 9 years of age and 2. Silky sharks in the Indian Ocean and in the Pacific Ocean achieve maturity at younger ages and at smaller sizes than silky sharks in other areas approximately two years younger and 0.
It is thought that the variation in size at maturity might be related to latitude, with sharks in tropical waters areas of low latitude tending to grow faster and mature at earlier stages of life. This may be due to warmer waters causing an increase in metabolism, thus speeding up growth rates, but the mechanism responsible is in need of additional research and confirmation.
Joung, et al. In tropical waters, silky sharks breed year round, and in warm-temperate waters, such as the Gulf of Mexico, silky sharks breed only during the summer months June, July, and August.
They breed every two years and typically produce between two and fourteen live offspring per litter. The gestation period averages 12 months. Silky sharks are considered capable predators at birth. Female silky sharks provide continual nutrition to their developing young through the placenta. The young are also protected due to their development inside their much larger mother's body.
These sharks are commonly found throughout the Pacific , Atlantic, and Indian Oceans. They have an extremely strong sense of hearing which helps them in locating their prey. Female silky sharks have a gestation period of around one year and they give birth to 15 to 20 pups at once.
This shark is brown-grey dorsally and white below. Juvenile or younger silky sharks are known to form large, loosely organized aggregations, possibly for mutual defense. During migrations, over a thousand individuals may gather. These groups are generally segregated by size, and in the Pacific research suggests also by sex. On occasion, Silky sharks have also been seen suddenly charging straight up, veering away just before reaching the surface and gliding back down to deeper water.
In a special Cuba edition of Bulletin of Marine Science, the peer-reviewed study sheds light on the life of this vulnerable species. Speed: Tagged Silky sharks have been recorded to swim up to speeds of 37 miles per hour. Best resource to find the status of a species. It is a target or bycatch species in pelagic tuna longline and purse seine fisheries where it is taken in high numbers. Silky Shark is one of the three most traded shark species in the global shark fin trade.
Estimates of trends in abundance over three generations 45 years from standardized catch rate and spawning biomass indices show declines of Silky Shark in the Eastern Central and Southeast Pacific Ocean, Western Central Pacific Ocean and the Atlantic Ocean.
Across all three ocean regions, there are the major uncertainties in estimates of catch rate and population changes, and an inability to conclusively attribute any declines solely to fishing mortality as there is some potential for environmental influences on catchability and sampling artifacts. The estimated level of decline and the uncertainties in the data warrants a global status of Vulnerable.
We are much more of a threat to the Silky shark. Silky shark. Family: Carcharhinidae — Requiem sharks.
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