Sharks of Onslow County Logo
Sharks of Onslow County
Bonnethead Shark

Taxonomy & Biology

Taxonomy

Common Name(s): Bonnethead, bonnet hammerhead, bonnet shark, bonnetnose shark, shovelhead.

Scientific Name: Sphyrna tiburo

Classification

  • Kingdom: Animalia
  • Subkingdom: Bilateria
  • Infrakingdom: Deuterostomia
  • Phylum: Chordata
  • Subphylum: Vertebrata
  • Infraphylum: Gnathostomata
  • Class: Chondrichthyes
  • Subclass: Elasmobranchii
  • Superorder: Euselachii
  • Order: Carcharhiniformes
  • Family: Sphymidae
  • Genus: Sphyrna
  • Species: tiburo

Biology

Population

Globally, the population of bonnethead sharks has been decreasing, up to 79% across the past three generations .(European Union et al., 2022). Regionally, some populations have declined more than 80%, with localized extinctions.

Body Size

The bonnethead shark is a small-bodied hammerhead shark species. Females grow to about 29.5 inches; males to about 23.6 inches. Babies are born at about 14 inches (NOAA, 2021).

Feeding & Diet

They typically feed during daylight hours when crustaceons and crabs are most prevalent (Bester & Bowling, 2024). Primary prey are blue crabs, mantis shrimp, pink shrimp, mollusks and small fishes that correlate to seasons when prey will be most abundant. They will occasionally feed on seagrasses, mostly when they are pups. They will burrow under coral heads in search of prey. When spider crabs, purse crabs, stone crabs, and various cephalopods are present, their prey diversity increases.

Females typically feed more than males because of the required energy required for reproduction.

They have molariform teeth that are used to crush their prey.

Position in the Food Web

The bonnethead shark is an important mesopredator of coastal ecosystems. They are prey for larger sharks.(Bester & Bowling, 2024)

The parasite, Erpocotyle tiburonis, a monogean, is known to cause gill lesions in these sharks. Copepods, such as the Eudactylina longispina, can be found in their gill filaments. They can also be infected by a fungus called Fusarium solani.

Reproduction

Bonnethead sharks are the only sharks known at this time to have sexual dimorphism (sexual differences) of their head (Bester & Bowling, 2024). Females will have a broadly rounded head, while males will have a bulge near the back of their head. In males, as they reach sexual maturity, this bulge will become more elongated when their claspers become more elongated.

Studies in Florida have shown that mating is believed to occur in spring and autumn, but could occur year-round. Females can store sperm for up to 4 months after mating and is believed to be a survival adaptation that ensures optimal timing for pup birth.

Females give live birth through eggs stored within their bodies, or vivaparous. Pups are nourished through these eggs until the yolk has been consumed and are then born.

Bonnethead sharks have the shortest gestation period of all sharks at 4-5 months. They will move inshore to give birth to 4-14 pups in late spring and early fall. Pups range from approximately 21.5- 29.7 cm (0.7-1 ft.), but have been known to be larger. Females lose their appetite during this time period and males move to other areas away from females so as not to feed on their pups for prey. Juvenile pups prefer seagrass beds for the first 2 years of their life.

Natural Mortality

Bonnethead sharks have an estimated lifespan of 16 to 18 years. They face natural mortality from predation from larger fish and other sharks when they are young, and from old age. They have a U-shaped mortality curve that shows that their mortality is higher at both younger and older ages (Simpfendorfer, Bonfil & Latour, n. d.). 

Biodiversity

Bonnethead sharks are currently listed on the IUCN Red List of Threatened Species as "endangered" due to declines in population, habitat loss and overfishing. According to CITES, this species has faced population declines up to 79% globally, and are listed in CITES Appendix II guidelines for marine species (CITES, n. d.).

Demographics

This tropical hammerhead shark is found in the warm, shallow waters of the western Atlantic and eastern Pacific Oceans. It is an important mesopredator of coastal ecosystems that are exploited in the international fin trade, with their fins being found in the Hong Kong fin market (CITES, n. d.).Their population declines are attributed to overfishing and the international shark fin trade (Save Our Seas, n. d.).

Migratory Pattern

Bonnethead sharks have seasonal movements in mid-Fall to Georgia and Florida. These migrations are primarily driven by winter water temperature. In a year where the water is warm, their southern migration was around 200 km and taking as long as 40 days to complete the journey (Keller, 2019). If a cold winter arrives, the same sharks will migrate over 450 km and nearly 80 days to complete their southern movement. The temperature difference between a warm winter versus a cold winter is about 13 °C. Specific estuaries are called "home" between April-November, however, it is the water temperature that determines overwintering habitat selection, not physical location.

Ecological Relationships

Bonnethead sharks inhabit nearshore environments that include seagrasses, estuaries, mudflats, mangroves and coral reefs (European Union et al., 2022). This makes them highly susceptible to loss of habitat and degradation.

Danger to Humans

These sharks are harmless and are considered shy (Bester & Bowling, 2024).

Fishing rEgulations

As of June 2025, in North Carolina, recreational shore anglers may keep one (1) bonnethead shark per person per day (Rawls, 2024). There are no minimum size requirements. For vessel fishing, anglers may keep one (1) bonnethead shark per person per day with an additional shark from the permitted vessel. There are gear and natural bait requirements. The head, tail, and all fins must remain intact, with no filleting, until they are landed at the dock or on shore. 

Please Note: The fishing regulations and information provided on this website are for general information purposes only. While we strive to ensure the accuracy and timeliness of the content, fishing laws and regulations can change frequently and vary by location. It is the responsibility of each angler to verify the current local, state, and federal fishing laws before fishing. Always consult the official website or contact the appropriate wildlife and fisheries agency for the most up-to-date rules and regulations.

We are not liable for any penalties, fines, or legal issues that may arise from the use or misuse of the information on this site.

References

References
Bester, C., & Bowling, T. (2024, January 1). Sphyrna tiburo. Florida Museum of Natural History. Retrieved December 9, 2024, from https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/sphyrna-tiburo/

CITES. (n.d.). Bonnethead shark. CITES Sharks and Rays. https://citessharks.org/bonnethead-shark

European Union, Brazil, Columbia, Ecuador, & Panama. (2022). Bonnethead shark (Sphyrna tiburo) with the remainder of Family Sphyrnidae as lookalikes. CITES Sharks and Rays. Retrieved December 9, 2024, from https://citessharks.org/bonnethead-shark#:~:text=The%20Bonnethead%20shark%20(Sphyrna%20tiburo,II%20guidelines%20for%20marine%20species

Keller, B. (2019, October 22). Sharky, it's cold outside. Save Our Seas Foundation. https://saveourseas.com/update/sharky-its-cold-outside

Rawls, K. (2024). Proclamation Re: Shark - Commercial and Recreational - Opening Date and Harvest Restrictions (FF-2-2024). NC Division of Marine Fisheries. https://files.nc.gov/deq/documents/2023-12/FF-2-2024_Shark_Opening.pdf?VersionId=ojmPIaCH.7VqI6F8cf_GTAY1fy80NCYY#:~:text=H.,Isurus%20oxyrinchus)%20for%20recreational%20purposes

Save Our Seas. (n.d.). Bonnethead shark. Save Our Seas Foundation. https://saveourseas.com/worldofsharks/species/bonnethead-shark

Simpfendorfer, C., Bonfil, R., & Latour, R. (n.d.). Management techniques for elasmobranch fisheries. FAO. https://www.fao.org/4/a0212e/a0212e12.htm
© 2024 Sharks of onslow county.