Bonnethead Shark (Sphyrna Tiburo)

Bonnethead Shark (Sphyrna tiburo)

Bonnethead sharks appear in the new shark exhibit which showcases Dr. Michelle Heupel’s research. Although much of her work in Terra Ceia was with blacktips, bonnetheads are exhibited because they are much easier to keep in an aquarium setting. Blacktips are fast swimmers and may harm themselves in the aquarium.

Characteristics:  Size: A smaller member of the hammerhead family, averaging 28” to 39” in length (from snout to the tip of the tail), reaching a maximum length of 43”.  Appearance: The characteristic bonnet or shovel-shaped head makes this hammerhead easy to identify. Gray or greenish gray above and pale below.  Habitat: Shallow bays, sounds and estuaries. Juveniles are common in estuarine waters.  Distribution: Confined to the warm waters of the western hemisphere. It is common in inshore waters of the Carolinas and Georgia in summer and off Florida and in the Gulf of Mexico in spring, summer and fall.  Diet: Feeds on shrimp, crabs, mollusks, and small fishes. It has small, sharp teeth in the front of the mouth for soft prey and flat molars in the back for crushing hard-shelled prey.  Behavior: Migrates southward in winter or to deeper offshore waters in Florida and Gulf of Mexico. Often travels in schools of 5 to 15 individuals. Bonnetheads are timid sharks, harmless to humans.  Reproduction: Sexual maturity is reached at approximately 30” in length. Viviparous (live bearing). Pups are born in late summer and early fall measuring 12 to 13 inches at birth. Eight to twelve pups are born in a litter.

Our exhibit:  Our bonnetheads are fed a variety of shrimp, herring, silversides and squid every other day.  The first sharks to be exhibited will be juveniles, approximately 3 years old. More mature bonnetheads will be added in the weeks to come.  The transmitter used in the sharks sends out a signal that the receiver hears. A similar example is a remote control. When the remote sends a signal the TV receives the signal and responds.

Filename: FI Bonnethead Shark Source: The Sharks of North American Waters, José Castro, 1983 Dr. Michelle Heupel, Interview, April 2006 Mike Collins, Aquarist Prepared by Carol Miller, Sherry Emigh 5/26/2006 Page 1 of 2

Dr. Michelle Heupel Interview on Bonnethead Sharks, April 2006

Guides had several questions for Dr. Heupel after viewing her briefing video. These are her responses.

1. How did you know that the fish that disappeared was caught by a fisherman? Several of the transmitters that disappeared were reported to the lab and were mailed back to us. I also know the northern end of the bay is a popular spot to fish for blacktips, so if they disappear up there it is usually due to fishing.

2. How did you anesthetize the sharks before inserting the tag? We do not anesthetize the animals. The FDA will not allow us to use chemicals on animals people could potentially eat. Many sharks go into a state of tonic immobility — that is, they stop moving if rolled on their back — so we take advantage of that to make sure they are still while we do the surgery. There is scientific evidence to show that sharks do not feel pain — they lack some of the neurological mechanisms to feel pain as we know it. In addition, releasing animals that have not been drugged gives them a better chance to avoid predators since they aren’t groggy from the anesthetic.

3. How long does the transmitter last? Approximately 2 years (at least 18 months and often longer).

4. Do the bonnetheads migrate or stay within a 100 km range? Bonnetheads appear to use an inshore/offshore migration along our coast. They are present along the shore in the summer and then probably move into slightly deeper waters in the Gulf where temperatures are more stable. When it warms up they come straight back in to the coast.

5. Do they form large groups? Hard to say. We didn’t find any evidence of animals grouping or schooling, but they certainly share habitat and have been seen milling around in small groups in some areas. I don’t think we know enough to provide a good answer to this one.

6. What age do these sharks begin to mate? Bonnetheads are mature around 4 years of age.

7. How long will these live in the tank? Hard to say. The published life span is around 9-10 years, but they could live longer. We also don’t know the ages of the animals now. I would guess that they should live several years as long as conditions are good and they adjust well to the tank.