Dr. Carrier's primary research interests center around the biology of nurse sharks (Ginglymostoma cirratum). His earliest studies examined aging, growth and movement of this species in and around Big Pine Key in the lower Florida Keys (Carrier, J.C. and C. A. Luer. 1990. Growth rates in the nurse shark Ginglymostoma cirratum. Copeia 1990: 676-682).

More recent studies have concentrated on reproductive biology in this species (Carrier, J.C., H.L. Pratt, Jr., and L.K. Martin. 1994. Group reproductive behaviors in free-living nurse sharks, Ginglymostoma cirratum. Copeia 1994: 646-656). For more than fifteen years Dr. Carrier has conducted studies of shark reproductive behavior in the Dry Tortugas, a chain of islands 78 miles west of Key West, Florida with long-time colleague Wes Pratt of Mote Marine Laboratory. Their studies have detailed mating behaviors in a wild population of sharks and have shown interactions and social structures never before reported (Pratt, H.L., Jr. and J. C. CARRIER. 2005. Elasmobranch Courtship and Mating Behavior IN: William Hamlett (Ed.) Reproductive Behavior and Phylogeny of Elasmobranchs.  Science Publishers, Inc. Queensland, Australia).

Studies of mating nurse sharks provide new insight into shark reproductive behaviors.

The study has been conducted with the assistance of SeaWorld Adventure Parks of Orlando, Florida where female sharks were help during their pregnancies. Ultrasound and endoscopic techniques were utilized to monitor the time course of gestation, shown by this study to be 4.5 to 5 months (Carrier, J., F. Murru, M. Walsh, and H.L. Pratt, Jr. 2003. Assessing reproductive potential and gestation in nurse sharks (Ginglymostoma cirratum) using ultrasonography and endoscopy: an example of bridging the gap between field research and captive studies. Zoo Biology 22(2): 179-187). Offspring born to the captive females also served to establish multiple paternity in this species (Saville, K, A. Lindley, N. Maries, J. CARRIER, H. Pratt, Jr. 2002. Multiple paternity in the nurse shark (Ginglymostoma cirratum). Environ. Biol. of Fishes 63(3): 347-351).

Intrauterine photograph of developing nurse shark embryo .

Litters of 26-30 nurse sharks were shown to have 4-6 fathers.

Additional studies with the National Geographic Society's Remote Imaging Laboratory and funded by Florida Sea Grant have used Geographic's Crittercam, a remote imaging and data acquisition system developed by Greg Marshall to follow nurse shark behaviors when out of sight of the investigators. The camera system continues to film what the sharks "sees" and is later recovered for analysis of the video footage and data. Conducted with Greg Marshall of the National Geographic Society and Dr. Mike Heithaus of Florida International University, the study provided additional information about the behaviors of male nurse sharks between mating events.

Nurse shark carrying a CritterCam. The above photograph is © Harold L. Pratt, Jr. Used by permission. All rights reserved.