One of the most charismatic shark species is the leopard shark, Triakis semifasciata, with its elongated body, flattened head, dual dorsal fins of nearly equal size, striking dark saddle-like spots against a sandy or silver background, and a stark white belly (Nosal et al., 2013; Tricas et al., 1997). These stunning features are why the leopard shark are one of the most commonly featured sharks in zoos and aquariums (Delius, 2015).
For their commonality in zoos and aquariums, these meso-predators are found in a surprisingly small region just off the Pacific Coast of the United States, reaching from Oregon to Northern Mexico (Hopkins & Cech Jr, 2003; Lewallen, Anderson, & Bohonak, 2007; Smith, 2001, 2007). Leopard shark tend to stay close to shore in the shallow bays and estuaries along the inter-tidal regions (Smith, 2001, 2007) where they actively use the rise and fall of the tides to navigate through their habitats, finding food, shelter, pupping grounds, and even each other when it is time to aggregate for reproduction (Ackerman, Kondratieff, Matern, & Cech, 2000; Carlisle & Starr, 2009, 2010).
Leopard sharks tend to aggregate together in social groups with individuals of similar size, age, and gender (Hight & Lowe, 2007). These social groups usually consist of juveniles, mature females of similar size, and mature males of similar size. However, what female leopard sharks are known to draw crowds each year between June and September in the warmer waters of Southern California and Northern Mexico when they aggregate in the shallows to pup (Jacoby, Croft, & Sims, 2012; Smith, 2007; Smith, 2001). Shallow embankments such as estuaries have been documented to serve as nurseries for several species of elasmobranchs (Carlisle & Starr, 2009) possibly because they provide abundant prey resources, nutrient rich waters, and low predation risks to the pups (Duncan & Holland, 2006; Knip, Heupel, & Simpfendorfer, 2010). If you ever get the chance to visit La Jolla, California in the summer months, take a snorkel just beyond the surf line. These sharks are timid so approach slowly. Trust me it is well worth it!
Rogeruzun (2016 September 16). Leopard Shark Invasion (4K UHD) [Video Clip]. Retrieved from https://www.youtube.com/
Like other near shore elasmobranch species, leopard sharks are threatened by human activity (Knip et al., 2010). In a California study of wetland destruction over the past century, it has been estimated that nearly 91% of all estuarine habitat in California has been altered or all together destroyed by anthropogenic forces (Larson, 2001). With their limited habitat range and dependence on these estuary environments throughout their life history, leopard sharks are particularly vulnerable to the loss of these critical environments (Carlisle & Starr, 2009). Some studies suggest that the habitat erosion of the California coast line continues to be high due to agriculture, development, and pollution (Smith, 2001, 2007), and have a potentially damning effect on the populations of leopard sharks off the coast of California (Carlisle & Starr, 2009). Earlier this year, leopard sharks were found in mass strandings across California from January through May. Researchers are still looking into the exact cause, however it has been suggested that terrestrial run off from increased storm activity may have been the catalyst (Pelagic Shark Research Foundation, 2017).
DNA sampling of leopard sharks in California waters have determined that genetic diversity is lower than previously anticipated because there appears to be seven distinct populations that are not interbreeding with the other populations (Lewallen et al., 2007). At present the IUCN has the leopard shark listed as “Least Concern” on the Red List of Threatened Species (Carlisle, Smith, Launer, & White, 2015). Although it has been suggested that due to their long gestation period, slow growth rates, limited genetic diversity, and delayed sexual maturity they should be declared “Vulnerable” (Smith, 2001, 2007).
Family: Triakidae (houndsharks); about 40 species
Length: 6.5 feet maximum (1.9 m)
Weight: 40 lbs (18.4 kg)
Habitat: Shallow coastal waters, bays, kelp beds, estuaries
Depth: Surface to 13 feet (4 m)
Gestation: 10 to 12 months
Litter Range: 4 – 33 pups
Home Range: temperate water in the eastern Pacific, coastal U.S. from Oregon to Baja, Mexico, most commonly found along California
Diet: Prey includes bottom fishes and invertebrates
IUCN Status: Least Concern
(Skomal, 2016; Carlisle, Smith, Launer, & White, 2015)
I hope you enjoyed learning about one of my favorite shark species! I feel like I say that about every shark species, but these guys have been the focus of some of my early graduate work. They are also the first shark species I took my husband snorkeling with. (My mother-in-law was soooooo happy with me!) I absolutely love this species and I truly recommend to anyone that is in southern California in the summer months to try heading out to La Jolla for an afternoon. It is an unforgettable experience!
Flannery, A. (Photographer). (2016 June). Grad studies and leopard sharks [Digital Image]. Original Content.
If you haven’t checked out the previous Feature Species, the Great Hammerhead, be sure to check it out! Leave me a comment and let me know what species you’d like to learn more about! I’d love to hear your thoughts!
The new Ocean For Sharks Shop is open! There’s handmade ocean inspired plush animals, canvas paintings, and of course my children’s book, Winifred the Wondrous Whale Shark, available in print and PDF. Be sure to stop by. Remember proceeds benefit shark research and conservation with a donation to Project AWARE!
Remember you can make a difference for marine ecosystems by calling your Congress man or woman and tell them that you care about the quality of our waters! Sharks, rays, and other marine organisms cannot speak or be represented in Congress. They need your voice. Get involved and stand up for sharks. Until next time finatics!
Featured Image Source
San Diego Zoo (Author). (2017 April). Leopard Shark [Digital Image]. Retrieved from http://adminanimals.sandiegozoo.org/
Ackerman, J. T., Kondratieff, M. C., Matern, S. A., & Cech, J. J. (2000). Tidal influence on spatial dynamics of leopard sharks, Triakis semifasciata, in Tomales Bay, California. Environmental Biology of Fishes, 58(1), 33–43.
Carlisle, A., Smith, S., Launer, A., & White, C. (2015). Triakis semifasciata. The IUCN Red List of Threatened Species. Retrieved June 24, 2016, from http://www.iucnredlist.org/details/39363/0
Carlisle, & Starr. (2009). Habitat use, residency, and seasonal distribution of female leopard sharks Triakis semifasciata in Elkhorn Slough, California. Marine Ecology Progress Series, 380, 213–228.
Carlisle, & Starr. (2010). Tidal movements of female leopard sharks (Triakis semifasciata) in Elkhorn Slough, California. Environmental Biology of Fishes, 89(1), 31–45.
Delius, B. (2015). Triakis semifasciata. Retrieved July 10, 2016, from https://www.flmnh.ufl.edu/fish/discover/species-profiles/triakis-semifasciata
Duncan, K. M., & Holland, K. N. (2006). Habitat use, growth rates and dispersal patterns of juvenile scalloped hammerhead sharks (Sphyrna lewini) in a nursery habitat. Marine Ecology Progress Series, 312, 211–221.
Hight, B. V., & Lowe, C. G. (2007). Elevated body temperatures of adult female leopard sharks, Triakis semifasciata, while aggregating in shallow nearshore embayments: Evidence for behavioral thermoregulation? Journal of Experimental Marine Biology and Ecology, 352(1), 114–128.
Hopkins, T. E., & Cech Jr, J. J. (2003). The influence of environmental variables on the distribution and abundance of three elasmobranchs in Tomales Bay, California. Environmental Biology of Fishes, 66(3), 279–291.
Jacoby, D. M. P., Croft, D. P., & Sims, D. W. (2012). Social behaviour in sharks and rays: Analysis, patterns and implications for conservation. Fish and Fisheries, 13(4), 399–417.
Knip, D. M., Heupel, M. R., & Simpfendorfer, C. A. (2010). Sharks in nearshore environments: models, importance, and consequences. Marine Ecology Progress Series, 402, 1–11.
Larson, E. J. (2001). Coastal wetlands-emergent marshes. California’s Living Marine Resources: A Status Report. California and California Department of Fish and Game, Sacramento, California, 483–486.
Lewallen, E. A., Anderson, T. W., & Bohonak, A. J. (2007). Genetic structure of leopard shark (Triakis semifasciata) populations in California waters. Marine Biology, 152(3), 599–609.
Nosal, A. P., Cartamil, D. C., Long, J. W., Lührmann, M., Wegner, N. C., & Graham, J. B. (2013). Demography and movement patterns of leopard sharks (Triakis semifasciata) aggregating near the head of a submarine canyon along the open coast of southern California, USA. Environmental Biology of Fishes, 96(7), 865–878.
Pelagic Shark Research Foundation (2017). San Francisco Bay, Stranding Report Update for late May and June 1, 2017. Retrieved from https://www.facebook.com/Pelagic-Shark-Research-Foundation-167200017410/?ref=page_internal
Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.
Smith, S. (2001). California’s Marine Living Resources: A Status Report. California Department of Fish and Game.
Smith, S. (2001). Leopard shark. California’s Marine Living Resources: A Status Report, (December), 252–254.
Smith, S. (2007). Leopard shark. Status of the Fisheries Report, (14), 1–7.
Tricas, T. C., Deacon, K., Last, P., McCosker, J. E., Walker, T. I., & Taylor, L. (1997). The Nature Company Guides: Sharks and Rays. (L. Taylor, Ed.). Hong Kong: The Nature Company, Time Life Books.