Featured Species: Winghead Shark (Eusphyra blochii)

This week’s featured species is a wonderfully weird looking species from the Indian and Western Pacific Oceans. The Winghead Shark (Eusphyra blochii) is a the only hammerhead species in the genus Eusphyra; the other 9 members of the family Sphyrnidae are in the genus Sphyrna (Ebert, Fowler, & Dando, 2015).  The winghead shark is one of the smaller hammerhead species, reaching about 6.1 feet (1.86 m) at maximum length (Tricas et al., 1997). Like most hammerheads, the winghead shark has a tall first dorsal fin. However, the winghead shark’s first dorsal fin is much further forward than other hammerhead species, with its origin over the pectoral fin bases (Ebert, Fowler, & Dando, 2015).

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CSIRO National fish Collection (Photographer). (2013). Winghead shark (Eusphyra blochii) [Digital Image]. Retrieved from https://commons.wikimedia.org/

There are 10 species of hammerhead sharks known to science today:

Common Name

Scientific Name

IUCN Status

Winghead Shark Eusphyra blochii Endangered
Great Hammerhead Sphyrna mokarran Endangered
Whitefin Hammerhead Sphyrna couardi Endangered
Scalloped Hammerhead Sphyrna lewini Endangered
Smalleye Hammerhead Sphyrna tudes Vulnerable
Smooth Hammerhead Sphyrna zygaena Vulnerable
Scalloped Bonnethead Shark Sphyrna corona Near Threatened
Bonnethead Shark Sphyrna tiburo Least Concern
Scoophead Shark Sphyrna media Data Deficient
Carolina Hammerhead Sphyrna gilberti Yet To Be Assessed

Each species – with the exception of the cryptic species the Carolina Hammerhead (Sphyrna gilberti) – is identifiable by their unique head shape (Quattro, Driggers III, Grady, Ulrich, & Roberts, 2013). The winghead shark is known and named for the immense, dramatic blades of the cephalofoil. The distance between its eyes can measure about half its body length (Ebert, Fowler, & Dando, 2015)! It is thought that that having the eyes set so far apart may improve the winghead shark’s stereoscopic vision (Tricas et al., 1997). With that elongated head comes elongated nostrils, which we will talk about in greater detail a little later in this post. They have been called the “ultimate example of [a] cephalofoil” (Tricas et al., 1997).

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Drawings 1 to 9: Hammerhead sharks (fam. Sphyrnidae) are easily recognizable by the typical highly depressed, wide head with eyes on the outer side of the two lobes. The individual species, whose common denominator is this unusual head, can be distinguished by differences in horizontal profile, which can be almost straight or markedly curved. (1) Eusphyra blochii (2) Sphyrna tudes (3) Sphyrna couardi (4) Sphyrna corona (5) Sphyrna tiburo (6) Sphyrna mokarran (7) Sphyrna lewini* (8) Sphyrna zygaena (9) Sphyrna media (Mojetta, 1997). *Since publication Sphyrna gilberti has also been discovered as a cryptic species, and is only distinguishable from S. lewini by number of precaudual vertebrae (Quattro, Driggers III, Grady, Ulrich, & Roberts, 2013).

 

The hammerheads are relative new comers in the shark world. They are actually the most recent shark family to evolve around 20 million years ago (Mojetta, 1997). DNA testing of modern hammerheads have revealed that big hammerheads most likely evolved into smaller hammerheads, and the smaller hammerhead species actually evolved independently… twice (Lim, Motta, Mara, & Martin, 2010). The winghead shark evolved very early on in the waters around Australia; while the lineage that would produce the bonnethead shark evolved later on in the Caribbean and eastern Pacific (Lim, Motta, Mara, & Martin, 2010). It is suspected that the ancestor of the hammerhead lived in the Miocene epoch about 20 million years ago, with the modern Great Hammerhead first appearing around 10 million years ago (Lim, Motta, Mara, & Martin, 2010).

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Fig. 6. Ultrametric tree estimation of the diversification within the family Sphyrnidae based on the nuclear genes in which a time axis is drawn assuming a divergence time of 40 and 50 million years between Carcharhinus and Sphyrnidae (Lim, Motta, Mara, & Martin, 2010).

 

The winghead shark’s incredibly exaggerated cephalofoil may also be an evolutionary advantage in detecting prey. All sharks have external nostrils, or nares. The nares allow the shark to detect odors in the water by passing odors over an olfactory sac. The nares have a nasal flap that separates the incoming water from the exiting water (Skomal, 2016).

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Fig. 2. Ventral view of the head of a specimen of the hammerhead shark S. tudes. Right nasal region outlined. a: Anterior; l: lateral; m: medial; p: posterior. Scale bar: 5 cm (Abel et al., 2010).

 

The nares of the winghead shark are located in the middle of the head, but the nasal grooves extend almost the full width of the cephalofoil (Tricas et al,. 1997). It was hypothesized for some time that the distance between the nares along the cephalofoil gave the winghead shark an advantage when hunting. Using comparative morphology, scientists at Florida Atlantic University and the University of California at Irvine investigated whether the lateral elongation of the rostrum had enabled hammerheads to better perform olfactory klinotaxis (Kajiura, Forni, & Summers, 2005). Olfactory klinotaxis is a shark’s ability to compare odor stimulus intensities between the right and left nares; in other words, how well a shark can determine the direction an odor is coming from by comparing the strength of the scent in the left and right nostril. In general, the winghead shark has a 49% greater nare separation than even a scalloped hammerhead, and the scalloped hammerhead has a 79% greater nare separation than the sandbar shark (Carcharhinus plumbeus). In their studies, the team found that the scalloped hammerhead had a 1,300% greater effective sampling time when compared to a similarly sized sandbar shark. The winghead shark was even more effective than the scalloped (Kajiura, Forni, & Summers, 2005). In addition to excellent olfactory klinotaxis abilities, the winghead shark’s cephalofoil also extends the distribution of electroreceptors of the ampullae of Lorenzini and the mechanoreceptors of the lateral line (Tricas et al., 1997). These senses are useful for detecting and localizing their prey buried below the sediment.

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Raredon, S. (Photographer). (2016). Eusphyrna blochii X-ray [Digital Image]. Retrieved from https://commons.wikimedia.org/

The winghead shark has a relatively small mouth. As such they prey on small prey items such as crustaceans, cephalopods, and small bony fishes (Stevens & Lyle, 1989). In their upper jaw, they have 15 to 16 small teeth on each side. The lower jaw has 14 similar teeth on each side. The smooth-edged angled triangular cusps are designed for piercing slippery prey items (Last & Stevens, 2009). They are not meant for tearing away flesh in chunks, but for piercing and swallowing prey relatively whole.

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Queensland Department of Agriculture and Fisheries (Author). (n.d.). Winghead Shark tooth [digital image]. Retrieved from https://www.daf.qld.gov.au

The winghead shark is currently categorized as an Endangered species by the International Union for the Conservation of Nature (IUCN). The winghead shark is slow to reach sexual maturity. Females do not reach sexual maturity until they are over 3 feet (1 m) in length (Tricas et al., 1997). Once females do reach sexual maturity, they give birth to a small number of pups, usually between 6 to 20 pups, after a gestation period between 8 and 11 months (Stevens & Lyle, 1989). These life history characteristics leave the winghead shark susceptible to the heavy fishing pressures throughout their home range (Smart & Simpfendorfer, 2016). While there are no specific population data available for the winghead shark, global elasmobranch landings have declined by at least 20% since 2003 (Smart & Simpfendorfer, 2016). The Indo-Pacific, where the winghead shark calls home, is among the most severely impacted regions (Dulvy et al., 2014). Net and trawl fisheries are extensive throughout Indonesia, where many elasmobranch species are highly exploited (Blaber et al., 2009). And there is evidence to suggest that the winghead shark has suffered population decline. In a survey of Indonesian fish markets where nearly 20,000 sharks were recorded, only 1 winghead shark was observed. India’s catch data make no mention of the winghead shark as bycatch or a targeted species (Varghese, Vijayakumaran, & Gulati, 2013). The winghead shark makes up less than 0.75% of the total fisheries in Queensland, Australia, where they are typically taken accidentally in gillnets and trawls when their elongated heads become entangled (Stobutzki, Miller, Heales, & Brewer, 2002; Harry, et al., 2011; DAFF, 2012). Effective fisheries management is crucial for the preservation of this species. Beyond the threat of the fisheries industry, the winghead shark faces habitat loss and degradation throughout its habitat. Coastal mangroves have been extensively reduced by more than 30% since 1980 (Polidoro et al., 2010). Continued monitoring of the winghead shark’s available habitat should be a priority throughout its entire range.

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Fisheries of Australia (Photographer). (n.d.). Winghead shark hooked [Digital Image]. Retrieved from http://fishesofaustralia.net.au

Shark Stats

Authority: Cuvier, 1816

Family: Sphyrnidae; 10 species

Length: Maximum of 6.2 feet (1.86 m)

Weight: Maximum weight is undocumented/unknown

Habitat: Shallow waters, found along continental and insular shelves

Depth: Shallow water species

Reproduction: Ovoviviparous

Gestation: 8 – 11 months

Litter Range: 6 – 25 pups; mean size 11 pups

Home Range: North Indian Ocean, along Northern Australia and Southern China

Diet: Small bony fishes, cephalopds, crustaceans

IUCN Status: Endangered

(Stevens & Lyle, 1989; Ebert, Fowler, & Dando, 2015; Smart & Simpfendorfer, 2016)

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. Proceeds benefit shark research and conservation with a donation to Project AWARE!

Thanks so much for checking out the other worldly Winghead Shark! If you missed last week’s featured species, please be sure to check out the deep water Bluntnose Sixgill Shark! If there is a species of elasmobranch you’d love to know more about, leave me a comment or send me a message! I would love to do a feature on your favorite species. Also connect with me on Instagram and Facebook for even more elasmo fun!

Conservation legislation needs public support in order to become law and help protect the environment and wildlife. Tell your representatives that you care about environmental and wildlife conservation.  It only takes a moment to make a change that will last a lifetime. Until next time finactics!

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Featured Image Source

Morgan, D. (Photographer). (2016). Mature Winghead shark caught King Sound, Derby (WA) [Digital Image]. Retrieved from https://twitter.com/

Literature Cited

Abel, R. L., Maclaine, J. S., Cotton, R., Xuan, V. B., Nickels, T. B., Clark, T. H., … & Cox, J. P. (2010). Functional morphology of the nasal region of a hammerhead shark. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology155(4), 464-475.

Blaber, S. J. M., Dichmont, C. M., White, W., Buckworth, R., Sadiyah, L., Iskandar, B., … & Andamari, R. (2009). Elasmobranchs in southern Indonesian fisheries: the fisheries, the status of the stocks and management options. Reviews in Fish Biology and Fisheries19(3), 367-391.

DAFF. (2012). Gulf of Carpentaria Inshore Fin Fish Fishery 2012 fishing year report.

Dulvy, N. K., Fowler, S. L., Musick, J. A., Cavanagh, R. D., Kyne, P. M., Harrison, L. R., … & Pollock, C. M. (2014). Extinction risk and conservation of the world’s sharks and rays. elife3, e00590.

Ebert, D. A., Fowler, S. L., & Dando, M. (2015). Sharks of the world: a fully illustrated guide. Wild Nature Press.

Harry, A. V., Tobin, A. J., Simpfendorfer, C. A., Welch, D. J., Mapleston, A., White, J., … & Stapley, J. (2011). Evaluating catch and mitigating risk in a multispecies, tropical, inshore shark fishery within the Great Barrier Reef World Heritage Area. Marine and Freshwater Research62(6), 710-721.

Kajiura, S. M., Forni, J. B., & Summers, A. P. (2005). Olfactory morphology of carcharhinid and sphyrnid sharks: does the cephalofoil confer a sensory advantage?. Journal of Morphology264(3), 253-263.

Klimley, A. P. (2013). The biology of sharks and rays. University of Chicago Press.

Last, P. R., & Stevens, J. D. (2009). Sharks and rays of Australia. 2nd Edit.

Lim, D. D., Motta, P., Mara, K., & Martin, A. P. (2010). Phylogeny of hammerhead sharks (Family Sphyrnidae) inferred from mitochondrial and nuclear genes. Molecular Phylogenetics and Evolution55(2), 572-579.

Mojetta, A. (1997). Sharks: History and biology of the lords of the sea. (E. McNulty, Ed.). San Diego: Thunder Bay Press.

Polidoro, B. A., Carpenter, K. E., Collins, L., Duke, N. C., Ellison, A. M., Ellison, J. C., … & Livingstone, S. R. (2010). The loss of species: mangrove extinction risk and geographic areas of global concern. PloS one5(4), e10095.

Quattro, J. M., Driggers III, W. B., Grady, J. M., Ulrich, G. F., & MA, R. (2013). Sphyrna gilbert sp. Nov., a new hammerdead shark (Carcharhiniformes, Sphyrnidae) from the western Atlantic Ocean. Zootaxa3702(2), 159-178.

Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.

Smart, J.J. & Simpfendorfer, C. (2016). Eusphyra blochiiThe IUCN Red List of Threatened Species. Retrieved from https://www.iucnredlist.org/species/41810/68623209

Stevens, J. D., & Lyle, J. M. (1989). Biology of three hammerhead sharks (Eusphyra blochii, Sphyrna mokarran and S. lewini) from northern Australia. Marine and Freshwater Research40(2), 129-146.

Stobutzki, I. C., Miller, M. J., Heales, D. S., & Brewer, D. T. (2002). Sustainability of elasmobranchs caught as bycatch in a tropical prawn (shrimp) trawl fishery. Fishery Bulletin100(4), 800-821.

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.

Varghese, S. P., Vijayakumaran, K., & Gulati, D. K. (2013). Pelagic megafauna bycatch in the tuna longline fisheries off India (p. 15). IOTC–2013–WPEB09–36.

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