This week’s featured species is a shark that is Vulnerable to extinction from the Indian Ocean. The Sicklefin Weasel Shark (Hemigaleus microstoma) is one of eight species in the family Hemigaleidae and they are found primarily in the Indian Ocean from India to the Philippines and China, though they can be found in the Red Sea as well (Ebert, Fowler, & Dando, 2015; Skomal, 2016). The sicklefin weasel shark has a fairly long, rounded snout with a very short, arching mouth (Ebert, Fowler & Dando, 2015). They have a nictitating membrane that folds over their eyes to protect from damage, especially during feeding (Ebert, Fowler, & Dando, 2015). They are generally light gray to bronze colored with occasional white splotches along their sides.
But what gives the sicklefin weasel shark its name sake are its fins. The dorsal, pectoral, pelvic fins, and ventral causal lobe are all strongly falcated (Ebert, Fowler, & Dando, 2015). In other words, they are hooked or curved like a sickle. These fins are sometimes harvested for the fin trade, but due to the sicklefin weasel shark’s small size (only around 3.04 feet (0.94 m)), their fins do not fetch a great value on the market (White, Last, Stevens, & Yearsly, 2006).
The sicklefin weasel shark has a highly specialized diet. They feed almost exclusively on cephalopods, including squids and octopods (Compagno, 2001). To adapt to a diet comprised of soft-bodied prey items, the sicklefin weasel shark has a small mouth and short gill slits, which may aid the shark in capturing cephalopods via suction feeding (Compagno, 2001). Their jaws, on the other hand, are relatively weak and their teeth are very small. In the upper jaw, the teeth are broad and have a smooth leading edge contrasting a strongly serrated trailing edge. The lower jaw is compromised of teeth that are narrow and erect with straight edges (Compagno, 2001).
The sicklefin weasel shark is currently categorized by the International Union for the Conservation of Nature (IUCN) as a species that is Vulnerable to extinction (White, 2009). These sharks are a naturally uncommon species, and are not as fecund as other weasel shark species, like the closely related Australia Weasel Shark (Hemigaleus australiensis) (White, Last, & Compagno, 2005). The sicklefin weasel shark is not directly targeted by fisheries industries; however, they are taken in both inshore and offshore fisheries as bycatch in drifting and bottom gillnets and longlines (White, 2006). When they are caught, their meat is utilized for human consumption and processed for fishmeal; while their fins are sold in the fin trade (White, Last, Stevens, & Yearsly, 2006). Currently, there are no targeted conservation actions in place for the sicklefin weasel shark, but monitoring of their populations and catch data should be closely monitored.
Authority: Bleeker, 1852
Family: Hemigaleidae; 8 species
Length: 3.04 feet (0.94 m)
Weight: Maximum weight unknown
Habitat: Bottom continental shelves
Depth: Up to 555 feet (170 m)
Reproduction: Placental Viviparous
Gestation: Less than 6 months, possibility of 2 pregnancies per year
Litter Range: 2 -4 pups
Home Range: Tropics of the Indian Ocean; ranging from India to the Philippines and China; possibly the Red Sea
Diet: Specialty feeder, feeding almost exclusively on cephalopods
IUCN Status: Vulnerable
(White, 2009; Ebert, Fowler, & Dando, 2015; Skomal, 2016)
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Thanks so much for checking out the Sicklefin Weasel Shark! If you missed last week’s featured species, please be sure to check out the Caribbean Reef 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!
Featured Image Source
Randall, J.E. (Photographer). (n.d.). Sicklefin Weasel Shark [Digital Image]. Retrieved from https://www.inaturalist.org/taxa/102560-Hemigaleus-microstoma
Compagno, L. J. (2001). Sharks of the world. An annotated and illustrated catalogue of shark species known to date, vol 2. Bullhead, mackerel and carpet sharks (Heterodontiformes, Lamniformes and Orectolobiformes). FAO species catalogue for fishery purposes, 1, viii+-1.
Ebert, D. A., Fowler, S. L., & Dando, M. (2015). Sharks of the world: a fully illustrated guide. Wild Nature Press.
Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.
White, W. T., Last, P. R., & Compagno, L. J. (2005). Description of a new species of weasel shark, Hemigaleus australiensis n. sp.(Carcharhiniformes: Hemigaleidae) from Australian waters. Zootaxa, 1077(7th November), 37-49.
White, W. T., Last, P. R., Stevens, J. D., & Yearsly, G. K. (2006). Economically important sharks and rays of Indonesia (No. 435-2016-33677).
White, W.T. (2009). Hemigaleus microstoma. The IUCN Red List of Threatened Species. Retrieved from https://www.iucnredlist.org/species/41816/10569394