Unique deep-water shark that may live in extreme conditions

The Bigeye houndshark (Iago omanensis) is a species of shark belonging to the family Triakidae. It is found in the deep waters of the continental shelf in the western Indian Ocean, from the Red Sea to southwestern India. They are unique in that more than likely they can survive in excessively salty and low oxygenated waters, suggested by the size of the gill slits. The large eyes could suggest a very dark environment or one with little visibility.


Family: Triakidae – Houndsharks

Genus: Iago 

Species: omanensis


Phylum– Chordata

Class– Chondrichthyles


Common NameGround Sharks

Family– Triakidae

Common NameHoundsharks




Average Size and Length: They are born greater than 17 cm/6.6 inches. Mature males have been measured under 30 cm/11.8 inches, and mature females under 40 cm/1.3 feet. The maximum recorded for a female has been 58 cm/1.9 feet. Males are much smaller than females.

Teeth and Jaw: The teeth are small and blade-like. The are somewhat fat with a short, angled main cusp.

Head: Like its name, the eyes are extremely large.  

Tail: There is a small ventral caudal lobe.

Demographic, Distribution, Habitat, Environment and Range: The Bigeye houndshark can be found in the Indian Ocean in the Red Sea, the Gulf of Oman, Pakistan, southwest India and possible the Bay of Bengal and Myanmar in Burma (30° N and 10° N). They can be found on or near the bottom on the continental shelf and slope in water shallower than 361 feet to depths greater than 3,281 feet, possibly as deep as 7,201 feet in the Red Sea. They are often found in warm water, with poor oxygen conditions (water temperature: 16-25°C and an oxygen level of 0.2-2.4 ppm.). They are considered bathydemersal.

Diet: They eat bony fish and cephalopods.

Aesthetic Identification: The Bigeye houndshark is slender and a uniform greyish-brown color dorsally, and lighter ventrally. The dorsal fin margins are sometimes darker. The gill slits are larger. The width of the longest is nearly equal to the length of the of the extremely large eyes. The dorsal fins are small. The origin of the first dorsal fin is set far forward over the pectoral fin bases.

Biology and Reproduction: They are viviparous, with a yolk-sac placenta, and they have between 2-10 pups per litter. Gestation is possibly between 10-12 months and the type of water. The enlarged gills may allow survival in warm, low-oxygenated, hyper-saline waters.

Behavioral Traits, Sensing and Intelligence: Unknown, but they could possibly segregate by sex.

Bigeye Houndshark Future and Conservation: They are currently of least concern.

Bigeye Houndshark Recorded Attacks on Humans: Not a threat to humans.