The Daggernose shark (Isogomphodon oxyrhynchus) is a species of requiem shark, in the family Carcharhinidae, and the only extant member of its genus. There is very little known about this shark. What is most unique about the Daggernose shark, as its name suggests, it has a long, flat, triangular pointed snout. It can be found off the northeastern coast of South America.
Family: Carcharhinidae – Requiem sharks
Genus: Isogomphodon
Species: oxyrhynchus
Phylum– Chordata
Class– Chondrichthyles
Subclass– Elasmobranchii
Common Name– Ground Sharks
Family– Carcharhinidae
Common Name– Requiem Sharks
Genus– Isogomphodon
Species– oxyrhynchus
Status: IUCN Red List CRITICALLY ENDANGERED
Average Size and Length: Male Daggernose sharks can grow as long as 4.6 feet and females 1.6 m 5.2 feet. There is a possibility that they could reach between 6.6 and 7.9 feet long.
Average Weight: The maximum known weight is 29 pounds.
Teeth and Jaw: There are short but deep furrows at the corners of the mouth of the Daggernose shark on both jaws. The tooth rows number 49–60 and 49–56 in the upper and lower jaws. Each tooth has a single narrow, upright cusp. The upper teeth are broader and flatter than the lower teeth, with serrated edges.
Head: The Daggernose shark has a very long, flattened snout with a pointed tip and A triangular profile from above. The eyes are very small and circular with nictitating membranes. The nostrils are small and don’t have protruding skin flaps.
Tail: The caudal fin has a well-developed lower lobe and is preceded by a crescent-shaped notch on the upper side of the caudal peduncle.
Demographic, Distribution, Habitat, Environment and Range: The Daggernose shark is found along the northeastern coast of South America. Specifically, they can be found off Guyana, Trinidad, French Guiana, Suriname and northern Brazil. Some reports are as far south as Valença in the central Brazilian state of Bahia, but this is unsupported by surveys. The Daggernose shark can be found over the continental shelf in habitats with a lot of mangroves and a very humid climate. The Daggernose shark prefers coastal waters between a depth of 13 and 131 feet deep, typically estuaries, river mouths and shallow muddy banks. It also favors highly turbid waters. Research suggests that the female Daggernose sharks are found at greater depths than the male sharks. It is typically found where there is river drainage, especially the Amazon. Water salinity ranges from 20 to 34 ppt, and the tidal amplitude can measure up to 23 feet. It seems to be intolerant of low salinity, moving inshore during the dry season (June to November) and offshore during the rainy season (December to May). Research suggests based on these movements, they do have localized seasonal movements, but do not travel long distances.
Diet: The Daggernose shark seems to eat small schooling fishes like herring, anchovies, catfish, and croakers.
Aesthetic Identification: The Daggernose shark has a robust build with large, broad, paddle-like pectoral fins that originate under the fifth gill slit. They are grey, plain, and sometimes even with a brow or yellowish cast above, and counter-shaded light underneath. The first dorsal fin originates over the posterior half of the pectoral fin bases. The second dorsal fin is about half as tall as the first and located over or slightly ahead of the anal fin. The anal fin is smaller than the second dorsal fin and has a deep notch in the rear margin.
Biology and Reproduction: The Daggernose shark is viviparous. Females give birth to litters of 2–8 pups every other year (there is no correlation between female size and number of pups), following a year-long gestation period. Mating and parturition take place over about a 6-month period from the beginning to the end of the rainy season. One interesting fact is that the Daggernose shark is capable of shifting the timing of its reproductive cycle by at least 4 months. This could be because of the changing environmental conditions. Females move into shallow coastal nurseries to give birth. One known nursery is off Brazilian state of Maranhão.
Newborn Daggernose sharks measure 15–17 inches in length. Males mature at 41 inches long (between 5–6 years), and females mature at 45 inches long (between 6–7 years).
The lifespan of female Daggernose sharks is around 12 years, and 7 years for males based on the scientific data collected thus far. However, scientists believe males could live up to 12 years, and females 20.
Behavioral Traits, Sensing and Intelligence: The Daggernose shark has an adaptive emphasis on electroreception and other rostral senses rather than vision in response to environmental and habitat living conditions.
Daggernose Shark Future and Conservation: The Daggernose shark is rare and critically endangered. It is caught in small numbers by local fishers in Trinidad, Guyana, Suriname, and French Guiana to support their village food needs. However, and unfortunately, the Daggernose shark comprises about one-tenth of the catch of a northern Brazil floating gillnet fishery targeting Acoupa weakfish, Serra Spanish mackerel which operates in estuaries during the dry season. The Daggernose shark is often found in markets, but is not highly regarded as a food fish.
Daggernose Shark Recorded Attacks on Humans: No threat to humans.