Isogomphodon
1 species
The daggernose shark (Isogomphodon oxyrhynchus) is a little-known species of requiem shark, in the family Carcharhinidae, and the only extant member of its genus. It inhabits shallow tropical waters off northeastern South America, from Trinidad to northern Brazil, favoring muddy habitats such as mangroves, estuaries, and river mouths, though it is intolerant of fresh water. A relatively small shark typically reaching 1.5 m (4.9 ft) in length, the daggernose shark is unmistakable for its elongated, flattened, and pointed snout, tiny eyes, and large paddle-shaped pectoral fins.
Daggernose sharks are predators of small schooling fishes. Its reproduction is viviparous, with females give birth to 2–8 pups every other year during the rainy season; this species is capable of shifting the timing of its reproductive cycle by several months in response to the environment. Harmless to humans, the daggernose shark is caught for food and as bycatch in artisanal and commercial fisheries. Limited in range and slow-reproducing, it has been assessed as Critically Endangered by International Union for Conservation of Nature in light of a steep population decline in recent years. The current population is believed to be extremely low, with no more than 250 individuals believed to be in existence as of 2023. Indeed, it may even be in reproductive collapse, in which case it will likely become extinct in the near future.
The daggernose shark is found along the northeastern coast of South America, off Trinidad, Guyana, Suriname, French Guiana, and northern Brazil. It reportedly occurs as far south as Valença in the central Brazilian state of Bahia, though fishery surveys have not detected this species in the area and it is apparently unknown to local fishermen.
An inhabitant of coastal waters at a depth of 4–40 m (13–131 ft), the daggernose shark prefers highly turbid waters and decreases in number with increasing water clarity. Females tend to be found at greater depths than males. Its range encompasses a wide continental shelf with a humid tropical climate, extensive mangroves, and draining by numerous rivers including the Amazon. Water salinity in this area ranges from 20 to 34 ppt, while the tidal amplitude can measure up to 7 m (23 ft). Daggernose sharks are most common over shallow muddy banks and in estuaries and river mouths. 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). This species is not known to make long-distance movements, though some local seasonal movements are possible.
The daggernose shark (Isogomphodon oxyrhynchus) is a little-known species of requiem shark, in the family Carcharhinidae, and the only extant member of its genus. It inhabits shallow tropical waters off northeastern South America, from Trinidad to northern Brazil, favoring muddy habitats such as mangroves, estuaries, and river mouths, though it is intolerant of fresh water. A relatively small shark typically reaching 1.5 m (4.9 ft) in length, the daggernose shark is unmistakable for its elongated, flattened, and pointed snout, tiny eyes, and large paddle-shaped pectoral fins.
Daggernose sharks are predators of small schooling fishes. Its reproduction is viviparous, with females give birth to 2–8 pups every other year during the rainy season; this species is capable of shifting the timing of its reproductive cycle by several months in response to the environment. Harmless to humans, the daggernose shark is caught for food and as bycatch in artisanal and commercial fisheries. Limited in range and slow-reproducing, it has been assessed as Critically Endangered by International Union for Conservation of Nature in light of a steep population decline in recent years. The current population is believed to be extremely low, with no more than 250 individuals believed to be in existence as of 2023. Indeed, it may even be in reproductive collapse, in which case it will likely become extinct in the near future.
The daggernose shark is found along the northeastern coast of South America, off Trinidad, Guyana, Suriname, French Guiana, and northern Brazil. It reportedly occurs as far south as Valença in the central Brazilian state of Bahia, though fishery surveys have not detected this species in the area and it is apparently unknown to local fishermen.
An inhabitant of coastal waters at a depth of 4–40 m (13–131 ft), the daggernose shark prefers highly turbid waters and decreases in number with increasing water clarity. Females tend to be found at greater depths than males. Its range encompasses a wide continental shelf with a humid tropical climate, extensive mangroves, and draining by numerous rivers including the Amazon. Water salinity in this area ranges from 20 to 34 ppt, while the tidal amplitude can measure up to 7 m (23 ft). Daggernose sharks are most common over shallow muddy banks and in estuaries and river mouths. 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). This species is not known to make long-distance movements, though some local seasonal movements are possible.