Giant freshwater stingray

Lore & Background

The first scientific description of the giant freshwater stingray was authored by Dutch ichthyologist Pieter Bleeker in an 1852 volume of the journal Verhandelingen van het Bataviaasch Genootschap van Kunsten en Wetenschappen. His account was based on a juvenile specimen 30 cm (12 in) across, collected from Jakarta, Indonesia. Bleeker named the new species polylepis, from the Greek poly ("many") and lepis ("scales"), and assigned it to the genus Trygon. However, in subsequent years Bleeker's description was largely overlooked, and in 1990 the giant freshwater stingray was described again by Supap Monkolprasit and Tyson Roberts, who gave it the name Himantura chaophraya. In 2008, Peter Last and B. Mabel Manjaji-Matsumoto confirmed that T. polylepis and H. chaophraya refer to the same species, and since Bleeker's name was published earlier, the scientific name became Himantura polylepis.

This species has a relatively thin, oval pectoral fin disc that is widest anteriorly, and a sharply pointed snout with a protruding tip. Its tail is thin and whip-like, and lacks fin folds. It is uniformly grayish brown above and white below; the underside of the pectoral and pelvic fins bear distinctive wide, dark bands on their posterior margins. Bottom-dwelling in nature, it inhabits sandy or muddy areas and preys on small fishes and invertebrates. Females give live birth to litters of one to four pups, which are sustained to term by maternally produced histotroph ("uterine milk").

Reader's Guide

The giant freshwater stingray faces heavy fishing pressure for meat, recreation, and aquarium display, as well as extensive habitat degradation and fragmentation. These forces have resulted in substantial population declines in at least central Thailand and Cambodia. As a result, the International Union for Conservation of Nature (IUCN) has assessed the giant freshwater stingray as Endangered. In June 2022, it was reported that a specimen caught in the Mekong river had broken the record for the largest strict freshwater fish ever documented; the individual weighed 661 lb (300 kg), and was measured at 3.98 m (13.1 ft) long and 2.2 m (7.2 ft) wide. The species is also notable for its taxonomic history, having been described twice under different names before being reconciled. Its fossil caudal spines have been attributed to this species from late middle Pleistocene deposits in the Madura Strait and possibly older Pleistocene deposits from Trinil in eastern Java.

Did You Know?

• The giant freshwater stingray is the widest freshwater fish in the world, growing up to 2.2 m (7.2 ft) across.
• Its stinging spine can reach up to 38 cm (15 in) long, the largest of any stingray species.
• A specimen caught in the Mekong River in June 2022 weighed 661 lb (300 kg) and set a record for the largest strict freshwater fish.
• The species was first described by Pieter Bleeker in 1852, but was later redescribed in 1990 as Himantura chaophraya before being synonymized.