Largest freshwater fish (specimen)

To date, the largest reliably measured specimen of fish that spends its whole life in fresh/brackish water is a female giant freshwater stingray, aka whipray (Urogymnus polylepis) collected by fishermen in the Mekong River in the Stung Treng region of Cambodia on 13 June 2022. Assessed by international scientists from the US-Cambodian “Wonders of the Mekong” project (funded by the United States Agency for International Development), the stingray (dubbed "Boramy") weighed approximately 300 kg (661 lb) and measured 3.98 m (13 ft) long (including tail) with a disc width of 2.2 m (7 ft 2 in). After measuring, Boramy was returned to the river with a tracker so her movements could be followed as very little is known about the behaviour of these elusive giants.

The discovery of the 300-kg giant freshwater stingray followed a month after a 180-kg (397-lb) specimen of the same species was found in the same stretch of the Mekong River.

This is not the first record-breaking megafish found in the murky and little-studied waterways of this region. The previous holder of this record was a 293-kg (646-lb) Mekong giant catfish ( Pangasianodon gigas), measuring 2.7 m (8 ft 11 in) long, caught in the Mekong River in Thailand in June 2005.

Other giant freshwater fish species that could be eligible for this title include the arapaima ( Arapaima gigas) of South America, reported to attain a maximum length of 4.5 m (14 ft 9 in), but weighing “only” 200 kg (440 lb).

A former contender for this title was the Chinese paddlefish ( Psephurus gladius), once native to the Yangtze River Basin, which grew to at least 3 m (9 ft 10 in) and also weighed up to 300 kg (661 lb) – although much larger, uncorroborated examples have been reported, one as long as 7 m (23 ft) and weighing 450 kg (990 lb)! However, in January 2020, this species was officially declared extinct by the Chinese Academy of Fishery Sciences and the IUCN, who consider that it likely died out sometime between 2005 and 2010, owing to overfishing and habitat loss.

In the 19th century, the European catfish or wels ( Silurus glanis) was reputed to attain lengths of 4.6 m (15 ft) and weights of 336 kg (720 lb) were reported for Russian specimens – but today anything over 1.8 m (6 ft) and 90 kg (200 lb) is considered large. A particularly large specimen of wels was caught in the River Po in Italy on 19 February 2015 by twin brothers Dario and Dino Ferrari; it weighed 127 kg (279 lb) and measured 2.7 m (8 ft 10 in) long. According to Dr Zeb Hogan, an expert in giant fish and presenter of TV series Monster Fish, the largest wels are now most common in Italy, France and Spain (outside of its native range), where it is an invasive species.