With a total length possibly up to 5 m (16 ft) and a maximum weight of over 300 kg (660 lb), the wels catfish is by some margin the largest true freshwater fish (as opposed to anadromous or catadromous) in its region (Europe and parts of Asia).
Such lengths are rare and unproven during the last century, but there is a somewhat credible report from the 19th century of a wels catfish of this size.
Brehms Tierleben cites Heckl's and Kner's old reports from the Danube about specimens 3 m (9.8 ft) long and 200–250 kg (440–550 lb) in weight, and Vogt's 1894 report of a specimen caught in Lake Biel which was 2.2 m (7 ft 3 in) long and weighed 68 kg (150 lb).
In 1856, K. T. Kessler wrote about specimens from the Dnieper River which were over 5 m (16 ft) long and weighed up to 400 kg (880 lb). (
According to the Hungarian naturalist Ottó Hermann [1835-1914], catfish of 300–400 kilograms were also caught in Hungary in the old centuries from the Tisza river.)

Most adult wels catfish are about 1.3–1.6 m (4 ft 3 in–5 ft 3 in) long; fish longer than 2 m (6 ft 7 in) are a rarity.
At 1.5 m (4 ft 11 in) they can weigh 15–20 kg (33–44 lb) and at 2.2 m (7 ft 3 in) they can weigh 65 kg (143 lb).

Only under exceptionally good living circumstances can the wels catfish reach lengths of more than 2 m (6 ft 7 in), as with the record wels catfish of Kiebingen (near Rottenburg, Germany), which was 2.49 m (8 ft 2 in) long and weighed 89 kg (196 lb).
This giant was surpassed by some even larger specimens from Poland (2,61 m. 109 kg.),
the former Soviet states (the Dnieper River in Ukraine, the Volga River in Russia and the Ili River in Kazakhstan), France, Spain (in the Ebro), Italy (in the Po, where a record 2.78m long wels catfish was caught, and Arno), Serbia (in Gruža Lake, where a 2.4 m (7 ft 10 in) long specimen weighing 117 kg (258 lb) was caught on 21 June 2018.
and catfish with length of 275cm and weight 117kg at Đerdap gorge on Danube River during the same year ), and Greece, where this fish was released a few decades ago.
Greek wels grow well thanks to the mild climate, lack of competition, and good food supply.

Wels have also been observed thriving in the cooling pond of the damaged Chernobyl Nuclear Power Plant.
Although believed by tourists to have mutated into large sizes as a result of radioactive fallout, in reality the fish are growing to such proportions due to the absence of humans, hunting and fishing having been outlawed in the exclusion zone following the accident.

The largest accurate weight was 144 kg (317 lb) for a 2.78 m (9 ft 1 in) long specimen from the Po Delta in Italy.

Exceptionally large specimens are rumored to attack humans in rare instances, a claim investigated by extreme angler Jeremy Wade in an episode of the Animal Planet television series River Monsters following his capture of three fish, two of about 66 kg (145 lb) and one of 74 kg (164 lb), of which two attempted to attack him following their release.
A report in the Austrian newspaper Der Standard on 5 August 2009, mentions a wels catfish dragging a fisherman near Győr, Hungary, under water by his right leg after the man attempted to grab the fish in a hold.
The man barely escaped with his life from the fish, which must have weighed over 100 kg (220 lb), according to him.
With a total length possibly up to 5 m (16 ft) and a maximum weight of over 300 kg (660 lb), the wels catfish is by some margin the largest true freshwater fish (as opposed to anadromous or catadromous) in its region (Europe and parts of Asia). Such lengths are rare and unproven during the last century, but there is a somewhat credible report from the 19th century of a wels catfish of this size. Brehms Tierleben cites Heckl's and Kner's old reports from the Danube about specimens 3 m (9.8 ft) long and 200–250 kg (440–550 lb) in weight, and Vogt's 1894 report of a specimen caught in Lake Biel which was 2.2 m (7 ft 3 in) long and weighed 68 kg (150 lb). In 1856, K. T. Kessler wrote about specimens from the Dnieper River which were over 5 m (16 ft) long and weighed up to 400 kg (880 lb). (According to the Hungarian naturalist Ottó Hermann [1835-1914], catfish of 300–400 kilograms were also caught in Hungary in the old centuries from the Tisza river.) 
Most adult wels catfish are about 1.3–1.6 m (4 ft 3 in–5 ft 3 in) long; fish longer than 2 m (6 ft 7 in) are a rarity. At 1.5 m (4 ft 11 in) they can weigh 15–20 kg (33–44 lb) and at 2.2 m (7 ft 3 in) they can weigh 65 kg (143 lb).
Only under exceptionally good living circumstances can the wels catfish reach lengths of more than 2 m (6 ft 7 in), as with the record wels catfish of Kiebingen (near Rottenburg, Germany), which was 2.49 m (8 ft 2 in) long and weighed 89 kg (196 lb). This giant was surpassed by some even larger specimens from Poland (2,61 m. 109 kg.), the former Soviet states (the Dnieper River in Ukraine, the Volga River in Russia and the Ili River in Kazakhstan), France, Spain (in the Ebro), Italy (in the Po, where a record 2.78m long wels catfish was caught, and Arno), Serbia (in Gruža Lake, where a 2.4 m (7 ft 10 in) long specimen weighing 117 kg (258 lb) was caught on 21 June 2018. and catfish with length of 275cm and weight 117kg at Đerdap gorge on Danube River during the same year ), and Greece, where this fish was released a few decades ago. Greek wels grow well thanks to the mild climate, lack of competition, and good food supply.
Wels have also been observed thriving in the cooling pond of the damaged Chernobyl Nuclear Power Plant. Although believed by tourists to have mutated into large sizes as a result of radioactive fallout, in reality the fish are growing to such proportions due to the absence of humans, hunting and fishing having been outlawed in the exclusion zone following the accident.
The largest accurate weight was 144 kg (317 lb) for a 2.78 m (9 ft 1 in) long specimen from the Po Delta in Italy.
Exceptionally large specimens are rumored to attack humans in rare instances, a claim investigated by extreme angler Jeremy Wade in an episode of the Animal Planet television series River Monsters following his capture of three fish, two of about 66 kg (145 lb) and one of 74 kg (164 lb), of which two attempted to attack him following their release. A report in the Austrian newspaper Der Standard on 5 August 2009, mentions a wels catfish dragging a fisherman near Győr, Hungary, under water by his right leg after the man attempted to grab the fish in a hold. The man barely escaped with his life from the fish, which must have weighed over 100 kg (220 lb), according to him.
Wels catfish