Fish experts baffled by trout caught with massive lump on head

A fisherman’s catch has baffled experts and social media users alike after he caught a trout with what appears to have a large tumour.

Fisherman Adrian James caught a rainbow trout in Goulburn River, near Thornton in Victoria’s northeast, recently and shared pictures of the fish on Instagram.

The fish, which weighs about 4.5kg, has a large lump behind its head and the fisherman wrote he’s not sure why this is.

Yahoo News Australia contacted a number of experts in fisheries and professional fishers but no one has an answer.

Dr Andrew Chin of James Cook University’s Centre for Sustainable Tropical Fisheries and Aquaculture said he “had no idea” what the lump is.

Andrew James caught this rainbow trout in the Goulburn River in Victoria. No one knows why but it has a large lump on it. Instagram/ adrian_james1

His colleague Professor Dean Jerry added he’s never seen a lump like it before.

But he suggested it could be “some type of cyst” possibly caused by either parasite inflammation or a cancerous growth.

“I wouldn’t know, sorry,” Professor Jerry said.

Professor Culum Brown, who works at Macquarie University’s Department of Biological Sciences, said a biopsy would need to be performed on the fish.

But his “money was on cancer”.

Steph Watts, from Recfishwest in Perth, said after sending it around the office no one could determine what the lump was either.

“No one had seen anything like this before,” she said.

The fish weighs 4.5kg and was a catch and release. Source: Instagram/ adrian_james1

However, she added it is “particularly interesting for a few reasons”.

“First of all, this fish appears it was caught from a wild population, and not an aquaculture facility where some fish are more exposed to infections,” she said.

“Secondly the growth appears in an unlikely area on its back and is not close to organs.”

A biopsy of the fish is unlikely now too as it was a catch and release.

People on Instagram were also in awe of the “strange catch”.

“A rare one lump rainbow camel fish,” one man wrote.

“Nice catch.”

It was also shared on Facebook by TV show iFish.

One man referenced Arnold Schwarzenegger movie Kindergarten Cop.

“It’s not a tuna,” he wrote.

Another man dubbed it the “Hunchback of Trout-in-the-dam”.

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