"I've been fishing up there for 40 years but never seen a salmon let alone catch one," Mr Pritchard said.
"And she got two and nearly a third. She's mad on fishing and she's a natural angler - her father taught her to fish back in Thailand."
When Mr Kemsley became aware of the catch his, along with Mr Winlove's, his first reaction was that the fish were actually brown trout, as those that ran out to sea and then returned to eventually spawn often took on a silvery appearance similar to salmon.
"It's a mystery how they got here," Mr Kemsley said.
One scenario was they escaped from a salmon farm, although that meant they would have had to make their way up along the eastern coastline from Marlborough, before heading upriver.
The other scenario was they could be salmon "three or four" generations down the line since salmon were released into the Mohaka more than 10 years ago.
That release had not been a success however, with only one small salmon found at the release point three years later.
One was also caught in that region eight years ago but since then nothing.
"They can switch rivers easily," Mr Kemsley said, adding that when they went out to sea they did not always return to the river they came from.
The fact three had caught in the same general area of the Ngaruroro, and that they were in "magnificent" condition, was an exciting development, he said.
"There possibly could be a number of them there - we just don't know, but it could be the start of something."
For Neeracha Pritchard, who hooked the estimated 4kg salmon, it was a great day out, and she and her husband Martin were able to carry out the ultimate identification process later.
Mr Pritchard said it looked like a salmon, smelled like a salmon and very much tasted like a salmon.
"Very nice."
Mr Winlove said it was impossible to know how many may be there, but doubted the river was "awash" with them.
"But we just don't know."
He said Fish and Game were keen to hear from anyone who hooks a salmon in the Bay's rivers, and asked they take photos and provide them with the head for bone identification.