North·FEATURE

N.W.T.'s Husky Lakes trout live, and spawn, in salty water

'I didn't think it was possible,' says Ben Kissinger, a PhD student who spent the past four-years studying the inner earbones of lake trout near Tuktoyaktuk, N.W.T., and found that many of them never leave the brackish water of the Husky Lakes.

'I didn't think it was possible,' says Ben Kissinger, PhD student

Dougie Esagok, president of the Inuvik Hunters and Trappers group, and Ben Kissinger of the University of Manitoba hold lake trout from Inuvik's Husky Lakes. Kissinger's research found that the vast majority of the trout spend their entire lives in the salty water. (submitted by Ben Kissinger)

A PhD student who spent the past four summers studying lake trout near Tuktoyaktuk, N.W.T., has made a surprising find: the vast majority of the trout in the Husky Lakes spend their whole lives in salty water.

"I didn't think it was possible," says Ben Kissinger of the University of Manitoba.

The Husky Lakes are a series of five interconnecting lakes that span about 150 kilometres to the south and southeast of Tuktoyaktuk. The lakes are fed by both freshwater and seawater, and are about half as salty as the ocean.

Though trout have been found in salt water before, they tend to return to freshwater to spawn. That's what Kissinger expected to find in the trout that he examined.

"But the vast majority of lake trout — 86 per cent of the samples that I analysed — actually spent their entire life within Husky Lakes, meaning that they spawned, hatched and actually had an established population in the brackish water for multiple generations."

Reading the inner earbone

The finding wouldn't have been possible if not for a unique feature in the inner earbones of fish.

"Similar to a tree, it lays down rings annually of calcium carbonate as it grows. From that you can tell how old the fish are because in the winter months, growth is slow and it creates a dark band."

The rings also contain trace elements, including strontium, which can be measured to find out whether the fish have spent time in fresh or brackish water.

"We take a laser, start in the middle of the otolith, burn a line to the outer edge, and from that we can get a chronology of the fish's entire life."

No surprise to locals

That trout live year-round in the Husky Lakes was no surprise to locals. The lakes have long been used as a source of fur and fish by the Inuvialuit who live in the area. Trout are caught spring, summer and fall.

"For them, it wasn't a huge surprise," said Kissinger. "But for me, I just thought, this is a fairly rare observation."

Lake trout are considered the least saline-tolerant of the salmonides, a group of fish that includes char, salmon, grayling and whitefish, Kissinger said.

"Within this entire family there's only a few species that have been observed to reproduce in brackish water, in select areas."

Those include chum salmon and pink salmon in Alaska and European whitefish in the Baltic Sea.

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