Officials are scaling back the test fishery on the Fraser River to conserve dwindling salmon numbers, following earlier closures of the commercial, sport and First Nations fisheries.

"We're cutting back the test fishery to about half," said Mike Lapointe, chief biologist with the Pacific Salmon Commission, referring to the system used to assess the health of the returning run.

This year's prized sockeye in the Fraser are the offspring of those in 2009, the year marked by a collapse of Fraser River fisheries. The sockeye return to spawn in a four-year cycle.

"For the fisheries that are operating, we're going to move to a mode that we call non-retention. In other words, all sockeye will be released. We'll be keeping a small sample for genetic analysis to tell us which stream these fish are headed to," Lapointe said.

"We're trying to reduce our impact in terms of the assessment needs on these fish, so we can maximize their prospects for having a good number on the spawning grounds," he added.

Lapointe says warm river temperatures are also hurting the returning sockeye, increasing their risk of cardiac arrest and disease.

The number of fish returning to spawn in 2009 was so low, all fisheries on the Fraser collapsed, which led to a federal inquiry. Dubbed the Cohen Commission, the probe failed to find exactly what caused the decline.

The next few years saw fish numbers recover, but this year brings another blow.

With files from the CBC’s Luke Brocki