Near the mouth of the Millstone River in Nanaimo. (Jordan Davidson/NanaimoNewsNOW)

By Jordan Davidson

make it rain

Drought conditions draining for spawning mid-Island fish populations

Oct 20, 2022 | 4:14 PM

NANAIMO — Projected rainfall is better late than never for spawning salmon strained by prolonged drought conditions causing low water levels.

Pieter Van Will, Fisheries and Oceans Canada head for the west coast Vancouver Island salmon stock assessment group, said local fish like chinook, pink, and sockeye salmon usually arrive in their spawning streams in late summer or early fall.

“One of the bigger concerns right now is a lot of the chum (salmon) that are on the way, they’re coming through right now, and they are going to be running into problems trying to get into the stream. The pinks and the chinooks that are already in a lot of the systems, those are the ones that are going to be suffering probably the most relative to the chum that hasn’t entered the system yet.”

This year, migrating salmon have to do their journey with less rain helping them up-steam, which also means lower oxygen levels for the fish.

A school of Chinook salmon in the lower Cowichan River patiently waiting for rain to resume migration. (Tim Kulchyski)

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Van Will said while cooler overnight temperatures created more suitable spawning temperatures, getting more rain soon is crucial.

“There’s only so much habitat for them. They’ve been staging in pools where the oxygen levels are starting to drop because there’s no new water coming in to help replenish that.”

As of Oct. 20, zero millimetres of rain has fallen at the Nanaimo Airport according to Environment Canada, with September being the fourth warmest month and 15th driest on record.

This causes those fish to spawn in smaller areas with less oxygen and spawn their eggs on top of each other, which reduces their viability, according to Van Will.

When rain is scarce, there are a few man-made solutions to help fish on their spawning journey.

Van Will said a lot of water systems, like the Cowichan, Nanaimo and Puntledge rivers are flow controlled and have water use plans that require a minimum flow level required for fish during this important spawning time.

“The various governments work together with the various companies or groups that are running those facilities to ensure that that is met, so if they have to release more water they can, or if they are at a point where they can’t release any more water, they have to work together in order to ensure if they are reducing flows they can get it to a level that’s still reasonable to ensure that as much of the water area those fish are utilizing is there.”

He said areas that don’t have flow-control systems will likely suffer the most from the warm and dry conditions.

Water restrictions have been put in place all along the island, which does help those fish-bearing systems.

However, mass fish mortality incidents have already been recorded this year.

“We are starting to see some pre-spawn mortality occurring, mainly due to those fish that have been holding in those systems for an extremely long time, waiting for that chance to spawn,” said Van Will. “That is a problem and it’s probably going to continue until we get a bit more rain.”

He said the extended and wet spring season helped with the adult fish returning to their spawning grounds, but it was hard to determine in what number due to the rushing water making it difficult to conduct an accurate count.

Chinook migrating through the Cowichan River counting fence during low water conditions. This project has been conducted annually since 1988 in cooperation with Cowichan Tribes and DFO. (Fisheries and Oceans Canada)

“Fish are pretty resilient up until a point… If we get that rain and keep it coming, I think it’ll be a better story. But if that rain doesn’t materialize, then yea, we’re going to be in some big trouble.”

Van Will said without immediate rain, the long-term effects of this year on those fish species could vary.

Some fish species only spawn every couple of years, like the pink salmon whose bi-annual spawning happens to fall on this year.

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jordan@nanaimonewsnow.com

On Twitter: @JordanDHeyNow