Rains will trigger delayed salmon spawning in many B.C. rivers

0

Salmon that have been waiting at the mouths of many rivers will begin their journey upstream with this week’s change in weather.

Rain bringing relief to the parched south coast from this weekend will also trigger a delayed start to the annual spawning salmon migration on many waterways.

Fortunately, the fish are surprisingly resilient, say local stream keepers and biologists who work with fisheries.

“There’s some flexibility in terms of when spawning occurs,” said Chuck Parken, area chief of stock assessment for the Fraser and Interior region at the Department of Fisheries and Oceans.

“Coho salmon can delay their spawning activity until late January, early February,” he said.

In many cases, if the creeks are too dry, “they will just sit in the ocean” and wait for the rains to arrive, Parken said. In other cases, fish spawn lower in the river system.

But the prolonged drought has also stressed many salmon migrations more than usual, said Shawn Hollingsworth, president of the Seymour Salmonid Society.

It’s something to keep in mind as the rivers begin to fill with fish again, he said. “We should be aware of allowing our dogs to go into streams,” for example, he said.

Chinook salmon tend to spawn on larger river systems like Capilano, Squamish, Harrison and Chilliwack, Parken said. On the Capilano and Seymour rivers, DFO requires Metro Vancouver to release minimum amounts of water into the river from upstream dams during dry spells. The salmon are already in the rivers, Parkyn said.

Hatcheries operate on the Seymour and Capilano rivers. A fish ladder works on the Capilano.

On the Seymour, volunteers from the Salmonid Society and Metro Vancouver have also successfully reintroduced wild runs of coho and rainbow trout to the river. They also worked to reopen the river and create new channels for salmon spawning after a huge rock slide in 2014 nearly ended the river’s viability as a fish habitat.

This summer, volunteers caught salmon in the mouth of the Seymour and in the estuary near Maplewood Flats with a beach seine and moved them upstream for spawning, Hollingsworth said.

Chum and coho tend to spawn in smaller streams, where it’s been very dry, Parken said.

These salmon will have waited at the mouths of streams for the coming rains, he said.

Surprisingly, the salmon can wait for the rains for several months.

In drier years, “they also spawn lower in the river system.” In some cases, the salmon will even divert to a nearby creek if dry conditions persist until late November.

Luckily, November is just the start of the usual chum salmon run, Parken said.

When the rains will raise the level of the river, starting this week, “we will see a lot of fish,” he said.

However, some other salmon runs face more difficulties.

A sockeye run on Weaver Creek in the Harrison-Agassiz area depends on a spawning channel and currently water levels there are very low. “Hopefully they get some rain in that area,” Parkyn said.

Other runs – such as Adams’ sockeye run on the Fraser River – have also been delayed as salmon wait for temperatures to cool on the river’s spawning grounds.

Juvenile salmon in small creeks can also be stressed by prolonged drought, Parken said, because young salmon are likely hatching under less than optimal feeding conditions.

In many small streams especially, “it can get very difficult for them,” he said.

Share.

Comments are closed.