It’s another 90 degree day in Mount Shasta – a good 5-6 degrees warmer than “normal.”

In fact, it’s been far warmer than “average” the last couple weeks, and while the heat feels good – especially after winter decided it was never going to leave – I am starting to wonder at the effects of sustained high temperatures on the trout.

Thunderclouds

The leading edge of last night's thunderstorm... which missed us to the North (damn).

For example, the water temps on the Upper Sacramento River (at the Delta – the warmest stretch) have oscillated between 65 and 70 degrees.

Trout tend to stop feeding at water temperatures much above 65 degrees (I’ve seen 68 degrees listed as the magic number), and 75 degree water is typically fatal to trout, who simply won’t get enough dissolved oxygen to breathe.

Note that I’m not advocating anglers avoid the Upper Sacramento River; the Upper Sacramento and Lower McCloud are essentially tailwaters, so temperatures on the upper/middle stretches of both will remain nicely fishable year-round.

But what happens to the lower stretches of the Upper Sacramento – or my beloved small streams – if our current heat wave continues?

Upper Sacramento River Water Temperatures

With temperatures swinging between 65-70 degrees, I don't know if I'd fish the lowest stretch of the Upper Sacramento River (click image for latest flow/temp info)

I’m not sure, though I’m taking a water thermometer on my next small stream trip.

I’ll probably discover temperatures are plenty low on the nearby small streams, which are running slightly higher than normal.

Still, if the current heat wave continues, things could get a little grim come mid-August. Will we come to the point on some waters where the Undergrounders stop fly fishing voluntarily?

Or should California Fish & Game follow Montana’s lead and institute water-temperature-based closures?

Local fly fishing guide Craig Nielsen offers a surprising (to me) admission:

“I already closed my season on the Klamath River. In fact, when fishing for rainbow trout, I tend to stop fishing stretches of water when the temperature goes over 65 degrees. You get temperatures in the higher 60s, and the mortality goes way up.”

Note that legislating closures would be difficult on waters like the Upper Sacramento, where temperatures vary widely over the length of the river. Close just the bottom five miles?

Unlikely.

Thoughts from the Undergrounders?

See you tapping the thermometer, Tom Chandler

Posted in Environment, mccloud river, Upper Sacramento and tagged , , , .