[Brian Curtis]

Yes, gillnets are sometimes set in the fall and left under the ice all winter. The gillnets typically used for high lake work are sunk with a lead line on the bottom and floats on top so they don't need to be vertical.

[Pyrites]

Does this get the bottom of the net below distinct thermocline common on iced over lakes?

[Brian Curtis]

To answer your question in the general sense, they can put gillnets wherever they want in a lake. They just need a line with a float long enough to be able to retrieve the net. But more specifically, there won't be a thermocline under the ice in winter. I suspect that you are referring to the fact that the warmest water will be at the bottom during winter so you might expect fish to be in the deepest part of the lake? They mostly won't be using gillnets on big, deep lakes where this is likely to make a difference. Gillnets are only an effective fish removal tool in smaller, shallower lakes. That being said, they do have one reasonably large, deep lake in their plan. The largest Golden Lake is over 18 acres and almost 80 feet deep. It will be interesting to see how they approach that one. It seems likely that gillnets will not do the job. The next deepest are 40', 30', 16', and shallower from there.

[Pyrites]

When we ice fish at Priest Lake there’s always someone who has a Fishfinder. The kokanee are concentrated at one depth, typically about 21’. They will be most dense at that depth, with a few fish wandering down a couple feet. No fish at all will be above that line. The generally accepted line is this is a themocline. Feed? Oxygen? No idea. There are a few trout. People seem to think they are wandering from max line to bottom. Yes, freshwater is most dense at 4 degrees, so bottom of lake is warmer than surface. There’s no limnologists on the lake so maybe accepted wisdom is wrong. Ice is quite different than a lake at Rainier. Safe to be on from 8-12 weeks, to not all for me. And snow is not present to a foot deep commonly. Yes, I am a Puget Sounder who owns an ice auger. Those miniature sockeyes taste good. Best. Pyrites

[Brian Curtis]

It has been the better part of 40 years since I took a limnology class so I don't know much, either. But from what I can recall thermoclines are generally summer phenomena. I assume that quite a bit is known about Priest Lake's limnology and, indeed, a quick google search turns this up: "Thermal stratification generally occurs mid-July through the end of October, with a thermocline at a depth of about 35–50 m...". Here is an interesting study of kokanee behavior during the winter in Stanley Lake that might help explain what you are seeing in Priest Lake.

[Pyrites]

Thanks. I’ll read the winter article tomorrow. They do talk about lakes turning over caused by that weirdness of water, that it’s most dense several degrees from freezing. I suppose that given that Priest had to be saved by the Corps when it drained that there are studies. For those not familiar it has thin layer of clay over the top of the Rathdrum Prairie aquifer gravels. In the late 19th or early 20th century piling were driven as part of using the lake as a mill pond. When the piling disappeared the lake drained quite a few feet. It’s not especially deep to start with. Best. Pyrites

[Pyrites]

As I was on the interest list I rec’d and email from T. Tucker with MRNP. It said the website had been updated to current regulations. In theory prior to this you’d have had to refer to the Code of Federal Regulations to be current! Only a Vogan would have enforced regs under those conditions.

[Brian Curtis]

I had to google Vogan. I'll leave it at that. (FWIW, they did have fishing regulations posted on their website prior to this so, fortunately, I don't think they needed any Vogans.)