I'm not trying to come across as a know it all or anything like that...Just my 2 cents...
Consider that late beaver under ice have a good chance of being downgraded pelt wise at auction because the long guard hairs will be singed. Castor and carcass value plus a lesser pelt value make it still worth taking a few for management purposes.
IMO only... I'm not knocking trapping late beaver for management purposes, to earn some cash from the pelts and other valuable parts, I'm just saying that to realize the best grade of beaver pelt and top lot pelts at auction late March is too late to trap top fur. Trapping is about producing quality fur, not just catching fur. This is why their is a fur primeness chart.
I used to catch late under ice and spring beaver and it is a nice time to be out. But that was long before I really understood producing quality fur and the management aspects of trapping an area.
This time of year females will have been bred so if you catch a few females you know will affect a beaver colony's population in spring. An excerpt from the 2007 trapping manual.." A colony usually produces only one litter per year, and that by the dominant pair."
The 2007 trappers manual's write up on beaver is worth the read on management strategies.
http://www.albertatrappers.com/pdf/e...al_109-114.pdf
My logic behind not catching pregnant beavers is also the same reason I don't hunt deer in spring and summer, or hunt birds when they are nesting or fish when fish spawn. Replenishing the species is why fur is considered a renewable resource.
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As far as using a chainsaw to cut holes don't use regular chain oil because it will contaminate the set area and water. biodegradable oil if any. Dry your saw really good after to avoid rusting too. A chainsaw in front of a lodge is very intrusive and might affect the colonies activities for a day or two.
A good ice chisel doesn't need anything except a little gumption. Less chance of accidental injuries with a chisel too, which is important when out on the land. And you can get thru thicker ice with a chisel.