In your opinion, what qualifies (or omits) a small culvert for a mink set along your trapline? What makes a small culvert a good spot for a mink set? Or what makes them a poor choice?

If it is a nice little continuous stream flow not prone to drying up….set it…

Like Les said, if it has water and I'm driving by or over it anyway I'm setting it.

Definitely needs steady water flowing through it.

What would be wrong with it if it doesnt have water flowing through it all the time?

Nothing! It’s a scientifically proven fact (Mink Habitat Suitability Indexing Study) that “mink” waterways do need to have water at least 9 months of any given year to be considered mink/prey habitat. Think about WHY a mink is using the waterway to begin with, heck they can run anywhere but why would they choose the waterway that has the culvert, no water for a month, still water, or water with some sort of current, it’s all about prey! Damp, wet, or flowing, is the mink’s prey still available in the waterway that contains the culvert???

Hopefully my competition this mink season will drive right on by those culverts because there’s only room for one and that’s me! LOL

I have taken both mink and otter miles from water. Yes, they spend the bulk of their time around water, but they also will go overland, and from one waterway or impoundment to another.
If you see sign in a dry culvert, set it.

sometimes dry culverts have good set locations under the downstream end of the culvert.

I can't remember how many mink i've taken on dry trails along a dry ditch. Quite a few with a mouse still in their mouth. Whether there's water or not, there's still alot of prey along the cricks. I'd prefer they had water but i won't pass up a dry one for sure.

True story about mink on dry trails…. Feel everything wants to eat that mink that didn’t get tucked underwater…

Same here Blee. Never had much of a problem with them not being underwater.

I check any old culverts of all sizes for mink sign.
Mink here for some reason make a toilet on top of the ends of culverts.
You can easily tell which ones to set by the different ages of turds on the top of the culvert.
Also look for a dryland crossover trail in the dry grass if you are trapping in the fall.
Otters often use a dryland crossover beside a culvert
I have baited boxes dug into the bank at active mink culverts that produce mink year after year including in winter long after freeze up.Before freeze up these sets will also produce some rats especially if you use half a rat carcass for bait.
After freeze up but before the snow gets deep these locations produce ermine,fairly regularly and the odd otter and even the odd fox.
If setting boxes in these locations and leaving them in place make sure to stake the box good so it doesnt float away in the spring freshet.