Otter Boards aren't illegal in Scotland in Fresh water for trout. It all comes down to the land owner and having permission to do so. If one considers the method, the "potential" for catching etc, ask your self: if you had a good loch holding good fish, would you give permission to someone wishing to fish with that method? I wouldn't (**See below).
Then there's the law in scotland to consider. It isn't a criminal offense to fish for trout in fresh water, provided there's no sea trout or salmon, the water hasn't been stocked, that there's no preservation order on the system "PO" and provided there are no illegal methods used, set lines (bait out and the line fixed, that could be a rod and line set in the same way a course fisher would, the rod/line has to be in the hand not to be considered fixed), netting etc.
So, not a criminal offense, rather it is a civil offense, and only if the land owner takes umbrage and decides to pursue it. Unlikely if the felon is simply using a rod in my experience, but get caught using questionable methods and I'd include Otter Boarding in that and the Police would likely get involved, because the greater the catching potential (measured in the number of hooks rather than actual fish) the more likely it is that the prep is at some sort commercial poaching, that is criminal and it would be up to the prep to prove otherwise, in court, thus making it easy and low cost for the owner
As a method,
in the right hands with the right amount of breeze and technique it enables the covering of a lot of water with a lot of baits, usually wet flies. So from that perspective on the face of it it seems a good method, right! Nah, wrong; it's a total faff and rather hit or miss
90% of the time it's a miss even for those that are good at it, because of the way it fishes. It fishes wet flies just sub-surface and the simple truth is that the fish are only there at certain times and even when they are they're usually after specific stuff. As Torjus states above, high summer is the most viable time as thats when the fish tend to be in the surface film.
Then there's the landing of fish that get hooked, a lot of fish get off on the retrieve.
For me there are far more viable and effective methods for fishing. Years back I was fishing a loch with a pal when two brothers arrived and put the board out. At the end of the day, they had banked around 20 trout for their efforts, we'd had around 40 between us using rod and reel, most of which we put back keeping only the best eaters.
It's not even a particularly viable method for survival situations, weight, quantity of material and the potential for the loss of the business end and all ones hooks etc make it an "all the eggs in one basket" method in that situation.
That said a slimmed down related method is the good old "bubble and fly" technique. The recipe for which is;
Spinning rod in the 5g to 25g cast weight class
Spinning reel with 6lb line (any lighter and one risks breaking it, any heavier and it's a pig to cast any distance)
Bubble float (1" to 2", 1.5" being best with 6lb line) tied to the end of the line and half filled with water
2, 3, or 4 flies depending on the length of the rod (different wet patterns bushiest nearest to the rod tip) tied to droppers of around 6" at 2' intervals up line from the bubble. So, typically an 8' rod would comfortably carry and cast the bubble and three flies.
Method
Only works in a breeze (the windier the better, bigger the wave the bigger and bushier the flies the faster the retrieve).
Cast into the wind, directly into the wind is best, but still viable across provided there's a bit of up wind in it.
The retrieve is quick but shouldn't be too much faster than the incoming wave, keeping the tip low until the line is almost ashore, raising the tip of the rod to dance the big bushy fly closest to the rod tip on and off the surface. Varying the retrieval speed until one finds the speed mojo, most people are surprised by just how fast one has to reel to induce a take, usually a lot faster than people think.
Variation (for fishing deeper, works in the sea also)
Replace the bubble with a 20g Toby, one really has to keep things moving to avoid snagging the bottom, but it can work well if you need to get deeper. In the sea spinning this way I've had sea trout pollock mackerel etc, sometimes on the tobby sometimes on the flies, bigger flies in the sea.
If the fish aren't taking?
Take off the flies add a bit of line to the end of the bubble tie on a hook and add bait, worm works best but if things are flat calm and fish taking on the surface a dry fly works too.
Or remove completely and tie on a spinner, mepps or small tobbys'.
I almost only ever fish with a fly rod these days as thats what floats my boat, but if I could only take one rod, it would be a 8' or 9' spinning rod as described above. With that I can fish in still or moving water but other than spinning and trotting the methods below are still water game fishing techniques;
Worm on the surface
Worm on the bottom (or just off the bottom etc)
Bubble and wet fly
Bubble and dry fly (set up like bubble and worm and left sitting until the fly becomes water logged)
Tobby and wet fly
Spinning
Trotting worms (in moving water works either on the bottom with or without weight or floated with a bubble float)
An Otter Board won't come close to covering that lot
**My objection to the Otter Board method is that it's not very environmentally friendly. The potential for snagging and losing lots of mono in lake/loch and thereby snagging and drowning the wildlife is too much of a risk due to the amount of line that one can have out, think diving birds and that mono will keep killing stuff until it's removed.
Same thing applies to all fishing, so be sure remove your scrap line and take it home with you
