I am going to put my cards straight on the table. I hate drones, I consider them annoying oversized mosquitoes that buzz around overhead ruining the tranquillity of an area. Sure, they produce some spectacular video footage, but that does not make them any less annoying.
Drones are more than just video devices, they can also be used for surveillance. When water conditions are clear enough, It is possible to fly a drone up river to scout out deep holes and ripples to try and locate groups of trout.
What might take several hours to scout on foot, can be covered in only a few minutes from above. This technique can be used to find the location of migrating fish, and even find the location of the bigger than average fish. From a purely sporting perspective, it simply feels like cheating. In clear water conditions, it allows anglers to head straight to where the fish are.
I have also seen them used at river mouths, by flying their drone out over the lake. They can see if there are trout or salmon massing to enter the river. They can also tell exactly where the trout are holding. Care must still be taken, fly to low and they risk spooking fish.
There is also the topic of legality. I am not going to go into details, but in some areas, the use of drones (especially flying ones) are banned or heavily restricted so it always pays to check local regulations before taking to the air.
Just how useful are drones?
In clear, calm conditions they can provide a birds eye view. If the water is cloudy or ripply then its usefulness is greatly reduced. I personally do not see them as a game changers, but when the right conditions present themselves they can help anglers know in advance where the fish are holding.
My local fisheries also have used them to survey and count the number of fish at spawning sites. In that regards, they act as a cheaper alternative to helicopters.
Even when the water is clear, the operator needs to know what they are doing. I once watched a newly brought drone turn into a submarine as it plunged straight into a weed infested pond. Apparently, there are water resistant drones that float meaning they have a better chance of surviving a splash landing.
Is it possible to troll behind a drone?
Maybe, and no. I would advise against doing it. I was once fishing at a small lake, and a few guys thought it would be fun to troll a lure behind their remote control boat. Everything went well for the first 10 minutes, until the inevitable happened and the lure caught the bottom and the boat become stranded until it was rescued by someone in a dinghy.
Trolling behind a flying drone is just a crash waiting to happen, and even if you were lucky enough to hook a fish, I doubt most consumer drones will be powerful enough to drag it back to shore.