You don't need a consultant, you need a trapper. Shucks otter season just ended here Mar 15. Your season probably just ended also. You could have easily got a trapper to trap your otters for free because believe it or not, their fur is worth over $100 a pop.
Careful, otters are a federally protected species. Lawfully you can only trap them, you can not shoot them.
Now the season is over (its only a winter season), you can possibly get a nuisance trapper to come and do it, but he will want to charge maybe $100 each to trap them. You may very well have more than one. They almost always travel in pairs or even groups. Bad news for your pond.
Otters can take anything they want out of a pond. Well, other than alligators.
I have trapped lots of otters and I am hunting/fishing all the time, but have very rarely seen one in the wild except in my traps. They mostly move at night.
I would say getting otters out is of the utmost importance.
Here I am relocating otters.
I have some very good pics of deadly otter sets I use. They are easy to trap. I can also walk you through trapping them.