You bet. First of all, it is an enormous concern for commercial fishermen. Lights were banned from commercial fishing in British Columbia some decades ago because they were known to attract everything. Herring fishermen used them to get herring, but they were also catching octopus and other species of fish.
The lights cause lice to reproduce more rapidly because they think it is summer. They also attract plankton. When I do plankton tows near fish farms with lights, I get far more plankton organisms than I do against the farms with no lights. They also attract fish.
There is a growing concern with the number of wild fish in these pens, and I actually laid a charge against Marine Harvest for having wild pink salmon in the pens. The lights are partly responsible for attracting the fish, so they're a very serious problem. Of course, this is a problem that's easily dealt with because they could just turn the lights off.