What causes lice on fish?

[AJ's Dad]

We had a good day ice fishing at Curlew lake last weekend catching mainly trout. It seems we may have been a little deep for the perch as we only caught one. For the most part the trout we caught were healthy beautiful fish but a few of them had lice on them. One was covered in them. It's was kind of eire looking and I got a little apprehensive even touching the fish to unhook and release it. Any ideas on what causes this to happen?

[hewesfisher]

They're copepods and nothing to worry about. Usually caused from stress of changing water temperature. See it most frequently in spring, especially if water temps rise quickly.

[AJ's Dad]

Thanks for the reply. They sure were ugly little critters. Kind of looked like instant rice stuck on the fish

[hewesfisher]

They are ugly and although I wouldn't hesitate to retain a rainbow with a few, I would release any with a heavy infestation simply because that fish would be heavily stressed and unlikely to be good table fare.