The lateral line, visible on the trout is for what? The usual explanation is it allows the fish to sense movement of ‘prey’ in order to avoid risk or find food. It also allows the trout, or other fish with a lateral line, to sense water pressure, which helps the fish know depth, location relative to other fish and objects and maintain their position in a migratory school.
Some studies suggest that a lack of vision (chemically induced in lab) is less important to the fish than a less efficient lateral line. The lateral line is the eyes, ears and remote touch in one placed wedged between beautiful dark olives and silver/white bellies.
It’s all more complicated than I muddled through, but again easy on that fish, when handling…nice and gentle. No squeezing, no holding it ever through/under the kill plate like some goofballs do, and again no dry hands or rough nets.