Nets, used to scoop up fish out of the water (landing nets), and nets used to hold fish at the angler’s pleasure (keep nets), harm fins, gills, scales, mucus covering, and can lead to death.
The University of Maryland found (Reiss, 2003) that nets harm fins, gills, scales and the protective mucus on the skin. Fish were also out of the water for longer, as hooks often catch on nets.
American and Canadian scientists (Cooke, 2000) discovered that fish are harmed in keep nets. Some fish die from their injuries straight away, others later.
Further research (Barthel, 2003) found a 14% death rate for landing nets. Fish swam erratically before dying. Most deaths were after 2 to 4 days after being caught. Fish landed by hand had lower injury rates and none of them died. The most lethal of the nets were knotted mesh. All nets caused extreme fin erosion. They also rub off the protective mucous layer from the skin, allowing fungal infections to take hold. The study found fungal lesions across 5 to 15% of the body of the fish, before they died.