The Environment Agency in Britain warns of the danger of the introduction of alien fish by anglers:
"Our National Fisheries Laboratory has found species of parasite that are new to the UK on fish examined during routine health checks. These were probably imported on fish from the European mainland."
"These parasites can have a devastating effect. For example, the parasitic fluke Gyrodactylus salaris wiped out salmon from several Norwegian rivers after it was accidentally introduced to that country. This had a huge impact on angling and tourism."
"The important message is: introducing fish can spread diseases and parasites, and can have unforeseen and irreversible effects on fisheries through predation, competition or habitat damage."
NETS AND ANGLERS' BOOTS INTRODUCE PARASITES, DISEASES,
AND INVASIVE PLANTS
"Parasites and diseases, such as crayfish plague and spring viraemia of carp, the seeds of undesirable exotic plants, such as giant hogweed and Himalayan balsam, and root-fragments of the invasive Japanese knotweed can all be carried on wet nets and boots."