1Tochigi Prefectural Fisheries Experiment Station, Nasu, Tochigi 324-0404, 2Freshwater Fisheries Research Division, National Research Institute of Fisheries Science, Fisheries Research Agency, Nikko, Tochigi 321-1661, 3Department of Aquatic Biosciences, 4Department of Marine Environmental Sciences, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
The destiny of hooks remaining in the body of hatchery-reared smaller (<15 cm in total length) and larger (≥15 cm) sized Japanese charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou masou after catch and release by bait and fly fishing using barbed hooks were examined in experiment ponds. When the hooks that lodged in the mouth remained, the rejection rate of the hooks within 21 days after catch and release was relatively high (70.0-100%) for each species, size and fishing method. In the bait fishing, when the hooks that lodged in the esophagus remained, the rejection rate of the hooks from the body was low (0-16.7% within 21 days and 15.0-50.0% within 81 days after release). Many hooks (41.2-75.0%) that lodged in the esophagus were rusted within 81 days, but few hooks were broken. Fish that have hooks in the esophagus are dangerous as food for not only humans but also other wild animals such as birds that eat fish. Anglers should take away the fish when the hook has lodged in the fish's esophagus. Also, anglers ought to use hooks that rust quickly, such as hooks without rust-proof coating.