Sea animals such as sea lions, earless seals, and fur seals lived in the cold current and were abundant; the tool to catch them, a harpoon with a detachable screw-head, was developed.
トド、アザラシ、オットセイという寒流系の海獣が豊富であり、それらを捕獲する為の回転式離頭銛が発達した。