Live Crab Decoys as Luring Method for the Pot Fishery of the Invasive Crab Charybdis japonica

摘要

The effectiveness of using live crab decoys for capturing the invasive shore swimming crab Charybdis japonica was tested during fishing trials. Live male or female crab decoys were placed in pots and their performances were compared to those offish bait and no bait. Pots were set in a pond from 22 July to 27 August 2002. They were divided into 4 treatments: fish bait, male decoy crab, female decoy crab and no bait. They were subjected to two different soaking times: 1 or 4 days. Catches were recordedaccording to treatment, species and size. When the soaking time was 1 day fish bait was most effective at luring crabs into pots (0.33 crabs pot~(-1)), while when the soaking time was 4 days female decoys were most effective (0.50 crabs pot~(-1)). Non-target catch was affected by treatment and was highest in fish baited pots, consisting mainly of snails, moray eels and rockfish; but octopus was common in pots containing crab decoys. A modified pot with a protective chamber containing a female decoy wastested during fishing trials in a commercial fishing ground together with fish baited and non-baited pots from 10-14 July 2006. The chamber prevented both decoy escape and octopus predation. Decoy containing pots caught 0.31 crabs pot~(-1) versus 0.25 in fish baited pots and the non-target catch was greatly reduced to 1.23 organisms pot~(-1) compared to 4.95 in baited pots. We conclude that female decoy crabs might be used to attract C. japonica conspecifics into pots and might be applied to remove crabs more selectively than using conventional fish bait.