Tentacle-breakage mechanism for the neon flying squid Ommastrephes bartramii during the jigging capture process

In squid jigging operations for neon flying squid (Ommastrephes bartramii), 30–40% of hooked squid are estimated to fall off (i.e., become detached) from the jigs during the drum-hauling process, caused by breakage/severance of the hooked tentacle(s). Reducing fall-off events can lead to higher productivity and more efficient use of the squid resource. In the present study, there were 950 fall-off events either directly observed or assessed from the residue of tentacle(s) left on the jigs compared with the 1720 total captures, which comprises 35.6% of 2670 total hooked squids. The fall-off ratio according to the mantle length (ML) was examined using logistic curve analysis and a higher fall-off ratio for smaller squid was confirmed through size selectivity curve analysis. F50, the 50% probability of fall off from the jig, was estimated to be 37.4cm ML. The breaking strength of a single tentacle was determined to be similar to the body weight (BW) of squid smaller than 41.4cm ML, indicating a high possibility of tentacle breakage in the case of 1 tentacle grabbing the jig for smaller-sized squid.