Marine & Environmental Sciences Faculty Reports

Document Type

Report

Publication Date

2007

Keywords

Pelagic longline, By-catch, Circle hooks, Survival, Discard mortality

Abstract

Preliminary studies in western North Atlantic pelagic longline fisheries indicate that a change in terminal gear from J-style hooks to circle hooks may reduce bycatch mortality. However, such studies have not examined the impact of this change in the equatorial fishery. Catch composition, catch rates, hooking location, and condition at haulback were monitored during 26 sets in the commercial longline fishery operating in the western equatorial South Atlantic where circle (size 18/0, non-offset) and J-style (size 9/0 and 10/0, 10° offset) hooks were deployed in an alternating fashion. Catch rates for yellowfin tuna, swordfish, and a composite “all fishes” category were significantly (P < 0.05) higher for circle hooks. Bigeye tuna, swordfish, sailfish, and yellowfin tuna were hooked significantly more often externally than internally. Yellowfin tuna were over eight times more likely to be hooked in the mouth with circle hooks than with J-style hooks. Bigeye tuna and sailfish showed significantly higher rates of survival at haulback with circle hooks. The results suggest that the use of size 18/0 non-offset circle hooks in the equatorial pelagic longline fishery may increase the survival of bycatch species at haulback with minimal detrimental effects on the catches of target species.

Report Number

SCRS/2006/150

Publication Title

Collective Volume of Scientific Papers – International Commission for the Conservation of Atlantic Tunas (ICCAT)

Volume

60

Issue No.

6

Additional Comments

The work described herein was conducted with financial assistance from the NMFS Southeast Fisheries Science Center (USA) and the Secretaria Especial de Aqüicultura e Pesca, da Presidência da República (Brazil).

ORCID ID

I-5396-2012

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