Marine & Environmental Sciences Faculty Reports


Preliminary Gear Comparison between 16/0 and 18/0 Sizes Non-Offset Circle Hooks in the Southeastern U.S. Coastal Pelagic Longline Directed Swordfish Fishery

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Twenty-nine voluntary directed swordfish (Xiphias gladius) pelagic longline sets were conducted in the Windward Passage (n=4) and the southern Gulf of Mexico (n=25) during February-April 2004 aboard the F/V Carol Ann, a U.S.-registered commercial pelagic longline vessel. The goal of this project was to assess differences in catch rate and hooking location between size 16/0 and 18/0 non-offset circle hooks baited with dead squid (Illex sp.) or mackerel (Scomber scomber). Protocols were similar to those developed by Dr. John Watson et al. of the NOAA Fisheries SEFSC-Pascagoula Laboratory for work with pelagic longline vessels in the northern Gulf of Mexico targeting tuna, although modified for the southern Gulf directed swordfish fishery.
Catch rates of the size 18/0 circle hooks were lower, but non-significant, in both locations than those of 16/0 hooks when using squid bait, although higher, but also non-significant, catch rates were noted with sets testing these hook combinations with mackerel. Trends in catches suggest that the non-significance of the results may reflect the low statistical power resulting from small sample sizes rather than a lack of relationship. Combined swordfish mortality at haulback for both hook types was relatively low, possibly a consequence of the fact that 51.2% of these swordfish were hooked in the corner of the mouth. Mortality rates at haulback also varied by species and fishing location.

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No. 2004-7

Publication Title

VIMS Marine Resource Report