We performed a quantitative review to evaluate circle hook use in recreational and commercial hook-and-line fisheries that interact with billfishes (Family: Istiophoridae). Specifically, we scrutinized the findings of 11 recent empirical studies that reported, on a species-specific basis, side-by-side measures of circle vs. J-hook fishing performance: catch, mortality, deep-hooking and bleeding rates. Of the 30 total comparisons extracted from the literature that satisfied our inclusion criteria, 13 indicated significant differences between hook types for the specific metric compared. No study reported significant billfish catch rate differences between hook types. However, when significant differences between hook types were found, higher mortality rates and higher rates of deep-hooking and bleeding were associated with J-hooks relative to circle hooks. We conclude that empirical evidence is sufficient to promote circle hook use in almost all hook-and-line fishery sectors that typically interact with istiophorids. However, billfish conservation benefits will only be realized if fishers use unmodified circle hooks, commit to releasing live fish and take other appropriate measures which maximize post-release survival. While there may be fishing modes where circle hook effects are negative, for billfish conservation, we recommend managers grant exceptions to circle hook use only when experimental results support such a practice.

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The first recorded incidence of dicephalia in a bull shark Carcharhinus leucas is reported from a foetus collected by a fisherman in the Gulf of Mexico near Florida, U.S.A. External examination, Radiography and magnetic resonance imaging revealed a case of monosomic dicephalia where the axial skeleton and internal organs were found to divide into parallel systems anterior to the pectoral girdle resulting in two well-developed heads.

Management and conservation of many highly migratory fish species are based on population assessments that rely heavily on catch and effort data from the pelagic longline fishing industry. In 2003, we monitored hook time at depth for shallow-set commercial longlines (i.e., four hooks between surface buoys) targeting swordfish Xiphias gladius in the Windward Passage between Haiti and Cuba. We deployed temperature-depth recorders (TDRs) on about every 13th hook and attached them to branchlines just above the hook. Most TDRs were placed on branchlines that were predicted by catenary geometry to be at the deepest hook position between floats. Additional TDRs were also placed at the shallowest predicted hook position. We monitored 10 pelagic longline sets with a length (mean 6 SE) of 44.9 6 2.0 km. Time at depth for each TDR was binned into 5-m depth intervals. The expected bimodal distributions of hook time at depth were not observed; modes were 40 m for both the shallowest and deepest predicted hook positions. The majority of the hook depth distributions for shallow and deep hook positions achieved only 43% and 31%, respectively, of the depths predicted by catenary equations (i.e., ,92 and ,127 m). Individual TDRs were poor estimators of hook time at depth for other TDRs in the same catenary hook position during the same set (significant mean depth differences ¼ 76.2-100%) and were even worse predictors of the depths fished during other sets (significant mean depth differences ¼ 100%). Hook depth predictions based on catenary geometry drastically overestimated actual fishing depth in this study. These results indicate that the use of catenary geometry for estimating hook depth and subsequent vertical fishing effort is inadequate and fails to capture both within-and among-set variability, potentially resulting in biased stock assessments.