Meeting Abstract

P1.51  Sunday, Jan. 4  Loggerhead Sea Turtle (Caretta caretta) Feeding on Mackerel-Baited Longline Hooks MARSHALL, C.D.*; MOSS, A.L.; GUZMAN, A.; Texas A and M University at Galveston marshalc@tamug.edu

The large longline fishery bycatch of loggerhead & leatherback sea turtles is a serious concern for both managers & conservationists. US longliners have switched from a J hook to a circle hook, & switched bait from squid to mackerel; both changes are thought to decrease bycatch. However, few studies have investigated loggerhead feeding in detail. Therefore, we conducted a kinematic study using 6 captive loggerhead turtles feeding on barb-less, mackerel-baited longline hooks (18-0 circle vs. J-25) to characterize loggerhead feeding on mackerel. Kinematic variables for loggerheads feeding on mackerel from 18-0 circle hooks were: max gape = 6.7 cm +/- 1.22, time to max gape = 798 ms +/- 379.4, max gape angle = 44.6+/- 9.84, max hyoid depression = 1.4 cm 0.60, time to max hyoid depression = 1002 ms +/- 396.5, open gape angle velocity = 517/s +/- 156.7, closing gape angle velocity = 741/s +/- 203.7, & gape cycle = 1030 ms +/- 412.7. Kinematic variables for loggerheads feeding from J-25 hooks were: max gape = 7.2 cm 1.2, time to max gape = 896 ms +/- 524.2, max gape angle = 47.4 +/- 1.03, max hyoid depression = 1.53 cm +/- 0.71, time to max hyoid depression = 927 ms +/- 349.7, open gape angle velocity = 516/s +/- 190.6, closing gape angle velocity = 999/s +/- 295.5, & gape cycle = 937 ms +/- 434.0. No significant differences were found between hook type, with the exception of max closing gape angle velocity, which was faster when feeding on the 18-0 circle hook (P<0.01). These data support a recent study using squid baited circle & J hooks, which suggested that loggerhead feeding kinematics were conserved regardless of hook type. However, in this study it was clear that turtles were feeding further from the hook compared to squid baited hooks.