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2nd
ASEAN Symposium and Workshop on
Sea Turtle Biology and Conservation
| SESSION
3: Beyond the Beach.... |
ABSTRACTS
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Turtles
on the edge: movement of loggerhead turtles (Caretta caretta) along
oceanic fronts in the central North Pacific, 1997-98
Jeffrey J. Polovina, Donald
Kobayashi, Denise Ellis, Michael Seki, and George Balazs
Honolulu Laboratory, Southwest
Fisheries Science Center National Marine Fisheries
Service, NOAA, USA
Analyses of nine juvenile loggerheads
tracked in 1997 and 1998 in the central North Pacific by satellite telemetry
together with satellite remote sensed data on sea surface temperature (SST),
chlorophyll, and geostrophic currents show all turtles traveling westward
along two convergent oceanic fronts, against prevailing currents. These
fronts are characterized by gradients in sea surface height producing an
eastward geostrophic current, gradients in surface chlorophyll, and SST.
Six of the turtles associated with a front characterized by 17 C SST, surface
chlorophyll of about 0.2 mg/m3, and eastward geostrophic current of about
4 cm/s, while the other three turtles associated with a front with 20 C
SST, surface chlorophyll of about 0.1 mg/m3, and eastward geostrophic of
about 7 cm/s. These results explain why incidental catch rates of loggerheads
in the Hawaii longline fishery are highest when gear is set at 17 C and
20 C SST. Further from the seasonal distribution of longline effort relative
to these fronts, it appears that the surface longline fishing ground lies
largely between these two fronts during the first quarter and well to the
south of the 17 C front but including the 20 C front in the second quarter.
Finally, these results illustrate the insights which can be achieved by
combining data on movement of pelagic animals with concurrent remotely
sensed environmental data.
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