SWFSC juvenile loggerhead sea turtle tracking 2002-2005

NOAA Southwest Fisheries Science Center (SWFSC)

Satellite telemetry data from 17 juvenile loggerhead turtles (43.5-66.5 cm straight carapace length) were used in conjunction with oceanographic data to analyze the influence of regional and seasonal oceanography on dive behavior in the North Pacific Ocean. Combined dive behavior for all individuals showed that turtles spent more than 80% of their time at 0-5 m depths, and more than 90% of their time at 0-15 m depths. Multivariate classifications of dive data revealed four major dive types, three representing deeper, longer dives, and one representing shallower dives shorter in duration. Turtles exhibited variability in these dive types across oceanographic regions, with deeper, longer dives in the Hawaii longline swordfish fishing grounds during the first quarter of the year, as well as in the Kuroshio Extension Bifurcation Region and the region near the Baja California Peninsula, Mexico. Turtles in the Kuroshio Extension Bifurcation Region also exhibited dive variability associated with mesoscale eddy features, with turtles making deeper, longer dives while associated with the strongest total kinetic energy. Turtles in the central North Pacific exhibited seasonality in dive behavior that appeared to reflect synchronous latitudinal movements with the North Pacific Subtropical Front and the associated seasonal, large-scale oceanography. Turtles made deeper, longer dives during the first quarter of the year within this region, the reported time and area where the highest loggerhead bycatch occurs by the longline fishery. These results represent the first comprehensive study of dive data for this species in this region. The increased understanding of juvenile loggerhead dive behavior and the influences of oceanography on dive variability should provide further insight into why interactions with longline fisheries occur and suggest methods for reducing the bycatch of this threatened species.

These results will aid in our understanding of juvenile loggerhead dive behavior during their oceanic phase. An increased understanding of potential effects of oceanography on loggerhead dive behavior should assist in future conservation and bycatch studies working toward the reduction of loggerheads by longline fisheries in the North Pacific.

N/A

Overview

This section explains attributes included in the original dataset. OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only. Should you need other attributes described here, you are encouraged to contact the data provider.

Attributes described below represent those in the original dataset provided by the provider.
All attributes are included in the downloadable file (CSV or ESRI File Geodatabase) for "Complete Set of Dataset".

Attributes in dataset

Attribute (table column)	Description
oid	Unique ID number (generated by OBIS-SEAMAP)
longitude	Longitude of animal in decimal degrees
latitude	Latitude of animal in decimal degrees
obs_date	Observed date
obs_time	Observed time
argosloc	Argos location code
series	Argos ID
obs_count	Observed count (1 for satellite tag data)
sp_obs	Species tagged
sp_tsn	Taxonomic Serial Number added by OBIS-SEAMAP
geom	Geometry field added by OBIS-SEAMAP