Pacific Turtle Tracks: Grupo Tortuguero

The oceanic movements of loggerhead turtles (Caretta caretta), green
turtles (Chelonia mydas), and a Pacific ridley turtle (Lepidochelys olivacea)
were monitored with satellite telemetry between 1996 and 2001 in the Pacific
Ocean. During this time several turtles migrated across the Pacific Ocean,
covering more than 11,500 km between Santa Rosaliita, Baja California, Mexico
(28 40N, 114 14W), and Sendai Bay, Japan (37 54N, 140 56E). These findings are
consistent with the hypothesis that loggerheads feeding in the eastern Pacific
eventually return to nest on western Pacific beaches. Baja California
loggerhead turtles have been shown, through molecular genetic analysis (Bowen
et al. 1995) and flipper tag returns (Uchida and Teruya 1988, Resendiz et al.
1998), to be primarily of Japanese origin. We conclude that loggerhead turtles
are capable of transpacific migrations and propose that the band of water
between 25 and 30 degrees North latitude, the Subtropical Frontal Zone, may be
an important transpacific migratory corridor. Recent findings (Polovina et al.
2000) indicate that juvenile loggerheads in the North Pacific move westward
against weak (0.1-0.3 km/hr) eastward geostrophic currents, demonstrating that
passive drift may not entirely explain the dispersal of loggerheads.

Juvenile loggerhead turtles, Caretta caretta, in the 20 - 85 cm straight
carapace length (SCL) size range have been observed in the offshore waters
along the Pacific coast of California, USA, and the Baja California peninsula,
Mexico (Pitman 1990, Nichols, in press). Bartlett (1989) suggested that these
turtles might be of western Pacific origin, migrating 10,000 km and feeding on
pelagic red crabs (Pleuroncodes planipes) along the Baja California coast.
Subsequently, Pacific loggerheads appear to utilize the entire North Pacific
during the course of development in a manner similar to Atlantic loggerheads'
use of the Atlantic Ocean (Bolten et al. 1998). After a period of more than 10
years (Zug et al. 1995), mature turtles evidently cross the Pacific Ocean from
pelagic waters and foraging areas along the Baja California coast to return to
natal beaches, a journey of more than 12,000 km in each direction. This is the
first effort to document pelagic movements of North Pacific loggerheads from
feeding grounds to nesting areas using satellite telemetry. Previous telemetry
studies of loggerhead turtles have documented post-reproductive movements
(Stoneburner 1982), pelagic movements (Polovina et al. 2000), home ranges
(Renaud and Carpenter 1994), navigational abilities (Papi et al. 1997) and
homing behavior (Luschi 1996). However, few studies of sea turtles have
documented pre-nesting movements from feeding grounds to breeding areas.
Notably, Renaud and Landry (1996) documented movement of a Kemp's ridley turtle
(Lepidochelys kempii) from feeding grounds in Louisiana, USA, to its successful
nesting in Rancho Nuevo, Mexico. A unique opportunity to track the movements of
an adult-sized loggerhead turtle, rarely encountered along the Baja California
coast, emerged in 1996. The turtle had been raised in captivity and used in the
initial genetic analysis of Baja California loggerhead turtles (Bowen et al.,
1995). Its mature size (Kamezaki and Matsui, 1997), genetic affinities with
Japanese turtles, and the existence of a previous tag return from Japanese
waters of a captive-raised, Baja California loggerhead turtle (Resendiz et al.,
1998) were the deciding factors in choosing this particular turtle for the
study. This turtle is included in the dataset as series 7667, named "Adelita".
The objective of the study was to monitor the oceanic movement, using satellite
telemetry, of a Pacific loggerhead turtle initially captured on feeding grounds
along the Baja California coast. Movement data also were examined with respect
to oceanographic and meteorological information in an effort to gain insight
into the navigational cues that guide adult sea turtles and to identify
possible transpacific movement corridors.

CURRENTNESS REFERENCE: ground condition

SPATIAL REFERENCE INFORMATION - GEODETIC MODEL
Horizontal Datum Name: D_WGS_1984
Ellipsoid Name: WGS_1984
Semi-major Axis: 6378137.000000
Denominator of Flattening Ratio: 298.257224

1996至2001年间，研究人员借助卫星遥测（satellite telemetry）技术对太平洋海域内的蠵龟（Caretta caretta）、绿海龟（Chelonia mydas）以及太平洋丽龟（Lepidochelys olivacea）的海洋活动进行了监测。此期间有多只海龟完成跨太平洋迁徙，从墨西哥下加利福尼亚州的圣罗萨利塔（28°40′N，114°14′W）迁徙至日本仙台湾（37°54′N，140°56′E），迁徙距离超过11500公里。上述发现与“在东太平洋觅食的蠵龟最终会回到西太平洋海滩筑巢”的假说相符。

通过分子遗传分析（Bowen等，1995）与鳍标记回捕数据（Uchida与Teruya，1988；Resendiz等，1998）已证实，下加利福尼亚海域的蠵龟主要起源于日本。研究团队推断，蠵龟具备跨太平洋迁徙能力，并提出北纬25°至30°之间的水域——亚热带锋面区（Subtropical Frontal Zone），可能是重要的跨太平洋迁徙通道。

近期研究（Polovina等，2000）显示，北太平洋幼年蠵龟会逆流向西移动，对抗微弱（0.1~0.3 km/hr）的东向地转流，这表明单纯的被动漂流或许无法完全解释蠵龟的扩散模式。

在美国加利福尼亚州太平洋沿岸及墨西哥下加利福尼亚半岛的近海水域，曾观测到背甲直线长度（SCL，straight carapace length）为20~85cm的幼年蠵龟（Caretta caretta）（Pitman，1990；Nichols，即将出版）。Bartlett（1989）提出，这些海龟可能起源于西太平洋，它们迁徙了10000公里，以下加利福尼亚沿岸的远洋红蟹（Pleuroncodes planipes）为食。

后续研究表明，太平洋蠵龟在整个发育过程中会利用整个北太平洋海域，这与大西洋蠵龟对大西洋的利用模式类似（Bolten等，1998）。经过十余年的生长（Zug等，1995），成熟个体显然会从远洋水域以及下加利福尼亚沿岸的觅食地横跨太平洋，回到出生地海滩筑巢，单程迁徙距离超过12000公里。

这是首次借助卫星遥测技术记录北太平洋蠵龟从觅食地到筑巢地的远洋活动。此前针对蠵龟的卫星遥测研究已记录了繁殖后移动（Stoneburner，1982）、远洋活动（Polovina等，2000）、活动范围（Renaud与Carpenter，1994）、导航能力（Papi等，1997）以及归巢行为（Luschi，1996）。但鲜有海龟研究记录了从觅食地到繁殖地的筑巢前移动。值得注意的是，Renaud与Landry（1996）曾记录了一只肯普氏丽龟（Lepidochelys kempii）从美国路易斯安那州的觅食地迁徙至墨西哥兰乔努埃沃成功筑巢的过程。

1996年，研究团队迎来了独特的研究契机：可对一只在下加利福尼亚沿岸罕见出现的成年体型蠵龟进行追踪。这只海龟曾在人工饲养环境下长大，并被用于下加利福尼亚海域蠵龟的首次遗传分析（Bowen等，1995）。其成熟体型（Kamezaki与Matsui，1997）、与日本海龟的遗传亲缘关系，以及此前一次回捕记录——一只人工饲养的下加利福尼亚蠵龟在日本海域被回收（Resendiz等，1998），这些因素共同促成了选择该海龟作为研究对象。该海龟被编入本数据集，编号为7667，命名为“Adelita”。

本研究的目标是借助卫星遥测技术，监测一只最初在下加利福尼亚沿岸觅食地捕获的太平洋蠵龟的海洋活动。研究还结合海洋学与气象学数据对移动数据进行分析，以期深入了解引导成年海龟的导航线索，并确定潜在的跨太平洋迁徙通道。

【时效性参考】：地面状况
【空间参考信息——大地测量模型】
水平基准面名称：D_WGS_1984
椭球体名称：WGS_1984
长半轴：6378137.000000
扁率分母：298.257224