赤蠵龜和欖蠵龜在北太平洋中央的覓食與棲地洄游

Forage and migration habitat of loggerhead (Caretta caretta) and olive ridley (Lepidochelys olivacea) sea turtles in the central North Pacific

OceanJEFFREY J. POLOVINA,, GEORGE H. BALAZS, EVAN A. HOWELL, DENISE M. PARKER, MICHAEL P. SEKI AND PETER H. DUTTON

Reporter : Yu-Tong HeFish. Oceanogr. 13:1, 36–51, 2004

A brief introduction of loggerhead

sea turtle & olive ridley sea turtle.

Why do this research ?

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http://www.seaworld.org/infobooks/SeaTurtle/stclass.htmlhttp://www.seaworld.org/infobooks/SeaTurtle/stclass.html

Kindom: AnimaliaPhylum: ChordataSubphylum: VertebrataClass: ReptiliaSubclass: Anapsida order: TestudinesSuborder: : Cryptodira Superfamily: Chelonioidea family: Cheloniidaegenus: Carettaspecies: Caretta

wikipediawikipedia

The top (dorsal) color is reddish brown with dark streaks The body length is 82 to 105 cm (32-41 in.) .The body length is 82 to 105 cm (32-41 in.) . Have an average weight just 66 to 101 kg 66 to 101 kg (146-223 lb.).(146-223 lb.).

Kindom: AnimaliaPhylum: ChordataSubphylum: VertebrataClass: ReptiliaSubclass: Anapsida order: TestudinesSuborder: : Cryptodira Superfamily: Chelonioidea family: Cheloniidaegenus: Lepidochelys species: olivacea

www.worldwildlife.orgturtlesspeciesort.cfmwww.worldwildlife.orgturtlesspeciesort.cfm

It is named for the olive color of its heart-shaped shell. Have an average weight just over 100 lb (up to 50 kg.) . Olive ridleys are regarded as the most abundant sea turtles in the world Carapace length of only 27 inches (70 cm). With Kemp’s Ridley the smallest species.

http://www.tortugamarina.org/downloads/images/coco-hookmouth.jpg

We investigated the oceanic habitat and movements of these 2 species because they caught by longline gear .

Circle hook is better than J hook.

http://ww

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http://www.wildcoast.net/mznews/archives/000037.htmlhttp://www.wildcoast.net/mznews/archives/000037.html

The Argos-linked Telonics ST-10 or ST-18 position transmitters.

Wildlife Computer Argos-linked satellite transmitter with dive recorder capabilities (SDR-T10).

Personnel of the National Marine Fisheries Service’s Observer Program.

Genetic analyses. The Sea-viewing Wide Fieldof- view Sensor (SeaWiFS) . TOPEX/Poseidon

Satellite telemetry from 26 Caretta caretta and 10 Lepidochelys olivacea captured and released from pelagic longline fishing gear provided information on the turtles’ position and movement in the central North Pacific.

3 loggerheads and 2 olive ridleys to be sexually mature; however, all the other turtles were likely immature.

The time period from January 1997 to August 2001 for a total of 2470 transmission days.

http://tw.search.yahoo.com/language/translatedPage?tt=url&text=http%3a//www.mrf-asia.org/projects_view.cfm%3fTHE_ID=14&lp=en_zt&.intl=tw&fr=notfound_dichttp://tw.search.yahoo.com/language/translatedPage?tt=url&text=http%3a//www.mrf-asia.org/projects_view.cfm%3fTHE_ID=14&lp=en_zt&.intl=tw&fr=notfound_dic

The Argos-linked Telonics ST-10 or ST-18 position transmitters were attached to 32 turtles .

http://www2.dmu.dk/1_Viden/2_Publikationer/http://www2.dmu.dk/1_Viden/2_Publikationer/3_Fagrapporter/rapporter/FR484_1-25.PDF3_Fagrapporter/rapporter/FR484_1-25.PDF

2 loggerhead and 2 olive ridley turtles were instrumented with a Wildlife Computer Argos-linked satellite transmitter with dive recorder capabilities (SDR-T10).

This transmitter provides 3 frequency distributions for each of four 6-h (21:00~03:00, 03:00~09:00, 09:00~15:00, and 15:00~21:00 ) time periods.

1. time spent in each of 14 (1, 3, 5, 10, 15, 25, 35, 50, 60, 75, 100, 125,

150, 150+.)preset depth bins. 2. duration of each dive.3. the depth for each dive.

http://www2.dmu.dk/1_Viden/http://www2.dmu.dk/1_Viden/2_Publikationer/3_Fagrapporter/2_Publikationer/3_Fagrapporter/rapporter/FR484_1-25.PDFrapporter/FR484_1-25.PDF

The National Marine Fisheries Service’s Observer Program attached transmitters to the turtles onboard commercial fishing vessels.

26 loggerheads were determined by genetic analysis to have come from Japanese nesting beaches.

9 olive ridleys showed that 6 came from eastern Pacific nesting beaches and 3 came from the western Pacific.

The SST data were multi-channel SST (MCSST) with weekly temporal resolution and one-tenth of one degree of longitude and latitude spatial resolution.

wikipediawikipedia

TOPEX/Poseidon :Launched in 1992, to map ocean surface topography and monitor water current and SSH.

Sea-viewing Wide Fieldof- view Sensor (SeaWiFS) :To estimate chlorophyll a concentration and provide useful data on ocean color to the Earth science community .The data resolution was monthly, September 1997~August 2001, at 0.088 latitude and longitude.http://visibleearth.nasa.gov/view_rec.php?id=5http://visibleearth.nasa.gov/view_rec.php?id=5

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Migration tracking lines. Dive depth. Distribution with geostrophic currents. Forage.

http://www.seawear.com/jewelry/turtles.html

Track lines of 26 loggerhead & 10 olive ridley : solid dots mar

k the start of each track line

Loggerheads : occupying the northern portion 22°N~41°N of the Subtropical Gyre (28°N) and the Transition Zone .Olive ridleys : a broader latitude range than for loggerheads, primarily from 6°N–31°N in the Subtropical Gyre and the equatorial regional.

greatest distance

赤 道135 0E 150

0E 1650E 1800E 1650

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Hawaii-based longline fishery 6°N~41°N;130°W~150°EThe spatial distribution of all track lines for the 36 turtles

The greatest distance traveled for each species group

The loggerhead (60.0 cm SCL) traveled over 9000 km in 458 days. The olive ridley (52.0 cm SCL) traveled 7282 km in 193 days.

Both of them more than twice the distance traveled by any other .

The physical and biological environmental data used to describe the environment at and around the migrating loggerheads and olive ridleys are sea surface temperature (SST), surface chlorophyll a concentration, and geostrophic current : Kuroshio Extension Current (KEC): south-eastward flowingNorth Equatorial Current (NEC) : westward -flowing.Equatorial Counter Current (ECC) : eastward -flowing.

http://news.zbedu.net/dili/uploadfile/200591313431235.jpghttp://news.zbedu.net/dili/uploadfile/200591313431235.jpg

SST-frequency distribution

Olive ridleys : occupied 23°C~28°C during all quarters.Loggerheads : occupied cooler water and broader : 15°C~25°C.

Many of the turtles remained in very narrow SST ranges during their entire transmission time.

TZCF (transition zone chlorophyll front) was an important forage habitat (including squid, albacore, and pomfret) representing a convergence zone where cool plankton-rich water from the north converges and sinks beneath warmer nutrient-poor water to the south , resulting in a gradient in SSH that generates a weak eastward flowing geostrophic current which the loggerheads swim against as they travel westward, and loggerheads occupy the TZCF throughout the year.

The TZCF represents the boundary between the stratified low surface chlorophyll (<0.15 mg m-3) waters of the Subtropical Gyre and the high surface chlorophyll (>0.3 mg m-3) vertically mixed waters in the Transition Zone and Subarctic Gyre.

Time-at-depth

Loggerheads : relatively shallow dives and they spent 40% of their time at the surface and about 90% of their time at depths < 40 m.Olive ridleys : they spent only about 20% of their time at the surface and about 40% of their time > 40 m.

Olive ridley : the chlorophyll maximum was deeper than 100 m, although it shoaled to the surface at 10°N latitude at the northern edge of the NEC.Loggerhead : with the subsurface chlorophyll maximum above 100m and reaching the surface at 33°N when it became the TZCF.

Temperature depth & chlorophyll depth

KEC (35°C) and sea surface height estimated together with the trackline and positions (dots) of the loggerhead turtle for 10 day periods in2.12~22; 3.13~23; 4.12~22.

KEC may be an important habitat (ex: juvenile bluefin from December through June.) because the strong meanders from the KEC entrain deep cool, productive waters rich in nutrients and possibly a biological community from the northern side of the KEC into cyclonic eddies.The KEC is shown as strong eastward flowing current along 35°N, and the turtle track line shows the turtle’s westward (24/26) movement was often assisted by the westward flow on the north side along 33°N of the 2 cyclonic eddies at 165°E and 180°E are regions of enhanced surface chlorophyll .

http://61.236.182.2/webmedia/html/movie_121.shtml

Geostrophic currents along the NEC with olive ridley track line

As olive ridley headed westward in the NEC, it traveled at about 71 cm s-1 and as the NEC traveled at only 32 cm s-1, the turtle appeared to be actively swimming and not just drifting as it rode the NEC, most likely to continually find needed prey.This olive ridley traveled eastward along the eastward-flowing ECC in September and then north and westward during October and November in the NEC .

http://www.montereybay.com/creagrus/sea_turtles.htmlhttp://www.montereybay.com/creagrus/sea_turtles.html

Geostrophic currents estimated along the NEC & ECC with olive ridley track line

Their most common prey from 53 loggerheads are floating organisms and organisms riding on floating objects. These include the predatory gastropod Janthina sp.(紫螺 ) , and its prey Vellela vellela (By-the-wind sailor), gooseneck barnacles, Lepas sp., and the pelagic crab Planes cyaneus which ride on logs, floats. The only common diet item not found exclusively at the surface was the heteropod Carinaria cithara .

http://tw.search.yahoo.com/language/translatedPage?tt=url&text=http%3a//earthguide.ucsd.edu/earthguide/imagelibrary/velellavelella.html&lp=en_zt&.intl=tw&fr=notfound_dic

Vellela vellelaVellela vellela

gooseneck barnaclesgooseneck barnacles

http://tw.search.yahoo.com/language/translatedPage?tt=url&text=http%3a//www.ncrcn.org/me/projects/tidepool/gooseneckbarnacle/gooseneckbarnacle.html&lp=en_zt&.intl=tw&fr=notfound_dic

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Carinaria citharaCarinaria cithara

Planes cyaneusPlanes cyaneus

http://www2s.biglobe.ne.jp/~palaemon/grapsida.htmhttp://www2s.biglobe.ne.jp/~palaemon/grapsida.htm

http://reproduce.nmmba.gov.tw/main04_1_4.htmhttp://reproduce.nmmba.gov.tw/main04_1_4.htm

Janthina spJanthina sp

An analysis of stomach contents from 8 olive ridleys caught in the Hawaii-based longline fishery indicates that while they do forage on some surface associated organisms including Janthina sp. and cowfish (Lactoria diaphana), their most common prey are pyrosomes (Pyrosoma atlantica) and salps (Salpidea), which are found subsurface.

Photograph by Dick Williams Photograph by Dick Williams

salps (Salpidea)salps (Salpidea)Lactoria diaphanaLactoria diaphana

http://www.julianrocks.net/portraits/cowfish.htmhttp://www.julianrocks.net/portraits/cowfish.htm

http://jellieszone.com/pyrosoma.htmhttp://jellieszone.com/pyrosoma.htm

Pyrosoma atlanticaPyrosoma atlantica

Habitats of loggerheads and olive ridleys.

Conservation.

Photo: Carlos Drews/World Wildlife Foundation/APPhoto: Carlos Drews/World Wildlife Foundation/AP

Loggerhead and olive ridley turtles occupy habitats with different physical and biological characteristics and as a result utilize different types of forage and migration habitat.

Loggerhead occupy the northern edge of the Subtropical Gyre and the Transition Zone, waters characterized by a shallow thermocline, strong thermal and chlorophyll gradients, and surface convergent fronts. As a result they tend to have a relatively shallow dive depth distribution, spend considerable time at the surface, (however, olive ridley is tatolly opposite from loggerhead.) and associate with eddies and fronts including the TZCF and the southern edge of the KEC.

Olive ridleys inhabit two different oceanic regions.Most of them tracked remained in the center of the Subtropical Gyre.In addition to inhabiting stratified Subtropical Gyre waters, three olive ridleys occupied a different habitat consisting of major oceanic currents. One traveled along the southern edge of the KEC at the north boundary of the Subtropical Gyre while two traveled in the equatorial region south of the Subtropical Gyre using the NEC and ECC.

While many turtles caught in the longline fishery were hooked in the mouth, externally hooked, or entangled, the observer was able to remove the hook before releasing the animal.However in both these turtles the hooks were deeply ingested, so they were released without removal of the hooks.

http://www.seashepherd.nl/news/media_040501_1.htmlhttp://www.seashepherd.nl/news/media_040501_1.html http://www.commondreams.org/headlines02/images/0521-04.jpghttp://www.commondreams.org/headlines02/images/0521-04.jpg

The reduction of incidental catches of sea turtles in pelagic fisheries is an important management goal.

All the incidental catches of loggerheads occurred on shallow sets <100 m depth

1. In March 2001, prohibited shallow longline sets in the Hawaii fishery.

2. The findings that the TZCF, the southern edge of the KEC, the NEC and ECC represent important forage habitat for loggerheads and olive ridley suggest that reducing fishing effort in these areas will also reduce the incidental take of these turtles.

Finally, our analyses should prove useful in identifying oceanic marine-protected areas designed to protect pelagic animals in their spawning and foraging habitats .

Legal notice posted by nest at Vero Beach, FloridaLegal notice posted by nest at Vero Beach, Florida

http://img.groundspeak.com/track/log/89112_200.jpghttp://img.groundspeak.com/track/log/89112_200.jpg

Report is end but conservation still continued

http://www.turtles.org/why.htmhttp://www.turtles.org/why.htm