Do No So Dutton

8/8/2019 Do No So Dutton

1/13

Sea turtle bycatch in the Chilean pelagic longline fishery in the southeasternPacific: Opportunities for conservation

Miguel Donoso a, Peter H. Dutton b,*

a Pacifico Lad, Freire 1364, Quilpu, Chileb Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration,

3333 North Torrey Pines Court, La Jolla, CA 92037, USA

a r t i c l e i n f o

Article history:

Received 14 November 2009

Received in revised form 9 June 2010

Accepted 11 July 2010

Available online xxxx

Keywords:

Sea turtles

Marine conservation

Bycatch

Longlines

Incidental take

Fisheries

a b s t r a c t

Data are presented on sea turtles caught in the Chilean longline fishery targeting swordfish, Xiphias gla-

dius, in international waters off Chile. A total of 10,604,059 hooks from 7976 sets were observed, repre-

senting 94% of the total number of hooks fished between 2001 and 2005. Leatherbacks, Dermochelys

coriacea, (n = 284) and loggerheads, Caretta caretta, (n = 59) were the most common species captured.

Leatherbacks were caught in less than 4% of the sets, with an overall mean of 0.0268 turtles per 1000

hooks. Loggerheads were caught in less than 1% of the sets with a mean catch rate of 0.0056 turtles

per 1000 hooks. Most leatherbacks (97.5% of total) were caught between 24 S and 38S, while logger-

heads were caught primarily in the northern portion of the area fished, between 24 190S and 25310S.

All loggerheads were dehooked where appropriate and released alive. A total of two leatherbacks were

found dead. Despite the lowcatchrate of leatherbacks, thepotential impact of this fishery on theseverely

depleted nesting populations in the eastern Pacific could be significant when combined with other fish-

eries and threats in the region. The very low mortality of bycaught sea turtles observed in our study is

encouraging and suggests that there are opportunities for further reducing harmful effects of swordfish

longline fishing on sea turtles. Results of spatial analysis of loggerhead bycatch relative to fishing effort

show that closure of the northernmost fishing area would eliminate the majority of the loggerheadbycatch.

Published by Elsevier Ltd.

1. Introduction

There is great concern over declining populations of sea turtles

in the Pacific and the extent to which fishing activities contribute

to these continued declines (Sarti et al., 1996; Eckert, 1997; Spotila

et al., 2000; Lewison et al., 2004; Kaplan, 2005; Peckham et al.,

2007). The four species of sea turtles that inhabit in the South East

Pacific Ocean (loggerhead, Caretta caretta, leatherback, Dermochelys

coriacea, green, Chelonia mydas and olive ridley, Lepidochelys oliva-

cea) are listed as endangered or critically endangered species on

the 2009 IUCN Red List of Threatened Species (IUCN1). Leatherback

populations are at risk of extirpation in the Pacific because of over

harvest of eggs, commercial and residential development on nesting

beaches, and incidental bycatch in fisheries (Spotila et al., 2000).

Declines have been documented at nesting beaches in the eastern

Pacific and throughout the Indo-Pacific region, with a complete loss

of the Malaysian nesting population (Chan and Liew, 1996), severe

declines at nesting beaches in Costa Rica and Mexico (Sarti et al.,

1996, 2007; Spotila et al., 2000), and lesser declines at western Paci-

fic nesting beaches (Dutton et al., 2007; Hitipieuw et al., 2007).

Pacific loggerheads generally consist of two distinct breeding

stocks; a North Pacific stock originating from nesting sites in Japan

(Kamezaki et al., 2003), and a South Pacific stock nesting in Austra-

lia and NewCaledonia. Both stocks have declined dramatically over

the last few decades (Chaloupka, 2003; Kamezaki et al., 2003; FAO,

2004). The North Pacific stock inhabits foraging and developmental

areas in coastal neritic and oceanic habitat all the way to the north-

east Pacific off the coast of the Baja California Peninsula, and is ex-

posed to threats from pelagic and coastal fisheries (Bowen et al.,

1995; Kamezaki and Matsui, 1997; Koch et al., 2006; Peckham

et al., 2007). The Australian stock has undergone population de-

clines as a result of nest predation and incidental capture in coastal

and pelagic fisheries in the southwest Pacific (Chaloupka and

Limpus, 2001; Chaloupka, 2003).

In contrast, key Eastern Pacific olive ridley and green turtle

nesting populations have increased significantly in recent years

0006-3207/$ - see front matter Published by Elsevier Ltd.doi:10.1016/j.biocon.2010.07.011

* Corresponding author. Tel.: +1 858 546 5636; fax: +1 858 546 7003.

E-mail address: [email protected] (P.H. Dutton).1 IUCN (International Union for Conservation of Nature), 2009. Species Survival

Commission. Red List Database 2009. Website: http://www.iucnredlist.org/ (accessed

on 19 December 2009).

Biological Conservation xxx (2010) xxxxxx

Contents lists available at ScienceDirect

Biological Conservation

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / b i o c o n

Please cite this article in press as: Donoso, M., Dutton, P.H. Sea turtle bycatch in the Chilean pelagic longline fishery in the southeastern Pacific: Oppor-

tunities for conservation. Biol. Conserv. (2010), doi:10.1016/j.biocon.2010.07.011
http://dx.doi.org/10.1016/j.biocon.2010.07.011mailto:[email protected]://www.iucnredlist.org/http://dx.doi.org/10.1016/j.biocon.2010.07.011http://www.sciencedirect.com/science/journal/00063207http://www.elsevier.com/locate/bioconhttp://dx.doi.org/10.1016/j.biocon.2010.07.011http://dx.doi.org/10.1016/j.biocon.2010.07.011http://www.elsevier.com/locate/bioconhttp://www.sciencedirect.com/science/journal/00063207http://dx.doi.org/10.1016/j.biocon.2010.07.011http://www.iucnredlist.org/mailto:[email protected]://dx.doi.org/10.1016/j.biocon.2010.07.011


2/13

(Chaloupka et al., 2004). Olive ridleys are the most abundant spe-

cies encountered at sea in the Eastern Tropical Pacific (Eguchi et al.,

2007; Swimmer et al., 2010).

There is a growing effort to quantify the bycatch of sea turtles in

order to enable risk assessment and develop mitigation measures

for different fisheries (Carretta et al., 2005; Watson et al., 2005;

Lewison and Crowder, 2007; Cox et al., 2007; Gilman et al., 2007,

2010; Brazner and McMillan, 2008; Oceanic Fisheries Programme,

2001; Swimmer et al., 2010). Bycatch rates and species composi-

tion vary by fishery type and geographic region (Wallace et al.,

2010). The level of threat posed by individual fisheries to sea tur-

tles depends on status of the affected population(s), the level of in-

jury or mortality caused by the gear, the life stages of the bycaught

turtles, and the level of fishery effort (Soykan et al., 2008; Lewison

et al., 2009; Moore et al., 2009; Wallace et al., 2008, 2010).

Several studies have examined sea turtle bycatch in pelagic

longline fisheries in the Atlantic (Witzell, 1998; Domingo et al.,

2006; Kotas et al., 2004; Lpez-Mendilaharsu et al., 2007;

Marcovaldi et al., 2006; Pons et al., 2010), Mediterranean (Aguilar

et al., 1995; Camias, 2005; Alessandro and Antonello, 2009) the

North Pacific (Kleiber, 1998; McCracken, 2000; Yokota et al.,

2009) and the Eastern Tropical Pacific (Swimmer et al., 2010).

However there is a paucity of high quality information on bycatch

rates in comparable pelagic fisheries operating in the Southeastern

Pacific (Lewison et al., 2004; Lewison and Crowder, 2007; Wallace

et al., 2010). Furthermore, the data that are available in many cases

consist of estimates extrapolated from observer data collected

from a small (220%) portion of the fleets. These estimates typi-

cally have large errors associated due to the relatively low encoun-

ter rates between pelagic longline fishing gear and sea turtles in

the Pacific (Kleiber, 1998; McCracken, 2004). High bycatch rates

have also been shown to be associated with low observed effort

in a given region (Sims et al., 2008) and Wallace et al., 2010 point

out the importance of comprehensive and stratified observer cov-

erage to improving the accuracy of bycatch assessments.

Telemetry and tagging studies have shown that the coastal and

oceanic habitats in the southeastern Pacific are vital foraging desti-nations and migratory pathways for the depleted eastern Pacific

leatherback populations (Eckert, 1997; Shillinger et al., 2008). Mor-

tality resulting from bycatch in small-scale coastal fisheries off Peru

and Chile is believed to have contributed to the decline of eastern

Pacific leatherback nesting populations (Frazier and Brito-Montero,

1990; Eckert, 1997; Alfaro-Shigueto et al., 2007), however the ex-

tent to which leatherbacks and loggerheads interact with high seas

fisheries operating in international waters in thesoutheast Pacific is

unclear. Foraging and developmental habitat for the South Pacific

loggerhead breeding stock is nowknownto extend across theSouth

Pacific to include coastal areasoff Peru, South America (Alfaro-Shig-

ueto et al., 2004; Boyle et al., 2009), further highlighting the need to

assess theadditional threatsposed to loggerheads by fisheries oper-

ating in the southeastern Pacific (Alfaro-Shigueto et al., 2008).In Chile a commercial fishery was established in 2001 that per-

mitted shallow-set longlining for swordfish ( Xiphias gladius) with

the requirement that vessels took an observer at all times to collect

information on the swordfish catch and that all vessels carried a

Vessel Monitoring System (VMS) to track their position in real time

over the Marynsis-based satellite system (Ley 19521, 19972). The

restrictions on swordfish catch include a minimum allowable size

of 184 cm Lower Jaw Fork Length (Decreto Supremo No. 406,

19973) with no discarded fish allowed. Fishers are allowed to retain

up to 30% of the swordfish below the minimum size, and any excess

is confiscated. At the onset of the fishery in 2001, vessels operating

in the north caught a large proportion of illegal-sized juvenile

swordfish. This area, demarcated by a boundary adjacent to the Cor-

dillera de Nazca (20S, 83300W; 20S, 78000W and 24S, 83300W)

was closed to fishing beginning in April 2001 to protect the sword-

fish nursery area.4 Furthermore, as a result of growing concern over

potential impacts of fishing on declining leatherback populations,

the Chilean swordfish observers were trained to collect informationstarting in 2001 on incidental take of sea turtles as part of a joint

program carried out under a bilateral Fisheries Cooperation Agree-

ment between the US National Oceanic and Atmospheric Adminis-

tration (NOAA) Fisheries Service and the Chilean National Fisheries

Service (SERNAPESCA).

Here we present information on incidental capture of sea turtles

by the commercial longline fishery targeting swordfish off the

coast of Chile (in Zone 87 FAO), based on 94% trip coverage by

observers over a 5-year period (20012005). We present seasonal

distribution and abundance of sea turtle bycatch relative to fishing

effort, present catch-per-unit-effort (CPUE) data, and discuss po-

tential measures to reduce bycatch.

2. Materials and methods

2.1. Fishery observations

Information was collected by a trained observer placed on fish-

ing vessels registered as part of the Chilean pelagic longline fleet

for the entire fishing season (FebruaryDecember) each year be-

tween 2001 and 2005 (Appendix A). Observers were on board for

the entire trip, which averaged 35 days for all trips except those

carried out by two of the vessels that were equipped with freezers,

which averaged 60 days at sea. This fleet comprised boats 1742 m

in length operating in international waters off the Chilean EEZ, be-

tween 70180W and 1739S. This area encompasses deep (ca.

20003000 m) abyssal waters.

All the observed vessels targeted swordfish and retained makoshark (Isurus oxirhynchus) and blue shark (Prionace glauca) as by-

catch (as well as other less important species). They used the

American monofilament longline system, as described in Vega

and Licandeo (2009) with non-offset J hooks (Mustad 9/0) baited

with Argentinean shortfin squid (Ilex argentinus), or occasionally

jack mackerel (Scomber japonicus). A yellow or pink chemical

light-stick was hung above each hook. Two vessels used the Span-

ish-style gear configuration where the gangions consist of poly-

ethelene multifilament nylon containing a 5.5 m stainless steel

leader (1.5 mm dia) attaching the hook, and are set closer together

than the American system, with approx 1012 gangions along each

350400 meter section (Barria et al., 2006; Vega and Licandeo,

2009). Vessels using the Spanish system set an average of 2000

hooks on 45 nautical miles (nm) of longline compared with an

average of 1300 hooks on 3555 nmof longline set by vessels using

the American system. Vessels fishing with the American configura-

tion generally began setting gear at dusk (18001900 h) with sets

lasting a total of 18 h including 4 h to set, 8 h soak time, and 6 h

haulback time. Vessels fishing with the Spanish configuration be-

gan setting gear around 18002000 h with sets lasting approxi-

mately 20 h including 5 h set time, 7 h soak time and 8 h haulback.

2.2. Bycatch observations

Observers collected data on sea turtle interactions, location, and

fishing effort (soak time, number of sets, and for each set the date,2 Ley No. 19521. Diario Oficial de la Repblica de Chile, Santiago, Chile, 30 de

Octubre de 1997.

3 Decreto Supremo No. 406. Diario Oficial de la Repblica de Chile, Santiago, Chile,2 de Abril de 1997.

4 Resolucin No. 157 & No. 641 de la Subsecretara de Pesca del 29 de Enero & del12 de Abril de 2001.

2 M. Donoso, P.H. Dutton/ Biological Conservation xxx (2010) xxxxxx


http://-/?-http://dx.doi.org/10.1016/j.biocon.2010.07.011http://dx.doi.org/10.1016/j.biocon.2010.07.011http://-/?-


3/13

time, location, number of hooks, and bait type). Sea surface water

temperature (SST) was recorded during the entirety of the set, and

observers noted temperatures whenever a turtle was encountered.

Sea turtles were identified by species, and where possible were

brought on board, measured, photographed, and a small skin sam-

ple collected for future genetic analysis (Dutton and Balazs, 1995)

to confirm species and determine stock origin (Dutton, 1996). The

curved carapace length (CCL) of turtles brought on board was mea-

sured (Bolten, 1999), and the turtles were tagged (inconel tags

style 681, National band and Tag Co., Newport, KY) following stan-

dard methods described in Balazs (1999). Hooks were removed

where possible and line disentangled prior to releasing turtles. In

cases where leatherbacks could not be brought on board, fishing

operations were suspended to bring the turtles close to the boat,

and crew or observers used line cutters (http://www.dehoo-

ker4arc.com) to release the turtle. Sizes were estimated in these

cases. Estimates were made of the CCL to the nearest 5 cm, in some

cases using a meter stick held alongside the turtle in the water for

reference. Skin samples were obtained from the carapace of

leatherbacks in the water using custom biopsy poles. When a hard-

shell turtle was not brought on board and species identity could

not be confirmed from photographs or genetic analysis, the turtle

was considered an unidentified hardshell species. We classified

loggerheads as juveniles, sub-adults and adults based on CCLs of

85 cm, respectively (Limpus and Limpus,

2003).

2.3. Data analysis

The locations (latitude and longitude) of sets as well as the loca-

tions of sea turtle encounters were mapped in order to visualize

the spatial distribution of sea turtle take relative to fishing effort

for each year using MAPTOOL (2002). Catch-per-unit-effort (CPUE)

was calculated as number of captured turtles/1000 hooks for each

species for each set and summarized by quarter for each year.

We used a simple general linearized model (GLM) to test for

seasonal and inter-annual differences in our observed bycatch

rates of leatherbacks and loggerheads, as follows: first, we deter-

mined the proportion of sets with turtle interactions as the ratio

between the number of sets with turtle interactions and the total

Table 1

Number of vessels, trips, sets and hooks of the Chilean longline fishery between 2001 and 2005.

Year No. vessels Total With observers

No. trips No. sets No. hooks No. trips No. sets No. hooks

2001 12 86 1985 2,689,914 86 1985 2,689,914

2002 13 82 1850 2,336,048 81 1835 2,316,248

2003 13 85 1773 2,243,495 85 1773 2,243,495

2004 10 58 1319 1,804,780 51 1185 1,632,120

2005 10 58 1465 2,161,482 43 1198 1,722,282

20012005 58 369 8392 11,235,719 346 7976 10,604,059

Table 2

Number of observed sets, hooks, captures and CPUE by year and quarter of the Chilean longline fishery between 20012005.

Year Quarter Number of sets Number of hooks Leatherback Loggerhead Green Unidentified

Captures CPUE Captures CPUE Captures CPUE Captures CPUE

2001 1 167 214,348 6 0.0280 26 0.1213 1 0.0047 0 0.0000

2001 2 602 831,822 19 0.0228 5 0.0060 0 0.0000 0 0.0000

2001 3 655 880,632 26 0.0295 2 0.0023 1 0.0011 0 0.0000

2001 4 561 763,112 12 0.0157 2 0.0026 0 0.0000 0 0.0000

2001 Total 1985 2,689,914 63 0.0234 35 0.0130 2 0.0007 0 0.0000

2002 1 194 245,965 9 0.0366 0 0.0000 0 0.0000 0 0.0000

2002 2 562 724,340 46 0.0635 2 0.0028 0 0.0000 0 0.0000

2002 3 620 763,452 52 0.0680 4 0.0052 0 0.0000 0 0.0000

2002 4 459 582,491 28 0.0481 2 0.0034 1 0.0017 0 0.0000

2002 Total 1835 2,316,248 135 0.0583 8 0.0034 1 0.0004 0 0.0000

2003 1 218 296,359 6 0.0202 0 0.0000 0 0.0000 1 0.0034

2003 2 661 863,266 10 0.0116 1 0.0012 1 0.0014 2 0.0023

2003 3 510 613,875 3 0.0049 0 0.0000 0 0.0000 2 0.0033

2003 4 384 469,995 17 0.0362 6 0.0128 1 0.0051 2 0.0043

2003 Total 1773 2,243,495 36 0.0160 7 0.0031 2 0.0020 7 0.0031

2004 1 67 74,366 2 0.0269 0 0.0000 0 0.0000 0 0.0000

2004 2 435 589,505 17 0.0288 1 0.0017 0 0.0000 1 0.0017

2004 3 422 586,930 2 0.0034 0 0.0000 0 0.0000 0 0.0000

2004 4 261 381,319 0 0.0000 1 0.0026 0 0.0000 1 0.0026

2004 Total 1185 1,632,120 21 0.0129 2 0.0012 0 0.0000 2 0.0012

2005 1 90 118,588 2 0.0169 0 0.0000 0 0.0000 4 0.0337

2005 2 383 564,037 12 0.0213 5 0.0089 0 0.0000 0 0.0000

2005 3 468 638,752 12 0.0188 2 0.0031 0 0.0000 0 0.0000

2005 4 257 400,905 3 0.0075 0 0.0000 0 0.0000 2 0.0050

2005 Total 1198 1,722,282 29 0.0168 7 0.0041 0 0.0000 6 0.0035

20012005 1 736 949,626 25 0.0263 26 0.0274 1 0.0011 5 0.0053

20012005 2 2643 3,572,970 104 0.0291 14 0.0039 1 0.0003 3 0.0008

20012005 3 2675 3,483,641 95 0.0273 8 0.0023 1 0.0003 2 0.0006

20012005 4 1922 2,597,822 60 0.0231 11 0.0042 2 0.0008 5 0.0019

20012005 Total 7976 10,604,059 284 0.0268 59 0.0056 5 0.0005 15 0.0014

M. Donoso, P.H. Dutton/ Biological Conservation xxx (2010) xxxxxx 3


http://www.dehooker4arc.com/http://www.dehooker4arc.com/http://dx.doi.org/10.1016/j.biocon.2010.07.011http://dx.doi.org/10.1016/j.biocon.2010.07.011http://www.dehooker4arc.com/http://www.dehooker4arc.com/


4/13

sets within each quarter and year respectively. We then estimated

the standard error of the proportion in each case using the

expression

r^p

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi^p1 ^p

n 1

r1

We then fitted a GLM with turtle interactions (presence/ab-

sence) as the response variable and year and quarter as predictors.

This model assumes the response variable has a Bernoulli probabil-

ity mass function, and a logit link function was used to relate the

expected value of the response and the linear predictor (Dobson,

2002). The probability of finding a turtle can be modeled by

px egx

1 egx2

where g(x) is the linear predictor:

gx X5i1

aiD1i X4j1

bjD2j 3

where ai is the parameter associated with the year effect, bj are theparameters of the quarter effect, and D are dummy variables. We

applied this analysis separately for leatherbacks and loggerheads.

3. Results

3.1. Fishing effort

The number of longline vessels fishing each year ranged from 10

to 13 (Appendix A). A total of 10,604,059 hooks from 7976 sets

were observed, representing 94% of the total number of hooks

fished between 2001 and 2005 (Table 1). Fishing effort decreasedslightly each year from 1985 sets in 2001 to 1319 sets in 2004

and 1465 sets in 2005 (Table 1). In general, effort was relatively

low during the first quarter each year, since the fishing season usu-

ally starts during March. Most of the fishing effort occurred in the

second (AprilJune) and third (JulySeptember) quarters, and ef-

fort decreased in the fourth quarter (OctoberDecember) (Table 2).

The spatial distribution of the fishing effort also varied from year to

year (Fig. 1).

3.2. Sea turtle bycatch

Leatherbacks (n = 284) and loggerheads (n = 59) were the most

common species captured over the 5-year period of this study (Ta-

ble 2). In addition a total of five green turtles were identified (two

Fig. 1. (AE)Distribution of sea turtle bycatch by species (red circles = loggerheads, blue diamonds= leatherbacks, green squares = green turtles, grey triangles = unidentified

hardshell turtles) relative to fishing effort (sets, black points) by year for the Chilean longline fishery 20012005 (For interpretation of the references to colour in this figurelegend, the reader is referred to the web version of this article.).



http://-/?-http://dx.doi.org/10.1016/j.biocon.2010.07.011http://dx.doi.org/10.1016/j.biocon.2010.07.011http://-/?-


5/13

in 2001, one in 2002 and two in 2003) and 15 unidentified turtles

were caught in the years 2003 (7), 2004 (2) and 2005 (6) (Table 2).

A total of 14 leatherback, 39 loggerhead and five green sea turtles

were brought on board, where they were tagged, measured andthen released after removing the entangled fishing line.

3.3. Loggerhead bycatch

The majority (n = 35) of the 59 observed loggerheads were

caught in 2001 (Table 2). Loggerhead encounters were rare in the

other 4 years. Of the loggerheads caught in 2001, 26 were captured

during the first quarter in March (Table 2), between 24190S and

25310S and 76580W and 84220W, predominantly by four vessels

fishing in that area 1131 March (Fig. 1). Quarterly CPUE for log-gerheads ranged from 0 to 0.1213/1000 hooks, with an overall

average of 0.0056/1000 hooks (Table 2). The loggerheads occurred

in waters with temperatures ranging from 16.8C to22.1 C,with a

bimodal frequency distribution with peaks at 21 C and 18C

(Fig. 2). The mean length of the 39 measured loggerheads was

63.5 cm CCL (range = 4784 cm, SD = 8.9) (Fig. 3a). The majority

0

5

10

15

20

25

30

35

40

13 14 15 16 17 18 19 20 21 22 23 24 25 26

Percent

Temperature (oC)

Fig. 2. Frequency of loggerhead (dashed line) and leatherback (solid line) bycatch relative to SST in the Chilean longline fishery between 2001 and 2005.

0

2

4

6

8

10

12

14

16

18

41-50 51-60 61-70 71-80 81-90

Numberoftu

rtles

CCL (cm)

0

2

4

6

8

10

12

14

16

61-70 81-90 101-110 121-130 141-150 161-170 181-190

Numberofturtles

CCL (cm)

A

B

Fig. 3. Curved carapace lengths (CCL) of sea turtles caught in Chilean longline fishery between 2001 and 2005. The lengths measured for loggerhead (white bars) and green

turtles (grey bars) are shown in (A). Lengths of 14 leatherbacks measured on board (black bars) as well as estimated lengths for 73 leatherbacks that were not brought onboard (white bars) are shown in (B).



http://dx.doi.org/10.1016/j.biocon.2010.07.011http://dx.doi.org/10.1016/j.biocon.2010.07.011


6/13

(82%) was in the juvenile size class range (


7/13

4. Discussion

4.1. Loggerheads

Loggerheads arecommonly encounteredin pelagic longline fish-

eries in theAtlantic,Mediterraneanand North Pacific (Witzell, 1984,

1998; Kotas et al., 2004; Lewison et al., 2004; Watson et al., 2005;

Lpez-Mendilaharsu et al., 2007; Marcovaldi et al., 2006; Ponset al., 2010). This species is known to forage in the northeastern Pa-

cificoff theBajaCaliforniaPeninsula(Peckhamet al.,2007), however

the presence of loggerheads in the southeastern Pacific has only re-

cently been reported from studies in Peru (Alfaro-Shigueto et al.,

2004, 2008; Boyleet al., 2009). Ourresultsconfirmthat loggerheads

foragein waters as far south as 32S off the Chilean coast, and taken

together with results ofAlfaro-Shigueto et al. (2008), indicate that

loggerheads are more commonin the southeastern Pacific than pre-

viously thought, with foraging aggregations concentrated between

15 and 25S off southern Peru and northern Chile. The sizes of the

loggerheads caught in the Chilean longline fishery are consistent

with sizes reported for loggerheads in high-seas longline fisheries

in general (see Lewison and Crowder, 2007) and comprise mostly

large juveniles and sub-adults (Bjorndal et al., 2001; Limpus and

Limpus, 2003). The loggerheads we report for the Chilean longline

fisheryare generally larger than those caughtby theartisanal fishers

inPeru (Alfaro-Shigueto et al., 2004, 2008), with 18% in the subadult

and adults size ranges (>70 cm CCL), as opposed to only 8.4% re-

portedby Alfaro-Shigueto et al. (2008) forthis sizerangein Peruvian

artisanal gillnet and longline bycatch.There were also a greaterpro-

portionof small juveniles(


8/13

(


9/13

4.5. Regional impacts of longline fisheries

Our results provide the first extensive data on sea turtle bycatch

in pelagic longline fisheries operating in the southeastern Pacific,

and the take of leatherbacks in particular is of concern given the

critically endangered status of this species in the Pacific. These

finding should be considered in a broader regional context to bet-

ter understand the extent of the threat of fisheries to the recovery

of the depleted Pacific leatherback populations. Likewise, it is

important to consider the landscape of threats from trawl, net

and other longline fisheries that impact the southern loggerheadstock in order to assess the relative impact of the Chilean longline

fishery on loggerheads.

While our data represent near 95% observed coverage of the

Chilean longline fishing effort, the bycatch data should be consid-

ered as a conservative indication of bycatch in thepelagic swordfish

fisheries operating in the region. There is a small Chilean artisanal

longline fleet, comprising two to six vessels (


10/13

and early 1990s were implicated in the decline of eastern Pacific

leatherbacks during that same time period (Eckert, 1997). The Chil-

ean gillnet fishery for swordfish collapsed in the 1990s and has

been almost non-existent in the last decade or so. However, there

has been a resurgence of this gillnet fishery in Chile in recent years

(Donoso, unpublished data), and this most likely poses a greater

threat to leatherbacks than the current declining Chilean longline

fishery.

The low number of loggerhead interactions and absence of mor-

tality observed in ourstudysuggeststhat thethreat fromtheChilean

longline fisheryon thesouthernloggerhead stock by itself cannotbe

considered significant. Furthermore, the nesting populations, while

declining, have not collapsed to the extent that eastern Pacific

leatherbacks have (Chaloupka et al., 2004). Wide-scale and sus-

tained predation of eggs by foxes is believed to have been a major

causal factorin thehistoric declineof theAustralian loggerhead pop-

ulation(Chaloupka,2003). This threathas been largelyeliminatedin

recent years, and mortality of adults and large juveniles in coastal

trawl, gillnet and crab trap fisheries off Australia and around the

westernPacific is nowbelieved to pose themost seriousthreat, since

these fisheries drownanimals of high reproductivevalue to thepop-

ulation (Poiner & Harris, 1996; Chaloupka, 2003; Limpus and

Limpus, 2003). Nevertheless, concern over the threat from bycatch

of oceanicjuvenilesin distantwaters longline fisheries is warranted.

Modelingof competingrisk factorsindicate that viability of theeast-

ern Australian loggerhead stock is negatively impacted by take of

juveniles in high seas fisheries (Heppell et al., 1996; Chaloupka,

2003). Our study adds to a growing body of literature highlighting

theneed to assess thecontributionfrom cumulative impactsof from

small-scaleartisanal and industrial fisheries in theeastern Pacific to

the continuing decline of the southern Pacific stocks of loggerheads

(Alfaro-Shigueto et al., 2008, 2010).

4.6. Potential bycatch reduction

Our findings, taken together with those ofAlfaro-Shigueto et al.,

2008 suggest that the northern Chilean swordfish fishing area clo-sure put in place in 2001 has most likely helped reduce loggerhead

bycatch. This closed area features a body of consistently warmer

water (>21 C SST) and is within the broader loggerhead hotspot

stretching between 15 and 25S off southern Peru and northern

Chile, evident from our findings combined with other studies

(see Alfaro-Shigueto et al., 2008). The Chilean vessels are moni-

tored in real-time with a satellite-based VMS by SERNAPESCA,

which provides an effective tool for enforcing the closure. Penalties

include fines and impoundment of vessels. This closure is only in

effect for Chilean-flagged vessels and there are foreign fleets that

remain unmonitored but are known to fish in the area adjacent

to Chiles EEZ, including the area closed to Chilean vessels (CPPS,

2004; Herv and Fuentes, 2004). It is notable that two of our ob-

served longline sets (19150

S, 81500

W and 22080

S, 81480

W) oc-curred just within the western-most boundary of this closed area

and that both sets caught loggerheads (Fig. 1), suggesting a high

probability of loggerhead encounters in this area. Our findings sug-

gest that the likelihood of loggerhead bycatch could be signifi-

cantly reduced by further extending the closed area south to 25S.

Further work to develop models that predict likelihood of log-

gerhead presence based on oceanographic parameters could allow

more adaptive real-time fisheries management (Howell et al.,

2008). The NOAA Fisheries Services Turtlewatch program (http://

www.pifsc.noaa.gov/eod/turtlewatch.php) provides tools that have

been developed to help Hawaii-based fishers avoid potential inter-

action with loggerheads in the North Pacific, and a similar ap-

proach could be developed for the southeastern Pacific based on

the further analysis of the findings from our study, given that thesouthernmost range of loggerhead distribution appears to be asso-

ciated with dynamic features associated with the 21 and to a les-

ser extent, 18 isotherms. This along with a suite of other

mitigation measures, including turtle take limits and gear modifi-

cations, have successfully reduced sea turtle bycatch in the Ha-

waii-based longline fishery (Gilman et al., 2007). Developing

similar approaches to avoid leatherback interactions is more chal-

lenging, since they occur throughout the area of operations of the

Chilean longline fleet. Until the fine scale differences in habitat

use by leatherbacks and swordfish adjacent to oceanic convergence

zones are better understood, modification in gear and fishing tech-

niques offer the best potential for reduction in sea turtle bycatch.

Use of circle hooks and mackerel type bait instead of the traditional

J hooks and squid bait has been shown to significantly reduce by-

catch of sea turtles in swordfish and tuna longline fisheries

(Watson et al., 2005; Gilman et al., 2007; Read, 2007). Experiments

have been initiated to test circle hooks and mackerel bait in the

Chilean longline fishery, and there is growing interest in participa-

tion by Chilean fishers (Donoso, unpublished data).

5. Conclusions and conservation recommendations

The extensive observer data collected for the Chilean swordfish

longline fishery in our study provides valuable new information on

the extent of sea turtle interactions with pelagic fisheries, as well as

insights into the biology of loggerheads, leatherbacks and green

turtles in the southeastern Pacific Ocean, including extension of

the documented southern range for these species in the region.

We show that loggerheads are restricted to the northernmost area

fished by the Chilean longline fleet, and that there are opportunities

for applying area closures to avoid loggerhead bycatch that are

compatible with measures designed to improve the sustainability

of the regional swordfish stock. Area closure does not appear to

be a viable approach for reducing leatherback interactions in the

Chilean swordfish fishery, however, given the extent of leatherback

bycatch observed in our study, we recommend the adoption and

further development of fishing techniques that have been shown

to reduce leatherback and loggerhead bycatch, such as use of circle

hooks and mackerel type bait (Watson et al., 2005; Gilman et al.,

2007; Yokota et al., 2009). Our finding that almost all the sea turtles

were caught and released alive suggests that training of crew and

observers in safe handling procedures to disentangle lineand hooks

with dehookers and line cutters, and to resuscitate comatose sea

turtles, has further potential to reduce injury from longlines. We

urge other countries with pelagic fleets that fish in the same inter-

national waters as the Chilean fishery to implement observer pro-

grams similar to the one reported in our study in order to obtain

a more comprehensive understanding of the spatial distribution

of fishing effort and corresponding sea turtle interactions in the re-

gion, and to facilitate the adoption of recommended guidelines to

reduce the mortality of sea turtles that are caught incidentally in

longline fisheries (FAO, 2005). Reduction of bycatch should be partof a holistic conservation strategy for sea turtles that addresses the

multiplerisk factors posedby different coastal and high seas fisher-

ies and anthropogenic threats on nesting beaches (Dutton and

Squires, 2008; Wallace et al., 2010).

Acknowledgements

This study was carried out as part of the USChile Fisheries

Cooperation Agreement between NOAA Fisheries Service and SER-

NAPESCA, with funding from NOAA Fisheries Service and the Insti-

tuto de Fomento Pesquero (IFOP). We thank the IFOP scientific

observers, as well as the captains and crew of the participating

fishing vessels. Carlos Montenegro assisted with statistical analy-

sis. We thank William Perrin, Kelly Stewart, James Carretta andtwo anonymous reviewers for helpful comments and suggestions.



http://www.pifsc.noaa.gov/eod/turtlewatch.phphttp://www.pifsc.noaa.gov/eod/turtlewatch.phphttp://dx.doi.org/10.1016/j.biocon.2010.07.011http://dx.doi.org/10.1016/j.biocon.2010.07.011http://www.pifsc.noaa.gov/eod/turtlewatch.phphttp://www.pifsc.noaa.gov/eod/turtlewatch.php


11/13

References

Aguilar, R.,Mas, J., Pastor, X.,1995. Impact of Spanish swordfish longline fisheries on

the loggerhead sea turtle Caretta caretta population in the WesternMediterranean. In: Richardson, J.I., Richardson, T.H. (Eds.), Proceedings of the

Twelfth Annual Workshop on Sea Turtle Biology and Conservation. National

Oceanic and Atmospheric Administration Technical Memorandum NMFS-

SEFSC-361, pp. 16.

Alessandro, L., Antonello, S., 2009. An overview of loggerhead sea turtle (Carettacaretta) bycatch and technical mitigation measures in the Mediterranean Sea.Review of Fish Biology and Fisheries. doi:10.1007/s11160-009-9126-1.

Alfaro-Shigueto, J., Dutton, P.H., Mangel, J., Vega, D., 2004. First confirmed

occurrence of loggerhead turtles in Peru. Marine Turtle Newsletter 103, 711.

Alfaro-Shigueto, J., Dutton, P.H., Van Bressem, M.-F., Mangel, J., 2007. Interactions

between leatherback turtles and Peruvian artisanal fisheries. Chelonian

Conservation and Biology 6 (1), 129134.

Alfaro-Shigueto, J., Mangel, J., Seminoff, J.A., Dutton, P.H., 2008. Demography of

loggerhead turtles Caretta caretta in the southeastern Pacific Ocean: fisheries-based observations and implications for management. Endangered Species

Research 5, 129135.

Alfaro-Shigueto, J., Mangel, J.C., Pajuelob, M., Dutton, P.H., Seminoff, J.A., Godley, B.J.,

2010. Where small can have a large impact: structure and characterization of

small-scale fisheries in Peru. Fisheries Research. doi:10.1016/

j.fishres.2010.06.004.

Balazs, G.H., 1999. Factors to consider in the tagging of sea turtles. In: Eckert, K.L.,

Bjorndal, K.A., Abreu-Grobois, A.F., Donnelly, M. (Eds.), Research and

Management Techniques for the Conservation of Sea Turtles. IUCN/SSC

Marine Turtle Specialist Group. Publication No. 4, pp. 101109.

Barra, P., Donoso, M., Azocar, R., Cerna, F., Catasti, V., 2006. Programa de

Seguimiento del Estado de Situacin de las Principales Pesquerias

Nacionales. Investigacion Situacion Pesqueria Recursos Altamente Migratorios,

2005. Instituto de Fomento Pesquero Subsecretaria de Pesca de Chile,Valparaiso.

Appendix A

Specifications of the commercial longline vessels operating in the Chilean swordfish fishery between 2001 and 2005.

Port Vessel

name

Year of operation Length

(m)

Breadth

(m)

Draft

(m)

Year Hold

(m3)

Horsepower Hull type

Coquimbo Brisca 20012002200320042005

32.6 6.8 3.9 1960 200 700 Steel

Coquimbo Kofuku Maru 200120022003 27.0 5.7 2.6 1964 115 560 Steel

Coquimbo Talcan 200120022003 26.6 8.0 4.2 1989 310 705 Fiberglass

Coquimbo Curaco 200120022003 26.6 8.0 4.2 1989 310 705 Fiberglass

Coquimbo Marleen 2001200220032004

2005

34.7 7.7 4.2 1980 128 660 Steel

Coquimbo Lucia 2001200220032004

2005

26.8 6.6 3.1 1967 103 660 Steel

Coquimbo Canadelo 2001200220032004

2005

28.8 6.5 3.8 1963 140 660 Steel

Coquimbo Las Nieves 2002200320042005 33.5 6.7 3.8 1961 130 660 Steel

Valparaso Pacific Sea 2001200220032004

2005

21.3 5.5 2.5 1949 40 300 Steel

Coquimbo Tami S. 2001200220032004

2005

42.2 8.5 3.6 1980 374 1300 Steel

Coquimbo Portugal II 2001200220032004

2005

28.2 6.9 3.6 1970 100 530 Steel

Coquimbo Elena S. 2001200220032004

2005

16.6 6.6 3.2 1989 47 350 Steel

Coquimbo Christina S. 2001200220032004

2005

16.6 6.6 3.2 1989 47 350 Steel

Appendix B

ANOVA results for generalized linear model (GLM) fitted to the presence of Leatherback turtle in the Chilean fishery of swordfish between

2001 and 2005.

Df Variance Resid. Df Resid. DevPr (Chi)

Null 7972 2230.112Quarter 3 1.906 7969 2228.207 0.592

Year 4 79.356 7965 2148.850


12/13

Benson, S.R., Hitipeuw, C., Dutton, P.H., Samber, B., Bakarbessy, J., Parker, D.,

2007a. Post-nesting migrations of leatherback turtles from Jamursba Medi,

Birds Head Peninsula, Indonesia. Chelonian Conservation and Biology 6 (1),

150154.

Benson, S.R., Forney, K.A., Harvey, J.T., Carretta, J.V., Dutton, P.H., 2007b. Abundance

and distribution of leatherback turtles (Dermochelys coriacea) in a foragingregion off California, 19902003. Fishery Bulletin 105 (3), 337347.

Bjorndal, K.A., Bolten, A.B., Koike, B., Schroeder, B.A., Shaver, D.J., Teas, W.G., Witzell,

W.N., 2001. Somatic growth functions for immature loggerhead sea turtles,

Caretta caretta, in southeastern U.S. waters. Fishery Bulletin 99, 240246.

Bolten, A.B., 1999. Techniques for measuring sea turtles. In: Eckert, K.L., Bjorndal,K.A., Abreu-Grobois, A.F., Donelly, M. (Eds.), Research and Management

Techniques for the Conservation of Sea Turtles. IUCN/SSC Marine Turtle

Specialist Group. Publication No. 4, pp. 126132.

Bolten, A.B., Bjorndal, K.A., 2005. Experiment to Evaluate Gear Modification on Rates

of Sea Turtle Bycatch in the Swordfish Longline Fishery in the Azores Phase 4.

Final Project Report Submitted to the National Marine Fisheries Service.

Southeast Fisheries Science Center. National Oceanic and Atmospheric

Administration Award Number NA16FM2589, 20 p.

Bowen, B., Abreu-Grobois, F., Balazs, G., Kamezaki, N., Limpus, C., Ferl, R., 1995.

Trans-pacific migrations of the loggerhead turtle (Caretta caretta) demonstratedwith mitochondrial dna markers. Proceedings of the National Academy of

Sciences, USA 92, 37313734.

Boyle, M.C., FitzSimmons, N.N., Limpus, C.J., Kelez, S., Velez-Zuazo, X., Waycott, M.,

2009. Evidence for transoceanic migrations by loggerhead sea turtles in the

southern Pacific Ocean. Proceedings of the Royal Society B. doi:10.1098/

rspb.2008.1931.

Brazner, J.C., McMillan, J., 2008. Loggerhead turtle (Caretta caretta) bycatch inCanadian pelagic longline fisheries: relative importance in the western North

Atlantic and opportunities for mitigation. Fisheries Research 91, 310324.

Camias, J.A., 2005. Interacciones entre las tortugas marinas y las flotas espaolas

en el Mediterrneo Occidental y Golfo de Cdiz. Taller de Coordinacin de

actuaciones relacionadas con la captura accidental de tortuga boba (Carettacaretta) por flotas espaolas en el Mediterrneo. Secretara General de PescaMartima (MAPA), Madrid 4 de octubre de 2005, 14 p.

Carretta, J.V., Price, T., Petersen, D., Read, R., 2005. Estimates of marine mammal, sea

turtle, and seabird mortality in the California drift gillnet fishery for swordfish

and thresher shark, 19962002. Marine Fisheries Review 66 (2), 2130.

Castelao, R.M., Mavor, T.P., Barth, J.A., Breaker, L.C., 2006. Sea surface temperature

fronts in the California Current System from geostationary satellite

observations. Journal of Geophysical Research 111 (C09026). doi:10.1029/

2006JC003541.

Chaloupka, M., Limpus, C.J., 2001. Trends in the abundance of sea turtles resident in

southern Great Barrier Reef waters. Biological Conservation 102, 235249.

Chaloupka, M., 2003. Stochastic simulation modeling of loggerhead population

dynamics given exposure to competing mortality risks in the Western South

Pacific. In: Bolten, A.B., Witherington, B.E. (Eds.), Loggerhead Sea Turtles.

Smithsonian Institution Press, Washington, DC, pp. 275294.Chaloupka, M., Dutton, P., Nakano, H., 2004. Status of sea turtle stocks in the Pacific.

In: Expert Consultation on Interactions between Sea Turtles and Fisheries

within an Ecosystem Context, 912 March 2004. FAO Fisheries Report No. 738,

Supplement FIRM/R738, pp. 135164.

Chan, E.H., Liew, H.C., 1996. Decline of the leatherback population in Terengganu,

Malaysia, 19561995. Chelonian Conservation and Biology 2 (2), 196203.

Cox, T.M., Lewison, R.L., Zydelis, R., Crowder, L.B., Safina, C., Read, A.J., 2007.

Comparing effectiveness of experimental and implemented bycatch reduction

measures: the ideal and the real. Conservation Biology 21, 11551164.

CPPS, 2004. Informe sobre la participacin de la Comisin Permanente del Pacifico

Sur (CPPS) en la Tercera Consulta Internacional sobre la Conservacin y Manejo

multilateral del pez espada en el Pacifico Sudeste. Santiago, Chile, 30 de junio y

1 de Julio de, 2004.

Crouse, D.T., Crowder, L.B., Caswell, H., 1987. A stage-based population model for

loggerhead sea turtles and implications for conservation. Ecology 68, 1412

1423.

Dobson, A.J., 2002. An Introduction to Generalized Linear Models. Chapman & Hall/

CRC Texts in Statistical Science Series. 225 p.

Donoso, M., Dutton, P.H., 2007. Numbers, distribution and stock origin of sea turtlescaught incidentally in the Chilean longline fishery for swordfish, 20012002. In:

Mast, R.B., Hutchinson, B.J., Hutchinson A.H., (Eds.), Proceedings of the Twenty-

Fourth Annual Symposium on Sea Turtle Biology and Conservation. National


SEFSC-567, p. 15 (205 p.).

Domingo, A., Sales, G., Giffoni, B., Miller, P., Laporta, M., Maurutto, G., 2006. Captura

incidental de tortugas marinas con palangre pelgico en el Atlntico Sur por las

flotas de Brasil y Uruguay. Collected Volume of Scientific Papers ICCAT 59 (3),

9921002.

Dutton, P.H., Balazs, G.H., 1995. Simple biopsy technique for sampling skin for DNA

analysis of sea turtles. Marine Turtle Newsletter 69, 910.

Dutton, P.H., 1996. Methods for collection andpreservation of samples for sea turtle

genetic studies. In: Bowen, B.W., Witzell, W.N. (Eds.), Proceedings of the

International Symposium on Sea Turtle Conservation Genetics. National


SEFSC-396, pp. 1724.

Dutton, D.L., Dutton, P.H., Chaloupka, M., Boulon, R., 2005. Increase of a Caribbean

leatherback turtle Dermochelys coriacea nesting population linked to long-termnest protection. Biological Conservation 126, 186194.

Dutton, P.H., Hitipeuw, C., Zein, M., Benson, S.R., Petro, G., Pita, J., Rei, V., Ambio, L.,

Bakarbessy, J., 2007. Status and genetic structure of nesting populations of

leatherback turtles, Dermochelys coriacea, in the western Pacific. ChelonianConservation and Biology 6 (1), 4753.

Dutton, P.H., Squires, D., 2008. Reconciling biodiversity with fishing: a holistic

strategy for Pacific sea turtle recovery. Ocean Development and International

Law 39 (2), 200222.

Eckert, S.A., 1997. Distant fisheries implicated in the loss of the worlds largest

leatherback population. Marine Turtle Newsletter 78, 27.

Eckert, S.A., 2002. Distribution of juvenile leatherback sea turtle Dermochelys

coriacea sightings. Marine Ecology Progress Series 230, 289293.Eguchi, T., Gerrodette, T., Pitman, R.L., Seminoff, J., Dutton, P.H., 2007. At-sea density

and abundance estimates of the olive ridley turtle (Lepidochelys olivacea) in theEastern Tropical Pacific. Endangered Species Research 3, 191203.

Fahy, C.,in press.Fisheries impactson seaturtlesin thePacificOceanIn:Dutton,P.H.,

Squires,D., Mahfuzuddin,A. (Eds.), Conservationand Sustainable Managementof

SeaTurtles in the PacificOcean. University of Hawaii Press, Honolulu.

FAO, 2004. Expert Consultation on Interactions between Sea Turtles and Fisheries

within an Ecosystem Context. FAO Fisheries Report No. 738. Food and

Agriculture Organization of the United Nations, Rome.

FAO, 2005. Report of the Technical Consultation on Sea Turtles Conservation and

Fisheries. Bangkok,Thailand, 29 November2 December 2004. FAO Fisheries

Report No. 765. Food and Agriculture Organization of the United Nations, Rome,

31 p.

Frazier, J.G., Brito-Montero, J.L., 1990. Incidental capture of marine turtles by the

swordfish fishery at San Antonio, Chile. Marine Turtle Newsletter 49, 813.

Fritts, T.H., 1981. Pelagic feeding habits of turtles in the eastern Pacific. Marine

Turtle Newsletter 17, 45.

Gilman, E., Kobayashi, D., Swenarton, T., Brothers, N., Dalzell, P., Kinan, I., 2007.

Reducing sea turtle interactions in the Hawaii-based longline swordfish fishery.

Biological Conservation 139, 1928.

Gilman, E., Gearhart, J., Price, B., Eckert, S., Milliken, H., Wang, J., Swimmer, Y.,

Shiode, D., Abe, O., Peckham, S.H., Chaloupka, M., Hall, M., Mangel, J., Alfaro-

Shigueto, J., Paul Dalzell, P., Ishizaki, A., 2010. Mitigating sea turtle by-catch in

coastal passive net fisheries. Fish and Fisheries 11, 5788.

Graham, W.M., Pags, F., Hamner, W.M., 2001. A physical context for gelatinous

zooplankton aggregations: a review. Hydrobiologia 451, 199212.

Hatase, H., Sato, K., Yamaguchi, M., Takahashi, K., Tsukamoto, K., 2006. Individual

variation in feeding habitat use by adult green sea turtles (Chelonia mydas): arethey obligately neritic herbivores? Oecologia 149, 5264.

Hays-Brown, C., Brown, W.M., 1982. Status of sea turtles in the southeasternPacific:

emphasis on Peru. In: Bjorndal, K.A. (Ed.), Biology and Conservation of Sea

Turtles. Smithsonian Institution Press, Washington, DC, pp. 235240.

Hays, G.C., Hobson, V.J., Metcalfe, J.D., Righton, D., Sims, D.W., 2006. Flexible

foraging movements of leatherback turtles across the North Atlantic Ocean.

Ecology 87, 26472656.

Herv, D., X. Fuentes, X., 2004. El caso del pez espada: una controversia de

jurisdiccin y de derecho sustantivo y los diversos argumentos para inclinar labalanza. Revista de Estudios Internacionales. Ao XXXVI. Abril Junio 2004. No.

145. Instituto de Estudios Internacionales. Universidad de Chile, pp. 83122.

Heppell, S.S., Limpus, C.J., Crouse, D.T., Frazer, N.B., Crowder, L.B., 1996. Population

model analysis for the loggerhead sea turtle, Caretta caretta, in Queensland.Wildlife Research (Australia) 23, 143159.

Hitipieuw, C., Dutton, P.H., Benson, S.R., Thebu, J., Bakarbessi, J., 2007. Population

status and inter-nesting movement of leatherback turtles (Dermochelyscoriacea) nesting on the northwest coast of Papua, Indonesia. ChelonianConservation and Biology 6 (1), 2836.

Howell, E.A., Kobayashi, D.R., Parker, D.M., Balazs, G.H., Polovina, J.J., 2008.

TurtleWatch: a tool to aid in the bycatch reduction of loggerhead turtles

Caretta caretta in the Hawaii-based pelagic longline fishery. Endangered SpeciesResearch 5, 267278.

Howell, E.A., Dutton, P.H., Polovina, J.J., Bailey, H., Parker, D.M., Balazs, G.H., 2010.

Oceanographic influences on the dive behavior of juvenile loggerhead turtles

(Caretta caretta) in the North Pacific Ocean. Marine Biology 157, 10111026.Kamezaki,N., Matsui, M., 1997. A reviewof biological studies on seaturtles in Japan.

Japanese Journal of Herpetology 17, 1632.

Kamezaki, N., Matsuzawa, Y., Abe, O., Asakawa, H., Fujii, T., Goto, K., Hagino, S.,Hayami, M., Ishii, M., Iwamoto, T., Kamata, T., Kato, H., Kodoma, J., Kondo, Y.,

Miyawaki, I., Mizobuchi, K., Nakamura, Y., Nakashima, Y., Naruse, H., Omuta, K.,

Samejima, M., Sugunuma, H., Takeshita, H., Tanaka, T., Toji, T., Uematsu, M.,

Yamamoto, A., Yamato, T., Wakabayashi, I., 2003. Loggerhead turtles nesting in

Japan. In: Bolten, A.B., Witherington, B.E. (Eds.), Loggerhead Sea Turtles.

Smithsonian Books, Washington, DC, pp. 210217.

Kaplan, I.C., 2005. A risk assessment for Pacific leatherback turtles (Dermochelyscoriacea). Canadian Journal of Fisheries and Aquatic Science 62, 17101719.

Kleiber, P., 1998. Estimating annual takes and kills of sea turtles by the Hawaiian

longline fishery, 19911997, from observer program and logbook data. National

Oceanic and Atmospheric Administration Administrative Report H-98-08, p. 21.

Kobayashi, D.R., Polovina, J.J., Parker, D.M., Kamezaki, N., Cheng, I.-J., Uchida, I.,

Dutton, P.H., Balazs, G.H., 2008. Pelagic habitat characterization of loggerhead

sea turtles, Caretta caretta, in the North Pacific Ocean (19972006): Insightsfrom satellite tag tracking and remotely-sensed data. Journal of Experimental

Marine Biology and Ecology 356, 96114.

Koch, V., Nichols, W.J., Peckham, H., de la Toba, V., 2006. Estimates of sea turtle

mortality from poaching and bycatch in Baha Magdalena, Baja California Sur,Mexico. Biological Conservation 128, 327334.



http://dx.doi.org/10.1098/rspb.2008.1931http://dx.doi.org/10.1098/rspb.2008.1931http://dx.doi.org/10.1029/2006JC003541http://dx.doi.org/10.1029/2006JC003541http://dx.doi.org/10.1016/j.biocon.2010.07.011http://dx.doi.org/10.1016/j.biocon.2010.07.011http://dx.doi.org/10.1029/2006JC003541http://dx.doi.org/10.1029/2006JC003541http://dx.doi.org/10.1098/rspb.2008.1931http://dx.doi.org/10.1098/rspb.2008.1931


13/13

Kotas, J.E., Dos Santos, S., Azevedo, V.G., Gallo, B.M.G., Barata, P.C.R., 2004. Incidental

capture of loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea)sea turtles by the pelagic longline fishery off southern Brazil. Fishery Bulletin

102, 393399.

Lewison, R.L., Freeman, S.A., Crowder, L.B., 2004. Quantifying the effects of fisheries

on threatened species: the impact of pelagic longlines on loggerhead and

leatherback sea turtles. Ecology Letters 7, 221231.

Lewison, R.L., Crowder, L.B., 2007. Putting longline bycatch of sea turtles into

perspective. Conservation Biology 21 (1), 7986.

Lewison, R.L., Soykan, C.U., Franklin, J., 2009. Mapping the bycatch seascape:

multispecies and multi-scale spatial patterns of fisheries bycatch. EcologicalApplications 19, 920930.

Limpus, C.J., Limpus, D.J., 2003. Biology of the loggerhead turtle in western South

Pacific Ocean foraging areas. In: Bolten, A.B., Witherington, B.E. (Eds.),

Loggerhead Sea Turtles. Smithsonian Books, Washington, DC, pp. 93113.

Lpez-Mendilaharsu, M., Sales, G., Giffoni, B., Miller, P., Niemeyer, F., Domingo, A.,

2007. Distribucin y composicin de tallas de las tortugas marinas (Carettacaretta y Dermochelys coriacea) que interactan con el palangre pelgico en elAtlntico Sur. Collected Volume of Scientific Papers ICCAT 60 (6), 20942109.

Marcovaldi, M.A., Sales, G., Thom, J.C., Dias da Silva, A.C., Gallo, B.M., Lima, E.H.,

Lima, E.P., Bellini, C., 2006. Sea turtles and fishery interactions in Brazil:

identifying and mitigating potential conflicts. Marine Turtle Newsletter 112, 4

8.

McCracken, M.L., 2000. Estimation of sea turtle take and mortality in the Hawaiian

longline fisheries. National Oceanic and Atmospheric Administration

Administrative Report NMFS-SWFSC-H-00-06.

McCracken, M. L., 2004. Modelling a very rare event to estimate sea turtle bycatch:

lessons learned. National Oceanic and Atmospheric Administration Technical

Memorandum, NMFS-03.

Mejuto, J., Garca-Corts, B., 2005. Documentacin sobre el preparacin de datos

cientficos de la pesquera espaola de pez espada ( Xiphias gladius) en lasregiones del Pacfico, con especial referencia a los aos ms recientes 2002 y

2003. Document DC-1-02d prepared for the Inter-American Tropical Tuna

Commission Data and Standards Review Meeting, La Jolla, California, April 29-

30, 2005.

Moore, J.E., Wallace, B.P., Lewison, R.L., Zydelis, R., Cox, T.M., Crowder, L.B., 2009. A

review of marine mammal, sea turtle and seabird bycatch in USA fisheries and

the role of policy in shaping management. Marine Policy 33, 435451.

Mrosovsky, N., 1980. Thermal biology of sea turtles. American Zoologist 20, 531

547.

Mrosovsky, N., Pritchard, P.C.H., 1971. Body temperatures of Dermochelys coriaceaand other sea turtles. Copeia 1971, 624631.

Oceanic Fisheries Programme, Secretariat of the Pacific Community, 2001. A review

of turtle by-catch in the western and central Pacific Ocean tuna fisheries. A

report prepared for the South Pacific Regional Environmental Programme, May,

2001.

Paladino, F.V., Oconnor, M.P., Spotila, J.R., 1990. Metabolism of leatherback turtles,

gigantothermy, and thermoregulation of dinosaurs. Nature 344, 858860.Peckham, S.H., Maldonado Daz, D., Walli, A., Ruz, G., Crowder, L.B., Nichols, W.J.,

2007. Small-scale fisheries bycatch jeopardizes endangered Pacific loggerhead

turtles. PLoS ONE 2, e1041. doi:10.1371/journal.pone.0001041.

Poiner, I.R., Harris, A.N.M., 1996. The incidental capture, direct mortality and

delayed mortality of turtles in Australias northern prawn fishery. Marine

Biology 125, 813825.

Polovina, J.J., Kobayashi, D.R., Parker, D.M., Seki, M.P., Balazs, G.H., 2000. Turtles on

the edge:movement of loggerhead turtles (Caretta caretta) along oceanic fronts,spanning longline fishing grounds in the central North Pacific, 19971998.

Fisheries Oceanography 9, 7182.

Polovina, J.J., Balazs, G.H., Howell, E.A., Parker, D.M., Seki, M.P., Dutton, P.H., 2004.

Forage and migration habitat of loggerhead (Caretta caretta) and olive ridley(Lepidochelys olivacea) sea turtles in the central North Pacific Ocean. FisheriesOceanography 13 (1), 3651.

Pons, M., Domingo, A., Sales, G., Fiedler, F.N., Miller, P., Giffoni, B., Ortiz, M., 2010.

Standardization of CPUE of loggerhead sea turtle (Caretta caretta) caught bypelagic longliners in the Southwestern Atlantic Ocean. Aquatic Living Resouces

23, 6575.

Pritchard, P.C.H., 1980. Dermochelys coriacea: the leatherback turtle. Catalog ofAmerican Amphibians and Reptiles 238, 14.

Read, A.J., 2007. Do circle hooks reduce the mortality of sea turtles in pelagic

longlines? A review of recent experiments. Biological Conservation 135 (2),

155169.

Roden, G.I., Paskausky, D.F., 1978. Estimation of rates of frontogenesis and

frontolysis in the North Pacific Ocean using satellite and surface

meteorological data from January 1977. Journal of Geophysical Research 83,

45454550.

Sarti, L., Eckert, S.A., Garca, N., Barragan, A.R., 1996. Decline of the worlds largest

nesting assemblage of leatherback turtles. Marine Turtle Newsletter 74, 25.Sarti, L., Barragn, A., Garca, D., Garca, N., Huerta, P., Vargas, F., 2007. Conservation

and biology of the leatherback turtle in the Mexican Pacific. Chelonian

Conservation and Biology 6 (1), 7078.

Maptool, 2002. SEATURTLE.ORG. .

Seminoff, J.A., Zrate, P., Coyne, M., Foley, D.G., Parker, D., Lyon, B.N., Dutton, P.H.,

2008. Post-nesting migrations of Galpagos green turtles Chelonia mydas inrelation to oceanographic conditions: integrating satellite telemetry with

remotely sensed ocean data. Endangered Species Research 4, 5772.

Shillinger, G.L., Palacios, D.M., Bailey, H., Bograd, S.J., Swithenbank, A.M., et al., 2008.

Persistent leatherback turtle migrations present opportunities for conservation.

PLoS Biology 6 (7), e171. doi:10.1371/journal.pbio.0060171.

Sims, M., Cox, T., Lewison, R., 2008. Modeling spatial patterns in fisheries bycatch:

improving bycatch maps to aid fisheries management. Ecological Applications

18, 649661.

Soykan, C.U., Moore, J.E., Zydelis, R., Crowder, L.B., Safina, C., Lewison, R.L., 2008.

Whystudy bycatch? An introduction to the Theme Section on fisheries bycatch.

Endangered Species Research 5, 91102.

Spotila, J.R., Reina, R.D., Steyermark, A.C., Plotkin, P.T., Paladino, F.V., 2000. Pacific

leatherback turtles face extinction. Nature 405, 529530.

Swimmer, Y., Arauz, R., Wang, J., Suter, J., Musyl, M., Bolan, A., Lopez, A., 2010.

Comparing the effects of offset and non-offset circle hooks on catch rates of fish

and sea turtles in a shallow longline fishery. Aquatic Conserv: Mar. Freshw.

Ecosyst.. doi:10.1002/aqc.1108.

Turtle Expert Working Group, 2007. An assessment of the Leatherback turtle

population in the Atlantic Ocean. National Oceanic and Atmospheric

Administration Technical Memorandum, NMFS-SEFSC-555, 116 p.

Vega, R., Licandeo, R., 2009. The effect of Americanand Spanish longline systems on

target and non-target species in the eastern South Pacific swordfish fishery.

Fisheries Research 98, 2232.

Wallace, B.P., Lewison, R.L., McDonald, S.L., McDonald, R.K., Kot, C.Y., Kelez, S.,

Bjorkland, R.K., Finkbeiner, E.M., Helmbrecht, S., Crowder, L.B., 2010. Global

patterns of marine turtle bycatch. Conservation Letters 90. doi:10.1111/j.1755-

263X.2010.00105.x.

Wallace, B.P., Heppell, S.S., Lewison, R.L., Kelez, S., Crowder, L.B., 2008. Impacts of

fisheries bycatch on loggerhead turtles worldwide inferred from reproductive

value analyses. Journal of Applied Ecology 45, 10761085.

Ward, P., Lawrence, E., Darbyshire, R., Hindmarsh, S., 2008. Large-scale experimentshows that nylon leaders reduce shark bycatch and benefit pelagic longline

fishers. Fisheries Research 90, 100108.

Watson, J.W., Epperly, S.P., Foster, D., Shah, A.K., 2005. Fishing methods to reduce

sea turtle mortality associated with pelagic longlines. Canadian Journal of

Fisheries and Aquatic Science 62, 965981.

Witt, M.J., Baert, B., Broderick, A.C., Formia, A., Fretey, J., Gibudi, A., Moussounda, C.,

Avery, G., Mounguengui, M., Ngouessono, S., Parnell, R.J., Roumet, D., Sounguet,

G.-P., Verhage, B., Zogo, A., Godley, B.J., 2009. Aerial surveying of the worlds

largest leatherback turtle rookery: a more effective methodology for large-scale

monitoring. Biological Conservation. doi:10.1016/j.biocon.2009.03.009.

Witzell, W.N., 1984. The incidental capture of sea turtles in the Atlantic U.S. fishery

conservation zone by the Japanese tuna longline fleet, 197881. Marine

Fisheries Review 46 (3), 5658.

Witzell, W.N., 1998. Distribution and relative abundance of sea turtles caught

incidentally by the U.S. pelagic longline fleet in the western North Atlantic

Ocean, 1992-1995. Fishery Bulletin 97, 200211.

Yokota, K., Kiyota, M., Okamura, H., 2009. Effect of bait species and color on sea

turtle bycatch and fish catch in a pelagic longline fishery. Fisheries Research 97,

5358.

http://dx.doi.org/10.1371/journal.pone.0001041http://www.seaturtle.org/maptool/http://dx.doi.org/10.1371/journal.pbio.0060171http://dx.doi.org/10.1002/aqc.1108http://dx.doi.org/10.1111/j.1755-263X.2010.00105.xhttp://dx.doi.org/10.1111/j.1755-263X.2010.00105.xhttp://dx.doi.org/10.1016/j.biocon.2009.03.009http://dx.doi.org/10.1016/j.biocon.2009.03.009http://dx.doi.org/10.1111/j.1755-263X.2010.00105.xhttp://dx.doi.org/10.1111/j.1755-263X.2010.00105.xhttp://dx.doi.org/10.1002/aqc.1108http://dx.doi.org/10.1371/journal.pbio.0060171http://www.seaturtle.org/maptool/http://dx.doi.org/10.1371/journal.pone.0001041

Date post:	29-May-2018
Category:	Documents
Upload:	tortugamarina
View:	222 times
Download:	0 times

Do No So Dutton

Documents