On Tuna and

Tuna-Related Activities at the

Southwest Fisheries Science Center

for the Period May 1, 2009

to April 30, 2010

National Marine Fisheries Service

Southwest Fisheries Science Center

ADMINISTRATIVE REPORT LJ-10-02

61st

Director’s Report

Tuna Conference

to the

61

st
"This report is used to ensure prompt dissemination of preliminary results, interim 

reports, and special studies to the scientific community. The material is not ready for 

formal publication since the paper may later be published in a modified form to 

include more recent information or research results. Abstracting, citing, or 

reproduction of this information is not allowed. Contact author if additional 

information is required."
61st

DIRECTOR’S REPORT TO

 THE 61st TUNA CONFERENCE ON

TUNA AND TUNA-RELATED ACTIVITIES

AT THE SOUTHWEST FISHERIES SCIENCE CENTER

FOR THE PERIOD MAY 1, 2009 TO APRIL 30, 2010

Usha Varanasi, Ph.D., Acting Director

National Marine Fisheries Service, NOAA

Southwest Fisheries Science Center

8604 La Jolla Shores Drive

La Jolla, CA 92037-1508

May 2010

ADMINISTRATIVE REPORT LJ-10-02

NAT

OI N

A

L

IC NAECO

INIST

R

AT

OI N

ND A ATMOSPHERIC ADM

U.S. DEPARTMENT OF

ECRE M OM C

Contents

Introduction...........................................................................................iii

I. Supporting U.S. Obligations of International Agreements..................................1 

II. Supporting Pacific Fishery Management Council Activities.............................3 

III. Highly Migratory Species Data Coordination................................................3 

IV. Advancing Tuna and Billfish Research......................................................4 

V. Advancing Pelagic Shark Research..........................................................12 

VI. IDCPA Research...............................................................................20 

VII. Publications......................................................................................25 

Introduction

This report highlights Southwest Fisheries Science Center activities during the past year relating

to tropical tunas, albacore, billfishes, oceanic sharks, and protected species associated with their 

fisheries. The Center’s biological, economic, and oceanographic research was focused on 

supporting the information needs of international scientific working groups and committees, the 

Pacific Fishery Management Council, and the National Marine Fisheries Service. Major tunarelated activities included stock assessments, socio-economic research, research on interactions 

between fisheries and protected species, and mathematical modeling of fish movements and 

fishery interactions. The data collection and analysis were aimed at maintaining healthy U.S. and 

world fisheries, populations of protected marine species, and fish habitat, and ensuring that the 

most effective fishing regulations and international treaties are carried out supported by best 

available science. Center scientists also were active in tuna-related international fora such as the 

International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean 

and the Scientific Committee of the Western and Central Pacific Fisheries Commission.

1 

I. SUPPORTING U.S. OBLIGATIONS OF INTERNATIONAL AGREEMENTS

The United States is party to a number of international agreements for the conservation of highly 

migratory species (HMS) in the Pacific Ocean. As such, it is obligated to collect fishery 

statistics from U.S. HMS fisheries and to participate in advancing fishery science for species of 

interest. Scientists at the Southwest Fisheries Science Center (SWFSC) have been tasked to 

fulfill this obligation. In this section, brief descriptions of some of the contributions and 

activities during the past year, May 2009–April 2010, are described.

Monitoring the Purse Seine Fishery in the Western-Central Pacific Ocean – The National 

Marine Fisheries Service (NMFS) collects and manages data from the U.S. purse seine fishery 

for tropical tunas in the western-central Pacific Ocean as part of U.S. obligations under the South 

Pacific Tuna Treaty. Information from U.S. vessels licensed to fish under the treaty is collected 

by the NMFS Pacific Islands Regional Office (PIRO) in American Samoa and transmitted to the 

SWFSC in La Jolla, California, where information from logbooks and landings and biological 

data from port sampling are processed.

The size of the U.S. purse seine fleet increased in 2009 to 38 vessels from 37 vessels in 2008. 

Preliminary estimates of the 2009 catch (164,797 metric tons, t) decreased 18% from the 202,030 

t caught in 2008. Skipjack tuna (Katsuwonus pelamis) dominated the 2009 catch (91%), followed 

by yellowfin tuna (Thunnus albacares) (8%), and bigeye tuna (T. obesus) (0.43%; percentages 

are not adjusted from species composition sampling). 

Purse seine sets on floating objects (logs and fish aggregation devices) in 2009 accounted for 

50% of the total sets, an increase from 41% of total sets recorded in 2008. Sets on freeswimming schools accounted for 50% of sets, a decrease from 59% in 2008. The overall catch 

rate (CPUE) was 35 t per day fished in 2009, a 21% increase from 29 t per day fished in 2008. 

Biological samples collected from the tuna catch provided estimates of sizes of fish caught on a 

species by species basis. Length measurements were taken from 40,478 yellowfin, skipjack, and 

bigeye tunas, a decrease of 39% from the 66,593 fish sampled in 2008. Preliminary estimates of 

average fork lengths (FL) of fish sampled in 2009 are not yet available. 

Contributing to the Work of the ISC – The United States is a member of the International 

Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean (ISC), along 

with Canada, China, Chinese Taipei, Japan, Korea, the Inter-American Tropical Tuna 

Commission (IATTC), North Pacific Marine Science Organization, Secretariat of the Pacific 

Community (SPC), and Food and Agriculture Organization. The purpose of the ISC is to 

enhance scientific research and cooperation for conservation and rational utilization of species of 

tuna and tuna-like fishes which inhabit the North Pacific Ocean, and to establish the scientific 

groundwork for the conservation and rational utilization of these species in the region through a 

multilateral regime. The ISC is organized into five Working Groups—statistics, bycatch, Pacific 

bluefin tuna, albacore, and billfish—that meet intercessionally and report to a Plenary body. The 

overall chairman of the ISC is Gary Sakagawa of SWFSC. Results of the ISC are made available 

to participating members and to HMS regional fisheries management organizations of the Pacific 

Ocean.
2 

The 9th Plenary meeting of the ISC was held in Kaohsiung, Taiwan, July 15-20, 2009, and hosted 

by Taiwan’s Council of Agriculture. Scientists from Canada, Chinese Taipei, Japan, Korea, 

United States, and SPC participated. A member of the WCPFC Secretariat attended as an 

observer. SWFSC Acting Director Norm Bartoo led the U.S. delegation at this meeting.

Key results of the 9th meeting.

1

 The ISC Plenary reviewed the results of work performed by the 

Working Groups since the 8th meeting. Considerable progress was made in stock assessment 

research and towards understanding the status of the North Pacific stocks. A Pacific bluefin tuna 

(T. orientalis) stock assessment involving the Stock Synthesis v.3 model was updated using 

improved mortality estimates. The ISC reiterated that it was important that the fishing mortality 

rate for Pacific bluefin tuna not be increased. A qualitative update using recent data was 

completed for North Pacific albacore tuna. Because a full stock assessment has not been 

conducted for albacore since 2006, it was agreed that a planned stock assessment in 2011 is 

critical. Until then, the 2007 ISC advice regarding albacore fishing mortality rate, i.e., that it 

should not be increased above recent levels, still holds. A swordfish (Xiphias gladius) stock 

assessment using the Bayesian Surplus Production model was completed. ISC found the stock to 

be healthy and above the level required to sustain recent catches. The 2007 advice for striped 

marlin (Tetrapterus audax), i.e., that fishing mortality should be reduced, still holds, and a new 

assessment is planned for 2011. 

Miscellaneous matters were also addressed during the 9th meeting, including a special seminar on 

biological reference points (BRPs) to facilitate discussion of how BRPs can be formulated, and a 

proposal for multispecies, multinational biological research was approved. In looking ahead, the 

Plenary agreed to prioritize and accelerate work on the ISC database and website in order to 

improve the interface between the ISC and its partners and constituents, and to continue 

preparations for upcoming stock assessments of albacore and striped marlin scheduled for 2011 

and for blue marlin and Pacific bluefin tuna scheduled for 2012. The ISC Plenary also agreed to 

pursue organizing a World Blue Marlin Symposium to convene experts on this species and 

gather information for the upcoming stock assessment. The next Plenary will be held in July 

2010 in Victoria, Canada. 

Albacore Stock Assessment and Research – The commercial surface albacore fishery is the 

most important fishery for HMS on the U.S. West Coast. As participants in the ISC Albacore 

Working Group, in 2009 SWFSC researchers began preparations for a full stock assessment of 

North Pacific albacore scheduled for early 2011. The working group is expected to move from a 

VPA-type model, used in previous assessments, to a length-based SS3 model for the upcoming 

stock assessment. 

To prepare for this stock assessment, a manuscript was recently completed that describes the 

changes in the distribution of catch and effort of the troll fishery from 1960 to 2008. One of the 

interesting changes has been the intense concentration of effort in the waters off Oregon and 

Washington over the past decade. From the 1970s to 1990s, a large proportion of the catch effort 

occurred along the transition zone of the North Pacific. However, from 2000 to 2008, ~75% of 

the catch and effort was concentrated in a 5° x 10° area off the Oregon and Washington coasts. 

 

1 Excerpted from the report “International agreements concerning living marine resources of interest to NOAA 

Fisheries. 2009. NMFS Office of International Affairs. Compiled and edited by Melanie D. King.
3 

We also investigated the CPUE and length-composition time series in 4 subareas (dividing lines 

at 40°N and 130°W). The range of lengths caught by the albacore troll fishery was similar in all 

areas (corresponding to approximately age-2, -3, and -4 year classes). Length compositions in 

all areas were multimodal, with the strongest mode at age-3 (~65 cm FL). However, areas south 

of 40°N showed a relatively higher proportion of age-4 fish, which explains the higher mean 

lengths reported by previous studies. The areas south of 40°N also showed a relatively higher 

variability in the relative proportions of age-3 and -4 cohorts as compared with the areas north of 

40°N, which has age-3 fish dominating the catch for most years. While the CPUE indices for the 

area south of 40°N were unreliable due to a lack of data, the CPUE indices for the other areas 

were relatively similar and highly correlated with each other (r ranged from 0.57 to 0.96, p < < 

0.001 for all correlations). 

In addition to analyzing the catch data for the troll fishery, other efforts related to albacore stock 

assessments are ongoing at the SWFSC. Currently, we are investigating the reliability and 

applicability of using albacore CPUE indices from pelagic longlines as indicators of spawning 

stock biomass as well as exploring options for suitable reference points. Longline CPUE indices 

may be useful for examining trends in abundance for the years between stock assessments that 

are typically conducted only every few years. SWFSC scientists are also investigating the 

effects of short- and long-term environmental change on the catch and population dynamics of 

North Pacific albacore tuna by incorporating information from traditional fisheries (catch and 

effort) and tagging (both electronic and conventional) data into a coupled environmentalpopulation dynamic model. 

II. SUPPORTING PACIFIC FISHERY MANAGEMENT COUNCIL ACTIVITIES

Center scientists Stephen Stohs, Kevin Piner and Suzanne Kohin served on the Highly Migratory 

Species Management Team (HMSMT) of the Pacific Fishery Management Council over the past 

year. Stephen Stohs has been HMSMT chair since April 2009 and was reappointed for a second 

term as of February 2010. The team met several times in 2009 and early 2010 to review fishery 

information, complete assignments from the Council, and evaluate provisions of the Fishery 

Management Plan for U.S. West Coast Fisheries for Highly Migratory Species. 

The main HMS issues facing the team and the Council over the past year have been (1) 

addressing requirements under revised National Standard 1 guidelines for establishing annual 

catch limits and biological reference points for highly migratory species; (2) reviewing the 

recommendations contained in a white paper to consider potential measures for limiting future 

effort on North Pacific albacore tuna by the West Coast commercial albacore fleet; (3) providing 

recommendations to the delegations of the WCPFC and IATTC for international fishery 

management; (4) developing protocols for improved recreational fishery data collection from 

Southern California shark anglers and the West Coast recreational for-hire fishery targeting 

albacore; and (5) preparing the 2009 Stock Assessment and Fishery Evaluation (SAFE) Report. 

III. HIGHLY MIGRATORY SPECIES DATA COORDINATION

The Pacific Islands Fisheries Science Center (PIFSC), PIRO, Southwest Regional Office 

(SWRO), and SWFSC share reporting obligations for HMS fisheries in the Pacific. Each office 
4 

is involved with the coordination of reporting obligations and collaborates to produce and 

provide HMS data summaries for these reporting obligations. Staff from each office routinely 

exchange information needed for various reports, data submissions and other reporting purposes 

such as informal data requests. Formal annual meetings of the staff members have not occurred 

since 2005, though ad hoc meetings and correspondence continue.

HMS staff are also involved with the Fisheries Information System (FIS) project based at NMFS 

headquarters. A representative of the SWFSC and the PIFSC is on the FIS Program 

Management Team. FIS funds numerous projects that contribute toward improving fisheriesdependent data that are collected and maintained by the agency. Staff members from SWFSC 

and PIFSC are leading several of these projects to improve data collection and management 

systems in their respective regions.

HMS information technology specialists at the SWFSC are also improving data collection 

methods. Current electronic data collection and monitoring projects include data collection 

systems for regional observer programs, electronic calipers and handheld computers used to 

collect length measurements, and electronic logbook software applications. These new 

monitoring and collection methods will increase data quality and timeliness of reporting and 

reduce operational costs while easing reporting burdens of fishermen.

IV. ADVANCING TUNA AND BILLFISH RESEARCH

The SWFSC research on tunas and billfishes in the Pacific Ocean has largely been focused on 

improving our understanding of the biology and ecology of the animals to support needs for 

assessing the effects of fishing and environment on the population or stock. Described below are 

studies that have been completed or are ongoing by Center staff. These studies are carried out 

largely in cooperation with stakeholders and in collaboration with colleagues both in the U.S. 

and abroad. 

Monitoring the U.S. Albacore Troll Fishery – U.S. troll vessels have fished for North Pacific 

albacore since the early 1900s and for South Pacific albacore since 1986. North Pacific albacore 

fishing areas range from Vancouver Island to the coast of Baja California and from the U.S. 

West Coast to approximately 160°E. The fishing season begins in late April and can last into 

mid-November. The size of the troll fleet for a season ranges from 500 vessels to over 1,000 

vessels. About 480 U.S. troll vessels fished for North Pacific albacore in 2008. 

Fishing areas for South Pacific albacore extend eastward from the east coast of New Zealand to 

approximately 110°W and between 30°S to 45°S. This fishery begins in late December and 

continues until early April of the following year. The international troll fleet in the South Pacific 

consists of 5 to 50 vessels. Factors such as increased fuel costs, lower ex-vessel prices and 

reduced availability of fish have contributed to a decrease in participation in the South Pacific 

troll fishery in recent years. Only three U.S. troll vessels fished for albacore in the South Pacific 

during the 2007-2008 season; they caught 150 t of albacore, a significant decrease from 271 t 

caught the previous season. Bycatch species are sometimes reported in vessel logbooks and 

include yellowtail, dolphinfish and skipjack, as well as yellowfin, bigeye and bluefin tunas. 
5 

The Center routinely collects, manages, and reports the following information for use in stock 

assessments and for monitoring the U.S. albacore troll fisheries in the Pacific: (1) landings data 

obtained from U.S. West Coast states and canneries in American Samoa; (2) logbook data 

collected from albacore troll and baitboat fishermen; and (3) length-frequency data obtained 

through port sampling of U.S. albacore troll and baitboat vessels operating in the Pacific Ocean.

The SWRO provides logbooks to fishermen, who record fishing information and return the 

logbooks to the Center. Beginning in April 2005, logbooks have become mandatory under the 

requirements of an HMS Fishery Management Plan. Length-frequency data are collected 

through a Pacific States Marine Fisheries Commission contract to Washington, Oregon, and 

California state fisheries agencies and from the NMFS office in American Samoa. Data 

collected during the 2008 season were analyzed by SWFSC staff and summarized in a report 

issued in January 2010 (Childers and Betcher 2010, LJ-10-01). Highlights of the report are 

given below. 

Summary of U.S. North and South Pacific Albacore Troll Fisheries – U.S. troll vessels in the 

North Pacific landed 10,254 t of albacore in 2008, compared to 11,887 t landed in 2007. Annual 

catches over the last 10 years averaged 11,183 t. The most productive fishing areas in 2008 were

in Pacific Northwest waters off Washington and Oregon. U.S. catches of South Pacific albacore 

decreased from 271 t in the 2006-2007 season to 150 t in the 2007-2008 season, the lowest catch 

on record for this fishery. South Pacific catches averaged 1,157 t over the past 10 years. 

CPUE in the North Pacific fishery remained relatively steady in 2008 at 71 fish per day. Total 

effort decreased from 24,000 days fished in 2007 to 20,582 days fished in 2008. CPUE for the 

South Pacific fishery decreased from 65 fish per day in the 2006-2007 season to 51 fish per day 

in the 2007-2008 season. Total effort decreased from 813 days fished in 2006-2007 to 239 days 

fished in 2007-2008. 

A total of 27,432 albacore were measured during the 2008 North Pacific season. The average FL

of albacore in 2008 was 70 cm (15.5 lb or 7 kg), nearly the same as the average size in 2007. A 

bimodal size distribution, with peaks at 65 cm and 75 cm FL (3- to 4-year-olds), was evident in 

the North Pacific length-frequency samples. No fish were measured during the 2007-2008 South 

Pacific albacore fishery. 

Cooperative Research with AFRF – SWFSC scientists are working with the American 

Fishermen’s Research Foundation (AFRF) on monitoring programs and other research efforts to 

improve knowledge of the biology and migration of North Pacific albacore in the waters off the 

U.S. Pacific coast. The cooperative research is described below. 

North Pacific Albacore Biological Data Sampling Program – Since 1961, a biological data 

collection program, or port sampling program, has been in place for collecting size data from 

albacore landings made by the U.S. and Canadian troll fleets at ports along the U.S. Pacific 

coast. State fishery personnel collect the biological data by following sampling and data 

processing instructions provided by the SWFSC, where the database is maintained. In recent 

years, with AFRF support, fishermen have collected biological data during selected fishing trips. 

These data are collected to augment data collected through the port sampling program. 
6 

Following procedures established by SWFSC scientists, fishermen on five vessels measured 

2,154 albacore during the 2008 season. During 2009, three vessels measured 280 fish. The 

sample information provided by the fishermen helped to fill in gaps missed by the port sampling 

program. Overall, the sizes were found to be generally similar to those collected through the port 

sampling program.

North Pacific Albacore Archival Tagging Project – The SWFSC and AFRF have been working 

together to use archival tags to study migration patterns and general life history strategies of 

subadult (ages 2-5) North Pacific albacore. Archival tags provide detailed information on 

migratory behaviors, distributions and habitat use. Since 2001, 594 archival tags have been 

deployed along the Oregon and Washington coasts and off Southern California and northern 

Baja California, Mexico. During 2009, one tagging trip was conducted in the northern fishery 

area off the Columbia River, where 41 tags were deployed. Recovery rates have been very low, 

with only 22 archival tags recovered to date. Two tags were recovered in 2008, both aboard 

longline vessels operating in the central Pacific. 

Data from the recovered tags demonstrate a wide range of behaviors of juvenile albacore. Most 

fish were at liberty for over a year and collectively have provided over 7,800 days of data. Daily 

location estimates refined with state-space models and the minute-by-minute depth and 

temperature data are providing new insights into the vertical and horizontal movements and 

feeding behavior of albacore; these data are impossible to obtain without this technology. 

Overall, geolocation estimates indicate that the tagged albacore ranged from the southern tip of 

Baja California to Vancouver Island and from the coast of North America to the eastern coast of 

Japan. Most fish demonstrated a diurnal pattern of daytime diving (routinely to depths of 250 to 

300 m) while remaining near the surface at night. At a finer-scale, temporal and spatial patterns 

in distributions and behaviors were observed. To compare behaviors and habitats in different 

regions, high-use or focal areas were identified both onshore and offshore. During summer and 

fall months near the U.S. West Coast off Oregon and Washington, the mean swimming depth of 

juvenile albacore was approximately 19 m, and greater than 70% of their time was spent in the 

surface mixed layer. During summer months off Southern California and northern Baja 

California, Mexico, mean swimming depth was similar (approximately 25 m). In contrast, in 

offshore areas during the winter and spring, the mean swimming depth ranged from 41 to 92 m 

depending upon the region, and average time spent in the upper isothermal layer ranged from 

40% to 81%. Satellite-derived chlorophyll-a concentrations and sea surface temperature (SST) 

were shown to be variable across the different focal areas with higher chlorophyll-a values and 

cooler SST near shore. In areas were chlorophyll-a concentrations were lower and the mixed 

layer depth was poorly defined, albacore spent more time at depth, suggesting a deeper foraging 

strategy where productivity in the top 50 m may be lower. Average SST ranged from 16.7 °C to 

20.7 °C while average chlorophyll-a values ranged from 0.07 mg m-3 to 0.4 mg m-3. A 

manuscript detailing the results from this study has been submitted for publication and is 

currently under peer review. 

Cooperative Research with Billfish Anglers – The SWFSC and billfish angling community have 

been working together since 1963 to study various aspects of billfish biology and to obtain an index 

of angler success in the Pacific Ocean. This collaboration has resulted in one of the longest time-
7 

series available for recreational billfishing, charting trends in catch-per-unit-effort for key species. 

The research has also included recreational and commercial fishery monitoring, stock 

assessments efforts, biological research into the life history and ecology of specific billfish 

species, and determining the economic importance of billfish resources. Two major components 

of the cooperative research that were the focus of 2009 efforts are the International Billfish 

Angler Survey and the Billfish Tagging Program. 

International Billfish Angler Survey – In 2009, SWFSC researchers summarized the results 

from the 2008 Billfish Angler Survey. Initiated in 1969, the survey now provides a 40-year time 

series of billfish angling effort and catch in the Pacific Ocean. Billfish anglers reported catching 

a total of 3,008 billfish in 4,217 fishing days during 2008. While overall fishing effort reported 

was down compared to 2007 (5,654 days fished), catch rates were relatively high. Overall, mean 

CPUE (number of billfish caught per angler-day) for all billfish in the Pacific Ocean was 0.72 in 

comparison to 0.68 in 2007. CPUE time series were also examined for the main species caught 

[Pacific blue marlin (Makair nigricans), striped marlin, Pacific sailfish (Istiophorus platypterus), 

and black marlin (Makaira indica)] in the main fishing areas (Tahiti, Hawaii, Baja California, 

Mexico, Southern California, Guatemala, Costa Rica, Panama, and Australia; Fig. 1). Blue 

marlin catch rates reported from Hawaii were the second highest on record. Similarly, striped 

marlin catch reported from Mexico remained high after a very good year in 2007. High striped 

marlin CPUE off Baja California Sur, Mexico, contributed to this result. To the south, total 

sailfish catch off Central America was lower off Panama and Costa Rica compared to the 

previous year. Finally, respondents from Panama indicated a continuing upward trend in black 

marlin catch rates. 

Recreational Billfish Tagging Program – The SWFSC’s Billfish Tagging Program has provided 

tagging supplies to recreational billfish anglers for 47 consecutive years. Tag release and 

recapture data are used to determine movement and migration patterns, species distribution, and 

age and growth patterns. This volunteer tagging program depends on the participation and 

cooperation of recreational anglers, sportfishing organizations, and commercial fishers. Since its 

inception, over 59,000 fish of 75 different species have been tagged and released. Emphasis 

continues to be on the skillful tagging of billfish. In 2008, 863 billfish were tagged and released 

by a combination of over 550 anglers and 113 participating captains. The number of fish tagged 

increased in 2008 from 2007, which is a positive sign considering our International Survey 

indicated a drop in fishing effort in 2008. In total, 501 blue marlin, 177 striped marlin, 75 

sailfish, 100 shortbill spearfish (Tetrapturus angustirostris), 1 black marlin, and 9 unidentified 

billfish were reported tagged and released. Table 1 shows the tagging effort for 2008 and the tag 

recoveries throughout the program’s history. The data include releases made by SWFSC 

scientists during research cruises in addition to the angler releases.
8 

 

Figure 1. CPUE as catch-per-angler-day is shown from 1969 through 2008 for A) Pacific blue 

marlin, B) striped marlin, C) Pacific sailfish, and D) black marlin. 

C)

A)

B)

D)

B)

A)
9 

Table 1. Summary of all fish tagged through the Billfish Tagging Program in 2008 with releases 

and recoveries for 1963–2008, including fish tagged and released as part of the SWFSC’s 

ongoing research efforts. 

SPECIES NAME RELEASE 

2008

RELEASE 

TOTAL

RETURN 

TOTAL

RETURN 

RATE %

Striped Marlin 177 22,818 343 1.50

Pacific Blue Marlin 501 9,768 85 0.87

Sailfish 75 9,120 49 0.54

Billfish, unidentified 9 4,361 6 0.14

Black Marlin 1 3,384 69 2.04

Shortfin Mako Shark 55 2,041 77 3.77

Shortbill Spearfish 100 2,046 2 0.10

Blue Shark 268 890 35 3.93

Common Thresher Shark 283 853 34 3.99

Broadbill Swordfish 0 521 17 3.26

Yellowfin Tuna 0 348 25 7.18

Skipjack Tuna 1 100 2 2.00

Albacore 0 87 1 1.15

Bigeye Tuna 0 79 2 2.53

Bluefin Tuna 0 58 8 13.79

Bronze Whaler Shark 0 51 1 1.96

Hammerhead Shark 0 50 1 2.00

Atlantic Blue Marlin 0 43 0 0.00

Salmon Shark 0 33 1 3.03

Silky Shark 0 21 0 0.00

White Marlin 0 13 1 7.69

Basking Shark 0 7 0 0.00

Longbill Spearfish 0 4 0 0.00

Other Tunas 0 21 1 4.76

All Others 6 2,634 98 3.74

TOTAL 1,476 59,351 858 1.45

Swordfish Research and SLUTH – Since 2006, NMFS has been studying swordfish in the 

Southern California Bight to examine migratory patterns, foraging ecology, and local stock 

structure. In 2008, researchers in the Fisheries Resources Division (FRD) teamed up with the 

Protected Resources Division (PRD) and the Southwest Region (SWR) to launch a new 

initiative, Swordfish and Leatherback Use of Temperate Habitat (SLUTH). The overarching 

objective of SLUTH is to integrate studies of swordfish and leatherback sea turtles to inform 

management and conservation efforts. The endangered leatherback is taken incidentally in 

swordfish fisheries, and concerns about leatherback populations are currently shaping the 

management of swordfish fisheries along the U.S. West Coast. The first step in this process was 

a stakeholder workshop that was conducted in May of 2008. A report detailing the content and 

discussions of the workshop was published as an Administrative Report in 2009 (Benson et al.

2009, LJ-09-06).
10 

While a large organized initiative has yet to be established, FRD has initiated a number of 

research projects directed towards specific SLUTH goals. These research projects include 

characterizing the environmental conditions associated with fishing, swordfish and leatherback 

catch, assessing the rates of blue shark bycatch in drift gillnet and longline fisheries, and 

deploying additional electronic tags to quantify the movements and habitat of swordfish. 

Incidental Take of Blue Sharks in the U.S. West Coast Drift Gillnet and Longline Fisheries 

for Swordfish – Blue sharks (Prionace glauca) are the most commonly caught non-target species 

in the longline fishery and the second most common bycatch species taken in the drift gillnet 

fishery. With funding from the NOAA Bycatch Reduction Engineering Program, we have been 

analyzing observer and logbook data to characterize the catch of blue sharks and to identify 

seasons, areas and gear configurations that yield the lowest blue shark to swordfish catch ratios. 

To compare catch ratios for drift gillnets and longlines, over 250,000 sets from logbooks and 

over 100,000 observed sets have been compiled for the California drift gillnet and longline 

fisheries and the Hawaii longline fishery. The ratio of blue shark catch to swordfish catch per set 

was analyzed with respect to a range of factors related to fishing methods and temporal and 

spatial patterns as well as regional oceanography. Preliminary results show that on average the 

drift gillnet fishery has a lower blue shark to swordfish catch ratio than the California and Hawaii

longline fisheries combined; however, significant differences were apparent between the logbook 

and observer data for each of the fisheries, likely due to under-reporting of blue shark catch in 

the logbooks. For example, the median ratios for the drift gillnet logbook and observer datasets 

are 0.0, and 0.4, respectively, whereas those for the California longline logbook and observer 

datasets are 0.34 and 0.52, respectively. Lower blue shark to swordfish ratios were observed 

during the month of August for both fisheries. Additional analyses using multivariate statistical 

methods are currently underway to tease apart the complex relationships among the environment, 

location, data type and gear type. 

Characterizing Target and Non-target Species Catch and the Behavior of Fishermen – Part of 

the SLUTH initiative is to better understand the environmental factors that affect the distribution 

of leatherbacks, swordfish, and the fishers themselves. Working together, researchers from the 

PRD and FRD are using novel statistical approaches to model the relationships between the 

distribution and abundance of these focal species, fishing effort, and environmental drivers such 

as SST, oceanic fronts, and primary productivity. Data are being analyzed at a variety of scales, 

ranging from the entire Pacific Ocean down to the Southern California Bight ecosystem, and 

using several complementary techniques including kriging, Bayesian hierarchical modeling, 

regression trees and their derivatives (random forests, boosted trees, etc.). At the largest scales 

the objective is to identify general regions where fisheries-leatherback interactions are most 

likely to occur so as to focus management efforts. At smaller scales the goal is to identify 

environmental features that separate swordfish from leatherbacks, if they exist, thereby 

improving fishing efficiency and reducing bycatch encounters. This work is currently ongoing 

and will help toward efforts to develop a real-time model to predict encounters between turtles 

and fishing vessels. 

Electronic Tagging of Swordfish – In addition to characterizing swordfish habitat using catch 

data, electronic tags are also being used. Efforts are focused both on deploying archival tags and 
11 

towed Fast-Loc GPS satellite tags that will provide regular, highly accurate locations. Of two 

archival tags deployed this summer in conjunction with the juvenile shark longline survey, one 

was recovered near the tagging location. The two swordfish tagged during the survey were the 

first longline-caught swordfish to be tagged in the Southern California Bight. The detailed 

temperature and depth data from the recovered fish reveal the typical day/night dive patterns 

observed in other records. Interestingly, however, the swordfish made only three basking events 

in 106 days resulting in very low vulnerability to the harpoon fleet. This rate of basking is less 

than expected based on data from fish tagged at the surface with pop-off satellite archival 

(PSAT) tags using a modified harpoon. 

Foraging Ecology – With the reauthorization of the Magnuson-Stevens Fishery Conservation 

and Management Act in 2006, there is a move towards ecosystem-based management. This 

approach requires information on ecological relationships among species, one of the most 

important being trophic interaction. To determine the trophic relationships of highly migratory 

species in the Southern California Bight, the SWFSC has been investigating the foraging ecology 

of a range of species since 1999. 

Biological Sampling of Tunas in the Southern California Bight – Tuna in the Southern 

California Bight, including U.S. and Mexico waters, support substantial commercial and 

recreational fisheries and are also important components of the local food web. To better 

understand their basic biology and ecological role in the U.S. Southern California Bight, the 

SWFSC and the Sportfishing Association of California initiated a biological sampling program 

in 2007 to collect data on tuna and other HMS. Utilizing the commercial passenger fishing 

vessels (CPFV) and recreational anglers based out of San Diego, we collected samples from 

albacore, bluefin, yellowfin, skipjack, and dorado (Coryphaena hippurus). To date we have 

collected approximately 200 samples from each species of tuna excluding skipjack (n=15), 

which are not commonly targeted by the CPFV fleet. In 2009, we expanded the program to the 

northeast Pacific Ocean and are working with commercial fishermen to collect samples from 

albacore off Oregon and Washington. This year the program will be further expanded to include 

Monterey Bay, where albacore are commonly encountered from August through December. 

While we are collecting a range of tissues, including otoliths and gonads, the initial focus has 

been on stomach content analysis. 

Preliminary analysis of stomach contents shows that tuna forage almost exclusively on juvenile 

fish and squid (average standard fish prey length of 5.3 cm, average squid lower rostral length of 

0.34 cm). In 2007, small teleosts comprised the dominant prey category by frequency of 

occurrence (89%), followed by cephalopods (18%) and crustaceans (16%). In 2008, results 

show a shift in prey composition with cephalopods [(Abraliopsis felis), California market squid

(Loligo opalescens), and jumbo squid (Dosidicus gigas)] playing a more important role by 

frequency of occurrence (86%), followed by teleosts (84%) and crustaceans (56%). While 

teleosts were important in both years, the species composition changed. In 2007, 80% of the 

stomachs contained northern anchovies (Engraulis mordax), whereas in 2008 this dropped to 

only 2% of stomachs. Juvenile Sebastes spp., myctophids, and jack mackerel (Trachurus 

symmetricus) made up the majority of teleost prey in 2008. The samples collected in 2009 have 

yet to be processed. The appearance of tuna and other HMS in the Southern California Bight 
12 

during summer and fall likely coincides with the peak in abundance of a range of juvenile fish 

and squid species. 

In addition to studying the HMS themselves, the predators can be used as biological samplers 

and provide a snapshot of the forage base. Linking changes in environmental factors that 

influence the recruitment, fecundity, and resulting availability of forage prey types may reveal 

insight about habitat quality and migration patterns of HMS in the Southern California Bight. By 

characterizing the pelagic food web in the Southern California Bight and California Current we 

hope to better understand how predators and prey utilize the diverse habitats found along U.S. 

West Coast. By sampling over multiple years we can gain insight into the impacts of changes in 

climate on local ecosystems. 

V. ADVANCING PELAGIC SHARK RESEARCH

The SWFSC’s shark research program focuses on pelagic sharks that occur along the U.S. 

Pacific coast, including shortfin mako (Isurus oxyrinchus), blue sharks, and three species of 

thresher sharks: common thresher (Alopias vulpinus), bigeye thresher (A. superciliosus), and 

pelagic thresher (A. pelagicus). Center scientists are studying the sharks’ biology, distribution, 

movements, stock structure, population status, and potential vulnerability to fishing pressure. 

This information is provided to international, national, and regional fisheries conservation and 

management bodies having stewardship for sharks and other HMS. Some of the recently 

completed and ongoing shark research activities being carried out at the SWFSC are discussed 

below. 

Abundance Surveys – The blue, shortfin mako, and thresher sharks are all taken in regional 

commercial and recreational fisheries. Common thresher and mako sharks have the greatest 

commercial value and are also specifically targeted by sport fishers, especially off Southern 

California. Although the blue shark is targeted in Mexico, it has little market importance in the 

U.S. but is a leading bycatch species in the U.S. West Coast drift gillnet and high-seas longline 

fisheries. Although catches of adult blue, thresher, and shortfin mako sharks do occur, the 

commercial and sport catch of these species off Southern California consists largely of juvenile 

sharks. 

To track trends in the abundance of juvenile and subadult blue and shortfin mako sharks and 

neonate common thresher sharks, surveys are carried out in the Southern California Bight each 

summer. Efforts to determine abundance trends from commercial fishery data have been 

complicated by changes in regulations, targeted areas and fishing methods over time. These 

changes have resulted in inconsistent capture rates and catch distributions that are difficult to 

interpret. Therefore, fishery-independent sampling was initiated, with slightly different survey 

strategies required for the more oceanic shortfin mako and blue sharks compared to the more 

coastal common thresher shark. 

Offshore longline surveys from relatively large research vessels have proved most effective for 

sampling and estimating abundance trends of the more oceanic species (shortfin mako and blue 

sharks). For mako sharks, the surveys have enabled the SWFSC to obtain a valuable abundance 

index, which can be linked to a historical time series of logbook and landings data from a former 
13 

experimental shortfin mako longline fishery in the Southern California Bight in 1988-1991. 

Abundance trend information is also obtained for the blue shark, which is compared to that 

obtained by observers of the California/Oregon drift gillnet and U.S. and Japanese high-seas 

longline fisheries. 

Surveys for neonate thresher sharks are conducted using small commercial driftnet and longline 

vessels. Initial studies demonstrated that neonate threshers are rarely encountered in waters 

deeper than about 90 m. Therefore, surveys are conducted in the shallower nearshore waters 

between Point Conception, California, to the north and the U.S.-Mexico border to the south. The 

primary purpose of the surveys is to produce a relative abundance index for the West Coast 

population by periodically sampling 0-year pups (neonates) in their nursery grounds off Southern 

California. Once the core nursery area was defined, representative areas were identified and are 

now sampled annually. The resulting neonate index of abundance should mirror adult abundance 

because adult population and recruitment should be tightly linked in K-selected species such as 

sharks. This study complements the fishery-dependent data available through the nearshore 

small mesh net fisheries and pelagic driftnet fishery to provide measures of relative abundance of 

common thresher sharks for stock assessment models. 

Juvenile Mako and Blue Shark Survey – In 2009, the SWFSC conducted its sixteenth juvenile 

shark survey since 1994. The annual abundance survey for juvenile mako and blue sharks was 

completed between July 30 and August 15, 2009. Working aboard F/V Southern Horizon, the 

team of scientists and volunteers fished a total of 5,575 hooks during 27 daytime sets inside 

seven focal areas within the Southern California Bight. Average water temperature in 2009 was 

the second highest on record (Fig. 2), although in only three other years were survey sets 

conducted during the month of August (1995, 1996, and 1997) when surface temperatures tend 

to be warmer. From the catch data, the index of relative abundance for juvenile sharks, defined as 

catch per 100 hook-hours, was calculated for the seven target survey areas. Survey catch totaled 

100 shortfin mako, 67 blue sharks, 31 pelagic rays (Pteroplatytrygon violacea), and 7 opah 

(Lampris guttatus). The preliminary data indicate that the nominal survey catch rate was 0.453 

per 100 hook-hours for shortfin mako and 0.314 per 100 hook-hours for blue sharks. The 

nominal CPUE for blue sharks dropped substantially from 2008 and was the second lowest in the 

survey’s history. There is a declining trend in nominal CPUE for both species over the time 

series of the survey (Fig. 2). 
14 

Figure 2. Average (± standard error) temperature and catch per survey set for shortfin mako and 

blue sharks, 1994 – 2009. No data were collected in 1998 and 1999. 

Additional research projects were also conducted during the cruise and after the shark survey 

was completed. An experiment directed by graduate student Melanie Hutchinson of the 

University of Hawaii and John Wang of PIFSC was conducted to examine the potential for using 

rare earth metals to reduce shark bycatch. The metal was secured close to the baited hooks and 

catch rates on treatment and control hooks were compared. Preliminary analyses from over 25 

sets indicate that the rare earth metals did not reduce the catch rate of shortfin mako sharks. 

These results differ from those found for some coastal shark species in warmer water where the 

deterrents proved effective at lowering catch rates. The data are being further examined based 

on size, sex, and other potential factors before drawing final conclusions. 

Other objectives of the cruise were to deploy satellite tags and conventional spaghetti tags, 

continue age and growth studies, and collect biological samples from sharks and swordfish. A 

total of 337 conventional tags were deployed on a range of species. One hundred and ninetyeight shortfin mako sharks were conventionally tagged, compared to only 40 in 2008. A total of 

377 DNA samples were collected including samples from 225 shortfin mako and 136 blue 

sharks. One hundred and seventy-eight shortfin mako, 114 blue, and 2 common thresher sharks 

were injected with oxytetracyline (OTC), a chemical marker used for age validation studies. 

Twenty-nine electronic tags were deployed to examine the movements and habitat use patterns 

of several species in the California Current System. Two archival tags were deployed on healthy 

broadbill swordfish caught during nighttime sets. One of these tags was recovered, providing 

minute-by-minute data on temperature and depth for 106 days (see above). Fourteen shortfin 

mako sharks ranging from 149 to 250 cm FL were released with satellite tags (SPOT tags) that 

transmit when the shark’s fin breaks the water’s surface, and one of these sharks was doubletagged with a PSAT tag. Ten blue sharks ranging from 158 to 224 cm FL were released with 

SPOT tags. PSAT tags were also deployed on one ocean sunfish (Mola mola) and a 224-cm-FL

hammerhead shark (Sphyrna sp.). This is only the second hammerhead tagged in the history of 

the survey. A more detailed analysis of the results from satellite tag deployments is provided 

below. 
15 

Neonate Common Thresher Shark Survey – The common thresher shark pre-recruit index and 

nursery ground survey was initiated in 2003 to develop a fisheries-independent index of prerecruit abundance and has been conducted in each year since. Common thresher sharks are the 

most valuable sharks taken in commercial fisheries off California and are also frequently caught 

by recreational fishermen. In 2009, the SWFSC team worked aboard the F/V Outer Banks and 

sampled in the Southern California Bight from Point Conception to the Mexico border. Fifty 

longline sets were made in relatively shallow nearshore waters. Over the 18-day cruise, shark 

catch included 216 common thresher, 11 soupfin (Galeorhinus galeus), 7 shortfin mako, 3 spiny 

dogfish (Squalus acanthias), 1 leopard (Triakis semifasciata), and 1 Pacific angel (Squatina 

californica) shark. Two hundred and six sharks were tagged with conventional tags; 190 sharks 

were marked with OTC for age validation studies; 212 DNA samples were collected. In 

addition, colleagues from Scripps Institution of Oceanography tagged 17 neonate common 

thresher sharks with mini PSATs.

 

The preliminary survey data indicate that the average nominal catch rate by set was 2.13 per 100 

hook-hours for common thresher sharks. This is down from 2008 when the catch rate was 3.32 

per 100 hook-hours. The distribution of common threshers is very patchy and areas of high 

abundance are not consistent across years. In all years, a large percentage of the catch has been 

neonates, which were found in all areas surveyed. In addition to providing important information

on abundance and distributions, the thresher shark pre-recruit survey enhances other ongoing 

research at SWFSC, including age and growth, feeding, and habitat utilization studies.

Electronic Tagging Studies – Since 1999, NOAA has been using satellite technology to study 

the movements and behaviors primarily of blue, shortfin mako and common thresher sharks, 

while other species are tagged opportunistically. In recent years, tag deployments have been 

carried out in collaboration with the TOPP program (www.topp.org), Mexican colleagues at 

CICESE (Centro de Investigación Científica y de Educación Superior de Ensenada), and 

Canadian colleagues at the DFO (Department of Fisheries and Oceans) Pacific Biological Station 

in Nanaimo, British Columbia. The goals of the projects are to document and compare the 

movements and behaviors of these species in the California Current and to link these data to 

physical and biological oceanography. This approach will allow us to characterize the habitats 

of greatest use by the sharks and subsequently to better understand how populations might shift 

in response to changes in environmental conditions on short or long time scales. 

Overall, during the juvenile shark abundance surveys conducted in the summer of 2009, 14 

shortfin mako sharks, 10 blue sharks, 1 hammerhead shark and 1 ocean sunfish were tagged with 

PSAT tags and/or SPOT tags. Since 1999, a total of 91 makos, 76 blue sharks, 27 common 

threshers, 2 hammerheads and 4 ocean sunfish have been satellite tagged through these 

collaborative projects. 

SPOT tag deployments from 2009 have provided relatively long-term records for 3 blue and 12 

mako sharks whose tags were still transmitting in early 2010. Two satellite tags deployed in 

2008 on mako sharks were also still reporting. These longer-term and multiyear records provide 

an incredible opportunity to examine seasonal movement patterns and regional fidelity. An 

ongoing analysis of blue shark habitat use reveals a range of patterns. A number of these 
16 

patterns are apparent in one blue shark for which the PSAT tag was recovered and the minuteby-minute data on temperature depth and light were obtained (Fig. 3). This shark moved 

offshore from July through October. As the track progressed and SST increased, the swimming 

depth increased. This is seen both in the overall record as well as in a one-week representation 

of the detailed archival data. The archival record also reveals a distinct diel pattern with 

substantially deeper depths attained during the day than at night. The regular timing of the 

individual dives is consistent with behavioral thermoregulation; the shark returns to the surface 

mixed layer between foraging bouts to warm. The diel shift in depth distribution and increase in 

depth as sharks moved offshore is consistent with daytime foraging on organisms associated with 

the deep scattering layer (DSL) and similar to what has been observed for swordfish. The depth 

of the DSL increases offshore due to the increased penetration of light in more oligotrophic 

waters. 

Figure 3. Top left: Argos track of a 157-cm-FL male blue shark. Top right: seven days of 

temperature (red), depth (dark blue) and light (yellow) data for the same blue shark. Bottom: 

temperature coded by depth over the duration of the archival record. 

Age Validation Studies – Age and growth of mako, common thresher, and blue sharks are being 

estimated from band formation in vertebrae. SWFSC scientists are validating aging methods for 

these three species based on band deposition periodicity determined using OTC. When the shark 

is recaptured and the vertebrae recovered, the number of bands laid down since OTC injection 

 0

100

300

500

200

30

15

10

5

July 1 Aug 8

25

20

Aug 28 Sept 17

400

July 19 Oct 7

0

5

10

15

20

25

30

35

4-Aug-04 6-Aug-04 8-Aug-04 10-Aug-04

Date

Temperature ( oC) 

Relative Light

0

50

100

150

200

250

300

350

400

450

500

Depth (m)

Temperature Relative Light Depth

Depth (m) • Temperature (o

C) 
17 

can be used to determine band deposition periodicity. In 2009, OTC validation studies on mako, 

blue, and thresher sharks continued. 

Since the beginning of the program in 1997, over 2,000 OTC-marked individuals have been 

released during juvenile shark surveys. In 2009, 184 mako, 114 blue, and 186 common thresher 

sharks were tagged and marked with OTC. As of March 2010, recaptured OTC-marked sharks 

included 81 mako, 56 common thresher, and 56 blue sharks. Vertebrae were returned for 

roughly 60% of the recaptures. Time at liberty ranged from 1 to 1,938 days, and the maximum 

net movement for an individual shark was 3,410 nmi. An analysis of mako shark band 

deposition patterns is now nearly complete and a manuscript is being drafted. 

Foraging Ecology of Shortfin Mako, Blue and Common Thresher Sharks – The California 

Current is a productive eastern boundary current that is an important nursery and foraging

ground for a number of highly migratory shark species. As mentioned above, three of the most 

abundant juvenile sharks in the California Current are the shortfin mako, blue and common 

thresher sharks. To better understand niche separation and the ecological role of these 

overlapping species, stomach content analyses have been ongoing at the SWFSC since 2002. 

Stomachs are obtained primarily from the California/Oregon drift gillnet fishery observer 

program. 

To date a total of 713 stomachs have been collected and analyzed. Stomach contents were 

identified to the lowest possible taxonomic level. Analytical approaches to characterize prey 

composition and examine inter- and intra-specific patterns include both univariate (Geometric 

Index of Importance or GII, Shannon and Simpson diversity, Sorensen and Morisita-Horn 

overlap indices) and multivariate (regression trees, cluster, and discriminate analysis) methods. 

Of the 330 shortfin mako shark stomachs examined (sizes 53 to 248 cm FL), 238 contained 43 

prey taxa. Jumbo squid (GII=46.0) and Pacific saury (Cololabis saira, GII=25.5) were the most 

important prey. Of the 158 blue shark stomachs examined (sizes 76 to 248 cm FL), 114 

contained 38 prey taxa. Jumbo (GII=33.9) and Gonatus spp. squids (GII=33.6) were the most 

important prey. Of the 225 thresher shark stomachs examined (sizes 108 to 228 cm FL), 157 

stomachs contained 18 prey taxa. Northern anchovy (GII=68.4) and Pacific sardine (Sardinops 

sagax, GII=48.5) were the most important prey. 

The Sorensen index shows that blue and mako shark diets were most similar, while dietary 

overlap was lowest between blue and thresher sharks as revealed by the the Morisita-Horn index 

and regression tree analysis. Inter-annual variation in diet was greatest for blue sharks. Overall, 

results from the Sorensen index and multivariate analyses reveal that mako sharks have the most 

diverse diet, feeding on a range of teleosts and cephalopods; blue sharks generally prefer 

cephalopods; and thresher sharks are more specialized, feeding primarily on coastal pelagic 

teleosts. Despite similarities in life history characteristics and spatial and temporal overlap, diets 

of the three species are strongly differentiated. 

Survival after Capture and Release – Common thresher, mako, and blue sharks are captured in 

both commercial and recreational fisheries in the California Current. The drift gillnet fishery is 

the commercial fishery which catches the greatest number of each of these species. While 
18 

thresher and mako sharks are landed, almost all blue sharks are discarded. For thresher and 

mako sharks, regional recreational fisheries are growing in popularity. Recreational fishers are 

often only interested in the challenge of the fight and will frequently release their catch. The 

survival rate of sharks released both from the drift gillnet fishery and by recreational anglers is 

unknown. Reliable estimates of removals (i.e., mortality) are necessary in order to adequately 

assess the status of the stocks and determine the effects of the fisheries on their abundance.

Blue Sharks Released from the Drift Gillnet Fishery – The California/Oregon drift gillnet 

fishery targets swordfish in the California Current. With the exception of ocean sunfish, blue 

sharks are caught in greater numbers than any other finfish species taken in this fishery. Nearly 

all blue shark are discarded at sea due to lack of market value. A 2009 analysis of the 1990-2008 

observer data reveals that 32% of blue sharks captured were released alive, and an additional 5% 

were discarded with their disposition unknown. The remaining 63% are discarded dead. 

In 2007, the SWFSC and the SWR began deploying PSAT tags on sharks released from the drift 

gillnet fishery to assess survivorship. The tags were programmed to pop-up after 30 days. The 

goal was to tag sharks such that the sex ratio, range of sizes, and condition at release are 

comparable to those released from the fishery. As a part of the study, a set of criteria was 

developed to document the condition of all blue sharks released: good, fair or poor. 

Since initiating the study in 2007, 11 blue sharks (100 to 200 cm FL, median 155 cm) have been 

tagged by fishery observers; one shark was tagged during the 2009-2010 season. Nine of these 

animals were male, and the sex of 2 animals was unknown. Three of the 11 sharks were released 

in “good” condition while the remaining 8 were released in “fair” condition. To date, no sharks 

released in “poor” condition have been tagged. Satellite tag records suggest that all animals 

survived the acute effects of capture in the drift gillnet fishery. Temperature, depth and 

movement data demonstrated behavior of blue sharks that was similar to that reported in other 

studies. One tag appears to have been ingested after 17 days and regurgitated 3 days later. 

To meet the goal of matching the general composition of the catch, additional tag deployments 

are necessary. To date no sharks in poor condition have been tagged. In the fishery, 27% of blue 

sharks released during the 2007-2008 and 2008-2009 seasons (the only seasons for which this 

information has yet been collected and compiled) were released in poor condition. For seasons 

1990-2008, the median overall FL of blue sharks caught was 112 cm, and 61% were female. 

Tagging efforts during the 2010-2011 season will focus on smaller sharks, females and animals 

released in poor condition. Results to date suggest a 100% survival rate for male blue sharks 

released in fair or better condition after capture. 

Thresher Sharks Released from the Recreational Fishery – A recreational fishery for thresher 

sharks has become increasingly popular off Southern California. Anglers often hook the tails of 

thresher sharks and pull the fish backwards to the boat. This technique has the potential to 

prevent sufficient oxygenation as thresher sharks are obligate ram ventilators. When the fight 

time is long, the fish may be exhausted by the time it reaches the boat and survivorship may be 

reduced. 
19 

To document survivorship for tail-hooked sharks, a collaborative project was initiated by the 

SWFSC, the SWR Sustainable Fisheries Division, and the Pfleger Institute of Environmental 

Research. For the survivorship study, 20 thresher sharks were hooked in the tail and pulled to 

the boat using standard recreational tackle. PSAT tags were deployed on 18 of the adult and 

subadult sharks and 2 sharks died before they could be tagged. The tags were programmed to 

release after 10 days to determine survivability. The records from the 17 PAT tags that reported 

to the satellites indicated that 3 additional sharks died following release (one tag did not report). 

Our findings suggest a hooking mortality rate of 26%, with a post-release mortality estimate of 

17% for adult and subadult thresher sharks. All individuals with fight times less than 85 minutes 

survived the acute effects of capture as determined by the PSAT records. All sharks sustaining 

fight times of greater than 85 minutes died. The longest fight times were recorded for the largest 

individuals that tend to be harder to bring to the boat. Consequently, mortality due to capture 

stress is likely higher for larger individuals. Further tagging is planned for the 2010 season to 

increase the sample size and experiment with alternative fishing techniques, including teasers 

with drop-back bait, and corrosive links to reduce trailing gear. 

Blood chemistry was analyzed to assess the stress response associated with tail-hook capture. 

Eight blood and plasma parameters were examined (Na+

, Cl-, K+, Ca++, Mg++, glucose, lactate, 

and hematocrit). Blood was drawn from 9 thresher sharks that were not included in the tagging 

study; 6 of these were tail hooked. The two parameters that showed a significant increase with 

fight time were lactate and hematocrit. 

In an effort to educate the recreational fishermen about the biology and conservation of the 

thresher sharks and to promote responsible fishing techniques, an outreach brochure was

developed and distributed among the community. Outreach included seminars and presentations 

at sportfishing club meetings, tournaments, and fishing/boating shows. Public education about 

effective catch and release methodologies and gear innovations to increase post-release 

survivorship and reduce trailing gear will continue through the 2010 season. 

 

Genetic Analysis of Highly Migratory Species –

Shortfin Mako Shark – The shortfin mako is a commonly encountered shark in temperate 

marine fisheries but little is known about regional connectivity. Amber Michaud’s recent 

master’s thesis completed in collaboration with the University of San Diego and SWFSC 

provided evidence of regional stock structure within the Pacific. Her study, using mitochondrial 

haplotype data, showed a strong subdivision between northern and southern hemisphere 

populations, with additional subdivision between southeast and southwest Pacific populations. 

Unfortunately, insufficient samples were available from the northwest Pacific to evaluate 

whether a subdivision exists between northeast and northwest Pacific populations. As part of his 

Ph.D. work at UC Davis and San Diego State University in collaboration with the SWFSC, Dovi 

Kacev has been developing a suite of nuclear microsatellite markers to further refine the spatial 

and temporal resolution of shortfin mako stocks within the Pacific. In addition to studies of 

stock structure, these markers will be used to develop estimates of effective population size 

within the California Current region. Application of these markers will commence this year.
20 

Common Thresher Shark – Common threshers are commonly encountered in temperate coastal 

marine fisheries but little is known about regional connectivity. In recent years they have 

become part of an increasingly important recreational fishery in Southern California in addition 

to being an important component of local drift gillnet fisheries. In order to better understand 

population connectivity, Dovi Kacev has been developing nuclear microsatellite markers for this 

species as well. Application of these markers will also commence this year.

Opah – The opah or moonfish is found worldwide in tropical and subtropical waters. Though 

caught mainly as bycatch in pelagic tuna fisheries, opah command a high price in the market and 

thus few are discarded. Despite being known to science for over 230 years, the existence of two 

morphotypes in the North Pacific was only recently discovered by PIFSC port samplers in 

Honolulu. The most conspicuous difference between these morphotypes is the relative size of 

the eye, leading to the labeling of the morphotypes as “big-eye” and “small-eye” opah. Genetic 

analyses performed at the SWFSC confirm that the two morphotypes are genetically distinct and 

in fact represent separate species. Additionally, DNA sequence data provided by Bob Ward 

(CSIRO, Australia) suggests that there is yet another cryptic species of opah in the South Pacific, 

although additional samples are needed to confirm this finding and describe spatial patterns. A 

description of this species complex, the distribution of the component species, and identification 

key is currently in preparation. 

VI. IDCPA RESEARCH

The SWFSC research conducted under the International Dolphin Conservation Program Act 

(IDCPA) during 2009 was focused on evaluating line transect methodology and the potential 

roles of the fishery and ecosystem in the apparent lack of recovery of depleted dolphin stocks in 

the eastern tropical Pacific Ocean (ETP). This lack of recovery follows a period of significant 

reductions in observed dolphin mortality in the ETP tuna purse seine fishery. Research activities 

included (1) analysis of data collected during the 2007 survey designed to collect fine-scale 

ecosystem data and assess standard methods for collecting dolphin sighting data; (2) other data 

analyses, processing, and publication; and (3) a small purse seine vessel monitoring and observer 

program via contract. 

Analysis of Stenella Abundance Research-Line Transect and Ecosystem Survey Data – In 

2007, SWFSC conducted a Stenella Abundance Research-Line Transect and Ecosystem (STARLITE) cruise to survey marine mammals and their habitat in the ETP. The primary objective of 

the STAR-LITE cruise was to investigate line transect methods used on surveys in the ETP and 

to explore fine-scale spatial and temporal variability in the ecosystem using a multidisciplinary 

approach. 

Two different cetacean survey methodologies (“passing mode” and “closing mode”) were 

compared using both empirical data and simulation models, and a manuscript has been submitted 

for publication to the Journal of Cetacean Research and Management (Schwarz et al., in review). 

Passing survey mode -- when the survey ship does not make any changes in course to approach a 

cetacean sighting -- was compared with closing survey mode -- when such course changes are 

made to further investigate the sighting. The results of the analysis indicated that observers are 

able to identify animals to species less often and that estimates of dolphin group size are lower 
21 

when surveys are conducted in passing mode (no course changes are made). However, 

conducting surveys in closing mode results in lower encounter rates due to the stop-start nature 

of the survey method. Continuing to explore potential sources of bias in our methods and 

explicitly accounting for these in our models is critical to refining our models and ultimately 

improving our approaches to estimating abundance of ETP dolphins and other cetaceans. 

This is the eleventh year of similar investigations conducted during the past 20 years, with 

previous cruises in 1986-1990, 1998-2000, 2003, and 2006. Using an ecosystem approach, we 

conducted research on physical and biological oceanography (dolphin habitat); midtrophic-level 

fishes and squids (dolphin prey); and seabirds, marine turtles and other cetaceans (dolphin 

commensals, competitors, and predators). Data and analyses resulting from STAR surveys form 

the basis for many international measures adopted to conserve dolphin stocks and manage the 

tuna purse seine fishery in the ETP. STAR 2009 was postponed by one year due to ship time 

constraints. On April 6, 2010, STAR 2010 was again postponed due to the same constraints. 

NMFS fully intends to conduct STAR beginning in July of 2011. 

Data Analyses, Processing, and Publication – The SWFSC’s investigations of dolphin stocks 

historically depleted by the ETP tuna purse seine fishery (spinner and pantropical spotted 

dolphins) are conducted with an ecosystem approach. In addition to investigating the status and 

trends of these dolphin stocks, auxiliary projects are conducted to improve our understanding of 

their surrounding environment. Data analyses, processing, and publications in 2009 included (1) 

investigations of cetacean biodiversity hotspots; (2) assessment of relative fishery exposure for 

ETP dolphins; (3) variation and predictors of vessel response behaviors in ETP dolphins; (4) 

dolphin swimming kinematics research; (5) investigations of dolphin reproductive biology; (6) 

investigations of the ETP ecosystem and its change over time; and (7) metrics of ecosystem 

impact of the ETP purse seine fishery. 

Investigations of Cetacean Biodiversity Hotspots – A paper is in preparation investigating 

species richness hotspots for 28 species of cetaceans in the ETP (ca. 20 million km2

) based on 

data collected using line transect methods aboard NOAA research vessels, August–November, in 

each of 10 years during a 21-year period (1986-2006). Density was calculated using species- and 

area-specific published values of g(0) and f(0), and interpolated throughout a 1° x 1° grid of the 

study area using two smoothing algorithms and two resolutions. Density was converted to 

presence/absence on a species-specific basis, and species richness (number of species recorded in 

a particular grid cell) was mapped for all years combined. Richness hotspots were defined as 

any grid cell that contained greater than 40% of the total species pool (≥11 species) and were 

clearly evident in three distinct regions: the Equatorial Front, the Costa Rica Dome, and waters 

to the southwest of the Baja California peninsula. Although these hotspots encompassed areas of 

highest density for a few species, the correlation between richness and density for any given 

species was generally low (mean 0.25, range 0.03 to 0.44), as was the proportion of cells where a 

particular species was present and encompassed by a hotspot (mean 20%, range 4% to 56%). 

These results were robust to smoothing algorithm and spatial resolution. 

Assessment of Relative Fishery Exposure for ETP Dolphins – For the past half century, the 

purse seine fishery for yellowfin tuna has been a significant factor in the lives of dolphins in the 

ETP. However, little is known about how frequently an individual dolphin is exposed to the 
22 

fishery, and there are no methods available for accurately assessing the prior exposure of 

dolphins encountered at sea. Archer et al. (accepted for publication) developed a method to 

estimate an index of exposure based on a model of dolphin movement derived from data 

collected from multiple tracking studies. Based on this movement model, the method weights 

purse seine sets given their distance from a particular school of dolphins sighted at sea and how 

long ago they occurred. The method also takes into account the species composition and school 

size in the set. In their paper, as a demonstration, the authors use the method to examine the 

spatial and temporal distribution of this index over an 11-year period for which we have detailed 

data on purse seine sets. While the method was designed for examining exposure to the ETP 

purse seine fishery, it is also applicable to studies of other anthropogenic effects where there is 

concern about exposure rates, such as underwater sound, pollution, or ship strikes. Planned 

studies for this index include examining its relationship to evasive behavior, calf production as 

assessed from aerial photographs, and reproductive rates as measured from skin biopsies. 

Variation and Predictors of Vessel Response Behaviors in ETP Dolphins – Dolphins exhibit a 

range of vessel response behaviors, from those that readily approach and bow-ride, to others that 

are indifferent, or actively evasive. However, the factors responsible for this variation have not 

been examined. Archer et al. (2010) used a tree-based modeling method to investigate the 

influence of geography, time of day, species composition, and fishery exposure on the responses 

of five species of dolphins in the ETP, comprising ten management stocks. Data were collected 

for 2,667 sightings during four research cruises between 1998 and 2003. The relative frequency 

of five responses (approaching the vessel, bow-riding, running, school splitting, and lowswimming) showed significant (p < 0.0005) variability among species, as well as stocks within 

the same species. Striped (Stenella coeruleoalba), whitebelly spinner (S. longirostris), and 

western-southern pantropical spotted dolphins (S. attenuata attenuata) tended to be evasive, 

while coastal spotted (S. attenuata graffmani) and common bottlenose dolphins (Tursiops 

truncatus) tended to be attracted to the vessel. There was a strong tendency of dolphins sighted 

offshore to be significantly more evasive than those less than about 100 nmi from the coast. The 

degree of evasiveness in stocks that are frequently targeted by the tuna purse seine fishery 

(northeastern spotted, S. attenuata; eastern spinner, S. longirostris orientalis; and short-beaked 

common, Delphinus delphis) was greater with more purse seine activity in the vicinity, while no 

significant relationship was found for those stocks that are rarely set on. For each stock, vessel 

response had a relatively unique suite of predictors, indicating an interplay of intrinsic, natural 

extrinsic and anthropogenic factors. 

Dolphin Swimming Kinematics Research – During 2009, SWFSC continued a series of studies 

investigating swimming kinematics of mother and calf dolphins, as part of an effort to determine 

whether chase and encirclement of dolphin mother-calf pairs by tuna purse seiners in the ETP 

may be contributing to lack of population recovery. The study during 2009 (Noren and Edwards, 

in prep.) examined the effects of late pregnancy on swimming kinematics of bottlenose dolphins. 

The study compared swimming kinematics (swim speed, fluke stroke amplitude, and fluke stroke 

frequency) of two bottlenose dolphins within 1-10 days pre-parturition, and up to two years 

postpartum. During late-term pregnancy, body surface area increased, stroke amplitude 

decreased, distance per stroke decreased, and swim speed decreased, all significantly. The 

results demonstrate for the first time that late-term pregnancy in dolphins significantly decreases 
23 

swim performance, implying altered maternal energy budgets as well as decreased foraging and 

predator evasion efficiencies. 

Investigations of Dolphin Reproductive Biology – A doctoral dissertation (Kellar et al. 2008) 

was completed examining the pregnancy patterns of spotted dolphins in the ETP. One 

hypothesis for the lack of recovery of the spotted dolphin population in the ETP is that continued 

chase and encirclement by the tuna fishery negatively affects reproduction. 

Insufficient life history sampling in this region over the last decade makes traditional estimation 

of population reproductive rates impossible. The current reproductive patterns of these dolphins 

were examined using a molecular method to assess pregnancy state from blubber progesterone 

concentrations in biopsy samples. Blubber progesterone was quantified in 212 biopsies from 

female offshore spotted dolphins sampled between 1998 and 2003 in the northeastern tropical 

Pacific. These concentrations were found to be sharply bimodal with no value observed between 

49 ng/g and 87 ng/g, a finding consistent with the concentration gap between known pregnant 

and non-pregnant dolphins. Given that high blubber progesterone (≥ 87 ng/g) indicates 

pregnancy, we found that 11.8% of the biopsied females were pregnant. This is substantially 

lower than an estimate of the proportion pregnant found in the fishery kill over the same region 

(22.3%) between 1973 and 1992. To try to ascertain the potential cause of this discrepancy, the 

relationship between pregnancy and fishery exposure was analyzed, and we found that pregnant 

females were exposed to significantly less fishery activity than non-pregnant ones (P < 0.046), 

suggesting that the fishery has an inhibitive effect on pregnancy. However, there are several 

caveats to this finding, and how this relationship might explain the discrepancy between these 

data sets is unclear. We also examined and modeled spatial patterns of reproduction and found 

that pregnancy was more aggregated than random (P = 0.020), with the highest proportion 

pregnant in the mouth of the Gulf of California, an area with relatively low reported fishery 

activity. Because this is a first attempt at applying this technique to a wild population, we are 

careful in the interpretation of the results. However, it appears that it is a promising tool for 

assessing reproductive rates in populations of free-ranging cetaceans.

In 2009, work began quantifying the levels of progesterone in spinner dolphins to replicate this 

study in another fishery-impacted species. To date 189 animals have been processed; hormones 

have been measured and pregnancy determination is complete. The next step is to analyze and 

add a spinner dolphin-specific fishery exposure index to these data and assess the relationship 

between reproduction and exposure. 

Investigations of the ETP Ecosystem and Its Change over Time – A new study of variations in 

thermocline depth and stratification in the eastern tropical and North Pacific is underway (Fiedler 

et al., in prep.). Seasonal anomalies were analyzed to quantify spatial patterns of temporal 

variations on interannual and longer time scales. On shorter time scales, interannual variations 

related to El Niño-Southern Oscillation are seen, as expected in both tropical (Wyrtki 1985) and 

extratropical waters (Miller et al. 1997). Long-term positive and negative trends from 1958 to 

2007, equivalent to changes of 15 m in thermocline depth and up to 20% in stratification, are 

seen throughout the region. Such changes in thermal structure, and associated ecosystem effects, 

are well-known in some regions. For example, Roemmich and McGowan (1995) found 

increasing thermocline stratification in the California Current with a concomitant decrease in 
24 

zooplankton biomass. In the central equatorial Pacific, the thermocline has shoaled but become 

more stratified, while changes in the rest of the ETP are more complicated. The thermocline 

influences nutrient input to surface waters, which limits primary productivity throughout this 

region. The ecosystem effects of these long-term changes can be further explored through 

analyses of historical data and ecosystem models. 

Vilchis and Ballance completed a retrospective study analyzing trophic level of seabirds in the 

eastern Pacific warm pool during the past 50 years. They set out to gauge effects of the 1976-

1977 regime shift of the Pacific Ocean in a tropical and pelagic community of seabirds. Using 

study skins of historical specimens from museum collections, they retrospectively (1960-2006) 

measured stable carbon (δ13C) and nitrogen (δ15N) isotopes for a suite of ecologically and 

phyolgenetically diverse seabirds from the eastern Pacific warm pool. In this region, seabirds 

generally forage by depending on subsurface predators to drive prey to the surface or by 

associating with oceanographic features that increase productivity or aggregate prey in space or 

time. They did not find community-wide changes in response to the 1976-1977 regime shift. 

Instead, they found evidence suggesting a trophic shift and or change in foraging area for sooty 

terns (Onychoprion fuscatus) and a long-term decrease in feather δ13C for the eastern Pacific 

warm pool seabird community. This long-term decrease in feather δ13C can be accounted for by 

the Suess effect and not a decline in primary productivity of the system. Vilchis and Ballance 

hypothesize that a deepening trend in thermocline depth in the eastern Pacific warm pool is 

affecting sooty terns more so than other species in the subsurface predator-dependent guild 

which depend less on smaller subsurface predators like skipjack tuna. The manuscript of this 

study is being submitted for publication to a peer-reviewed scientific journal.

Metrics of Ecosystem Impact of the ETP Purse Seine Fishery – Previous analyses in the ETP 

compared the relative impacts of three methods of purse seine fishing based only on numbers of 

individuals in the bycatch (defined here as non-target species, either retained or discarded), and 

found levels of discarded bycatch in floating-object sets thousands of times greater than in 

dolphin sets and hundreds of times greater than in unassociated tuna sets. We expanded the 

analysis by examining a mix of ecosystem indicators based on the type and amount of biomass of 

species and functional groups caught (total removals) by the fishery. Removals (landings and 

discards) were compared in three ways: trophic level, replacement time, and diversity. Mean 

trophic level was computed as the biomass-weighted mean of the trophic level of each ecological 

group, the mean replacement time as the biomass-weighted mean of the replacement time 

(1/(production/biomass ratio)) of each ecological group, and diversity of removals using the 

Shannon diversity index. 

Total annual biomass removals averaged more than 500,000 t per year over the 16-year period 

from 1993 to 2008 and were dominated by the primary target species, yellowfin, skipjack and 

bigeye tunas. Fishing by setting on dolphins, floating objects, and unassociated schools of tuna 

averaged 30%, 44%, and 26% of the biomass removed, respectively. The mean trophic levels of 

total removals were similar for the three fishing methods, and there was no indication of a 

decline in trophic level over the 16-year period. Mean time to replace biomass varied by fishing 

method: lowest for dolphin sets (0.48 years), intermediate for unassociated sets (0.57 years), and 

highest for floating-object sets (0.74 years). Diversity of removals across the whole time period 

was lowest for dolphin sets (0.64), intermediate for unassociated sets (1.30) and highest for 
25 

floating-object sets (1.41). Diversity declined over time for floating-object and unassociated sets 

and increased for dolphin sets, so that the differences among the three fishing methods were less 

in 2008 than in 1993. Discards (non-retained bycatch and target species), as a percentage of total 

removals in biomass, were 0.8% for dolphin sets, 11.0% for floating-object sets, and 2.3% for 

unassociated sets. The tunas were the major component (77%) of the discards. Discarded 

bycatch in floating-object sets was 16 times greater than in dolphin sets and 9 times greater than 

in unassociated sets, not thousands and hundreds of times greater, when biomass and 

replacement time are considered. Additional studies into the ecological impacts of ETP fisheries 

are planned with the aim of advancing ecosystem approaches to management in this ecosystem 

and more broadly. A manuscript is under preparation for publication. 

Port Sampling and Observer Program to Monitor Small Purse Seine Vessels – In January 

2006, SWFSC awarded a contract to the IATTC to expand the at-sea observer and in-port 

sampling programs currently implemented in the ETP tuna purse seine fishery under the 

Agreement on the International Dolphin Conservation Program. Upon completion of this 

program in May 2009, a total of 750 unloadings by Class 4 and 5 international purse seine 

vessels have been sampled. SWFSC and IATTC staffs are collaborating to analyze tuna species 

and size composition data along with other catch characteristics to explore the feasibility of using 

this type of data to identify if small purse seine vessels have harvested tuna in association with 

dolphins. The selected approach relies on marked differences in the species and size of tunas 

generally caught in dolphin sets versus other set types. We then use the length-frequency data of 

vessels carrying onboard observers to build a classification algorithm for predicting the purse 

seine set type (dolphin sets versus non-dolphin sets) of a length-frequency sample collected from 

a vessel of a size not required to carry observers.

Pending further refinements, this work has several potential applications, including using 

unusual length-frequency data from small vessels to estimate potential unobserved dolphin 

mortality for inclusion in stock assessments and for consideration in management. A report 

along these lines is likely to be completed during 2010. 

VII. PUBLICATIONS

Published 

Archer, F. I., S. L. Mesnick, and A. C. Allen. 2010. Variation and predictors of vessel response 

behavior in a tropical dolphin community. U.S. Dep. Commer., NOAA Tech. Memo. 

NMFS-SWFSC-457, 53 p. 

Cartamil, D., N. C. Wegner, D. Kacev, N. Ben-aderet, S. Kohin, and J. B. Graham. 2010. 

Movement patterns and nursery habitat of the juvenile thresher shark Alopias vulpinus in 

the Southern California Bight. Mar. Ecol. Prog. Ser. 404:249–258. 

Miller, A. J., W. B. White, and D. R. Cayan. 1997. North Pacific thermocline variations on 

ENSO timescales. J. Phys. Oceanogr. 27:2023–2039. 
26 

Nasby-Lucas, N., H. Dewar, C. H. Lam, K. J. Goldman, and M. L. Domeier. 2009. White shark 

(Carcharodon carcharias) offshore habitat: a behavioral and environmental 

characterization of the eastern Pacific shared offshore foraging area. PLOS One 

4(12):e8163. doi:10.1371/journal.pone.0008163. 

Nielsen, A., J. R. Sibert, S. Kohin, and M. K. Musyl. 2009. State space model for light-based 

tracking of marine animals: validation on swimming and diving creatures. In J. L. 

Nielsen et al. (eds.), Methods and Technologies in Fish Biology and Fisheries: Tagging 

and Tracking of Marine Animals with Electronic Devices. Series Vol. 9:295–309. 

Perrin, W. F. 2009. Early days in the tuna/dolphin problem. Aquat. Mamm. 35:292–305. 

Roemmich, D., and J. McGowan. 1995. Climatic warming and the decline of zooplankton in the 

California Current. Science 267:1324–1326. 

Schick, R. S., and M. E. Lutcavage. 2009. Inclusion of prey data improves prediction of bluefin 

tuna (Thunnus thynnus) distribution. Fish. Oceanogr. 18(1):77–81. 

Suk, S. H., S. E. Smith, and D. A. Ramon. 2009. Bioaccummulation of mercury in pelagic sharks 

from the northeast Pacific Ocean. Calif. Coop. Ocean. Fish. Investig. Rep. 50:172–177. 

Walli, A., S. L. H. Teo, A. Boustany, C. J. Farwell, T. Williams, H. Dewar, E. Prince, and B. A. 

Block. 2009. Seasonal movements, aggregations and diving behavior of Atlantic bluefin 

tuna (Thunnus thynnus) revealed with archival tags. PLOS One 4(7):e6151. 

doi:10.1371/journal.pone.0006151. 

Wyrtki, K. 1985. Water displacements in the Pacific and the genesis of El Niño cycles. J. 

Geophys. Res. 90(C4):7129–7132. 

Technical Reports, Administrative Reports, and Working Papers

Bartoo, N. W. 2009. Director's report to the 60th Tuna Conference on tuna and tuna-related 

activities of the Southwest Fisheries Science Center. SWFSC Admin. Rep., La Jolla, LJ09-02, 35 p. 

Benson, S., H. Dewar, P. Dutton, C. Fahy, C. Heberer, D. Squires, and S. Stohs. 2009. Workshop 

report: Swordfish and leatherback use of temperate habitat (SLUTH). SWFSC Admin. 

Rep., La Jolla, LJ-09-06, 35 p. 

Carretta, J. V., and L. Enriquez. 2009. Marine mammal bycatch in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. SWFSC Admin. Rep., La Jolla, 

LJ-09-03, 10 p. 

Childers, J., and A. Betcher. 2010. Summary of the 2008 U.S. North and South Pacific albacore 

troll fisheries. SWFSC Admin. Rep., La Jolla, LJ-10-01, 22 p. 
27 

Fiedler, P. C. et al. (In prep). Tropical and North Pacific thermocline variations, 1950–2008. 

Kellar, N. M., M. L. Trego, S. J. Chivers, and F. I. Archer. 2008. Pregnancy patterns of spotted 

dolphins in the eastern tropical Pacific determined from hormonal analysis of biopsies 

and their correlation with the purse-seine tuna fishery. Ph.D. thesis, University of 

California, San Diego, La Jolla, Calif., 186 p. 

Olson, R., T. Gerrodette, S. Reilly, G. Watters, and W. Perrin. (In prep). It’s about total 

removals, not just the bycatch: metrics of ecosystem impact of the ETP purse-seine 

fishery. 

Teo, S. T. H., H. Lee, and S. Kohin. 2010. Spatiotemporal characterization and critical time 

series of the US albacore troll fishery in the North Pacific. ISC-ALBWG working 

document submitted for the ISC Albacore Working Group Meeting, April 20-27, 2010. 

Shimizu, Japan.

Approved by the Science Director

Archer, F. I., J. V. Redfern, T. Gerrodette, S. J. Chivers, and W. F. Perrin. (In press). 

Estimation of relative exposure of dolphins to fishery activity in the eastern tropical 

Pacific. Mar. Ecol. Progr. Series. 

Childers, J., S. Snyder, and S. Kohin. (Submitted). Migration and behavior of juvenile North 

Pacific albacore (Thunnus alalunga). For consideration for publication in Fish. Oceanogr.

Dewar, H., E. Prince, M. K. Musyl, R. W. Brill, C. Sepulveda, J. Lou, D. Foley, E. S. Orbesen, 

M. L. Domeier, N. Nasby-Lucas, D. Snodgrass, R. M. Laurs, B. A. Block, and L. A. 

McNaughton. (Submitted). Movements and behaviors of swordfish in the Atlantic and 

Pacific oceans examined using pop-up satellite tags. For consideration for publication in 

Fish. Oceanogr. 

Dewar, H., T. Thys, S. L. H. Teo, C. Farwell, J. O’Sullivan, T. Tobayama, M. Soichi, T. 

Nakatsubo, Y. Kondo, Y. Okada, D. J. Lindsay, G. C. Hays, A. Walli, K. Weng, J. T. 

Streelman, and S. A. Karl. (Submitted). Satellite tracking the world’s largest jelly 

predator, the ocean sunfish, Mola mola, in the western Pacific. For consideration for 

publication in J. Exp. Mar. Biol. Ecol. 

Hoolihan, J. P., J. Luo, F. J. Abascal, S. E. Campana, G. De Metrio, H. Dewar, M. L. Domeier, 

L. A. Howey, M. E. Lutcavage, M. K. Musyl, J. D. Neilson, E. S. Orbesen, E. D. Prince, 

and J. R. Rooker. Evaluating post-release behavior modification in large pelagic fishes 

deployed with pop-up satellite archival tags. For consideration for publication in ICES J. 

Mar. Sci.

Olson, R. J., B. N. Popp, B. S. Graham, G. A. López-Ibarra, R. Galván-Magaña, C. E. LennertCody, N. Bocanegra-Castillo, N. J. Wallsgrove, E. Gier, B. Alatorre-Ramírez, L. T. 

Ballance, and B. Fry. (In press). Food web inferences of stable isotope spatial patterns in 
28 

copepods and yellowfin tuna in the pelagic eastern Pacific Ocean. Progr. Oceanogr.

doi:10.1016/j.pocean.2010.04.026. 

Schwarz, L., F. I. Archer, and T. Gerrodette. (In review). Comparison of closing and passing 

mode from a line-transect survey in the eastern tropical Pacific. J. Cetacean Res. Manag.