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Pelagic Fisheries Conservation Program (PFCP) |
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Mission:
The goal of PFCP is to foster interdisciplinary research on pelagic
fishes that will be used to conserve biodiversity and maintain
pelagic fish stocks in the Atlantic and Pacific, with a special
emphasis on fishes in the Gulf of Mexico. Dr. Jay Rooker is the
Director of PFCP and his team works with
scientists from several
institutions on a variety of research projects. |
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Pelagic Projects:
- Trans-Atlantic mixing and natal homing of bluefin tuna
- Blue marlin tracking with electronic tags
- Evaluating the stock structure of billfishes using otolith chemistry
- Early life ecology of billfishes
- Origin of yellowfin tuna in Hawaiian Islands using natural markers in otoliths
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Bluefin tuna project
Click on photos to enlarge |
School of bluefin tuna |
Tuna pens in Cartagena, Spain |
Tuna pens in Cartagena, Spain |
Sampling tuna pens in Spain |
Sampling giant bluefin from
Gulf of St. Lawrence (Canada) |
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Blue marlin project
Click on photos to enlarge |
Blue marlin being caught on the ‘Billy B’ by Bill Lyons, Mark Lyons, and Capt. John Cochrane for PAT tagging study |
Blue marlin research trip to Virgin Islands with Guy Harvey for 'Portraits of the Deep' |
PAT tagging blue marlin |
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PAT Tag on blue marlin |
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Early life billfish project
Click on photos to enlarge |
Baby blue marlin from the Gulf of Mexico |
Larval and juvenile blue marlin and sailfish collected in the Gulf of Mexico |
Hawaiian tuna project
Click on photos to enlarge |
Research on yellowfin tuna aboard the Kraken with Capt. Brett Falterman |
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1. Trans-Atlantic mixing and natal homing of bluefin tuna |
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Management of Atlantic bluefin tuna (Thunnus
thynnus) is currently based on the premise of two principal zones of
spawning and juvenile production, which occur in the Mediterranean Sea
and Gulf of Mexico. Although trans-Atlantic migration of members from
both production zones is well documented through conventional and
electronic tags, some degree of residency to spawning/nursery grounds is
assumed, justifying International Commission for the Conservation of
Atlantic Tunas’ (ICCAT)
separate assessments and regulations for “eastern” and “western” stocks.
This assumption has been challenged in recent times due to the seasonal
progression of Atlantic bluefin tuna across the 45°W meridian management
boundary, as observed through recent landings data and electronic
tagging results. As a consequence, there is a clear need for empirical
methods to directly estimate the contributions of recruits originating
from eastern (Mediterranean) and western (Gulf of Mexico) nurseries to
the fisheries that depend upon these recruits. PFCP scientists and
Dr. David Secor (University of
Maryland) are using natural tracers in otoliths (ear bones) of Atlantic
bluefin tuna to predict nursery origin, and use these natural markers to
estimates mixing rates of sub-adult and adult tuna.
Elements in otoliths of Atlantic bluefin tuna have been used to
delineate yearlings (age-1) from eastern and western Atlantic nurseries
(Rooker et al. 2003); however, classification success for several
year-classes has been moderate and classification functions show strong
year to year variability. The utility of an alternative chemical marker
in otoliths, carbon and oxygen stable isotopes, have been used recently
to discriminate bluefin tuna from natal regions. The discriminatory
power of stable isotopes (d13C, d18O) in otoliths of yearlings (age-1)
was high, with over 90% of individuals classified correctly (based on
cross-validated classification) to eastern and western nurseries (Figure
1). In contrast to trace element analyses, year to year variation in
stable isotope signatures was minimal over five year classes (1999-2003)
of yearlings. Thus, these stable isotopes and in particular d18O can be
used to reliably predict nursery origin of Atlantic bluefin tuna. In an
initial application, we compared otolith core material (corresponding to
the first year of life) of large school, medium, and giant category
bluefin tuna to reference samples of yearling signatures to determine
their origin. A large fraction of the Atlantic bluefin tuna collected in
the western Atlantic fishery originated from nurseries in the east.
Alternatively, medium and giant category bluefin tuna from the
Mediterranean were largely of eastern origin. Thus, initial evidence
suggests that the western fishery received high subsidy from the
Mediterranean population.
Click graphic to enlarge
Distribution of bluefin tuna larvae showing the location of spawning
grounds in the Gulf of Mexico and Mediterranean Sea (Rooker et al. 2007). Circle size a function of catch number per location.
Click on graphic to enlarge
Stable isotope signatures in the otoliths of yearling bluefin tuna
collected from the western Atlantic and Mediterranean Sea. Results show
a clear difference in the oxygen signatures with individuals from the
Mediterranean having enriched oxygen values in the otoliths relative to
their western counterparts.
Further Reading
Rooker JR, Alvarado Bremer JR, Block BA, Dewar H, De Metrio G, Kraus RT,
Prince ED, Rodriquez-Marin E, Secor DH (2007). Life history and stock
structure of Atlantic bluefin tuna (Thunnus thynnus). Reviews
in Fisheries Science 15(4):265-310
Rooker JR, Secor DH, De Metrio G, Rodríquez-Marín E, A. and Fenech
Farrugia (2006) Evaluation of population structure and mixing rates of
Atlantic bluefin tuna from chemical signatures in otoliths. ICCAT
Collective Volume of Scientific Papers 59(3): 813-818
Rooker JR, Secor DH, Zdanowicz VS, DeMetrio G, Relini LO (2003)
Identification of Atlantic bluefin tuna stocks from putative nurseries
using otolith chemistry. Fisheries Oceanography 12: 75-84
Secor DH, Campana SE, Zdanowicz VS, Lam JWH, McLaren JW, Rooker JR
(2002) Inter-laboratory comparison of Atlantic and Mediterranean bluefin
tuna otolith microconstituents. ICES Journal of Marine Science
59:1294-1304
Rooker JR, Secor DH, Zdanowicz VS, Relini LO, Santamaria N, Deflorio M,
Palandri G, Relini M (2002) Otolith elemental fingerprints of Atlantic
bluefin tuna from eastern and western nurseries. ICCAT Collective
Volume of Scientific Papers 54: 498-506
Rooker JR, Secor DH, Zdanowicz VS, Itoh T (2001) Discrimination of
northern bluefin tuna from nursery areas in the Pacific Ocean using
otolith chemistry. Marine Ecology Progress Series 218: 275-282
Rooker JR, Zdanowicz VS, Secor DH. (2001) Otolith chemistry of tunas:
assessment of base composition and post-mortem handling effects.
Marine Biology 139: 35-43
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2. Blue marlin tracking with electronic tags |
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Recent stock assessments of Atlantic blue marlin (Makaira
nigricans) by
ICCAT reported that stocks are well below the level to
support maximum sustainable yield (MSY). Although blue marlin are
managed under ‘single-stock’ paradigm, major uncertainties in stock
structure exist because the nature and extent of movement is poorly
understood. Through support of The
McDaniel Charitable Foundation, CFER
scientists are currently using pop-up satellite archival tags to assess
the stock structure of blue marlin in the Gulf of Mexico and assist in
the identification of site fidelity. Pop-up tags are designed to track
large-scale movements of pelagic fishes, and during deployment these
tags collect detailed depth, temperature and light-level data. Data
readings are provided in four types of summarized data: depth
distribution (diving behavior), depth-temperature profiles, migration
path during period of deployment, and GPS data on pop-up location.
Blue marlin and other istiophorid billfishes are capable of traveling
long distances, moving across ocean basins or between hemispheres.
Because such movements can cross political boundaries, information on
migration is crucial for coordinating international management and
conservation of these species. The scale of movements and the habitat
conditions of billfishes presents a difficult challenge to quantifying
migratory pathways. Archival tags that record depth, temperature, and
light intensity are a relatively new technology that offers the
potential to reconstruct movements of fishes. Since 2003,, we have
deployed 21 pop-up archival transmitting (PAT) tags on blue marlin
during the summer spawning period in the Gulf of Mexico. To date, 18 PAT
tags (30-180 day deployments) have reported, and the majority of pop-up
locations have been within the Gulf of Mexico (82%) or in the Straits of
Florida. Net movement per day of these blue marlin was low (~5 nautical
miles per day) relative to rates reported for studies on blue marlin in
the Atlantic Ocean ( in the Atlantic Ocean (e.g. Graves et al. 2002 [18
nm/day]; Kerstetter et al. 2003 [15-39 nm/day]), suggesting increased
retention within the Gulf. Also, several blue marlin frequenting
spawning grounds off Texas and Louisiana during the summer remained in
the Gulf through the fall and winter.
Vertical habitat use: Oceanography of E vs W GOM
(Left) Percent of time as a function of depth and change in temperature.
(Right) Change in temperature with depth in the western and eastern Gulf.
Click on graphic to enlarge
Further Reading
Kraus RT, Rooker JR (2007). Patterns of vertical habitat use by Atlantic
blue marlin (Makaira nigricans) in the Gulf of Mexico. Gulf
and Caribbean Research 19: 89-97.
Tracks of tagged blue marlin
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Click on graphics to enlarge |
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3. Evaluating the stock structure of billfishes using otolith
chemistry |
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Using a combination of stable isotopes (d13C, d18O) and trace elements
(Mg, Ca, Mn, Sr and Ba), we are investigating large scale connectivity
of highly migratory species. Specifically, we are using otolith
signatures of blue marlin (Makaira nigricans), white marlin (Tetrapturus
albidus), and sailfish (Istiophorus platypterus) to investigate if
regional differences exist among fish collected from the Atlantic,
Caribbean Sea, and Gulf of Mexico. This research is in collaboration
with colleagues at the Southeast Fisheries Science Center NMFS
laboratory where otoliths have been archived from billfish fishing
tournaments since the early 80’s. This research will provide additional
insight into movement patterns and connectivity of highly migratory
species and complement our existing blue marlin tagging program.
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4. Early life ecology of billfishes |
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Adult blue marlin, white marlin, and sailfish are commonly
taken by recreational and commercial anglers (bycatch from US longline
fleet) during late spring to early fall, which happen to coincide with
presumed spawning periods of all three species. Moreover, larval
billfishes are commonly reported from the Gulf, possibly indicating the
region represents an important spawning and nursery area of billfish. In
response, PFCP scientists are currently examining the early life ecology
of billfishes in the northern Gulf of Mexico (GOM). Our working
hypothesis is that the NW GOM represents essential habitat (spawning &
nursery habitat) of blue marlin, white marlin, and sailfish. The goal of
this work is to identify spawning/nursery grounds and describe
oceanographic features (upwelling zones, Loop Current and associated
fronts, warm/cold core eddies) that favor the production, retention, and
survival of larvae and juveniles. Using samples collected with net gears
(neuston, larval purse seine) from our sampling corridor in the NW GOM,
we are examining basic life history parameters (age, hatch-date, growth
rate) of billfishes, and assessing the habitat quality through the use
of biochemical condition (RNA:DNA) and growth (otolith microstructure)
measures.
Several data sources indicate the Gulf of Mexico (GOM) may serve as
important spawning and/or nursery habitat of blue marlin, white marlin,
and sailfish. In response, the productivity and sustainability of
Atlantic billfish populations may be determined in part by environmental
conditions and/or anthropogenic activities in the GOM, and thus there is
a need to further evaluate the role of the GOM as it relates to fish
habitat of Atlantic billfishes. Research cruises in the GOM sampling
corridor (27-28 N to 90-94 W) were conducted in 2005 during putative
spawning periods (May, July, and September 2005) of all three species to
identify spawning times/locations and assess early life patterns of
habitat use. Larvae of sailfish, white marlin, and blue marlin were
collected in 2005 (N > 1000) and identifications have been confirmed
genetically for all three taxa (see photos in Figure 1). Highest numbers
of istiophorid larvae were present near the western margin of Loop
Current on the continental shelf in relatively warm waters (> 27° C). Sailfish were collected
during all three survey, while white marlin and blue marlin have been
confirmed in May and July surveys, respectively. Although ichthyoplankton surveys are ongoing, current data suggest that blue
marlin, white marlin, and sailfish aggregate and spawn in the northern
GOM.
Distribution & abundance of blue marlin larvae
Distribution and abundance of blue marlin larvae collected in the northern GOM. Density, SSH, and SST plots for cruises in 2005 and 2006
Click graphic to enlarge
Further Reading
Simms, JR Holt SA, Holt GJ, Bangma J, Rooker JR (2008) Age and growth of
larval sailfish in the northern Gulf of Mexico, Proceedings of the Gulf
and Caribbean Fisheries Institute, 60 (In press)
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5. Origin of yellowfin tuna in the Hawaiian Islands using
natural markers in otoliths
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The current work is a collaborative effort
with David Itano of University of Hawaii. The aim of the proposed work is
to provide information on the origin of young yellowfin tuna (age-1 and
age-2) in the Hawaiian Islands using natural tracers that are linked to
ambient physicochemical conditions of the water. Our first step will be
to develop a reference library that describes the otolith chemical
signatures of age-0 yellowfin from putative spawning/nursery areas in
Hawaii and the broader WCPO (i.e. are ambient chemical conditions in
regional nurseries sufficient to impart unique signatures in the otoliths
of yellowfin?). It has long been assumed that juveniles from the
equatorial region are purported to be the main source of recruits to the
Hawaii-based fisheries and will therefore be a critical sampling location
for the proposed work. Next, we will target age-1 and age-2 (sub-adult to
young adult) yellowfin from the Hawaiian Island fisheries to determine
their source (natal origin). Three hypotheses will be tested using
otolith chemistry: H1: chemical signatures in the otoliths of yellowfin
from regional nurseries differ, H2: inshore fisheries for yellowfin
around the Hawaiian Islands are supported primarily by local recruitment
(i.e. resident populations), H3: juveniles from the equatorial region are
the main source of the recruits to the Hawaii-based fishery. We will then
be able to determine whether residents (versus transients) constitute the
primary source of yellowfin recruits to the Hawaii-based fisheries.
Collection of yellowfin from the Hawaiian Islands and areas of the
broader WCPO are currently underway and preliminary results are expected
by summer 2008.
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Dr. Jay R. Rooker · Department of Marine Biology
Texas A&M University @ Galveston
5007 Ave U, Galveston, Texas 77551
rookerj@tamug.edu · 409-740-4744
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