““ECOSYSTEM CONSIDERATIONS” – IATTC ECOSYSTEM CONSIDERATIONS” – IATTC FISHERY STATUS REPORTFISHERY STATUS REPORT

Robert Olson

8th Meeting of the Working Group on Stock Assessments8a Reunión del Grupo de Trabajo sobre Evaluación de

Poblaciones  

IATTC Fishery Status Report – “Ecosystem Considerations”

• Call attention to the Ecosystem Considerations section

• Overview of the section’s contents

• Briefly highlight some ecological studies in the EPO (IATTC and NMFS-SWFSC)

Ecosystem Considerations

• International calls for ecosystem considerations in fisheries management– FAO Code of Conduct for Responsible Fisheries

– Reykjavik Declaration on Responsible Fisheries in the Ecosystem

• Focus on the ecosystem as a whole– Direct impact of fisheries on species and groups in ecosystem

– Indirect effects of fisheries

– Physical environment

• Bring together information and updates on the status and trends of ecosystem components.

• Spur improved understanding of the connections between ecosystem components by bringing together diverse research efforts into one document.

Fishery Status Report - Ecosystem Considerations

• Introduction• Components impacted by catches

– Single species assessments• Tunas• Billfishes• Summary catch statistics by gear

– Species groups• Marine mammals-2006 dolphin mortality est.• Sea turtles – 2006 mortality est. (PS)• Sharks and other large fishes

• Other ecosystem components– Seabirds– Forage taxa– Larval fishes and plankton

Stenella Abundance Research (STAR) 2006

R/V McArthur IIR/V David Starr Jordan

STAR Ecosystem Research

• Marine mammal abundance

• Sea turtles

• Seabird ecology and abundance

• Forage organisms

• Planktonic organisms

• Physical environment

STAR - Prey Fishes and Squids

• Acoustic backscatter• Net sampling

– Manta tows– Bongo tows

• Dipnetting surveys• Collection of squid• Collection of jellyfish (sea turtle diet SIA)• Several components provided to IATTC for

studies of tropho-dynamics based on stable isotope analysis

Date Time Yellowfin Skipjack Squid Yellowfin Skipjack Tuna Squid5-May-2002 18:17 50 100 48 51 (4.2) 2.7 3314-May-2002 13:54 48 10 8 51 (4.2) 2.7 6330-Nov-2002 12:42 11.2 1.2 50 0.2 0.2 39/50 1.5/2.6 22

Tuna length (cm)mean (sd)

Mean Wt (kg)Catch (mt) Discarded damaged (mt)

Pelagic ommastrephid squids (e.g. Dosidicus gigas): ecosystem indicators?

Olson, R.J., M.H. Román-Verdesoto, and G.L. Macías-Pita. 2006. Bycatch of jumbo squid Dosidicus gigas in the tuna purse-seine fishery of the eastern Pacific Ocean and predatory behaviour during capture. Fish. Res. 79(1-2): 48-55.

Fishery Status Report -Ecosystem Considerations (continued)

• Trophic interactions• Physical environment• Aggregate indicators• Ecosystem modeling• Actions by the IATTC and the AIDCP

addressing ecosystem considerations– Dolphins– Sea turtles– Other species– All species

• Future developments

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Tunas

Dolphins

Sharks

BillfishesMahi,Wahoo, R. Runner

0%

20%

40%

60%

80%

100%

Dieta de los depredadores del OPODiet data for EPO predators

δ15N: posición trófica - δ15N: trophic position

Isotopic fractionation – the light 14N isotope is excreted more than the heavy 15N isotope, leaving the animal enriched by 3‰ in δ15N relative to its food source.

δ15Npredator 3.0 + δ15Nprey (‰)=

Samples for stable isotope analysis from STAR 2003 Research Cruises

Type Taxon Number of samples Forage flyingfishes -- Forage cephalopods -- Forage mesopelagic fishes 400 Primary consumers zooplankton 156 Primary producers phytoplankton 199

-25

-15

-5

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-160 -150 -140 -130 -120 -110 -100 -90 -80 -70

R/V David Starr Jordan

R/V McArthur II

Zooplankton Sample Locations

156 bongo tows30 July - 8 December 2003

Fishery Status Report -Ecosystem Considerations (continued)

• Trophic interactions• Physical environment• Aggregate indicators• Ecosystem modeling• Actions by the IATTC and the AIDCP

addressing ecosystem considerations– Dolphins– Sea turtles– Other species– All species

• Future developments

Fishery Status Report - Physical Environment

• Fiedler, P.C. 2002. Environmental change in the eastern tropical Pacific Ocean: review of ENSO and decadal variability. Marine Ecology Progress Series 244: 265-283.

• Fiedler, P.C., and M.F. Lavin (Editors) 2006. A review of eastern tropical Pacific oceanography. Progress in Oceanography 69: 94-100.

Fishery Status Report -Ecosystem Considerations (continued)

• Trophic interactions• Physical environment• Aggregate indicators• Ecosystem modeling• Actions by the IATTC and the AIDCP

addressing ecosystem considerations– Dolphins– Sea turtles– Other species– All species

• Future developments

Red trófica del ecosistema pelágico en el OPOFood web of the pelagic ecosystem in the EPO

Olson, R.J., and G.M. Watters. 2003. A model of the pelagic ecosystem in the eastern tropical Pacific Ocean. Inter-Am. Trop. Tuna Comm., Bull. 22(3): 133-218.

Physical forcing simulations with ENSO-scale and global-warming climate drivers

Axis of the Auxis

Axis of the Squid

Watters, G.M., R.J. Olson, R.C. Francis, P.C. Fiedler, J.J. Polovina, S.B. Reilly, K.Y. Aydin, C.H. Boggs, T.E. Essington, C.J. Walters, and J.F. Kitchell. 2003. Physical forcing and the dynamics of the pelagic ecosystem in the eastern tropical Pacific: simulations with ENSO-scale and global-warming climate drivers. Can. J. Fish. Aquat. Sci. 60(9): 1161-1175.

Fishery Status Report -Ecosystem Considerations (continued)

• Trophic interactions• Physical environment• Aggregate indicators• Ecosystem modeling• Actions by the IATTC and the AIDCP

addressing ecosystem considerations– Dolphins– Sea turtles– Other species– All species

• Future developments

0.0

1.0

2.0

3.0

4.0

5.0

Longliners Dolphin Sets Floating-objectSets

Unassoc. Sets Pole-and-Line

4.4

4.5

4.6

4.7

4.8

4.9

5.0

Longliners Dolphin sets Floating-object sets

Unassoc. sets Pole-and-Line

4.98

4.64 4.634.59 4.59

Sm.YFT/SKJ/ALB

3.0

3.5

4.0

4.5

5.0

5.5

Lg.marlins

Lg.BET

Lg.YFT

Misc.piscivores

Sm.BET

Auxis spp.

Lg.sharks

Misc.epi.fishes

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Sm.BET

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Trophic Levels of Catches (1993-97)

Lg.YFT

Retained catches

Discarded catches

4.5

4.6

4.7

4.8

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Dolphin sets

Floating-object sets

Unassociated sets

Pole and line

Dolphin sets - Lances sobre delfines

4.0

4.2

4.4

4.6

4.8

5.0

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Average Trophic Levels (surface gear)

Floating object - Objeto flotante

4.0

4.2

4.4

4.6

4.8

5.0

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Unassociated sets - Lances no asociados

4.0

4.2

4.4

4.6

4.8

5.0

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

0

1

2

3

4

5

1998 1999 2000 20010

1

2

3

4

5

1998 1999 2000 2001

0

1

2

3

4

5

1998 1999 2000 2001

Retained catches, Unassociated sets

0

1

2

3

4

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1998 1999 2000 2001

Discarded catches, Unassociated sets

Average Trophic Levels (surface gear)Discarded catches, Floating-object setsRetained catches, Floating-object sets

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Sm.YFT

Rays

Lg.SHKLg.SHK

Rays

Misc.Pisc.

Lg.MLN Lg.MLN

Sm.Dor Sm.Dor

Sm.Dor

Sm.SHK

Lg.SLF

Lg.WahLg.Wah

Misc.Epi.Fish

Lg.SHK Lg.SHKLg.MLN

SKJSKJ

Sm.YFT

Lg.YFT

Lg.BET Lg.BET

SKJ

SKJ

Sm.BET

Sm.YFTSm.YFT

Lg.YFT