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““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
Po
rcen
taje
po
r p
eso
- P
erce
nt
wei
gh
t
Cepha
lopod
s
Crusta
cea
Misc
. fish
es
Myc
toph
idae
Phosic
hthy
idae
Nomeid
ae
Exoco
etida
e
Tetra
odon
tiform
es
Caran
gidae
Coryp
haen
idae
Wah
oo
Black s
kipjac
k tun
a
Skipjac
k tun
a
Yellow
fin tu
na
Auxis
sp.
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
5
15
25
-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
Lg.BETSKJLg.YFT
Sm.BET
Sm.YFTLg.Marlin
ALBMisc.Pisc.
Lg.Wah.
Sm.Shark
Sm.YFT
SKJ
Lg.BET Lg.YFT
Tro
ph
ic le
vel –
Niv
el t
rófi
co
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
5
1998 1999 2000 2001
Discarded catches, Unassociated sets
Average Trophic Levels (surface gear)Discarded catches, Floating-object setsRetained catches, Floating-object sets
Tro
ph
ic le
vel –
Niv
el t
rófi
co
Lg.YFT
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