Isotope Biogeography and Trophic Dynamics of Billfish Collected in the Equatorial Pacific Ocean.

Transcription

1 Isotope Biogeography and Trophic Dynamics of Billfish Collected in the Equatorial Pacific Ocean Brittany Graham Dept of Oceanography, Univ of Hawaii, Honolulu, HI Brian Popp Dept of Geol and Geophysics, Univ of Hawaii, Honolulu, HI Valerie Allain Secretariat of the Pacific Community, Noumea, New Caledonia Robert Olson Inter-American Tropical Tuna Commission, La Jolla, CA Felipe Galvan CICIMAR-IPN, Baja California, Mexico Brian Fry Coastal Ecology Institute, Louisiana State Univ, Baton Rouge, LA

2 Objectives: PFRP Funded Project (1) Regional Food Web Structure - Chemical Tags (2) Basin-Wide Patterns - Isotope Biogeography Study Region

3 Pelagic Food Web Trophic Position δ 15 N Nutrient Dynamics at Base 12 Food Web Complexity (TL) Depth of Forage Top Predators (9 ) δ 15 N ( ) 8 4 Shrimp (3 ) Fish (6 ) 0 N 2 Fixing Phytoplankton (0 )

4 REGIONAL DYNAMICS: 15 New Caledonia Fishery (1) Food Web Structure Variations δ 15 N ( ) Striped Marlin Blue Shark Albacor Shortbill Spearfish e Sailfish Mahima hi Silky Shark Pelagic Stingray Yellowfin Tuna Skipjack Tuna d 13 C ( ) Bigeye Tuna Swordfish 22 (1) Regional chemical tags δ 15 N ( ) ** * * * * * * * * Albacore 6 9 Bigeye Tuna 2 5 Blue Marlin 5 1 Mahimahi 6 6 Longsntd lancetfish 6 2 Pelagic Stingray Shortbill Spearfish Skipjack tuna New Caledonia French Polynesia Striped Marlin 3 6 Ono/Wahoo 7 2 Yellowfin Tuna 7 0 Silky Shark

5 Western Tropical Pacific Higher Trophic Levels δ 15 N ( ) New Caledonia Striped Marlin Blue Shark Sailfish Swordfish Bigeye Tuna Albacore Shortbill Spearfish Mahimahi Pelagic Stingray Yellowfin Tuna Silky Shark Skipjack Tuna δ 13 C ( )

6 French Polynesia Western Tropical Pacific Higher Trophic Levels Escolar Family Bigeye Tuna δ 15 N ( ) Longsnouted Lancetfish Pelagic Stingray Striped Marlin Mahimahi Yellowfin Tuna Albacore Blue Marlin Shortbill Spearfish Skipjack Tuna Ono/Wahoo δ 13 C ( ) -15

7 Regional Trophic Dynamics * α = 01 * * * * * * * * * Bigeye Tuna Blue Marlin Mahimahi Longsntd lancetfish Pelagic Stingray Shortbill Spearfish Skipjack tuna Striped Marlin Ono/Wahoo Yellowfin Tuna Silky Shark New Caledonia French Polynesia Albacore δ 15 N ( )

8 Basin-Wide Information Isotope Biogeography δ 15 N, Longitude (deg) Latitude (deg) Amino Acid Nitrogen Isotopic Analysis Non-Essential AA Same TL 1 TL Essential AA Shift at the Baseline

9 Isotope Biogeography Yellowfin Tuna 20 EQ

10 YELLOWFIN TUNA δ 15 N, Papua New Guinea French Polynesia Longitude (deg) = 4 TL 10 = 1 TL 8 Latitude (deg)

11 Tuna Tank Hawaii Institute of Marine Biology (HIMB)

12 Experimental Diet Shift (Calculating Tissue Turnover Rates) White Muscle Tissue Liver δ 15 N ( ) b = δ 15 N/day Half-life: 396 days R 2 = b = δ 15 N/day Half-life: 161 days R 2 = Time (days) Time (days)

13 YELLOWFIN TUNA δ 15 N, Papua New Guinea French Polynesia Longitude (deg) = 4 TL 10 = 1 TL 8 Latitude (deg)

14 Bigeye Tuna Papua New Guinea δ 15 N, French Polynesia

15 Isotope Biogeography Yellowfin Tuna Bigeye Tuna δ 15 N, ( ) Longitude (deg) Latitude (deg) Latitude (deg)

16 Skipjack Isotope Biogeography

17 Skipjack Tuna Latitude (deg) δ 15 N, δ 15 N, Longitude (deg)

18 Isotope Biogeography Yellowfin Tuna Bigeye Tuna Skipjack Tuna δ 15 N, ( ) Longitude (deg) Latitude (deg) Latitude (deg) Latitude (deg)

19 Compound-Specific Stable Isotope Analysis of Amino Acids δ 15 N, Non-Essential AA Same TL Longitude (deg) TL Essential AA Shift at the Baseline Latitude (deg)

20 Conclusions: Regional Trophic Dynamics Ecopath TL parameters Unique regional δ 15 N values will be used as chemical tags to model migration habits of pelagic predators Basin Wide Trophic Dynamics Isotope biogeography provides a large-scale, time-average image of a population s trophic history Amino acid research will determine if observed changes in food web structure are a function of shifts in trophic or nutrient dynamics

21 ACKNOWLEDEMENTS Continual Research Support: John Sibert & Pelagic Fisheries Research Program Special thanks for logistical support: Johnoel Ancheta, Rich Brill, Andrew Carter, Derek Cuny, Dean Grubbs, Kim Holland, Dave Itano, Dodie Lau, Mike Musyl, Terri Rust, Jamie Tanimoto, Natalie Wallsgrove, NOAA R/V Sette and Kaimimoana Crew and Science Party, and JIMAR staff