Contribution of cephalopod prey to large pelagic fish diet in the central N. Atlantic http://www.mafmc.org/ J. Logan, R. Toppin, S.C. Smith, J.M. Porter, M. Lutcavage Fisheries and Oceans Canada
Central N. Atlantic Bluefin Scientific Steering Committee, Bermuda
Research Longline Cruises, commercial vessels
Longline Sets: 2 2001: Hamilton Banker 2002: Eagle Eye II 3 1 Update ecological and oceanographic information for large pelagic fishes
Additional sampling via RV Shoyo Maru, See: Satoh et al., 2004 ICCAT Coll. Vol Sci. Pap.
Historical perspective: Matthews et al. 1977, RV Crawford, RV Delaware cruises,1960s-70 s Stomach content analyses of tunas and lancetfish Yellowfin n= 281 Bluefin n= 52 Albacore n = 48 Bigeye n = 14 Lancetfish n= 89 Total N= 224
2001 SCA samples 2002 Area 1 Area 2 Albacore (Thunnus alalunga) 10 14 Bigeye (Thunnus obesus) 12 2 Swordfish (Xiphius gladius) 5 23 Yellowfin (Thunnus albacares) 8 6 White Marlin (Tetrapturus albidus) 2 0 Blue Marlin (Makaira nigricans) 0 1 Total 37 46 Area 3 (all) Leg 1 Leg 2 Albacore 7 5 Bigeye 3 3 B. Marlin 1 1 Longbill spearfish 4 0 Dolphin 11 0 Swordfish 36 11 White marlin 3 4 Yellowfin 3 15 Total 68 39
SCA Sampling Protocol Stomachs removed from fish, stored frozen Thawed, weighed whole Contents washed over sieve 60 micron (2001), 1,000 micron (2002) Lining blotted dry, reweighed for total contents weight Remaining contents transferred to 70% EtOH and sorted in lab (some photographed) Specimens identified to closest possible taxon Beaks and otoliths stored for identification after 1 o sort
% Weight by Class 2001 Mean percent weight (MW%) 100% 80% 60% 40% 20% 0% 100% 80% 60% 40% 20% 0% Cephalopoda Crustacea Fish Other Albacore Bigeye Swordfish Yellowfin Area 1 Area 2
2001 Cephalopod Prey Species Area 1 Area 2 Albacore Bigeye Swordfish Ommastrephidae, Gonatidae, Enoploteuthidae, Chiroteuthidae Gonatidae, Enoploteuthidae, Architeuthidae, Octopodidae Ommastrephidae, Octopodidae Ommastrephidae Gonatidae, Ocotopodidae Ommastrephidae, Gonatidae, Enoploteuthidae, Chiroteuthidae, Architeuthidae, Histioteuthidae, Octopodidae Yellowfin Octopodidae Octopodidae
% Weight by Class, 2002 Yellowfin White marlin Swordfish Dolphinfish Longbillspearfish Blue marlin Bigeye Albacore 100% 80% 60% 40% 20% 0% Cephalopoda Fish Crustacea Other Mean percent weight (MW%)
Cephalopod Prey List 2002 Albacore Bigeye Blue marlin Longbill spearfish Dolphinfish Swordfish White marlin Yellowfin Ommastrephidae Ommastrephidae Stomach not retained Ommastrephidae Ommastrephidae Ommastrephidae, Mastigoteuthidae, Loliginidae Ommastrephidae Ommastrephidae, Chiroteuthidae
Cephalopod % Weight - 2002 Unidentifiable Ommastrephidae Mastigoteuthidae Chiroteuthidae Loliginidae Yellowfin White marlin Swordfish Dolphinfish Longbillspearfish Bigeye Albacore 100% 80% 60% 40% 20% 0%
Depth Profiles of Large Pelagic Fishes and Cephalopod Prey Epipelagic 0 200 Swordfish Bathypelagic Squids Bigeye Epipelagic Squids Albacore White marlin Blue marlin Longbill spearfish Yellowfin Dolphinfish 400 Mesopelagic 600 800 Bathypelagic 1,000 Large Pelagic Fishes Bathypelagic Squids: Gonatidae, Architeuthidae, Chiroteuthidae, Mastigoteuthidae, Enoploteuthidae Epipelagic Squids: Ommastrephidae, Loliginidae
1977 Summary Ommastrephidae dominant prey for tunas Deep sea squids (Cranchiidae, Histioteuthidae, and Bathyteuthidae) main lancetfish prey 2001 Area 1: Ommastrephidae Area 2: Gonatidae and Ommastrephidae 2002 Ommastrephidae dominant overall prey
Next steps : Beak and otolith identification, Stable Isotope Analysis (SIA): δ 15 N and δ 13 C of fish predators and prey Develop broader picture of trophic dynamics and energy sources Potential for use in squid trophic ecology studies Controlled diet switch validations (Hobson and Cherel 2006, Stowasser et al. 2006) Trophic analyses from soft tissues ( Ruiz-Cooley et al. 2004, Takai et al. 2000) Trophic analyses of beaks (Cherel and Hobson 2005, Ruiz-Cooley et al. 2006)
Nova Scotia 0-100 -200-300 -400-500 -600 Open Ocean Gulf of Mexico -700-800 Archived Depth Real Time Depth 10/15/05 11/4/05 11/24/05 12/14/05 1/3/06 1/23/06 2/12/06 3/4/06 In oceanic areas, repetitive deep descents by ABFT suggest extensive foraging on squids, as in Matthews et al. 1977
Acknowledgements Crews F/V Hamilton Banker and Eagle Eye II Ben Galuardi, LPRC, UNH Funding: USA NOAA, DFO Canada Chief scientists Scott Heppell (OSU), Lisa Natansen (NEFSC), and Mike Musyl (SWFSC) Larry Harris, UNH