Trophic Relationships Between Predators Caught
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TROPHICTROPHIC RELATIONSHIPSRELATIONSHIPS BETWEENBETWEEN PREDATORSPREDATORS CAUGHTCAUGHT BYBY TUNATUNA PURSEPURSE--SEINERSSEINERS ININ THETHE EASTERNEASTERN PACIFICPACIFIC OCEANOCEAN DR. FELIPE GALVAN- MAGAÑA CENTRO INTERDISCIPLINARIO DE CIENCIAS MARINAS. LA PAZ, BAJA CALIFORNIA SUR, MEXICO DR. ROBERT J. OLSON INTERAMERICAN TROPICAL TUNA COMMISSION LA JOLLA CALIFORNIA 30 25 Area A 20 15 Area C 10 5 Area B 0 Area D -5 LATITUDE (DEG.) -10 Area F Dolphin Sets -15 School Sets Area E Floating Object Sets -20 -140 -130 -120 -110 -100 -90 -80 LONGITUDE (DEG.) Table I. Stomachs sampled from predators in the bycatch of tuna purse-seiners in the Eastern Pacific Ocean during 1992 – 1994. Samples Predator Number Stenella attenuata Spotted dolphin 311 Stenella longirostris Spinner dolphin 209 Delphinus delphis Common dolphin 51 Stenella coeruleoalba Striped dolphin 5 Thunnus albacares Yellowfin tuna 4831 Katsuwonus pelamis Skipjack 1205 Thunnus obesus Bigeye Tuna 80 Euthynnus lineatus Black skipjack 100 Auxis spp. Bullets 55 Carcharhinus limbatus Black tip shark 262 Carcharhinus falciformis Silky shark 64 Carcharhinus Whitetip shark 30 longimanus Carcharhinus leucas Bull shark 2 Carcharhinus spp. Carcharhinid sharks 82 Sphyrna spp. Hammerhead sharks 48 Isurus oxyrinchus Mako shark 4 Prionace glauca Blue shark 2 Alopias spp. Thresher shark 12 Nasolamia velox White nose shark 2 Makaira indica Black marlin 25 Makaira mazara Blue marlin 15 Makaira spp. Marlins unidentified 18 Tetrapturus audax Striped marlin 8 Istiophorus platypterus Sailfish 49 Coryphaena hippurus Mahi-mahi 545 Acanthocybium solandri Wahoo 235 Elagatis bippinulata Rainbow-runner 48 Total 8298 50% Predator and prey in dolphins sets 40% 30% 20% Weight percentage 10% 0% Epi Cephalopods Meso Cephalopods Crustacea Misc.Fishes Mesopelagic Fishes Myctophidae Phosichthyidae Gempylidae Carangidae Coryphaenidae Exocoetidae Nomeidae Tetraodontiformes Wahoo Black Skipjack Big Eye Skipjack Sharks 36 (31) 14,157g Yellowfin Billfishes 9 (2) 1,615g Other species 4 (3) 418g Auxis spp. Dolphins 389 (187) 18,133g Tunas 1579 (505) 336,128g 70% Predators and prey in school sets 60% 50% 40% 30% Weight percentage 20% 10% 0% Epi Cephalopods Meso Cephalopods Crustacea Misc.Fishes Myctophidae Phosichthyidae Gempylidae Carangidae Coryphaenidae Exocoetidae Nomeidae Tetraodontiformes Wahoo Black skipjack Skipjack Yellowfin tuna Auxis spp. BillfishesSharks 52 124 (10) (26) 17,004 99,577 g g TunasOther 1242 species (979) 126,327 23 (22) 5,483g g 60% 50% 40% 30% Predators and prey in Log sets Weight percentage 20% 10% 0% Epi Cephalopods Meso Cephalopods Crustacea Misc.Fishes Mesopelagic Fishes Myctophidae Phosichthyidae Gempylidae Carangidae Coryphaenidae Exocoetidae Nomeidae Tetraodontiformes Wahoo Black skipjack Big eye Skipjack Yellowfin tuna Auxis spp. Tunas 261 (1706) 12,643g Other species 389 (388) 49,913 g Billfishes 27 (15) 23,533 g Sharks 233 (58) 292,660 g TUNASTUNAS Tunas 100% 90% 80% 70% 60% 50% 40% Weight percentage 30% 20% Yellowfin Tuna 2,895 (1,936) 464,891g 10% Skipjack135 (1,070) 7,939g 0% Bullets 2(53) 8g Black Skipjack 12 (88) 577g Big eye 38 (42) 1,638g Crustacea Misc.Fishes Myctophidae Carangidae Epi Cephalopods Nomeidae Skipjack Phosichthyidae Exocoetidae Meso Cephalopods Coryphaenidae Auxis spp. Black Skipjack Yellowfin Tuna Tetraodontiformes DOLPHINSDOLPHINS DOLPHINS 100% 90% 80% 70% 60% 50% 40% 30% Weight percentage 20% 10% 0% Striped dolphin 5 (0) 125g Spotted dolphin 231 (80) 12,080g Spinner Dolphin 139 (70) 5,611g Common dolphin 14 (37) 317g Crustacea Misc. FishesMyctophidae Epi Cephalopods Carangidae Meso Cephalopods Phosichthyidae ExocoetidaeNomeidae Skipjack Coryphaenidae Auxis spp. Tetraodontiformes SHARKSSHARKS Sharks 100% 90% 80% 70% 60% 50% 40% White nose shark 2(0) 6,660g Carcharhinids Sharks 57 (25) 44,368g Weight percentage 30% Thresher shark 9(3) 6,653g Silky Shark 51 (13) 61,444g 20% White tip shark 15(15) 18,661g Mako Shark 3(1) 3,621g 10% Hammerhead sharks 44(4) 31,238g Bull shark 2(0) 410g 0% Blue shark 1(1) 125g Black tip shark 209 (53) 233,214g Crustacea Misc. Fishes MyctophidaeCarangidae Wahoo Epi Cephalopods ExocoetidaeNomeidae Big eye Meso Cephalopods Coryphaenidae Skipjack Black Skipjack Auxis spp. Tetraodontiformes Yellowfin tuna BILLFISHESBILLFISHES Billfishes 80% 70% 60% 50% 40% 30% Weight percentage 20% Unidentified Marlins 16(2) 9,134g 10% Striped marlin 5(3) 7,082g Sailfish 43(6) 5,166g 0% Blue marlin 9(6) 11, 563g Black marlin 15 (10) 9,207g Crustacea Misc.Fishes Myctophidae Carangidae Epi Cephalopods Nomeidae Skipjack Meso Cephalopods Phosichthyidae Exocoetidae Coryphaenidae Auxis spp. Yellowfin tuna Tetraodontiformes OTHEROTHER PREDATORSPREDATORS 50% 40% 30% Other predators 20% Weight percentage 10% 0% Epi Cephalopods Meso Cephalopods Crustacea Misc.Fishes Myctophidae Phosichthyidae Carangidae Coryphaenidae Exocoetidae Nomeidae Tetraodontiformes Wahoo Black skipjack Big eye Skipjack Yellowfin tuna Auxis spp. Wahoo 113(122) 21, 325g Mahi-MahiRainbow 271(274) runner 34,805g32(16) 2,834g 30 25 Area A 20 15 Area C 10 5 Area B 0 Area D -5 LATITUDE (DEG.) -10 Area F Dolphin Sets -15 School Sets Area E Floating Object Sets -20 -140 -130 -120 -110 -100 -90 -80 LONGITUDE (DEG.) Table. Overlapping between predators in the Eastern Pacific Ocean. T=Tuna, D=Dolphin, S=Shark, B=Billfishes, O= Other predators (Mahi-mahi, wahoo, rainbow runner) Numbers in bold indicate values higer than 0.6, which could indicate overlapp between predators Area/set type T-D T-S T-B T-0 D-S D-B D-O S-B S-O B-O Area A/Dolphin set 0.43 0.04 0.2 0.27 0.17 0.18 0.28 0.02 0 0.02 Area B/Dolphin set 0.41 0.26 0.39 Area C/Dolphin set 0.24 0.11 0.77 0.75 0.18 0.16 0.11 0.05 0 0.95 Area D/Dolphin set 0.29 0.52 0.55 Area E/Dolphin set 0.47 Area F/Dolphin set 0.50 0 0.01 Area A/School set 0.67 0.48 0.24 0.44 0.1 0.41 Area B/School set 0 0 0 Area C/School set 0.39 0.23 0.15 Area D/School set 0.16 0.03 0.21 0.42 0.14 0.12 Area E/School set 0 0 0.35 0.28 0 Area F/School set 0.01 0.99 0 Area B/Log set 0.02 0.1 0.33 0.6 0.45 0.51 Area C/Log set 0.69 Area D/Log set 0.11 0.11 0.49 0.55 0.27 0.29 Area E/Log set 0.18 0.12 0.43 0.46 0.3 0.45 Area F/Log set 0.08 0 0.44 0.75 0.56 0.46 Tabla 2. Breadth niche recorded in predators by each area in the EPO. D=Dolphins sets, S= School sets, L= Log sets Area A Area B Area C D S L D S L D S L TUNAS 2.8 7.0 3.4 1.0 2.5 1.8 2.3 1.8 DOLPHINS 6.4 6.2 5.1 OTHER PREDATORS 3.0 2.0 4.9 1.0 3.0 BILLFISHES 1.7 6.4 1.0 1.8 1.0 1.9 SHARKS 1.4 3.9 3.0 1.0 4.1 1.6 3.1 Area D Area E Area F D S L D S L D S L TUNAS 1.7 2.1 8.9 1.1 1.1 1.7 1.3 1.0 1.2 DOLPHINS 6.1 17.6 4.5 OTHER PREDATORS 2.2 11.9 2.0 6.3 1.4 1.0 4.7 BILLFISHES 2.2 5.3 1.0 2.0 2.0 SHARKS 3.2 3.3 2.6 2.7 5.1 1.6 2.9 Dolphin Sets 100% 90% Misc. fishes 80% Crustacea 70% Cephalopoda Myctophidae 60% Carangidae 50% Tetraodontiformes 40% Exocoetidae Prey Biomass Phosichthyidae 30% Nomeidae 20% other Scombridae 10% Auxis spp. 0% 300-600 601-800 801-1000 1001-1200 1201-1400 1401-1889 72 227 344 556 254 108 Fork Length (mm) Sample Size Schoolfish Sets 100% 90% Misc. fishes 80% Crustácea Cephalopoda 70% Myctophidae 60% Carangidae 50% Tetraodontiformes 40% Exocoetidae Prey Biomass Phosichthyidae 30% Nomeidae 20% other Scombridae 10% Auxis spp. 0% 300-600 601-800 801-1000 1001-1200 1201-1400 1401-1889 237 392 258 123 84 22 Fork Length (mm) Sample Size Log Sets 100% 90% Misc. fishes 80% Crustacea 70% Cephalopoda 60% Myctophidae Carangidae 50% Tetraodontiformes 40% Prey Biomass Exocoetidae 30% Nomeidae 20% other Scombridae 10% Auxis spp. 0% 300-600 601-800 801-1000 1001-1200 1201-1400 135 24 19 9 6 Fork Length (mm) Sample Size .