Aggregation, exploitation and scales of spatial variability ...

of bigeye and yellowfin tuna in the Central Pacific: ….

application of the “dumb” tag technology Tuna Tagging Pelagic Fisheries Research Program Project University of Hawaii

Steve Kajiura David Itano Gary Eldridge Randy Kosaki Kim Holland Gary Dill

160 W 155 W Necker

Nihoa Main

Niihau ? / /

20 N

Hawaii ??? Fishing grounds - the Hawaiian Ridge 30 N

Offshore weather buoys Kure Pearl & Hermes Inshore FADs Northwest Hawaiian Salmon Lisianski Islands Isolated reef or atoll Bank 25 N French Frigate B1 Necker Nihoa Main Hawaiian Islands Kaula Rock 20 N Bigeye 1

Cross B3 Seamount

Johnston Atoll B4 B2

15 N 180 175 W 170 W 165 W 160 W 155 W 150 W

Hawaii’s Tuna Fisheries vLongline Bigeye, yellowfin, albacore vPole-and-line Skipjack, yellowfin vTroll Yellowfin, skipjack u Charter, commercial, combination recreational/subsistence/p-t commercial vHandline Yellowfin, bigeye, albacore uPalu ahi - daytime handline (med Yellowfin) uIka shibi - night time handline (large Yellowfin) uOffshore “handline” (small/medium Bigeye, yellowfin)

Tag releases and recaptures (HTTP to October 31, 2000)

Bigeye Yellowfin Total

Releases 7665 7469 15134 Recaptures 1140 980 2131

Recapture 14.99% 13.12% 14.08% Rate Fishing Grounds & Tag

30 N 200 mile Exclusive Economic Zone release areas NWHI Longline prohibited zone Midway Atoll MHI Longline prohibited zones Throughout the year October 1 - January 31 Northwest Hawaiian Islands

15 N

B1 Main Hawaiian Islands

20 N

B3 Cross Smt Johnston Atoll B4 B2

15 N 180 175 W 170 W 165 W 160 W 155 W Length Frequency of releases

3000

2500 BE YF 2000

1500

1000

Number of fish 500

0 >130 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99 100-109 110-119 120-129 Fork Length (cm)

Range Median Mode Mean Std Dev Count BE 29-133 58 53 61.45 14.37 9181 YF 20-143 55 48 58.05 17.52 7960 Recaptures from releases made at these areas Area Total BE return YF return Total return releases rate (%) rate (%) rate (%) Midway 2257 0 % 0.8 % 0.8 %

B1 - Nihoa I. 244 20.0 % 14.6 % 14.8 % Oahu FADs 738 23.5% 26.0% 25.7% Big Island 1261 15.7 % 15.9 % 15.9 % FADs Offshore 3074 17.5 % 21.8 % 18.5 % FADs Cross 9606 13.5% 18.7% 15.4% Seamount NMFS 77 15.6 % NA 15.6 % Archival Movements from 160 W 155 W Necker NOAA B-1

Nihoa offshore FADs Main Hawaiian Islands Kauai

Niihau Oahu

Kaula Kaena Pt. Rock Molokai / Lanai / Maui

Bigeye 1 20 N

Keahole Pt. Hilo Bay Hawaii NOAA B-3 Cross Seamount South Point

NOAA B-4 NOAA B-2 Yellowfin and bigeye movements 160 W 155 W Necker NOAA B-1 from Cross Seamount Nihoa Main Hawaiian Islands Kauai

Niihau Oahu

Kaula Kaena Pt. Rock Molokai / Lanai / Maui Penguin Bank

Bigeye 1 20 N

Keahole Pt. Hilo Bay Hawaii NOAA B-3 Cross Seamount South Point

NOAA B-4 NOAA B-2 Movements from 35 N Cross Seamount

30 N

25 N

20 N

15 N

170 W 160 W 150 W 140 W 130 W 10 N 120 W 160 W 155 W Necker NOAA B-1 To Big Island Nihoa Main Hawaiian Islands Kauai

Niihau Oahu

Kaula Kaena Pt. Rock Molokai / Lanai / Maui Penguin Bank

Bigeye 1 20 N

Keahole Pt. Hilo Bay Hawaii NOAA B-3 Cross Seamount South Point

NOAA B-4 NOAA B-2 All recaptures by association

Seamount Offshore Inshore Bank Unassociated Total FAD FAD or Koa Bigeye 741 354 40 4 40 1179 Yellowfin 645 85 216 40 23 1009 Total 1386 439 256 44 63 2188 % of 63.3% 20.1% 11.7% 2.0% 2.9% Total Main Hawaiian Island recaptures by association

Un Log FAD Bank or Total koa BE 2 3 40 4 49

YF 4 1 216 40 261

Total 6 4 256 44 310

% of 1.9 1.3 82.6 14.2 Total % % % % 150 E 160 E 170 E 180 170 W 160 W Midway releases

JAPAN 30 N

Minami Tori Shima HAWAII

20 N Wake CNMI Johnston

Guam Marshall Islands

10 N

Federated States of Micronesia Palmyra Palau

Line Islands

Howland & Baker Kiribati 0 PNG Nauru Jarvis 150 E 160 E 170 E 180 170 W 160 W 150 W 140 W 130 W USA

JAPAN All recaptures 30 N Mexico

Minami Tori HAWAII Shima

20 N Wake CNMI Johnston

Guam Marshall Islands 10 N Federated States of Micronesia Palmyra Palau

Howland Indonesia 0 Kiribati & Baker PNG Nauru Jarvis Phoenix Line Islands Islands

Tuvalu Solomon Tokelau Islands 10 S Cook Islands W&F SamoaAm Fiji Samoa Australia Vanuatu Tonga Niue French Polynesia New Caledonia Pitcairn Recaptures by gear and flag

Gear Type Area Fleet Bigeye Yellowfin Total Mix HL/Troll Inshore HW 31 144 175 Mix HL/Troll Offshore HW 1044 717 1761 Handline Inshore HW 9 32 41 Ika shibi Pole and line Inshore HW 3 86 89 Pole and line Offshore JP 0 1 1 Longline Offshore JP 8 7 15 Longline Cross HW 59 1 60 Longline Offshore HW 33 9 42 Purse seine Mexico US 0 1 1 1187 998 2185 points of interest v Significance of Aggregation and Vulnerability u Seamounts u FADs u Inshore aggregation areas or Ahi Koas vRole of Hawaiian Archipelago as FADs u relatively “local” behavior of bigeye and yellowfin vLarge data set on Cross Seamount u estimates of interaction, residency, exchange rates, N, F vBigeye - “wandering” offshore, between different vulnerability points, … and then ? ? vYellowfin - inshore and offshore movement ? Cross Seamount tag attrition rates

80 70 be 60 yf 50 40 30

% recovery 20 10 0 30 60 90 120 150 180 210 240 270 300 330 360 More Days at liberty Mean size of recaptures by fishery

125

100

75

Bigeye 50 Yellowfin

Mean fork length (cm) 25

0 Pole and HL/Troll HL/Troll HL Ika LL Cross LL line Inshore Cross shibi Offshore Fishery Depth distributions from archival and sonic tags

Bigeye Yellowfin

What do we have ? vSpecies specific data for BET and YFT vFine scale recapture date and location and school aggregation vAbility to track the vulnerability of both species, seasonally and by area as they grow and recruit to different fisheries = data for analyses Relevant publications v Holland, K.N., Kleiber, P., Kajiura, S.M., 1999. Different residence times of yellowfin tuna, Thunnus albacares, and bigeye tuna T. obesus, found in mixed aggregations over a seamount. Fish Bull. 97, 392-395. v Itano, D.G., and K.N. Holland. 2000. Movement and vulnerability of bigeye (Thunnus obesus) and yellowfin tuna (T. albacares) in relation to FADs and natural aggregation points. Aquat. Living Resour. 13:1 -11. v Sibert, J., Holland, K., and D. Itano. 2000. Exchange rates of yellowfin and bigeye tunas and fishery interaction between Cross Seamount and near- shore FADs in Hawaii. Aquat. Living Resour. 13: v Holland, K.N., S. M. Kajiura, D.G. Itano and J. R. Sibert. 2000. Tagging techniques can elucidate the biology and exploitation patterns of aggregated pelagic fishes. Proceedings of the Symposium on the Charleston Bump. Trans. Am. Fish. Soc. (In Press). NMFS archival tagging of bigeye FAD Tagging Keep those tags coming !! Thanks to: PFRP v Hawaii’s fishermen v United Fishing Agency v Midway Phoenix Corporation v National Marine Fisheries Service, v Department of Aquatic Resources v US Fish and Wildlife Service v NMFS Pago Pago, American Samoa v Secretariat of the Pacific Community v Forum Fisheries Agency v Inter-American Tropical Tuna Commission v National Research Institute of Far Seas Fisheries (Japan) v National Fisheries Research & Development Institute (Rep of Korea) v National Taiwan University the end