Tagging tuna in the Central Pacific:

Transcription

1 Tagging tuna in the Central Pacific: ecological and management related issues. David Itano, Kim Holland, Steve Kajiura

2 JAPAN 150E 160E E 170W 160W 150W Yellowfin movements 140W USA 30N Northern Marianas Minami Tori Shima Wake Johnston Hawaii 20N Mexico Guam Marshall 10N Palau Federated States of Micronesia Papua New Guinea Nauru Kiribati Howland and Baker Phoenix Palmyra Jarvis Line 0 Australia New Caledonia Solomon Is Vanuatu Matthew & Hunter Tuvalu Fiji Wallis & Futuna Tokelau Samoa Am Samoa Tonga Western Niue Cook French Polynesia 10S 20S Pitcairn Norfolk

3 JAPAN 150E 160E E 170W 160W Bigeye movements 150W 140W USA 30N Northern Marianas Minami Tori Shima Wake Johnston Hawaii 20N Mexico Guam Marshall 10N Palau Federated States of Micronesia Papua New Guinea Nauru Kiribati Howland and Baker Phoenix Palmyra Jarvis Line 0 Australia New Caledonia Solomon Is Vanuatu Matthew & Hunter Tuvalu Fiji Wallis & Futuna Tokelau Samoa Am Samoa Tonga Western Niue Cook French Polynesia 10S 20S Pitcairn Norfolk

4 W 160W 150W 140W 30N 20N Johnston 10N Palmyra Line

5 What do we know of the fishery? HDAR & NMFS catch statistics Year Total (lbs) 619, ,664 % Bigeye % Yellowfin , ,055, , , ,035, , , Total 27.9 % 72.1%

6 What do we know of the fishery? NMFS dock sampling Category Small YF Medium YF Weight (kgs) Per cent six vessels Large YF 6.4 Aprill 94 Aug 95 Small BE 33.1 Categories Small = 3-17 lbs Medium BE Large BE Medium = lbs Large = 40 lbs ALL YF ALL BE 11,180 44, % 80.1 % TOTAL 56,162

7 What do we know of the ecology of the Cross Seamount? HTTP tag release data 13,433 YF & BE from Cross or weather buoys Estimated weight ratio YF = 21.7% BE = 78.3% Rectuitment size YF = ~ 28 cm BE = ~ 30 cm Exit size?? need to examine landing data Fork Length (cm) Yellowfin Fork Length (cm) Bigeye

8 B1 Residence times Bigeye 1 B3 X B2 B4

9 B1 Transfer rates Bigeye 1 B3 238 days X 542 days B2 B4

10 Ecological hypotheses Yellowfin: recruit from?? (local + immigrants), after which they remain island associated. Bigeye: recruit from down south, remain a few years cycling between fishing grounds and open water areas - and then leave, south to spawn or north to feed?? Tuna cycle on and off vulnerability points (seamounts, FADs & koas), moving between them but not remaining long. Emmigration is the major source of losses from the Seamount. See inshore and offshore movements, but general conclusion is for low interaction rates between offshore handline fishery and inshore fisheries. See measurable transfer rates between Seamount and Longline fishery, but note a relatively stable longline CPUE. Management?

11 150E 160E E 170W 160W 150W 140W JAPAN USA 30N Northern Marianas Minami Tori Shima Wake Johnston Hawaii 20N Mexico Guam Marshall 10N Palau Federated States of Micronesia Papua New Guinea Nauru Kiribati Howland and Baker Phoenix Palmyra Jarvis Line 0 Australia New Caledonia Solomon Is Vanuatu Matthew & Hunter Tuvalu Fiji Wallis & Futuna Tokelau Samoa Am Samoa Tonga Western Niue Cook French Polynesia 10S 20S Pitcairn Norfolk

12 14 th meeting of the Standing Committee on Tuna and Billfish Noumea, New Caledonia 9-16 August 2001 Expressed concern on the status of yellowfin and bigeye in WCPO Recognized increasing catchability of juveniles, particularly by FAD based purse seine fisheries Recommended no further increases in fishing mortality in surface fisheries for yellowfin and bigeye, until

13 Local concerns for management Gear interaction: shallow-set Longline vs handline Limited area of fishing grounds Limited market niche for juvenile fish Low value of product, low yield per recruit Viewed as waste of resource to take juveniles Manage on social or economic basis

14 B1 Bigeye 1 The Big FAD B3 X B2 B4

15 Kaena Point Penguin Banks Kona B-3 Cross Seamount

16 Summary and recommendations Fix the seamount data, monitor fishery closely Improve data reporting and accessibility Direct further discussion of Cross Seamount management to social and economic considerations Refine estimates of residence times and transfer rates,. using fishery independent means Encourage data exchange and dialogue with the bigger picture Support research on the mechanisms of aggregation Support research linking the physical environment (islands, seamounts, currents) with the life history of pelagic species.

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