David Itano 1, Kim Holland 2 and Kevin Weng 3

Transcription

1 PFRP PI Meeting 2008 David Itano 1, Kim Holland 2 and Kevin Weng 3 1 Pelagic Fisheries Research Program, University of Hawaii at Manoa 2 Hawaii Institute of Marine Biology, University of Hawaii, 3 University of Hawaii at Manoa, School of Earth Science Technology

2 Hawaii Tuna Tagging Project ( ) (archipelagic scale, conventional dart tags for bigeye and yellowfin tuna) Movement of bigeye and yellowfin within the Hawaii EEZ and between major fishing grounds. (exchange rates) Interaction direct gear interaction / concurrent interaction sequential or growth interactions spatially segregated interaction Exploitation rates and differential vulnerability (local fishing mortality) of tuna around seamounts and FADs Aggregation effects - retention rates of bigeye and

3 HTTP: objectives and outcomes 17,986 bigeye and yellowfin 53:47 ratio 12.6% overall recapture rate Bulk transfer model developed to describe tag loss by all means between offshore FADs/seamount, inshore areas and offshore LL fishery Estimated transfer (movement) rates Estimated size and species-specific M and F rates Calculated residence times and exploitation rates Provided a closer definition of fisheries and exploitation patterns

4 150 E 160 E 170 E W 160 W 150 W 140 W 40 N USA JAPAN 30 N MEXICO Minami Tori Shima HAWAII CNMI Wake (US) Johnston (US) 20 N Guam Marshall Islands 10 N Palau Federated States of Micronesia Palmyra (US) Indonesia Papua New Guinea Australia New Caledonia Nauru Solomon Islands Vanuatu Kiribati Tuvalu Fiji Howland & Baker New Zealand Phoenix Islands (Kiribati) WF Samoa American Samoa Cook Islands Niue Tonga Jarvis (US) Line Islands (Kiribati) French Polynesia 0 10 S 20 S Pitcairn (U.K.)

5 W 160W 150W 140W Yellowfin in red Bigeye in blue 30N 20N Johnston 10N Palmyra Line Islands

6 Necker NOAA B W 155 W Nihoa Main Hawaiian Islands Kauai Niihau Oahu Kaula Rock Kaena Pt. Molokai / Lanai / Maui Penguin Bank Bigeye 1 20 N Keahole Pt. Hawaii Hilo Bay NOAA B-3 Cross Seamount South Point NOAA B-2 NOAA B-4

7 Meanwhile, changes in Hawaii-based tuna fisheries: A decline in effort in the surface fisheries for juvenile bigeye and yellowfin on the Cross Seamount and offshore weather buoys; The development and expansion of a deep-set short longline fishery on the Cross Seamount to target larger bigeye tuna and seamount associated pomphrets; An increase in the setting and exploitation of privately set FADs close to the main Hawaiian islands, primarily aggregating and harvesting sub-adult bigeye tuna; increased harvesting of very small yellowfin tuna from the inshore Hawaii State FADs; A steady increase in tuna longline effort by the domestic fishery due to conversion of swordfish effort and a steadily increasing number of hooks per tuna directed set. Increasing fuel costs

8 The HTTP 2: Justification HTTP concentrated on interaction issues relevant to the Cross Seamount and offshore weather buoy fishery (YF and BE) The Cross seamount handline fishery has evolved, shifting to short longline gear and multi-species targeting Nearshore issues relevant to Hawaii domestic fisheries remain unresolved Need to update movement parameters, M and F estimates and examine AREAS and SPECIES under-represented during the HTTP Lack of knowledge of skipjack resources when they may become increasingly important to local fisheries Continued uncertainty as to the connectivity of tropical tuna between Hawaii and the broader WCPO biomass

9 HTTP2: objectives 1) update estimates of fishing mortality (F), natural mortality (M) and movement parameters for yellowfin and bigeye tuna in Hawaiian waters while deriving initial estimates of M and F and movement parameters for skipjack. To include a continuation of existing PFRP tagging projects to define the typical home range for Hawaiian tuna using sonic, archival and PAT tags, with a greater emphasis on areas and species underrepresented during HTTP, i.e. bigeye tuna found around the main Hawaiian Islands and targeted by the private FAD fishery, and yellowfin and skipjack tuna on FADs and near shore aggregation sites, with increased emphasis on tagging unassociated or near shore bank associated tuna schools with both conventional dart and acoustic tags.

10 HTTP2: objectives 2) Document the FAD-associated temporal and vertical behavior of skipjack tuna. Using acoustic pinger and depth reporting tags on receiver equipped FADs with simultaneous releases with yellowfin and bigeye tuna to provide species-specific comparisons in mixed aggregations. 3) Determine the diurnal vertical behavior of bigeye tuna and lustrous pomphret (Eumegistis illustris) associated with the Cross Seamount. Using acoustic depth reporting tags on all three species in simultaneous seamount residence, which will require deployment of acoustic receivers on bottommounted acoustic release systems.

11 a comparison between HTTP and HTTP2

12 Project outline Species Skipjack, yellowfin, bigeye, lustrous pomphret (Eumegistis illustris) Tag types (conventional, acoustic, archival, PAT) Release sites State anchored FAD system Private bigeye FADs Banks (koas) Open water areas Cross Seamount Release timetable 2 years, start late 2008

13 Project outline Tagging platforms Fishing gears and methods Key personnel Holland, Itano, Weng Data processing and analysis Integrated with PTTP

14 R Oahu Honolulu 20 km

15 Cross Seamount Pomphret funding from NMFS

16 20km 40km 0m 38kHz 200m 400m 600m 120kHz 0m 200m 400m 19:00 21:00 Cross Seamount acoustic images (R. Domokos, NMFS) 23:00

17 20km 30km 25km 0m 200m 38kHz 400m 600m 800m 1000m 120kHz 0m 200m 400m 21:30 22:30 23:00 Cross Seamount acoustic images (R. Domokos, NMFS)

18 Cross Seamount acoustic tagging and imaging 2km 4km 200m 400m 38 khz 600m 11:40 12:00 Cross Seamount acoustic images (R. Domokos, NMFS)

19 Nearshore FAD Issues Interrupt normal movement routes? Decrease catches in traditional koas and fishing grounds? Increases vulnerability of very small tuna Burn out an area, reduce productivity? Private FADs Selectivity Seasonality Bigeye behavior

20 SPC PACIFIC TUNA TAGGING PROJECT Cruise 1 and Papua New Guinea Tuna Tagging Project Central Pacific: Cruise 1

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22 HTTP 2 Cruise 1 Cruise 2: Micronesia, Marshall Islands to Wallis and Futuna

23 Mahalo