Marine Resources Assessment for the Marianas Operating ... - SPREP

AUGUST 2005 FINAL REPORT
Currently, no data are available to determine if the PMUS are approaching an overfished condition
(NMFS 2004a) except for the bigeye tuna. NMFS (2004b) determined that overfishing was occurring
Pacific wide on this species. In addition, the shark species are afforded protection under the Shark
Finning Prohibition Act (NMFS 2002).
The broadbill swordfish, albacore tuna, common thresher shark (Alopias vulpinus), and salmon shark
(Lamna ditropis) have been listed as data deficient on the IUCN Red List of threatened species (Safina
1996; Uozumi 1996a; Goldman and Human 2000; Goldman et al. 2001). The shortfin mako shark (Isurus
oxyrinchus), oceanic whitetip shark (Caracharhinus longimanus), and the blue shark (Prionace glauca)
have been listed as near threatened (Smale 2000a; Stevens 2000a, 2000b). The bigeye tuna is listed as
vulnerable (Uozumi 1996b).
Distribution—PMUS occur in tropical and temperate waters of the western Pacific Ocean. Geographical
distribution among the PMUS is governed by seasonal changes in ocean temperature. These species
range from as far north as Japan, to as far south as New Zealand. Albacore tuna, striped marlin
(Tetrapurus audax), and broadbill swordfish have broader ranges and occur from 50°N to 50°S
(WPRFMC 1998).
Habitat Preferences—PMUS are typically found in epipelagic to pelagic waters, however, shark species
can be found in inshore benthic, neritic to epipelagic, and mesopelagic waters. Factors such as gradients
in temperature, oxygen, or salinity can affect the suitability of a habitat for pelagic fishes. Skipjack tuna
(Katsuwonus pelamis), yellowfin tuna (T. albacares), and Indo-Pacific blue marlin (Makaira nigricans)
prefer warm surface layers, where the water is well mixed and relatively uniform in temperature. Species
such as albacore tuna, bigeye tuna, striped marlin, and broadbill swordfish, prefer cooler temperate
waters associated with higher latitudes and greater depths. Certain species, such as broadbill swordfish
and bigeye tuna are known to aggregate near the surface at night. However, during the day broadbill
swordfish can be found at depths of 800 m and bigeye tuna around 275 to 550 m. Juvenile albacore tuna
generally concentrate above 90 m with adults found in deeper waters (90 to 275 m) (WPRFMC 1998).
Life History—Migration and life history patterns of most PMUS are poorly understood in the Pacific
Ocean. Additionally, very little is known about the distribution and habitat requirements of the juvenile
lifestages of tuna and billfish prior to recruitment into fisheries. Seasonal movements of cooler-water
tunas such as the northern bluefin and albacore are more predictable and better defined than billfish
migrations. Tuna and related species tend to move toward the poles during the warmer months and
return to the equator during cooler months. Most pelagic species make daily vertical migrations, inhabiting
surface waters at night and deeper waters during the day. Spawning for pelagic species generally occurs
in tropical waters but may include temperate waters during warmer months. Very little is known about the
life history stages of species that are not targeted by fisheries in the Pacific such as gempylids, sharks,
and pomfrets (WPRFMC 1998).
EFH Designations—(WPRFMC 1998; Figures D-4, D-5, and D-6; Table 4-3)
Eggs and Larvae―The (epipelagic zone) water column down to a depth of 200 m from the
shoreline to the outer limit of the EEZ.
Juveniles and Adults—The water column down to a depth of 1,000 m from the shoreline to the
outer limit of the EEZ.
HAPC Designations—HAPC for this group is the entire water column to a depth of 1,000 m above all
seamounts and banks with summits shallower than 2,000 m within the EEZ.
4.2.3 Crustacean Management Unit Species
Status—Five species are currently managed as CMUS by the WPRFMC through the Fishery
Management Plan of the Spiny Lobster Fisheries of the Western Pacific Region and the Final Combined
Fishery Management Plan, Environmental Impact Statement, Regulatory Analysis, and Draft Regulations
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