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

AUGUST 2005 FINAL REPORT
♦ Dasyatididae, Myliobatidae, and Mobulidae (Whiptail Stingrays, Eagle Rays, and Manta Rays)
Status—Six species of rays (four stingrays, the spotted eagle ray [Aetobatis narinari] and the manta
ray [Manta birostris]) are managed in Micronesia as part of PHCRT by the WPRFMC (2001). All six
species occur in the CNMI and Guam (Amesbury and Myers 2001; Myers and Donaldson 2003) and
have EFH designated within the boundaries of the study area (WPRFMC 2001; NMFS 2004c).
Currently, no data are available to determine if rays of the PHCRT are approaching an overfished
situation (NMFS 2004a). The white-spotted eagle ray is taken as a by-catch, while the manta ray is
neither a fisheries nor a by-catch species (Cavanagh et al. 2003). Eagle rays and devil rays are
attractive and desirable as captives in large aquaria and oceanaria (Compagno and Last 1999a,
1999b). Both of the above species are listed on the IUCN Red List of threatened species as data
deficient (Ishihara 2000; Ishihara et al. 2002). In addition, the porcupine stingray (Urogymnus
asperrimus) is listed as vulnerable on the IUCN Red List (Compagno 2000).
Distribution—Stingrays range throughout the Indo-Pacific region, while the spotted eagle and manta
rays are worldwide occurring in tropical and subtropical seas and warm temperate and tropical
oceans, respectively (Myers 1999; Hennemann 2001).
Habitat Preferences—Habitat preferences for most rays include sand and mud bottoms of
continental shelves with a few species occurring on coral reefs (Myers 1999). Juveniles inhabit a
variety of habitats from shallow clear lagoons to outer reef slopes, Nursery areas are associated with
seagrass beds, mangroves, and shallow sand flats (WPRFMC 2001). Adults utilize shallow clear
lagoons to outer reef slopes at depths ranging from 0 to 100 m (Myers 1999) or deeper (e.g., eagle
rays: 527 m, sting rays: 480 m) (Compagno and Last 1999a; Last and Compagno 1999).
Life History—Stingrays are viviparous (Last and Compagno 1999), whereas eagle rays and manta
rays are ovoviviparous (WPRFMC 2001). Stingrays produce a litter with two to six young with a 12month
gestation period (Last and Compagno 1999). The spotted eagle ray produces an average of
four pups per liter after a gestation period of about 12 months (Bester 2004), while the manta ray may
give birth to one pup during a breeding season (Passarelli and Piercy 2004). During the winter, manta
rays migrate to warmer areas, deeper waters or disperse offshore (Passarelli and Piercy 2004). Some
species of eagle rays breed in shallow bays and lagoons (Compagno and Last 1999a).
♦ Serranidae (Groupers)
Status—More than 40 species of groupers are managed in Micronesia as part of BMUS and PHCRT
by the WPRFMC (1998, 2001). All 40 species occur in the CNMI and Guam (Amesbury and Myers
2001; Myers and Donaldson 2003) and have EFH designated within the boundaries of the study area
(WPRFMC 2001; NMFS 2004c). Currently, no data are available to determine if groupers of the
PHCRT are approaching an overfished situation (NMFS 2004a). Groupers are most highly priced
food fishes and are actively caught by commercial and sport fishermen (Heemstra and Randall 1999).
The following groupers within the study area have been listed on the IUCN Red List of threatened
species: giant grouper (Epinephelus lanceolatus) as vulnerable (Sadovy 1996); brown-marbled
grouper (E. fuscoguttatus) as near threatened (Cabanban 2004); and humpback grouper
(Cromileptes atlivelis) as data deficient (Samoilys and Pollard 2000).
Distribution—Groupers are robust-bodied, long-lived, benthic fishes with a worldwide distribution
and occur in tropical and semitropical seas of the Indo-Pacific region (Debelius 2002). Their wide
geographic distribution is thought to be due to the relatively long pelagic phase as larvae (Allen et al.
2003).
Habitat Preferences—Serranids inhabit a wide variety of habitats (Myers 1999). Larvae tend to be
more abundant over the continental shelf than oceanic waters, avoid surface waters during the day,
are evenly distributed vertically in the surface water column at night, and may be influenced by
oceanic currents (Leis 1987; Rivera et al. 2004). Juveniles are found in shallow-water reef areas
(seagrass beds and tide pools) and estuarine habitats (WPRFMC 2001). Adults utilize shallow coastal
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