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

AUGUST 2005 FINAL REPORT
cuttlefish, and octopus are harvested for food items in the subsistence fishery (WPRFMC 2001) and
shells of nautiloids are used for ornamental purposes in the shell curio trade (Dunning et el. 1998).
None of the species found in the study area are listed on the IUCN Red List of threatened species
(IUCN 2004).
Distribution—Cephalopods are found in all tropical and temperate seas of the world except for the
nautiloids whose distribution are restricted to Indo-West Pacific region (Roper et al. 1984).
Habitat Preferences—Cephalopods occur over a wide variety of habitats, including deep coral reefs
(nautiloids), hole and crevices in rocky or coral areas and burrows in the sand (octopuses), and
seagrass beds and nearby reef areas over sandy, muddy, and rocky bottoms (cuttlefishes and
squids) (Dunning 1998a, 1998b; Norman 1998; Reid 1998). Their range of depth extends from the
surface to over 5,000 m (Roper et al. 1984). Some species (e.g., nautiloids, squids) exhibit diurnal
vertical migration, moving upward to feed during the night and dispersing into the deeper water during
the day (Dunning 1998a, 1998b).
Life History—Cephalopods have separate sexes and reproduction occurs through copulation (Colin
and Arneson 1995). Eggs are encapsulated in a gelatinous finger-like strings (squids), grape-like
clusters (cuttlefishes), attached to each other (octopuses), or in a capsule (nautiloids) adhering to
various substrates (e.g., rocks, shells, seagrass) (Dunning 1998a, 1998b; Norman 1998; Reid 1998).
Spawning varies between the various groups of cephalopods. Nautiloids have a single annual egg
laying season in shallow-water (80 to 100 m), peaking around October (Dunning 1998a; WPRFMC
2001), whereas squids and cuttlefish migrate in aggregations seasonally to spawn in response to
temperature changes twice a year (Dunning 1998b; Reid 1998). Octopuses lay eggs which are
tended by the female until hatching (Norman 1998).
♦ Ascidians (Tunicates)
Status—Tunicates (sea squirts) are managed in Micronesia as part of PHCRT by the WPRFMC
(2001). At least 117 species (87 colonial and 30 solitary) have been reported from Guam (Lambert
2003) and have EFH designated within the boundaries of the study area (WPRFMC 2001; NMFS
2004c). Ascidians are of economic importance for bio-prospecting and problematic as marine fouling
organisms by clogging cooling water intakes and interfering with boat operations (WPRFMC 2001).
Distribution—Ascidians are common worldwide and inhabit shallow-waters of the tropical Pacific
(Colin and Arneson 1995; WPRFMC 2001).
Habitat Preferences—Solitary and colonial tunicates are important components of the reef
cryptofauna ranging from high-light and high-energy environments to protected deeper water areas
(Sorokin 1995; WPRFMC 2001). Ascidians attach to inert surfaces such as dead corals, stones,
shells, pilings, ship bottoms and less durable surfaces of seaweeds, mangrove roots, sand, and mud,
or grow epizoically on other sessile organisms (e.g., soft corals, sponges, other tunicates) (Colin and
Arneson 1995). Solitary and colonial forms colonize new surfaces in disturbed areas, and are also
found on outer reef slopes (WPRFMC 2001). Larval and adult sea squirts occur from intertidal areas
to 120 m depth or greater (WPRFMC 2001).
Life History—Both sexual and asexual reproduction occurs in ascidians and is highly variable, both
by family and genera. Solitary forms release both eggs and sperm into the water, whereas the
colonial forms in ovoviviparous, releasing only larvae (Colin and Arneson 1995). The release of
certain chemicals by tunicates may trigger various processes, such as spawning, larval attraction, etc.
(WPRFMC 2001). Solitary and colonial ascidians are unisexual but reproduce asexually by budding
(WPRFMC 2001).
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