202
and the Caribbean Sea. Water temperatures have a major influence on longfin squid
growth rates and the effect of an increase in water temperature on growth rate is
most pronounced during the first 3 months of life.
Dosidicus gigas
D. gigas is an oceanic and neritic species occurring from the surface to 500 m depth.
It is most abundant and largest off South America, where adults are found in water
temperatures of between 26 and 28 °C to much colder. In nearshore waters, it occurs
near to the surface day and night. Their seasonal migration is similar to those of
other ommastrephids. The cohorts grow at different rates depending on the environmental conditions at the time of hatching, but all recruit into the fishery around May
each year. Longevity is about 1 year for the population in the northern hemisphere.
Mortality after spawning is high. This species feeds on larvae of pelagic fishes such
as lantern fishes, sardines, mackerels, and sauries, and on crustaceans. Cannibalism
is common. It is in turn preyed upon by swordfish, sharks, porpoises and other
mammals. D. gigas has relatively recently expanded its distribution northwards,
probably due to a combination of favourable environmental conditions and fishery
impacts interacting with physiological mechanisms (FAO 2019e).
Berryteuthis magister
B. magister is a widespread boreal North Pacific species of the oegopsid family
gonatidae. This species is highly abundant and plays an important role in various
ecosystems of the North Pacific Ocean. It is the only commercially harvested species of the family Gonatidae. It is a bentopelagic species. Most of commercial catch
is taken using bottom trawls and lesser amounts of squid are taken as by-catch using
mesopelagic trawl nets towed near the bottom (Katugin et al. 2013).
3.2.2 Cuttlefishes
3.2.2.1 General Information About Cuttlefishes
Biology of Cuttlefishes
Cuttlefishes are primarily demersal inhabitants of near shore and continental shelf
zones in warm and temperate waters. Although excellent swimmers, they generally
are bottom dwellers. Habitats range from rocky, sandy, and muddy bottoms to grass
flats, seaweed beds, coral reefs, etc. Many (but not all) species are known to migrate
seasonally in response to temperate changes. Spawning usually takes place with an
increase in water temperature, sometimes twice a year in areas where the hydrographical regime is strongly seasonal. During mating, males use their modified
arm(s) (hectocotylus) to transfer spermatophores to the females. Cuttlefishes spawn
relatively few and large eggs which the female attaches in grape like clusters to
plants, debris, gravel and other substrates. Sexual maturity often is attained as early
as a few months after hatching and it is not uncommon to find juveniles from the
3 Molluscan Shellfish
and the Caribbean Sea. Water temperatures have a major influence on longfin squid
growth rates and the effect of an increase in water temperature on growth rate is
most pronounced during the first 3 months of life.
Dosidicus gigas
D. gigas is an oceanic and neritic species occurring from the surface to 500 m depth.
It is most abundant and largest off South America, where adults are found in water
temperatures of between 26 and 28 °C to much colder. In nearshore waters, it occurs
near to the surface day and night. Their seasonal migration is similar to those of
other ommastrephids. The cohorts grow at different rates depending on the environmental conditions at the time of hatching, but all recruit into the fishery around May
each year. Longevity is about 1 year for the population in the northern hemisphere.
Mortality after spawning is high. This species feeds on larvae of pelagic fishes such
as lantern fishes, sardines, mackerels, and sauries, and on crustaceans. Cannibalism
is common. It is in turn preyed upon by swordfish, sharks, porpoises and other
mammals. D. gigas has relatively recently expanded its distribution northwards,
probably due to a combination of favourable environmental conditions and fishery
impacts interacting with physiological mechanisms (FAO 2019e).
Berryteuthis magister
B. magister is a widespread boreal North Pacific species of the oegopsid family
gonatidae. This species is highly abundant and plays an important role in various
ecosystems of the North Pacific Ocean. It is the only commercially harvested species of the family Gonatidae. It is a bentopelagic species. Most of commercial catch
is taken using bottom trawls and lesser amounts of squid are taken as by-catch using
mesopelagic trawl nets towed near the bottom (Katugin et al. 2013).
3.2.2 Cuttlefishes
3.2.2.1 General Information About Cuttlefishes
Biology of Cuttlefishes
Cuttlefishes are primarily demersal inhabitants of near shore and continental shelf
zones in warm and temperate waters. Although excellent swimmers, they generally
are bottom dwellers. Habitats range from rocky, sandy, and muddy bottoms to grass
flats, seaweed beds, coral reefs, etc. Many (but not all) species are known to migrate
seasonally in response to temperate changes. Spawning usually takes place with an
increase in water temperature, sometimes twice a year in areas where the hydrographical regime is strongly seasonal. During mating, males use their modified
arm(s) (hectocotylus) to transfer spermatophores to the females. Cuttlefishes spawn
relatively few and large eggs which the female attaches in grape like clusters to
plants, debris, gravel and other substrates. Sexual maturity often is attained as early
as a few months after hatching and it is not uncommon to find juveniles from the
3 Molluscan Shellfish