Doryteuthis (Amerigo) pealeii (Lesueur 1821)

Mantle long, moderately slender, cylindrical, the posterior end bluntly pointed. Eyes not unusually large, diameter of externally visible eyeball 8 to 18% of mantle length, and diameter of dissected lens 2 to 6% of mantle length. Fins rhomboidal, their sides nearly straight. Left ventral arm IV hectocotylized in mature males by modification of the distal third to fourth of arm, but the modification does not extend to arm tip; fewer than 12 of the suckers in dorsal row usually smaller than half the size of their counterparts in the ventral row; bases or pedicels of some of the modified suckers rounded, narrowly triangular. Gladius long, rather wide, feather-shaped, ratio of greatest width of vane of gladius to greatest width of rachis 2.7 to 3.7 in females, 2.4 to 2.9 in males; edge of vane curved (sometimes straight in males), thin, rarely ribbed.

Western Atlantic: 5° N to 50° N, including Gulf of Mexico and Caribbean Sea.

Maximum mantle length 50 cm in males, approximately 40 cm in females off the southern New England States of the USA; common length in catches ranges between 10 and 20 cm. Maturity is attained at about 15 cm in males and 13 or 14 cm in females.

A neritic speciesoccurring over the continental shelf and upper slope from the surface down to about 400 m depth,but rare or absent around islands.Optimum water temperatures for this species fluctuate between 10 and 14° C. Adults are demersal in daytime but disperse into the water column and many appear at the surface (in summer or in warm waters) at night. Longfin squid are known to effect seasonal migrations. They overwinter in dense concentrations in offshore areas at depths between 100 and 200 m, and move thereafter to the nearshore feeding and spawning areas where they are found from late spring through fall. Mature squids are encountered almost throughout the year, but two peak spawning periods generally are observed: the first and more important in spring, and the second, less intense, in late summer and fall, this leading to the differentiation of multiple cohorts each year. Eggs are laid in gelatinous, finger-like strands, many of which are attached together in large masses ("sea mops") to solid substrates (i.e. rocks, shells, shipwrecks) in depths between 10 and 250 m. The eggs hatch after approximately 27 days (at temperatures at 12 to 18° C) or after 11 days (at 21.5 to 23° C) (McMahon & Summers (1971). Planktonic larvae and juveniles are abundant in surface waters and resemble adults in appearance (no metamorphosis). Squid originating from the spring spawn reach maturity in summer of the following year (after about 14 months, while individuals hatched in early autumn will spawn only in spring of the second successive year, at about 20 months of age. This overcrossing of the life-cycles of two life successive groups of hatchlings is a phenomenon also observed in other squid and cuttlefish species. Postspawning mortality is very high, particularly in females, a fact that is reflected in the smaller maximum size of females.Longfin squid prey on euphausids, fishes and other squids. Cannibalism is common.The species is in turn preyed upon by yellowfin tuna (Thunnus albacares ), toothed whales and other pelagic predators.

Longfin squid was formerly taken only as bycatch to the shrimp and scale-fish trawl fishery, but in recent years an international fishery was developed, specifically for this species. The world catch of longfin squid fluctuated irregularly between about 10 700 t in 1978 and 23 600 t in 1980. In 1981 catches were back on the 1978 level. This can be explained by the absence of Spanish and Mexican vessels from Fishing Area 21 (northwestern Atlantic) where almost the entire catch is taken. The major exploiting countries are Japan, Italy and USA (FAO, 1983). Fishing operations are most intensive from November to March along the outer continental shelf of the New England and mid-Atlantic states where the overwintering stock is exploited. The identified longfin squid catch from the Gulf of Mexico and the Caribbean in 1981 was reported as only 40 t but it is suspected that this species accounts for part of the catch identified as Loligo spp. which amounted to almost 1 600 t in the same year (FAO, 1983). The flesh of longfin squid is of excellent quality and marketed fresh and frozen.The total catch reported for this species to FAO for 1999 was 18 749 t. The countries with the largest catches were USA (18 749 t).