Diversity, distribution and ecology of gonatid squids in the subarctic Pacific: A review

Current knowledge on biology of the squid family Gonatidae in the subarctic Pacific is reviewed. Up to this date, 10 species of the genus Gonatus (of which two are unnamed yet), a single species of the genus Eogonatus, six species of the genus Gonatopsis and two species of the genus Berryteuthis are known from the subarctic Pacific. Their distribution patterns can be classified into three major types: (1) trans-Pacific species (with two subtypes), (2) Northwest Pacific species, and (3) Northeast Pacific species. The family Gonatidae is divisible into two broad ecological types: (1) muscular, epi- to mesopelagic and eurybathic forms, and (2) lessmuscular, stenobathic and nektobenthic forms. Little is known about the prey of gonatids. However, their predators are diverse, including fishes, sea-birds and mammals, thus gonatids play an important role for the food-chain in the subarctic Pacific. Structures of the tentacular club, particularly metamorphose into hooks are important characters for tracing morphological changes in growth. Allametrie growth of some species has been clarified. The spawning biology of two commercially fished species (Gonatopsis boreaUs and Berryteuthis magister) is described, but spawning adults of non-commercial species have seldom been observed. The seasonal occurrence of planktonic juveniles of gonatids may be related to spring phytoplankton blooms