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Spawning area and season of butterfly kingfish (Gasterochisma melampus), a large scombrid adapted to cooler temperate southern water

Tomoyuki Itoh, Shiro Sawadaishi
Marine & freshwater research 2018 v.69 no.1 pp. 16-23
Gasterochisma melampus, eggs, females, fish, gonadosomatic index, latitude, longitude, oocytes, spawning, Pacific Ocean
In the present study we investigated spawning of the butterfly kingfish (Gasterochisma melampus), a Scombridae species distributed in circumpolar temperate waters of the Southern Hemisphere in the Atlantic, Indian and Pacific oceans. Using data from 25564 individuals collected by longline operations from 1987 to 1996, analysis of the gonadosomatic index, maturity based on oocyte size and the presence of hydrated eggs revealed that the spawning area was between longitude 85 and 130°W and latitude 28 and 41°S in the south-east Pacific Ocean, and that the spawning season was from mid-April to mid-July. Length–frequency data suggested that larger fish arrived and spawned earlier, whereas smaller fish did so later. The species has distinctive reproductive characteristics compared with other Scombridae: it produces large hydrated eggs 1.6mm in diameter, sea surface temperatures in the spawning area were as low as 14–18°C and more than 80% of fish were female. The south-east Pacific Ocean may be the only (and is at least the major) spawning area of the species. Butterfly kingfish is a single stock that migrates to the Atlantic, Indian and Pacific oceans to feed and returns to the south-east Pacific Ocean to spawn.