Reproductive biology of red squid (Ommastrephes bartramii) in the Southwest Atlantic
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Date
2006
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Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP)
Abstract
Red squid (Ommastrephes bartramii) samples were collected during six exploratory cruises carried out in the Southwest Atlantic region off Argentina and Uruguay (33° S-42° S; 43° W-55° W) during summer-autumn of the period 1997-2002 on board the japanese jigger “Shinko Maru N° 3” under a joint research programme approved by Japan and Argentina. Size ranges of the squids analyzed were 10-40 cm mantle length (ML) for males and 12-49 cm ML for females. Two groups of squids were identified: smaller and larger than 20 cm ML. The group under 20 cm ML was characterized by the presence of immature squids and a sex ratio of around 1:1 in the whole study area. The squids of more than 20 cm ML included from immature to mature individuals. The mean sizes, proportion of mature individuals and proportion of males within this group increased northwards. Mature individuals were captured north of 39°S. The size and weight at 50% maturity were estimated at 30.48 cm ML and 852.95 g body weight (BW) for males and 42.30 cm ML and 2,287.18 g BW for females. The growth in weight of the reproductive system in both sexes was slow until the onset of maturity (males: 27-32 cm LM; females: 37-45 cm LM). The quantitative indices of maturity based on gravimetric measurements of the reproductive system structures showed that in both sexes the reproductive system total weight (RSW) represented less than 1% of BW by the onset of maturity. Then, the growth of the reproductive system accelerated, with RSW reaching 5% of male BW and 8% of female BW by the end of maturity.
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Revista de Investigación y Desarrollo Pesquero, 18. p. 5-19