A contribution to the biology of the ommastrephid squid Martialia hyadesi (rochebrune and mabille, 1889) from the south-west Atlantic

Updated knowledge on the distribution and biology of the ommastrephid squid Martialia hyadesi in the South-West Atlantic Ocean is presented. Although the species has an Antarctic circumpolar distribution, itsmost frequent area of appearance is in the South-West Atlantic, where commercial catches have been made. During the 1995 Illex argentinus fishing season, 852 tons of Martialia hyadesi were caught, the largest catches in recent years. The species was captured on the outer shelf and slope, between 38 and 50°S, from March until June. Catches of up to 40 tons per day were obtained in the area between 45 and 48°S (April–June), where surface temperatures ranged between 7 and 9°C. The squid caught were adults (221–375 mm mantle length ML), 70% of the males were mature and 90% of the females were immature. Statolith readings, assuming daily formation of increments, showed that most had hatched during the months October and November. According to stomachcontent analysis, fish represented 43.9% of the food consumed (90% myctophids), squid 36.6% (70% cannibalism on small juveniles) and zooplankton 19.5%. Juveniles of the same species were caught on the Patagonian slope and in the adjacent oceanic region during spring of 1988 and 1989, most of them in waters of the Malvinas Current (5–7°C). The sizes of those juveniles ranged between 15 and 81 mm ML and the ages (based on statolith increments) between 137 and 150 days, indicating that they had hatched during April