The biology of the bigeye grenadier Macrourus holotrachys caught as by-catch in the Patagonian toothfish Dissostichus eleginoides longline fishery conducted around South Georgia was investigated to improve data available for fisheries management. Age estimates suggest that M. holotrachys is a moderately slow growing species (K ¼ 0Á10), reaching ages of >30 years and attaining total lengths (L T ) >80 cm (L 1 ¼ 33). The size at which 50% of females had started to mature (L int50 ) for M. holotrachys was 21 cm pre-anal length (L PA ) and occurred at c. 9 years old. Estimates of natural mortality and Pauly's growth performance index were found to be low (M ¼ 0Á09 and F ¼ 2Á82 respectively). Gonad maturity stage was described from macroscopic and histological investigation. Mature ovaries had oocytes at all developmental stages with between 22 and 55% likely to be spawned each year. Absolute fecundity ranged from 22 000 to 260 000 eggs and was positively correlated with both pre-anal length and mass. A highly skewed sex ratio of 32 : 1, females : males, was found for specimens caught by longlines but not for a small sample of shallower trawl-caught specimens. It is suggested that females are far more susceptible to longline capture than males. Macrourus holotrachys is a bentho-pelagic predator and scavenger that feeds on a wide range of fishes and invertebrates. The fish are long lived, slow-growing species typical of deep-water grenadiers; fisheries management strategies should reflect their probable susceptibility to overfishing.
The diet of the seven star £ying squid, Martialia hyadesi, from the South Georgia sector of the Scotia Sea was described from stomach contents collected in winter (June) 2001. Diet was dominated by the hyperiid amphipod, Themisto gaudichaudii, ¢sh (nine species, mainly myctophids) and cephalopods (mainly cannibalism). The absence of krill, Euphausia superba, and the presence of larger myctophids in the diet are discussed in terms of seasonal and annual prey availability.
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