The biology of the bigeye grenadier at South Georgia

The biology of the bigeye grenadierMacrourus holotrachyscaught as by‐catch in the Patagonian toothfishDissostichus eleginoideslongline fishery conducted around South Georgia was investigated to improve data available for fisheries management. Age estimates suggest thatM. holotrachysis a moderately slow growing species (K = 0·10), reaching ages of >30 years and attaining total lengths (LT) >80 cm (L∞ = 33). The size at which 50% of females had started to mature (Lint50) forM. holotrachyswas 21 cm pre‐anal length (LPA) and occurred atc. 9 years old. Estimates of natural mortality and Pauly's growth performance index were found to be low (M = 0·09 and Φ = 2·82 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