Population structure, growth and reproduction of roughhead grenadier on the Flemish Cap and Flemish Pass

Roughhead grenadier Macrourus berglax were collected during the Flemish Cap bottom survey (1991–2001, NAFO division 3M, depth of 200–720 m) and on commercial vessels (1998–2000, NAFO divisions 3L, M and N, depth of 700–1700 m). The abundance of roughhead grenadier, as well as their average size, increased with depth. Age and length composition of the catches showed clear differences between the sexes. The proportion of males in the catch declined in the larger length classes and there were no males in the largest length classes (25 cm). There were differences in the growth trajectories of the two sexes; both sexes grew similarly up to 9 years, but the male growth was slower thereafter. The pre-anal fin length at first maturity ( L _PA50) for roughhead grenadier females was 28·5 cm, whilst the age at 50% maturity was 15–16 years. Individual total fecundity varied between 8522 and 61 844 oocytes. Macrourus berglax had a prolonged life cycle and multi-aged population structure, with differences in growth and mortality between males and females, slow maturation and low fecundity.