Reproductive biology of the roughhead grenadier (Macrourus berglaxLacepède) (Pisces, Gadiformes) from the continental slope of northern Norway

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Abstract
Size and age at maturation, gonad growth, oocyte differentiation and spawning season were investigated. Maturing oocytes increased in diameter from 1850 µm in August to 2490 µm in December; peak spawning seemed to occur in January. Males with running sperm were, however, observed at other times of the year. Age at maturity was found to be 15 years for females. Fecundity was weight-dependent and varied from 2 000 to 71 000 eggs per ovary. The hepatic-somatic index varied seasonally with higher values during the summer and decreasing values after September. The same pattern was observed in mature and immature specimens, although there was a more pronounced reduction in liver size in mature females, reflecting energy requirements for ovary growth.