Size-, energy- and stage-dependent fecundity and the occurrence of atresia in the Northeast Arctic haddock Melanogrammus aeglefinus

Abstract

The Northeast Arctic (NEA) haddock (Melanogrammus aeglefinus) population size has fluctuated greatly over the last few decades. Such fluctuations may be influenced by changes in reproductive investment, yet no fecundity study on this population has been undertaken since 1974 with which to address such a concept. We therefore estimated potential fecundity of >350 NEA haddock caught in February–March 2009–2011 and correlated this with potential fecundity proxies, i.e. female age, length, relative liver size and somatic condition and leading oocyte cohort development (diameter) (LC20). We also examined the incidence (prevalence) and intensity of atresia in histological ovary sections. Finally, we estimated population (total) egg production (TEP) for NEA haddock in 2010 and 2011. Fecundity was mainly determined by length, although it was also positively associated with our metric of liver size and somatic condition. Fecundity decreased with LC20, indicating atresia, confirmed by the direct observation of atresia in histological sections (n=185). Although 45% of the females possessed atretic oocytes, the intensity of atresia was low, typically only 1–5% of the oocytes with yolk granules were atretic, complete reabsorption of all vitellogenic oocytes was not observed. Our proxies give no indication of any change in reproductive investment for NEA haddock in the last few decades. The present study confirms the importance of liver and white muscle energy for oocyte recruitment and shows atretic down-regulation in NEA haddock. Further, NEA haddock females whose oocytes reach the yolk granule stage will likely spawn. NEA haddock TEP for females aged 4–8 years was estimated to be 4.5×1013 and 2.9×1013 in 2010 and 2011, respectively.