Publication Abstract

Advances in fecundity methodology applied to some marine fish.

P.R. Witthames, A.Thorsen, M.Fonn, L.N.Greenwood, F.Saborido-Rey, Rosario Dominguez H. Murua, M. Korta, O.S.Kjesbu

Estimation of individual egg production is a key step either to understand the relationship between stock and recruitment or to carry out fisheries independent assessment of spawning stock biomass using egg production methods. The work is demanding on human resources and some times requires large quantities of toxic fixative because many fish are highly fecund and their ovaries may weigh over a kilogram. On the other hand, it has recently been shown for cod (Gadus morhua) that image analysis can automate estimation of fecundity determination using the Auto-diametric method. In this paper, we focus on the precision of the Auto-diametric method applied to a range of species with different spawning strategies caught in ripe or spawning condition. A new method using a solid displacement pipette to remove small (<25-200 mg mass) fecundity samples is evaluated as are the underlying assumptions to effectively sub-sample the ovary. Finally, we demonstrate the interpretation of dispersed formaldehyde fixed ovary samples to assess the presence of atretic and post ovulatory follicles to replace labour intensive histology and consider how to estimate down regulation (production of atretic follicles) of potential fecundity during maturation.

Reference

P.R. Witthames, A.Thorsen, M.Fonn, L.N.Greenwood, F.Saborido-Rey, Rosario Dominguez H. Murua, M. Korta, O.S.Kjesbu (2009) Advances in fecundity methodology applied to some marine fish. Fishery Bulletin 107 (2) 148-164