Description and incidence of ovary cysts in two gadoids from the North Atlantic: Merluccius merluccius and Gadus morhua

Abstract

Spawning stock biomass (SSB) has been generally used as an indicator of spawning stock production but it is not exact because there are other factors like size, experience or condition that affect capacity of females to produce viable offspring that may eventually recruit to adult population or fishery. This ability is the Stock Reproductive Potential (SRP). Fish used to resorpt remanents oocytes prior or after batches release by atresia regulating its egg production. In some species oocytes are encapsulated in cystic structure that may remain in the ovary for several months, even years, without being reabsorbed, altering female reproductive potential in next spawning season. In the present work ovaries of Atlantic cod and European hake from Flemish Cap and Galician Shelf respectively, since 1999 to 2006, have been analysed. Prevalence and abundance of ovary cysts have been estimated by stereological methods. Results show a significant increase of cysts incidence with female size and age. Besides, presence of these structures is higher in recent years and it is related with female condition factor (K). Subsequently, influence of size/age structure of SSB, female condition and environmental factors like temperature could be affecting stay of cysts in ovaries which may reduce SRP