Aspects of reproduction of the deep water sharks Centroscymnus coelolepis and Centrophorus squamosus from west of Ireland and Scotland

Abstract

Aspects of the reproductive biology of two exploited deep water sharks, Centroscymnus coelolepis and Centrophorus squamosus were investigated, based on trawl and longline surveys of the continental slopes and commercial samples from fishing vessels. Gravid Centrophorus squamosus were totally absent from this area, but analysis of uterine width data showed that small numbers of post-natal females were present. Mature males and pre-ovulatory females predominated in the middle of the bathymetric range for both species, indicating that mating occurs at these depths. Gravid Centroscymnus coelolpeis occurred only in waters shallower than 1200 m, though peak abundance of the species was between 1300 and 1400 m. There was no obvious bathymetric segregation of male Centrophorus squamosus, contrary to Centroscymnus coelolepis, where immature males occurred deeper than 1100 m, and the proportion of mature males increased up-slope. Centroscymnus coelolepis apportions twice the resources to gonadal tissue as Centrophorus squamosus. Hepatosomatic index declined during vitellogenesis in Centroscymnus coelolepis. Both species have low reproductive outputs and commercial exploitation should proceed with caution.