The ability to accurately quantify ovarian condition in cultured species of fish is of paramount importance in the understanding of their reproductive biology and the development of appropriate culture conditions. Here, we discuss stereological analysis, a mathematically proven technique that determines 3-dimensional topology and geometry from 2-dimensional thin sections, as a safer and more precise replacement for existing methodology.

The direct amplification of length polymorphism technique (DALP) has been used to distinguish species-specific banding patterns in two marine gastropod oyster drills Ocenebra erinacea (Linnaeus, 1758) and Ocinebrellus inornatus (Récluz, 1851). Ocenebra erinacea is the European oyster drill, common along all European coasts. Ocinebrellus inornatus, the Japanese oyster drill, was recorded in oyster growing areas of the Marennes-Oléron Bay (SW France) for the first time in 1995. This new biological invasion could lead to an increase, which must be evaluated, in the predation risk for cultivated species i.e. oysters and blue mussels, and for littoral fishing resources along the French Atlantic coasts. As a result, since specific identification of early life stages of both species (egg capsules and juveniles) was previously found to be both difficult and unsure using only morphological criteria, four Ocenebra erinacea and two Ocinebrellus inornatus specific molecular markers were identified and sequenced. These markers will facilitate the assessment of respective ecological impacts (reproductive patterns, abundance and spatial distribution of juveniles), resulting from the exotic species versus the native species and will allow us to analyse with certainty demographic profiles of the two oyster drill populations.