First evidence of a new spawning stock of Illex coindetii in the North Sea (NE-Atlantic)

Global changes drive abundance and distribution of species worldwide. It seems that at least some cephalopodstocks profit from global changes as indicated by increases in biomass and/or expansion of their geographicaldistribution, as appears to be the case for the commercially important ommastrephid squidIllexcoindetii, in theNorth Sea. Based on the recently increased abundance of this species seen in research trawl hauls, here wepresent the first evidence of a summer spawning stock ofIllexcoindetiiin the North Sea and derive a descriptionof its life cycle. Neither mated females nor spent males were reported from the area previously. In quarter 1 themajority ofIllexcoindetiiwere immature (maturity stage 0) and maturing (maturity stage 1–3) while in quarter 3almost exclusively mature and spent individuals (maturity stage 4–6) were caught. We observed up to threespermatangia bundles attached to females in quarter 3, indicating that spawning and reproduction takes place inthe North Sea and that the species is already established in this area. Estimated egg hatching dates suggest aprolonged hatching period and therefore likely a long spawning season, although cold temperature seems tolimit year round reproduction. The intensity of individual migrations from adjacent waters into the North Sea isunknown and therefore the number of individuals staying permanently in the North Sea could not be estimated.It is consequently still unclear whether the North Sea individuals ofI. coindetiiconstitute a new separate stoc