Size and priority at settlement determine growth and competitive success of newly settled Atlantic cod

Research on the declining stocks of North Atlantic cod Gadus morhua has focused on the survival of planktonic larvae as a predictor of recruitment to the fishery. Very little is known of the ecology of benthic young-of-year cod, although it has been suggested that abundance of demersal 0+ fish may be a better indicator of year-class strength than larval abundance. We studied settlement and growth of individual age 0+ Atlantic cod in situ, using visual census and visual length estimation. Newly settled cod were site-attached and defended territories around a shelter site. Territory size increased exponentially with fish length. Growth and territory size were also determined by size at settlement and by priority; fish that settled largest/earliest grew more quickly and held larger territories than smaller/later settlers. Population dynamics of Atlantic cod may therefore be regulated in the early juvenile stage by post-settlement competition. Size at settlement, in addition to the timing of settlement, may determine the competitive success of an individual.