The reduction in growth in the late 17th century appears to represent slower growth of age 0+ juveniles (Fig 3). The North Atlantic cooled in the 17th century and historical documents report harsh winters and inshore conditions e.g. icebergs and ice covered fjords around Iceland [39, 40]. Juvenile Atlantic cod nursery areas are in inshore waters and age 0+ juveniles are particularly likely to be found in shallow nearshore waters [43, 44]. Atlantic cod age 0+ juveniles may therefore be more effected by local climate effects than older cod that can seek favorable temperature and foraging conditions [41, 42]. Previous research has shown that ocean temperature was not a primary source of otolith growth variation in juvenile Atlantic cod . However, lower sea temperatures in the 17th century may also have affected food availability. Juvenile cod feed predominantly on zooplankton and are dependent on phenological matching of zooplankton blooms [54–56]. This matching may be disrupted by climate effects suggesting that food limitation could also explain slower growth of age 0+ juvenile Atlantic cod in the 17th century.