Sea-Ice Interactions with Polar Fish - Focus on the Antarctic Silverfish Life History

The sea ice, extending seasonally over a vast area of the circumpolar Oceans, plays crucial roles in the climate, oceanographic and biogeochemical systems of the polar regions. Besides the roles played in shaping the polar environment, the occurrence of sea ice acts, for the polar organisms, as a driving evolutionary force. In fish, the presence of ice in the sea waters has driven the evolution of antifreeze biological responses that allows them to face the most fundamental survival challenge in polar waters, that is the threat to be frozen. In 2004, the discovery that Pleuragramma antarcticum (Antarctic silverfish) uses seasonal sea ice as nursery ground, further stimulated Antarctic researcher, including the Authors of the present review, to investigate the relationships between polar marine fish and sea ice. During IPY activities, a number of projects focused on P. Antarcticum: to clarify the life cycle and the nature of the silverfish relationship with sea ice is a need to make informed predictions about possible impacts that changes in the sea ic dynamics will have on the coastal Antarctic ecosystem where this small fish plays a pivotall role. In present chapter, the biological and ecological information on P. antarcticum, updated or achieved during IPY activities, are used to draw a picture of the relationship between the sea ice and this fish. By combining evidence and hypotheses, the interaction between the silverfish and the sea ice during early life and during reproduction emerge as major features in its life history.