A fundamental difference between Arctic (left) and Antarctic (right) regions is that the Arctic is a frozen ocean surrounded by continents, while the Antarctic is a frozen continent surrounded by oceanic waters. (Original images courtesy of NOAA www.climate.gov). 

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... over the next 50 –100 years (Barker and Knorr, 2007; Brander, 2007; Cheung et al. , 2009), and recent evidence shows that changes have already occurred in benthic community composition (Mecklenburg et al. , 2007; Kortsch et al. , 2012) and Arctic fish distribution (Wassmann et al. , 2011) have already occurred in asso- ciation with warming waters. In Arctic and Antarctic foodwebs, copepods / krill / amphipods and Antarctic krill, respectively, contribute to a significant part of the total zooplankton production and form a major link between phytoplankton and predators at higher trophic levels. Spatial and temporal changes in phytoplankton and zooplankton distribution and abundance can have major consequences for the recruitment potential of commercially important fish (Friedland et al. , 2012; Kristiansen et al. , 2014). Together, these direct and indirect impacts on fished species can have major economic implications for the fisheries sector (Allison et al. , 2009; Brander, 2013), although considerable uncertainty still remains regarding the magnitude of impacts and the mechanisms that underlie them (Brander, 2007). There are major differences in the number of publications available internationally on marine biology and ecology emanating from Arctic vs. Antarctic research. The mean number of Arctic publications on the subject is 51% of Antarctic publications over the period 1991–2008 (Wassmann et al. , 2011). In the Arctic, the lack of reliable baseline information, particularly with regard to the Arctic basin, is due to the relative scarcity of studies into the 1970s (Wassmann et al. , 2011). The reasons are multiple, but include that most research has been based on national efforts; international cooperation and access to the Arctic was difficult during the Cold War period—when most bases in the Arctic were military and international access to the Siberian shelf was banned. In contrast, substantial research activity has been focused on Antarctica and the Southern Ocean stimulated in connection with the Third International Polar Year in 1958. Subsequent signing of the Antarctic Treaty in 1961 also has provided substantial impetus for collaborative international research (Wassmann et al. , 2011). In recent years, the response to the climate change of marine ecosystems in the Polar Regions has been the topic of considerable international research activity, and understanding has improved as a result. Further improving the ability to determine how climate change will affect the physical and biological conditions in Arctic and Antarctic marine systems, and the mechanisms that shape recruitment variability and production of important fishery species in these regions, is essential to develop sound marine resource management policies (e.g. Stram and Evans, 2009; Livingston et al. , 2011). The salient question for this review is thus: how will the response to climate change of marine systems within these two regions affect their future fisheries? To address this question, we review the existing scientific literature to determine: 1. How and why do Arctic and Antarctic marine systems differ from each other; and how are these systems responding to climate forcing, particularly with regard to foodwebs and fishery productivity? 2. Which fishery resources are currently exploited in these regions? 3. What are the future prospects for fishery resource productivity in these regions? 4. What are important considerations for an ecosystem approach to management of future fisheries in these regions? Other authors have investigated the potential future impacts of climate change on fish and fisheries on regional (e.g. Wassmann et al. , 2011; Hollowed et al. , 2013a, b; Kristiansen et al. , 2014) and global scales (e.g. Brander, 2007, 2010) and have included consideration of key factors determining the response of plankton / zooplankton to climate forcing. Our review focuses on the effects of climate change on key zooplankton species which form the link between primary producers and upper-trophic levels (i.e. fish) in both the Arctic and Antarctic marine systems. Polar zooplankton species have larger lipid reserves than related species at lower latitudes, which serve as energy for species at higher trophic levels. If the abundance of zooplankton species in Polar marine systems should decline, the consequences for larger ocean animals would likely be severe (Clarke and Peck, 1991). Arctic and Antarctic marine systems have in common their high latitudes, seasonal light levels, cold air and sea temperatures, and sea ice. But, in other ways, they are strikingly different (Dayton et al. , 1994). The Intergovernmental Panel on Climate Change points out that “the Arctic is a frozen ocean surrounded by continental landmasses and open oceans, whereas Antarctica is a frozen continent surrounded solely by oceans” (IPCC, 2007; Figure 1). Delineations of these systems may vary. This review adopts the Arctic Climate Impact Assessment’s delineation of the marine Arctic as comprising the Arctic Ocean, including the deep Eurasian and Canadian Basins and the surrounding continental shelf seas (Barents, White, Kara, Laptev, East Siberian, Chukchi, and Beaufort Seas), the Canadian Archipelago, and the transitional regions to the south through which exchanges between temperate and Arctic waters occur (Loeng et al. , 2005). The latter includes the Bering Sea in the Pacific Ocean and large parts of the northern North Atlantic Ocean, including the Nordic, Iceland, and Labrador Seas, and Baffin Bay. Also included are the Canadian inland seas of Foxe Basin, Hudson Bay, and Hudson Strait (Loeng et al. , 2005; Huntington and Weller, 2005). Historically, sea-ice coverage ranges from year-round cover in the central Arctic Ocean to seasonal cover in most of the remaining areas (Loeng et al. , 2005). The area of sea ice decreases from roughly 15 million km 2 in March to 7 million km 2 in September, as much of the first-year ice melts during summer (Cavalieri et al. , 1997). The area of multiyear sea ice, mostly over the Arctic Ocean basins, the East Siberian Sea, and the Canadian polar shelf, is 5 million km 2 (Johannessen et al. , 1999). For Antarctica, we adopt the Aronson et al . (2007) delineation as the continent and southern ocean waters south of the Polar Front, a well-defined circum-Antarctic oceanographic feature that marks the northernmost extent of cold surface water. The total ocean is 34.8 million km 2 , of which up to 21 million km 2 are covered by ice at winter maximum and 7 million km 2 are covered at summer minimum (Aronson et al. , 2007). A number of other physical and biological characteristics differ between the Polar Regions (Table 1). The Arctic has broad shallow continental shelves with seasonally fluctuating physical conditions and a massive freshwater input in the north coastal zones. Historically, the Arctic has been characterized by the low seasonality of pack ice and little vertical mixing; this condition is changing, however, for large parts of the Arctic due to declining sea ice (e.g. Hare et al. , 2011). In contrast, the Antarctic has over twice the oceanic surface area, deep narrow shelves, and except for ice cover, a relatively stable physical environment with very little terrestrial input. The Antarctic has great pack-ice seasonality and much vertical mixing (Dayton et al. , 1994). The geological and evolutionary histories of these regions differ greatly (Dayton et al. , 1994). Antarctica is a very old system that tends to be thermally isolated from the rest of the planet. Biogeographers agree that most Antarctic biota are very old and unique (Rogers et al. , 2012). During its geological history, it was first isolated for some 20 –30 million years, and only then was it subject to intense cooling. This was followed by the opportunity to evolve in an isolated, relatively stable, and uniform system for perhaps another 20 million years (Dayton et al. , 1994), which has implications for evolution in response to current climate change. In contrast, the biogeography of the Arctic is neither ancient nor well established and seems to be in a state of active colonization over the last 6000–14 000 years (Dayton et al. , 1994). It is influenced strongly by seasonal atmospheric transport and river inflow from surrounding continents. The human imprint in these regions also differs. The Arctic has been populated for thousands of years. There is considerable economic activity, based on fishing and ship- ping. Recent decades have seen the establishment of urban areas and increased industrial activity related to petroleum, gas, and mining industries. In contrast, the Antarctic has limited resource use, apart from a history of industrial fishing for marine mammals and fish species, a fishery for krill (conducted since 1973), and a rapidly growing tourism industry (Dayton et al. , 1994; Leaper and Miller, 2011; Rintoul et al. , ...