The marine species of the cold regions are not really so many, as species diversity decreases as we get closer to the poles. The rather few subarctic and still fewer arctic species can on the other hand be extremely abundant. The most abundant large mammal in the world is probably the crabeater seal of the Antarctic. The harp seal of the Arctic is only slightly less abundant. The Atlantic herring might be the most abundant commercial fish in the world, followed closely by Atlantic cod and Alaska Pollack. While the animals above are quite large the most abundant animals in the world in term of total biomass might be the small copepod Calanus finmarchius in the far north and the krill species Euphausia superba in the far south. These two are vital links in the food chain from the phytoplankton to the fishes and mammals. Seabirds also nest in huge colonies in the polar regions.
It would be futile to write about all the species here on this page, that is what we have Wikipedia for.