This is a interesting development, especially in which to note, that sea creature spawns are often blocked by freezing ocean temperatures such as the polar glaciers and seasonal ocean freezes, which if your research shows to be promising, may trigger the rapid spawning (if there are any regionally at all just off map unable to access) of sea creatures native to that environment (on top of leftover vermin not killed in the freeze).
Giant sperm whales are particularly striking, because they offer immense amounts of food living in those regions, and though contact breeding (im personally experimenting with fishery designs with common domestic conger eels as test subjects, its difficult to obtain and keep said fish alive since they die on embark and it consumes time to obtain them from the mountainhome through traders, but im working on it *change the entity to OCEAN PRODUCTS and they'll trade them + trade goods related to conger eels*) and some [PET] tags, you could have a fully functional whale farm (they only take 1 year to grow up, mostly the same for most marine life) for these long lived creatures that give plentiful meat and calves (ontop of side experiments to weaponise them in conjunction of raw fiddled fish men military as work animals *aquatic crossbow sea hunters anybody?*)
If you do try a tundra sea/glacier embark to test this out sometime after your initial efforts, try a aquifer channel lined with cage traps and a floor grate ceiling + structured walls + floors to stop the refreezing of the channel. (4x4 recommended for continuous long line of 2x2 grates)
Only thing i could really suggest to keep the off embark ice away is a small pool of of lava or something.