Now is the time of the year where many animals head south to warmer climates for the winter. Birds seem to show the most familiar behavior, such as flocks of Canada geese in the "V" formation flying over head. It's as emblematic as the colorful tree foliage or waking to see that first crisp frost. These are signs of autumn's arrival as well as encroaching cold weather.

Fish are no exception to this annual phenomenon. Anglers and other fish enthusiasts know that many fish species migrate with the seasons. One of the more popular species that exhibit seasonal migration is Morone saxatilis — the striped bass. Arriving as early as April to feed in the Gulf of Maine, striped bass head south to warmer waters as early as August and can hang around until October. Water temperature seems to be a key factor in the timing of migration. Bluefish, Pomatomus saltatrix, is another warm weather visitor coming up from southern locations and heading back in the fall. Other species won't migrate as far but some will move from coastal waters to further offshore, such as some flounder species.

One estuarine dweller, Microgadus tomcod or the Atlantic tomcod, will reside in our estuaries year round only migrating into cooler freshwater streams and rivers for a short time in October and November. A member of Family Gadidae (the cod family), the tomcod resembles a small, camoflaged cod with a rounded tail. It feeds on amphipods, decapods, small crustaceans, and mollusks, worms, and juvenile fish. This fish also produces antifreeze proteins, similar to those found in some Arctic and Antartic fishes, which allow it to survive in water temperatures below freezing.

So the Atlantic tomcod is a hardy, year-round inhabitant that never abandons its home for the promise of warmer water. It remains with us through the changing seasons, like the bright forests and frosty fields — hence its other common name: frost fish.