Teacher Resources

Winter flounder are still caught in salt ponds and in Narragansett Bay. They were once very abundant. However, they are getting harder to find due to many environmental changes in the waters of this area. They are unique and interesting for several reasons. They have both eyes on one side of their heads. They can easily camouflage themselves. They can also live in freezing water.

Winter flounder move during the winter months to shallow inshore waters. They range from southern Labrador (Canada) to Georgia and are most abundant from the gulf of St. Lawrence to the Chesapeake Bay. The winter flounder has both eyes on the right side of its head. A newly hatched larva has one eye on each side of its head but within months it adapts to a bottom dwelling lifestyle, by which time one eye has moved to the other side of the head.

Unlike most other bottom dwelling fish that rest by lying on their bellies, a flat fish rests on its side. Having both eyes on one side of its head enables the flounder to rest on the ocean's floor while directing both eyes upward. The winter flounder is referred to as a right handed flounder because the eyes are located on its upper surface when the fish is pointing to the right. Female winter flounder grow faster than males and attain larger maximum sizes to about 8 pounds with a length of 25 inches.

Flounder can reproduce in 3 years. The fecundity (number of eggs produced each year) increases with body size, with smaller females producing about 500,000 per year and larger females around 1,500,00 eggs per year. In New England, flounder reproduce in estuaries from January to May with peak activity during February and March when the water temperatures are the coldest. The fish return for many years to the same spot to spawn. Unlike the floating eggs of all other local flatfish, eggs of the winter flounder clump together in masses on the bottom. Eggs hatch 15 to 18 days later.

Winter flounder have limited seasonal migration. Fish stay in inshore areas for the winter. They move to cooler offshore areas in the summer but are rarely found below 40 m. One very important and unusual characteristic is their ability to produce their own anti-freeze. This allows the fish to stay in very cold and frozen estuaries without freezing themselves.

Type 1 antifreeze proteins (AFP) are found in polar fish, such as the winter flounder. Their function is to protect the cells from dehydration and ultimately death upon exposure to hypothermal temperatures.

AFP's have significant importance in present and future applications. They may be injected into other species to allow them withstand colder temperatures. This would have a large impact on salmon farming and aquaculture. These proteins can also be used in gene transfer studies.