For winter flounder, it’s all about water temperature. For this fish loves cold water.
With water temperatures around New York Harbor still largely below 55 degrees F., conditions continue to be right for winter flounder, a flatfish species, to spawn and create the next generation. Winter flounder spawn from February to May, peaking in April, just before waters warm up.
Winter flounder spawning is sensitive to temperature. Unlike most fish that spawn in warmer waters, winter flounder are adapted to spawn in cold water. It’s a brilliant way to help protect their young from being eaten by too many predators, which are often active in late spring, summer and early fall.
Winter flounder are protected from freezing in cold water by a special anti-freeze protein in their body, which is found in most cold water fish that live in chilly Antarctic waters. Winter flounder can survive in water temperatures as low as 32 to 34 degrees F.
When local water temperatures turn cold, generally below 55 degrees F, winter flounder will move into New York Harbor from the Atlantic Ocean for spawning. When the water begins to warm up, winter flounder will migrate offshore into deeper, cooler waters for the summer.
Winter flounder typically spawn at night on sandy bottom areas in New York Harbor. Individual females produce an average of about 500,000 eggs annually.
Eggs hatch after 15-18 days depending on temperature of course. When flounders first hatch, they look like any other small fish, with an eye on both sides of its head. But as flounders grow and develop, the left eye will migrate across the top of its head to the right side. The fish then lays flat with both eyes facing upwards. Since both eyes are found on the right side of the body, the winter flounder is often called a right-eyed flatfish.
Juvenile winter flounders will remain in New York Harbor for usually two years to feed and mature. They exist mostly in coves with sandy or muddy bottoms. I often find juvenile winter flounder near the mouths of creeks, including the mouth of Many Mind Creek in Atlantic Highlands. The lower estuary seems to be an important nursery for winter flounder, including the Navesink River.
For me, winter flounder are beautiful and unique fish. A real treasure to have in New York Harbor.