Winter flounder are small flatfish belonging to the group known as “right-eyed flounder” because, when placed on a surface with their dark side facing up with their belly pointed toward the observer, their head (and eyes) will be facing toward the right.
Like most flounder, they feature a lower, white side, which normally remains pointed down toward the bottom, and a darker, cryptically colored upper side that helps to make them hard to see when lying motionless on the bottom. To further such camouflage efforts, the flounder often covers itself with sand, mud or gravel, so that only its eyes, poking above the substrate, are readily visible. From that position, it becomes an effective ambush predator, feeding on worms, sand shrimp and other invertebrates.
Winter flounder once supported one of the most popular recreational fisheries in the northeast. However, over the past few decades, the two inshore stocks have seen substantial declines in abundance, which has resulted in a decline in recreational fishing effort. Recreational landings peaked in 1985, when anglers took home more than 16,000,000 winter flounder; in 2016, that figure had shrunk to less than 88,000, reflecting anglers lack of interest in fishing on collapsed populations.
Winter flounder are a popular foodfish, and have long supported a large commercial fishery. The bulk of the harvest is and always have been taken by bottom trawls; a once-significant fyke net fishery that targeted flounder in the bays, after they moved inshore to spawn, still exists, but accounts for a very small part of the overall harvest.
Commercial winter flounder landings peaked in the mid-1980s, with more than 24,000,000 pounds landed in 1987; by 2015, that figure had dropped to somewhat more than 3,700,000. However, the two figures aren’t directly comparable. In 1987, the fishery was effectively unregulated; managers were free to tolerate overfishing and had no need to rebuild overfished stocks. That changed after the Sustainable Fisheries Act of 1996 became law; the commercial fishery was further constrained after the 2006 reauthorization of the Magnuson-Stevens Fishery Conservation and Management Act required managers to establish hard quotas.
Today, winter flounder remain a sought-after commercial species. However, given that both the Georges Bank and southern New England/Mid-Atlantic stocks are overfished, and the status of the Gulf of Maine stock is unknown, landings are much lower than they would be if the stocks were healthy.
Range and Biology
Winter flounder are a cool- to cold-water species; while individuals have been found in waters between Labrador and Georgia, for practical purposes the population never extended south of Delaware. They are a small fish, generally less than 18 inches in length and two pounds in weight, although some individuals, particularly those found on the offshore banks, can weigh as much as 7 or 8 pounds.
Winter flounder are managed as three distinct stocks, the Gulf of Maine and southern New England/Mid-Atlantic stocks, both of which spawn in inshore waters and often move into deeper waters when spawning is completed, and a Georges Bank stock, which spends its entire life in offshore waters on and near its namesake bank.
The reality of winter flounder stock structure is far more complex. The two inshore stocks appear to be composed of substocks unique to a particular bay or estuary, which may mix offshore, but do not mix on the inshore spawning grounds. Thus, when a local substock is depleted, it will not be replenished by fish from neighboring waters.
Recent research conducted in New York’s Shinnecock Bay suggest that the local substocks may be broken down even further. At one time, it was assumed that winter flounder entered the bays in the fall, spawned during the late winter and early spring, and then departed the bays for deeper, cooler waters once spawning was done (Gulf of Maine flounder may, due to cold winter temperatures, remain in deep waters during the winter, move inshore once waters warm in spring, spawn, and then move offshore again). Acoustic tagging studies now seem to have identified two separate populations of winter flounder, one of which engages in such seasonal migrations, and one of which remains inside the bay throughout the year. The existence of such inshore stocks, if confirmed, further complicate the management picture.
Winter flounder are managed by the National Marine Fisheries Service (NMFS), acting through the New England Fishery Management Council, while in federal waters, and by the Atlantic States Marine Fisheries Commission (ASMFC) when in state waters within three miles of shore. Unlike some species, which are managed jointly by NMFS and ASMFC pursuant to a single fishery management plan, winter flounder are subject to separate state and federal management plans that do not contain identical management measures.
The most recent stock assessment update, released in 2015, indicates that winter flounder are not faring very well. The Georges Bank stock is overfished, and overfishing is still occurring. The southern New England/Mid-Atlantic stock is also overfished, but not subject to overfishing. The Gulf of Maine stock is not subject to overfishing; scientists don’t know whether or not that stock is overfished, but the fact that the combined recreational landings for Maine, New Hampshire and Massachusetts have crashed, from more than 8,500,000 fish in 1982 to less than 41,000 fish in 2016, strongly suggests that there may be a problem with that stock as well.
However, the assessment did indicate a lowering spawning stock biomass. Right now, they are not quite at the target where they should be, but they are not below the threshold for management action either. Thus, the Council decreased the Acceptable Biological Catch by 10% for 2016 and 2017.