The winter flounder (''Pseudopleuronectes americanus''), also known as the black back, is a right-eyed ("

dextral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...

flatfish A flatfish is a member of the Ray-finned fish, ray-finned demersal fish Order (biology), suborder Pleuronectoidei, also called the Heterosomata. In many species, both eyes lie on one side of the head, one or the other migrating through or around ...

of the family

Pleuronectidae Pleuronectidae, also known as righteye flounders, are a family of flounders. They are called "righteye flounders" because most species lie on the sea bottom on their left sides, with both eyes on their right sides. The Paralichthyidae are the o ...

. It is native to coastal waters of the western north

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

coast, from

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United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, although it is less common south of Delaware Bay. It is the most common near-shore (shallow-water) flounder in the waters from Newfoundland down through Massachusetts Bay, reaching a maximum size around 61 cm in length and 2.25 kg in weight. The species grows larger on Georges Bank, where they can reach a length of 70 cm and weight of 3.6 kg. Although winter flounder historically supported large commercial and recreational fisheries, biomass and landings have decreased since the 1980s.

Life cycle

Winter flounder lay up to 3.3 million demersal, adhesive eggs that are retained within their spawning grounds. Depending on temperature, larvae of approximately 3 mm in length hatch in two to three weeks. These larvae are planktonic at first, but transition to a bottom-oriented lifestyle over time. Around five to six weeks after hatching, the left eye of the larval flounder begins to migrate to the right side of the body. The “flounder-like” juveniles then settle onto the seafloor and move into saltwater coves, coastal salt ponds, estuaries, and protected bays, where they may grow up to 100 mm within the first year. Adult winter flounder may grow as large as 70 cm and reach ages of 15+ years. Growth varies across their distribution, with northern populations generally growing slower than those at the southern end of their range.

Taxonomy

The winter flounder is one of five species in the genus ''Pseudopleuronectes'' along with the Yellow-striped flounder, Cresthead flounder, Marbled flounder, and Dark flounder. It is the only congener to inhabit the Atlantic Ocean. Winter flounder can be differentiated from the commonly co-occurring summer flounder (''Paralichthys dentatus'') by their small teeth and eyes nearly always positioned on the right side of their bodies. Meanwhile, summer flounder have their eyes on the left side of their bodies and possess large, conspicuous teeth.

Feeding and diet

Larval winter flounder are known to feed on nauplii, harpacticoids, calanoids, polychaetes, invertebrate eggs, and phytoplankton. As they grow, copepods, amphipods, and polychaetes all become more important elements of their diet. Adult winter flounder are opportunistic sight-feeders that target annelids, crustaceans, bivalves, and fish depending upon prey availability.

Reproduction

Winter flounder reach sexual maturity at about two to three years of age and a total length of 25–30 cm, with variance across their range. Mature adults (excluding those on Georges Bank) generally migrate in two phases, where adults enter shallow estuaries in the late fall and early spring to spawn in late winter or early spring before returning to deeper parts of the estuary or offshore waters. However, these migration patterns may be altered or individuals may stay inshore year round if temperatures remain at 15 °C or lower or if enough food is available. Genetic analyses and tagging studies indicate that there is little mixing between the Winter flounder populations in the Gulf of Maine, South of Cape Cod, and on Georges Bank.

Fisheries

Winter flounder are highly regarded for their delicious white meat and are sometimes called lemon sole in the U.S. They once supported large commercial and recreational fisheries, with peak harvests of 40.3 million pounds and 16.4 million pounds respectively. However, landings in both sectors have declined since the 1980s to 6 million pounds and 77,000 pounds respectively in 2013. Winter flounder are managed as three stock units in U.S. coastal waters; Southern New England/Mid-Atlantic (SNE), Georges Bank (GB), and Gulf of Maine (GOM), where the status of each stock is as follows: SNE-

overfished Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in the ...

, overfishing is not occurring; GB- not overfished and overfishing is not occurring; GOM- unknown if they are overfished, overfishing is not occurring. Despite continued management efforts,

habitat degradation Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...

, heavy fishing pressure, low

genetic variability Genetic variability is either the presence of, or the generation of, genetic differences. It is defined as "the formation of individuals differing in genotype, or the presence of genotypically different individuals, in contrast to environmentally ...

, and possibly

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

are combining to hinder the recovery of depleted Winter flounder populations.

References

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winter flounder The winter flounder (''Pseudopleuronectes americanus''), also known as the black back, is a right-eyed ("Sinistral and dextral, dextral") flatfish of the family Pleuronectidae. It is native to coastal waters of the western north Atlantic Ocean, A ...

Fauna of Atlantic Canada Fish of the Eastern United States

Taxa named by Johann Julius Walbaum