Winter flounder is an estuarine flatfish found in almost all shoal water habitats along the northwest Atlantic coast. The geographic distribution ranges from nearshore habitats to offshore fishing banks along the Atlantic coast of North America.
The name 'winter' flounder refers to their annual spawning migrations into nearshore waters in winter. Adults migrate in two phases; an autumn estuarine immigration prior to spawning, and a late spring/summer movement to either deeper, cooler portions of estuaries or to offshore areas after spawning. This pattern of seasonal distribution may change in the colder waters of the northern extent of the range where they migrate to shallow water in the summer and deeper waters in the winter. The annual spawning period varies geographically and although spawning periods overlap considerably, peak spawning times are earlier in southern locations.
During spawning, females release demersal (negatively or neutrally buoyant) adhesive eggs whose properties facilitate retention within spawning grounds. Many factors influence larval and juvenile growth and survival, including temperature, salinity, dissolved oxygen, and food availability. Nursery habitat for winter flounder larvae and juveniles is typically saltwater coves, coastal salt ponds, estuaries, and protected embayments; although larvae and juveniles have also been found in open ocean areas such as Georges Bank and Nantucket shoals. Larvae are predominantly found in the upper reaches of estuaries in early spring, moving into the lower estuary later in the season.
Winter flounder in eel grass. Photo credit: Carl Lobue, The Nature Conservancy
Historically valuable to commercial and recreational fishermen throughout New England and the Mid-Atlantic, winter flounder fisheries are a mere fraction of what they once were. Total landings (commercial and recreational) in both areas peaked in the early 1980s at approximately 10 million pounds for GOM and 36 million pounds for SNE/MA.
Over the last decade, commercial harvest has accounted for about 90% of total fishing mortality with half of the commercial landings occurring in state waters. Additionally, the vast majority of commercial harvest (~98%) has been taken by fishermen who possess a federal groundfish permit. The 2011 estimate for commercial landings of winter flounder was 4.6 million pounds. The majority of the recreational harvest occurs in state waters.
Winter flounder stocks were most recently assessed at the 52nd Northeast Regional Stock Assessment Workshop/Stock Assessment Review Committee (SAW/ SARC 52) in 2011. Consistent with previous assessments and management delineations, three regional assessments were produced: Gulf of Maine (GOM), SNE/MA, and Georges Bank (GBK). The GOM stock occurs the coastal waters north of Cape Cod, while the SNE/MA stock occurs in coastal waters south of Cape Cod. The offshore GBK stock does not fall under Commission management, and is managed solely by the Council and NMFS. The GBK stock is not overfished and not experiencing overfishing.
SAW/SARC 52 found that overfishing was not occurring in 2010 and the overfished status is unknown for the GOM stock. It also determined that the SNE/MA stock was overfished but not experiencing overfishing. SSB was estimated to be 15.6 million pounds in 2010, about 16% of the SSBTARGET (SSBMSY) of 96.3 million pounds, an improvement from 9% of SSBTARGET in 2007. Fishing mortality in 2010 was estimated to be 0.051, well below the FTHRESHOLD (FMSY) of 0.29.
The Commission and the New England Fishery Management Council jointly manage winter flounder with complementary management plans that regulate state and federal waters based on fisheries and the biology of winter flounder. The Council includes winter flounder as part of the Northeast Multispecies Fishery Management Plan (Groundfish FMP). Federal management focuses on the commercial fishery because the bulk of harvest in federal waters is from that sector.
The Commission’s Amendment 1 (November 2005) and Addendum I (May 2009) are designed to protect spawning females when they have migrated to inshore state waters spawning grounds because they are easily located and caught when congregated for spawning. The Commission and Council use stock area-specific management measures for both the recreational and commercial sectors of the fishery.
The Commission significantly reduced fishing on state waters spawning grounds in 2005 when Amendment 1 to the Interstate FMP for Inshore Stocks of Winter Flounder (Amendment 1) replaced all previous winter flounder management documents. Amendment 1 established a minimum size limit, shortened seasons, and lowered trip/bag limits to reduce fishing pressure on spawning fish and rebuild the spawning stock biomass to target levels. Amendment 1 complemented Amendment 13 and Framework 42 to the Groundfish FMP, which focused on offshore commercial fisheries (3 - 200 miles). Its goal is to rebuild overfished stocks by reducing fishing mortality and minimizing adverse effects on all essential fish habitat with seasonal closures, gear restrictions, minimum size limits, trip limits, limited access, and days at-sea restrictions.
Considerable management changes occurred in 2009 following the 2008 peer-reviewed benchmark assessment, which estimated the SNE/MA stock at 9% of the target biomass. To rebuild the depleted stock, the Commission initiated Addendum I, the Secretary of Commerce prohibited retention of SNE/MA winter flounder through interim action, and the Council included measures to incorporate the assessment results into Amendment 16 to the Groundfish FMP (Amendment 16). Rather than prohibit possession of winter flounder, resulting in increased discard mortality and loss of fishery-dependent data, the Commission opted to establish bycatch-only possession limits for the SNE/MA stock. Addendum I limits recreational fishermen to 2 fish and commercial fishermen can land a maximum of 50 pounds (or 38 fish) in the SNE/MA. For the GOM, Addendum I required states to reduce recreational fishing mortality by 11% and established a 250 pound commercial trip limit.
In October 2012, in response to updated stock status information and recent federal action to increase the GOM winter flounder state waters' estimated harvest level, the Commission's Winter Flounder Management Board approved Addendum II. The Addendum modified the commercial and recreational management requirements for the Gulf of Maine (GOM) stock. Specifically, the commercial trip limit was increased to 500 pounds per trip and the recreational season was expanded to become year round. These measures applied only to GOM state waters' fisheries until June 1, 2013.
In May 2013, the Board passed Addendum III for the GOM and SNE/MA fisheries in order to annually set commercial and recreational specifications. These specifications may be set for up to 3 years, and may be revised if new information is released within the 3 year period.