Flounders (Atlantic)

Summer flounder, Fluke; Winter flounder, Lemon sole, Blackback, dab; Witch flounder, Gray sole; Yellowtail flounder, Rusty flounder; Windowpane flounder, Sand dab

Flatfishes are a distinct group, consisting of eleven families, 123 genera and about 570 species worldwide. As the name implies, individuals in this order (Pleuronectiformes)generally lay flat, with skull development in the larval stage causing the migration of one eye around the head and distinct pigmentation between sides (bottom-facing side white, upwardfacing side pigmented for camouflage). Most commercially important flatfishes in the Atlantic are from the family Pleuronectidae (right-eye flounders), composed of 21 genera and 60 species, including witch, winter, and yellowtail flounder, American plaice and Atlantic halibut. Other important families are Paralichthyidae (lefteyed sand flounders, including summer flounder) and Scophthalmidae (windowpane flounder).

Most of the flatfishes discussed in this report have a relatively low age at maturity (<5 yrs, possibly with the exception of northerly ranging stocks), moderate (10-30 yrs) or unknown longevity, and a broad latitudinal range throughout the Atlantic Ocean basin. Most of these species are prolific spawners, broadcasting thousands to millions of eggs every year (larval mortality is unknown but presumed to be normal/high). These species of flatfish, therefore, are considered "resilient" to fishing pressure.

The summer and witch flounder stocks are not considered overfished, but overfishing is occurring. The Georges Bank (GB) yellowtail flounder stock is the only yellow-tail stock considered to be rebuilding from an overfished state and overfishing is not occurring. The last assessment of Gulf of Maine (GOM) and Georges Bank (GB) winter flounder stock in 2002 indicated that this stock was not overfished, and not experiencing overfishing. The Southern New England-Mid Atlantic Basin (SNE/MAB) winter flounder stock assessment reported that this stock complex is overfished and overfishing is occurring. Both the GOM/GB and SNE/MAB windowpane flounder stocks were not experiencing overfishing as of the last assessment in 2001. The SNE/MAB stock is currently considered overfished and the GOM/GB stock is not. Overall, the stock status of the aforementioned species is considered of “high” conservation concern.

Due to the mixed species nature of the Atlantic Groundfish fishery, as well as the gear type used(bottom/otter trawl), bycatch and subsequent discarding of unmarketable or otherwise illegal (e.g., undersized) species occurs frequently. In addition, trip limits, a management tool used to regulate catch, forces otherwise market-worthy fish to be discarded. Managers have mitigated this somewhat by increasing the allowable mesh size in the trawl gear, reducing the catch of smaller-sized fishes. There have been a small number of observed interactions with marine mammals and sea turtles in the trawl fisheries. In 2003, Fishery Observers on 590 trawling
(bottom otter) trips recorded a total of 21 interactions with marine mammals, and 4 interactions with sea turtles. According to the Multispecies Groundfish FMP, trawlers are
required to report all discards via logbooks and use bycatch reduction devices (BRDs) such as Nordmore grate and mesh panels. Observer coverage is only about 5%,
however, thus numbers of total discards may be underestimated. Overall bycatch in the Atlantic Groundfish fishery is considered a “moderate” concern.

Based on the published literature noting the adverse effects of trawling on the various habitat types where flounders are found, as well as the significant amount of fishing effort along the continental shelf over the last 50 years, it is reasonable to assume that trawling for flatfishes has significantly altered or damaged a large portion of the seabed and the ecosystem. The degree of
recovery from these actions is largely unknown and the effects of these fishing practices on habitats and ecosystems is ranked “severe”.

Managers of Northeastern groundfish resources assess stocks on a timely basis (annually or semi-annually) and use both fisheries dependent and independent data to determine stock status and fishing levels. Managers require specific mesh sizes and gear types to reduce wasteful discard, as well as implement seasonal and permanent closure areas to reduce trawling impacts.
Management has not, however, prevented the extreme declines of many commercially important flatfishes, and is therefore considered only “moderately effective”.

Consumption advisory due to PCBs, dioxins and pesticides. + No listing is available from the Environmental Defense Oceans Alive program