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North Carolina Department of Environment Quality

NC Department of Environment and Natural Resources
Marine Fisheries - Southern Flounder

Marine Fisheries

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SOUTHERN FLOUNDER, Paralichthys lethostigma

8-point rule

Southern flounder

Life History


Southern flounder (Paralichthys lethostigma) are a bottom dwelling species of the left eyed flounder family found in the Atlantic Ocean and estuaries from northern Mexico to Virginia. This species is one of three commonly caught left eyed flounder in North Carolina: Southern flounder, Gulf flounder (Paralichthys albigutta), and Summer flounder (Paralichthys dentatus). This species supports important commercial and recreational fisheries along the U.S. South Atlantic and Gulf coasts and are particularly important to fisheries in North Carolina. The biological unit stock for southern flounder inhabiting North Carolina waters may include fish from other southern states based on evidence from tagging and genetic studies, as well as differences in aging structures, which indicate one single unit stock of southern flounder from North Carolina to Florida. Evidence also suggests some adult southern flounder return to the estuaries after spawning in the ocean, while others remain in the ocean. Tagged fish are typically recaptured south of original tagging locations and often in other states once in the ocean. Limited data from South Carolina and Georgia tagging programs suggest a low probability of adult movement from South Carolina or Georgia to North Carolina waters.
Data collected from fall fisheries by the North Carolina Division of Marine Fisheries suggests that with the onset of maturity, fish of both sexes migrate out of inlets to ocean waters in the fall. Southern flounder can produce approximately 3 million eggs per female in multiple spawning events in a season, and spawning is thought to take place between November and April. Larval southern flounder pass through inlets within 30 to 45 days of hatching and settle throughout the sounds and rivers in the winter and early spring. Nearly half of female flounder are thought to be mature by ages 1 and 2 (at approximately 16 inches). Fish collected in the ocean tend to be larger and older with females attaining larger sizes. The largest southern flounder observed in North Carolina was a 33 inch long female and a 20 inch long male. The maximum observed age was 9 for a female and 9 for a male; southern flounder captured in North Carolina represent the oldest ages observed throughout the species range.
Juvenile and adult southern flounder are bottom dwelling and typically feed by camouflaging themselves and ambushing their prey with a quick upward lunge. Southern flounder diets switch to fish when they are between 3 and 4 inches long. Adult southern flounder feed almost exclusively on other fish, but will consume shrimp as well.

Fisheries

Records of commercial landings go back to the early 1960s and are among the highest of any finfish species in North Carolina. In 2013 it was the most commercially valuable finfish in the state. Gill nets, pound nets and gigs are the dominant commercial gears used to capture southern flounder (Figure 1). The pound net fishery in North Carolina was historically (pre 1990s) the predominate fishery for catching southern flounder. However, landings from the gill net fishery began to rise in the late 1980s and early 1990s, surpassing pound net landings from 1994 to 2013. Since 2014, pound net landings have again surpassed gill net landings. Total commercial landings have averaged 1.7 million pounds over the past 10 years.

Figure 1
Southern flounder are harvested recreationally in North Carolina by hook and line, gig, and the recreational use of commercial gears such as gill nets, trawls, pots and seines (Figure 2). Flounder are among the most commonly targeted finfish species by recreational fishermen and the recreational fishery has a significant economic impact in North Carolina. Flounder are caught year round throughout the estuaries, inlets and nearshore ocean waters of the state with the majority of the harvest occurring in the summer and fall. Most of the recreational harvest occurs inshore; however, the ocean harvest on or near reefs is an important component of the fishery, especially for hook and line harvest. Average recreational catch of southern flounder for the past 10 years is 144,987 fish with an average of 844,934 fish being released.

Figure 2

Management

The division is responsible for the management of estuarine and marine resources occurring in all state coastal fishing waters extending to 3 miles offshore. The management unit includes southern flounder and its fisheries in North Carolina's coastal fishing waters. The commercial fishery has been managed through the use of size limits, gear restrictions, area closures, reporting requirements, mandatory scientific observer coverage and seasonal closures. The recreational fishery is managed through a combination of size limits, bag limits and seasons in both the inland and ocean fisheries.

A Southern Flounder Fishery Management Plan was developed by the division in February 2005. Amendment 1 to the plan was adopted in February 2013. Supplement A to Amendment 1, which is intended to reduce catch from the southern flounder fishery by up to 60 percent, was approved by the North Carolina Marine Fisheries Commission at its November 2015 business meeting. Approved management measures implemented Jan. 1, 2016 include an increase of the minimum size limit to 15 inches total length, an increase in minimum mesh size to 6 inches stretched mesh for the harvest of flounder and an increase in mesh size for the escape panels in flounder pound nets to 5.75 inches stretched mesh. Additional management measures were approved, but not enacted due to an injunction through the North Carolina court system. The additional management measures not implemented include a closure of the recreational harvest from Oct. 15 through Dec. 31, a closure of the commercial gig fishery once the pound net quota was met and a 38 percent reduction to the flounder pound net fishery based on the average of the 2011 to 2014 landings.

Stock Overview

  • Assessment: Yes
  • Terminal Year of Last Assessment: 2015
    • Overfishing: Yes
    • Overfished: Yes

A regional stock assessment that included partners from North Carolina, South Carolina, Georgia and Florida was peer reviewed in December of 2017 at a three day stock assessment review workshop where members of the stock assessment subcommittee reviewed the model inputs and results with a panel of four experts on southern flounder biology and/or stock assessment modeling. The multistate assessment was the first attempt to model southern flounder as one single unit stock. The assessment used a statistical catch at age model using the Age Structured Assessment Program. The Southern Flounder Review Panel accepted the pooled sex run of the model presented at the Review Workshop and the assessment was approved as a valid basis of management for at least the next five years, with the expectation that the model will be updated with data through 2017 to provide the best, most up to date, estimate of stock status for management. The reviewers also noted that management advice based on the 2015 terminal year would be out of date by the time it could be implemented and that expected changes to recreational catch estimates (Marine Recreational Information Program) should be incorporated into the assessment model. Results from the model indicate the southern flounder stock is overfished and overfishing is occurring in the terminal year of the assessment. Moving forward, the division's intent is to update the approved pooled sex model using data through 2017 with the expectation that the updated model be completed by the fall of 2018. The division also plans to include updated recreational estimates if they are available as scheduled in July. Several of the division's independent sampling programs collect biological data on southern flounder and were evaluated as indices of abundance in the recent stock assessment. The primary surveys that collect length data for southern flounder include: Estuarine Trawl Survey, Pamlico Sound Survey, Striped Bass Independent Gill Net Survey and the Pamlico Sound Independent Gill Net Survey.

Data collected by the Pamlico Sound Independent Gill Net Survey were used to create an index of general (juvenile and adult) abundance. The abundance index peaked in 2010 and the low point was in 2016 for the time series analyzed (2008 to 2017) and has an overall decreasing trend (Figure 3). Data collected by the Albemarle Sound Independent Gill Net Survey shows abundance peaked in 2008 and the low points were in 2011, 2016 and 2017 for the time series 2008 to 2017 (Figure 4). Data collected by the Estuarine Trawl Survey and the Pamlico Sound Survey were used to produce southern flounder juvenile abundance indices from 2008 to 2017. The index for the Estuarine Trawl Survey peaked in 2010 and the low point was in 2016 for the time series 2008 to 2017 and shows a declining trend (Figure 5). The juvenile index for the Pamlico Sound Survey peaked in 2017 and the low point was in 2011 for the time series 2008 to 2017 and has been highly variable without a trend (Figure 5).
Figure 3
Figure 4

Figure 5

Research Needs

Research needs include determining discard and discard mortality estimates for commercial pound net and recreational and commercial gig fisheries, identifying migration patterns and rates, identifying offshore spawning locations, determining species composition of recreationally released flounder, developing fishery independent ocean surveys, expanding age data collection from commercial and recreational fisheries, validating mail survey estimates of recreational gigging using dockside surveys and expanding inshore independent gill net surveys.

Links

Management Agencies

North Carolina Division of Marine Fisheries

Fishery Management Plans Amendments, Revisions and Supplements

North Carolina Fishery Management Plan

Contacts

For more information, contact Michael S. Loeffler at Michael.Loeffler@ncdenr.gov or 252-264-3911
Southern flounder
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N.C. Division of Marine Fisheries • 3441 Arendell Street • Morehead City, NC 28557 • 252-726-7021 or 800-682-2632

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