Status of Fishery Resources off the Northeastern US
NEFSC - Resource Evaluation and Assessment Division


August 2010

Summer flounder

Summer flounder (Paralichthys dentatus)

by Mark Terceiro

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Figure 8.1 Statistical areas used to define the summer flounder stock.
Figure 8.1 Statistical Areas Used
Distribution, Biology and Management

The summer flounder or fluke, Paralichthys dentatus, is a demersal flatfish distributed from the southern Gulf of Maine to South Carolina. Important commercial and recreational fisheries exist from Cape Cod, Massachusetts to Cape Hatteras, North Carolina. The resource is managed as a unit stock from North Carolina to Maine (Figure 8.1). Summer flounder are concentrated in bays and estuaries from late spring through early autumn, when an offshore migration to the outer continental shelf is undertaken. Spawning occurs during autumn and early winter, and the larvae are transported toward coastal areas by prevailing water currents. Development of post larvae and juveniles occurs primarily within bays and estuarine areas, notably Pamlico Sound and Chesapeake Bay (Packer et al. 1999). Most fish are sexually mature by age 2 (O’Brien et al. 1993). Female summer flounder live to at least 14 years, and males to at least 12 years (NEFSC 2008). Growth rates differ appreciably between the sexes with females reported to have attained lengths to 97 cm (38 inches) and weights to 11.0 kg (24.3 lb).

U.S. commercial and recreational fisheries for summer flounder are managed under the Summer Flounder, Scup and Black Sea Bass Fishery Management Plan (FMP) administered jointly by the Atlantic States Marine Fisheries Commission (ASMFC) and the Mid-Atlantic Fishery Management Council (MAFMC). Amendment 2 to the Summer Flounder FMP implemented several major regulatory provisions, including annual commercial quotas, recreational harvest limits, a commercial vessel permit moratorium, minimum fish size and gear restrictions, and a recreational fishery possession limit. The threshold fishing mortality reference point of FMSY is defined to be F35% = 0.310, and the target and threshold spawning stock biomass (SSB) reference points are estimated to be 60,074 mt and 30,037 mt, respectively (NEFSC 2008).
The Fishery

Total combined commercial and recreational landings peaked at 26,100 mt in 1983, averaged 9,600 mt annually during 1990 1999, and have since ranged between 7,700 mt (in 2008-2009) and 13,000 mt (in 2004) (Table 8.1). The principal gear used in commercial fishing for summer flounder is the otter trawl. After peaking at 17,900 mt in 1979, commercial landings of summer flounder averaged 5,700 mt annually during 1990 1999, and ranged between 4,100 mt and 8,200 mt during 2000-2009 (Figure 8.2 [Fig 8.2 Data]). The recreational rod-and-reel fishery for summer flounder harvests a significant proportion of the total catch, and in some years recreational landings have exceeded commercial landings. After peaking at 12,700 mt in 1983, recreational landings of summer flounder averaged 3,900 mt annually during 1990-1999, and ranged between 2,900 mt and 7,500 mt during 2000-2009.

Summer flounder total catch in numbers historically was dominated by age 0 to age 2 fish (Figure 8.3 [Fig 8.3 Data]). The proportion of ages 0 and 1 summer flounder in the commercial and recreational catch has been greatly reduced since the mid 1990s, and the catch currently consists mainly of age 2 and older fish.

Research Vessel Survey Indices

NEFSC spring and autumn biomass indices for summer flounder have exhibited similar trends throughout the survey time series (Figure 8.4 [Fig 8.4 Data]). Biomass indices declined through the late 1970s into the early 1990s, but increased during the early 1990s and are currently at about the level of the mid-1970s. As stock biomass declined in the 1980s, the age structure of the summer flounder population became truncated, with a low proportion of fish at ages 3 and older (Figure 8.5 [Fig 8.5 Data]). Since 1990, the age structure of the population has expanded to approximate that observed in the mid-1970s.

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Figure 8.2.  Total commercian landings of summer flounder. Figure 8.2

Figure 8.3.  Age structure of the summer flounder catch.
Figure 8.3

Figure 8.4.  Biomass indices for summer flounder NEFSC from NEFSC research vessel surveys.Figure 8.4

Figure 8.5.  Age 1+ structure of the summer flounder population.
Figure 8.5


Figure 8.6.  Trends in catch and fishing mortality for summer flounder.Figure 8.6

Figure 8.7.  Trends in recruitment and SSB for summer flounder.
Figure 8.7

Figure 8.8.  Yield and SSB per recruit results for summer flounder.
Figure 8.8

Figure 8.9. Spawning stock-recruitment for summer flounder.Figure 8.9

Figure 8.10.  STrends in survival ratios for summer flounder.Figure 8.10

Assessment Results

Average fishing mortality (F, ages 3-7+) ranged between 1.10 to 2.00 during the 1980s and mid 1990s, but has declined to below 1.00 since 1997 and was 0.24 in 2009 (Figure 8.6 [Fig 8.6 Data]). SSB declined from 24,651 mt in 1983 to 7,018 mt in 1989, but with improved recruitment and decreased fishing mortality increased to 53,458 mt by 2009 (Figure 8.7 [Fig 8.7 Data]). Since 1982, recruitment at age 0 has ranged from 13 million fish (1988) to 82 million fish (2009 year class) (Figure 8.7 [Fig 8.7 Data]). Average recruitment was 42 million fish during 1982-2009 (Terceiro 2010).

Biological Reference Points

Biological reference points for summer flounder (Figure 8.8 [Fig 8.8 Data]) were updated in 2008 (NEFSC 2008) and are presented in Table 8.2. The relationship between SSB and recruitment for summer flounder for the 1983-2009 year classes is illustrated in (Figure 8.9 [Fig 8.9 Data]). The stock-recruitment trajectory indicates that recent levels of SSB and recruitment are on the far-right side of the plot. Survival ratios, recruits per unit of spawning biomass (Figure 8.10 [Fig 8.10 Data]), illustrate stabilization of the survival rate of recent year classes at the current level of the spawning stock.


Summer flounder SSB increased substantially from 7,100 mt in 1989 to 53,458 mt in 2009, above the biomass threshold of ½ BMSY. Fully recruited fishing mortality was estimated to be 0.237 in 2009, below the fishing mortality threshold of FMSY = F35% = 0.310. Thus, the stock was not overfished and overfishing was not occurring in 2009 (Terceiro 2010).


Old lineart drawing

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Table 8.1 Recreational and commercial landings of summer flounder (thousand metric tons).

1990-99 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
 US recreational 3.9 7.5 5.3 3.6 5.3 4.8 4.7 5.0 4.4 3.6 2.9
       US 5.7 5.1 5.0 6.6 6.5 8.2 7.8 6.3 4.5 4.1 4.8
       Canada 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
       Other - - - - - - - - - - -
 Total nominal landings 9.6 12.6 10.3 10.2 11.8 13.0 12.5 11.3 8.9 7.7 7.7








Table 8.2 Biological reference points for summer flounder.

 Biological reference points
 FMSY = F35% = 0.310
 MSY  = Y35% = 13,122 mt
 BMSY = SSB35% = 60,074 mt


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For further information

NEFSC. 2008. 47th Northeast Regional Stock Assessment Workshop (47th SAW) Assessment Summary Report. Northeast Fisheries Science Center Reference Document 08-11. 22p.

O’Brien, L., J. Burnett, and R.K. Mayo. 1993. Maturation of nineteen species of finfish off the northeast coast of the United States, 1985-1990. NOAA Tech. Report. NMFS 113, 66 p.

Packer, D.B., S.J. Griesbach, P.L. Berrien, C.A. Zetlin, D.L. Johnson, and W.W. Morse. Essential fish habitat source document: summer flounder, (Paralichthys dentatus), life history and habitat characteristics. NOAA Tech. Mem. NMFS-NE-151, 88 p.

Terceiro, M. 2010. Stock assessment of summer flounder for 2010. Northeast Fisheries Science Center Reference Document 10-14. 133 p.

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