WITCH FLOUNDER 2012 Assessment Update Report
WITCH FLOUNDER
2012 Assessment Update Report
U.S. Department of Commerce National Oceanic and Atmospheric Administration National Marine Fisheries Service Northeast Fisheries Science Center Woods Hole, Massachusetts
Submitted January 2015
This assessment of the witch flounder (Glyptocephalus cynoglossus) stock is an update of the existing 2008 benchmark assessment (NEFSC 2008). This assessment updates commercial fishery catch data, research survey indices of abundance, and the analytical assessment models through 2010. Additionally, stock projections have been updated through 2017. Reference points have been updated. State of Stock: witch flounder (Glyptocephalus cynoglossus) stock is overfished and overfishing is occurring (Figures 1-2). Spawning stock biomass (SSB) in 2010 was estimated to be 4,099 (mt) which is 41% of the SSBM SY proxy (10,051; Figure 1). The 2010 fully selected fishing mortality was estimated to be 0.47 which is 174% of the FM SY proxy (0.27; Figure 2). Table 1: Catch and status table for witch flounder. All weights are in (mt) recruitment is in (000s). In this report, FF ull is defined as the average fishing mortality on ages 8 and 9 (unweighted). 2004 2005 2006 2007 Data Commercial Landings 2,917 2,652 1,863 1,076 Commercial Discards 309 150 87 97 Catch for Assessment 3,226 2,802 1,950 1,173 Model Results Spawning Stock Biomass 4,221 3,756 2,757 2,710 FF ull 0.93 0.84 0.85 0.52 Recruits (age 3) 5,106 3,702 4,521 12,438
2008 2009 2010 1,009 954 63 104 1,071 1,058
759 89 848
3,194 3,900 4,099 0.55 0.41 0.47 7,277 3,962 5,119
Table 2: Biological references points for witch flounder from the previous and current assessments are given. An F40% proxy was used for the overfishing threshold and biomass and catch proxies were based on long-term stochastic projections.
FM SY SSBM SY (mt) MSY (mt) Median recruits (age 3) (000s)
2008 0.20 11,447 2,352 11,947
Current 0.27 10,051 2,075 9,301
Projections: Short term projection recruitment was sampled from a cumulative distribution function derived from ADAPT VPA (with split time series between 1994 and 1995) estimated age 3 recruitment between 1982 and 2009. Average 2006-2010 partial recruitment, average 2006-2010 mean weights, and maturation ogive representing 2007-2011 maturities were used.
2012 Assessment Update of witch flounder Draft Working Paper for Peer Review Only 1
Table 3: Short term projections of total fishery yield and spawning stock biomass for witch flounder based a harvest scenario of fishing at 75% FM SY between 2012 and 2017. Projections assumed 2011 catches = 2010 catches; initial 2011 stock sizes for ages 3 to 11+. Year 2011 2012 2013 2014 2015 2016 2017
Catch (mt) 848 1207 1273 1465 1660 1909 1991
SSB (mt) 5212 5995 6819 7741 8719 9343 9653
FF ull 0.47 0.27 0.27 0.27 0.27 0.27 0.27
Special Comments: • Low frequency of samples across market category and quarter results in imprecise mean weights at age and estimates of numbers at age in some years. • Lack of data to support direct estimates of discards at age requires use of various surrogate survey-based methods. • The research bottom trawl survey catches very few witch flounder; in many years,the stratified mean number per tow of witch flounder is less than 5 fish. Abundance of witch flounder in the late 1980’s and early 1990’s may have gone below levels that provide reliable estimates of trends in abundance and biomass. References: Wigley, S.E. and L. Col. 2008. In. Northeast Fisheries Science Center. 2008. Assessment of 19 Northeast Groundfish Stocks through 2007: Report of the 3rd Groundfish Assessment Review Meeting (GARM III), Northeast Fisheries Science Center, Woods Hole, Massachusetts, August 4-8, 2008. US Dep Commer, NOAA Fisheries, Northeast Fish Sci Cent Ref Doc. 08-15; 884 p + xvii. http://www.nefsc.noaa.gov/publications/crd/crd0815/
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Figure 1: Trends in spawning stock biomass of witch flounder between 1982 and 2010 from the current (solid line) and previous (dashed line) assessment and 1 the corresponding SSBthreshold ( SSBM SY ; horizontal dashed line) as well as 2 SSBtarget SSBM SY ; horizontal dotted line) based on the 2010 assessment.
2012 Assessment Update of witch flounder Draft Working Paper for Peer Review Only 3
Figure 2: Trends in the fully selected fishing mortality (FF ull ) of witch flounder between 1982 and 2010 from the current (solid line) and previous (dashed line) assessment and the corresponding Fthreshold (FM SY =0.27; horizontal dashed line) based on the 2010 assessment.
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Figure 3: Trends in Recruits (age 3) (000s) of witch flounder between 1982 and 2010 from the current (solid line) and previous (dashed line) assessment.
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Figure 4: Total catch of witch flounder between 1982 and 2010 by fleet (commercial) and disposition (landings and discards).
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Figure 5: Indices of biomass for the witch flounder between 1963 and 2011 for the Northeast Fisheries Science Center (NEFSC) spring and fall bottom trawl surveys. The 90% lognormal confidence intervals are shown.
2012 Assessment Update of witch flounder Draft Working Paper for Peer Review Only 7
2012 Assessment Update Report
U.S. Department of Commerce National Oceanic and Atmospheric Administration National Marine Fisheries Service Northeast Fisheries Science Center Woods Hole, Massachusetts
Submitted January 2015
This assessment of the witch flounder (Glyptocephalus cynoglossus) stock is an update of the existing 2008 benchmark assessment (NEFSC 2008). This assessment updates commercial fishery catch data, research survey indices of abundance, and the analytical assessment models through 2010. Additionally, stock projections have been updated through 2017. Reference points have been updated. State of Stock: witch flounder (Glyptocephalus cynoglossus) stock is overfished and overfishing is occurring (Figures 1-2). Spawning stock biomass (SSB) in 2010 was estimated to be 4,099 (mt) which is 41% of the SSBM SY proxy (10,051; Figure 1). The 2010 fully selected fishing mortality was estimated to be 0.47 which is 174% of the FM SY proxy (0.27; Figure 2). Table 1: Catch and status table for witch flounder. All weights are in (mt) recruitment is in (000s). In this report, FF ull is defined as the average fishing mortality on ages 8 and 9 (unweighted). 2004 2005 2006 2007 Data Commercial Landings 2,917 2,652 1,863 1,076 Commercial Discards 309 150 87 97 Catch for Assessment 3,226 2,802 1,950 1,173 Model Results Spawning Stock Biomass 4,221 3,756 2,757 2,710 FF ull 0.93 0.84 0.85 0.52 Recruits (age 3) 5,106 3,702 4,521 12,438
2008 2009 2010 1,009 954 63 104 1,071 1,058
759 89 848
3,194 3,900 4,099 0.55 0.41 0.47 7,277 3,962 5,119
Table 2: Biological references points for witch flounder from the previous and current assessments are given. An F40% proxy was used for the overfishing threshold and biomass and catch proxies were based on long-term stochastic projections.
FM SY SSBM SY (mt) MSY (mt) Median recruits (age 3) (000s)
2008 0.20 11,447 2,352 11,947
Current 0.27 10,051 2,075 9,301
Projections: Short term projection recruitment was sampled from a cumulative distribution function derived from ADAPT VPA (with split time series between 1994 and 1995) estimated age 3 recruitment between 1982 and 2009. Average 2006-2010 partial recruitment, average 2006-2010 mean weights, and maturation ogive representing 2007-2011 maturities were used.
2012 Assessment Update of witch flounder Draft Working Paper for Peer Review Only 1
Table 3: Short term projections of total fishery yield and spawning stock biomass for witch flounder based a harvest scenario of fishing at 75% FM SY between 2012 and 2017. Projections assumed 2011 catches = 2010 catches; initial 2011 stock sizes for ages 3 to 11+. Year 2011 2012 2013 2014 2015 2016 2017
Catch (mt) 848 1207 1273 1465 1660 1909 1991
SSB (mt) 5212 5995 6819 7741 8719 9343 9653
FF ull 0.47 0.27 0.27 0.27 0.27 0.27 0.27
Special Comments: • Low frequency of samples across market category and quarter results in imprecise mean weights at age and estimates of numbers at age in some years. • Lack of data to support direct estimates of discards at age requires use of various surrogate survey-based methods. • The research bottom trawl survey catches very few witch flounder; in many years,the stratified mean number per tow of witch flounder is less than 5 fish. Abundance of witch flounder in the late 1980’s and early 1990’s may have gone below levels that provide reliable estimates of trends in abundance and biomass. References: Wigley, S.E. and L. Col. 2008. In. Northeast Fisheries Science Center. 2008. Assessment of 19 Northeast Groundfish Stocks through 2007: Report of the 3rd Groundfish Assessment Review Meeting (GARM III), Northeast Fisheries Science Center, Woods Hole, Massachusetts, August 4-8, 2008. US Dep Commer, NOAA Fisheries, Northeast Fish Sci Cent Ref Doc. 08-15; 884 p + xvii. http://www.nefsc.noaa.gov/publications/crd/crd0815/
2012 Assessment Update of witch flounder Draft Working Paper for Peer Review Only 2
Figure 1: Trends in spawning stock biomass of witch flounder between 1982 and 2010 from the current (solid line) and previous (dashed line) assessment and 1 the corresponding SSBthreshold ( SSBM SY ; horizontal dashed line) as well as 2 SSBtarget SSBM SY ; horizontal dotted line) based on the 2010 assessment.
2012 Assessment Update of witch flounder Draft Working Paper for Peer Review Only 3
Figure 2: Trends in the fully selected fishing mortality (FF ull ) of witch flounder between 1982 and 2010 from the current (solid line) and previous (dashed line) assessment and the corresponding Fthreshold (FM SY =0.27; horizontal dashed line) based on the 2010 assessment.
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Figure 3: Trends in Recruits (age 3) (000s) of witch flounder between 1982 and 2010 from the current (solid line) and previous (dashed line) assessment.
2012 Assessment Update of witch flounder Draft Working Paper for Peer Review Only 5
Figure 4: Total catch of witch flounder between 1982 and 2010 by fleet (commercial) and disposition (landings and discards).
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Figure 5: Indices of biomass for the witch flounder between 1963 and 2011 for the Northeast Fisheries Science Center (NEFSC) spring and fall bottom trawl surveys. The 90% lognormal confidence intervals are shown.
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