Updated Survey Indices for Silver and Red hake through 2019 - - PowerPoint PPT Presentation

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Updated Survey Indices for Silver and Red hake through 2019 - - PowerPoint PPT Presentation

Apr 18, 2023 49 likes •305 views

Updated Survey Indices for Silver and Red hake through 2019 Background Relative index for the small mesh groundfish stocks are based on the seasonal NEFSC aggregate survey stratified catch weights Following the accepted approach from

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Updated Survey Indices for Silver and Red hake through 2019

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Background

  • Relative index for the small mesh groundfish stocks are based on the

seasonal NEFSC aggregate survey stratified catch weights

  • Following the accepted approach from SARC 51, a three year moving

average is applied to the annual indices and used for stock status determination

  • Silver hake is based on the NEFSC fall survey biomass
  • Red hake is based on the NEFSC spring survey biomass
  • Survey indices for both red and silver hake were last updated in 2017
  • Fall 2017: Reduced Survey coverage (No coverage in SNE and MA).
  • Missing strata in Fall 2018 – Imputed
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NEFSC Survey Strata Map for Red and Silver hake

Northern Strata: 20-30, 36-40 Missing strata in 2018

  • Str. 30 (3% stock Area)

Southern Strata: 01-19, 61-76 Missing Strata in 2017

  • Str. 1-12 and 61-76 (75% stock Area)
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Red hake: Last Assessment update (2017)

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016

Survey Weight (Kg/tow) Year

North

3-yr. avg Target (2.53kg/tow) Threshold (1.27kg/tow) Annual

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016

Year

South

3-yr Avg Spring Survey Target (1.01kg/tow)

51% below threshold > 3 times the threshold% above threshold

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Northern Red hake: Survey update through 2019

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018

Survey Weight (Kg/tow) Year

North

Annual 3yr Avg. Fall Survey Target (2.53kg/tow) Threshold (1.27kg/tow)

  • 43% Decline in 2019

annual index from 5.3kg/tow to 3.0kg/tow

  • 3 Yr mean continues

to decline. From 5.1 kg/tow to 4.3 kg/tow

  • Remains above target

and threshold

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Northern Red hake: Size Composition 2010-2019

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Mean 3-21cm 1.81 0.84 1.04 3.40 10.56 1.59 3.06 2.43 2.03 3.50 3.02 % from Prev Yr

  • 53%

23% 228% 210%

  • 85%

93% -21% -16% 73%

Recruitment (3-20cm)

  • Average and below

average recruitment from 2016-2018 explains the 2019 decline

  • Above average

2019 year class.

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SLIDE 7

Southern Red hake: Survey update through 2019

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018

Survey Weight (Kg/tow) Year

South

Annual 3 yr Avg. Spring Survey Target (1.01kg/tow) Threshold (0.51kg/tow)

  • Three year average

increased by 41% form 0.27kg/to 0.38kg/tow

  • Stock biomass remains

below the threshold

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Southern Red hake: Size Composition 2010-2019

Recruitment (1-20cm)

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Mean 1-21 cm 1.65 0.46 1.56 0.39 0.79 0.36 0.69 0.39 0.64 2.35 0.93 % from Prev Yr

  • 72% 241% -75%

103% -55% 91% -44% 67% 265%

  • Above average

recruitment in 2019

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Red hake

  • Three year mean of the spring survey continues to decline in the

north but still well above the target and threshold

  • In the south, the 3 yr average increased in 2019, owing to the above

average incoming year class. However the stock still remains below the threshold.

  • There appears to be an above average incoming year class in 2019 in

both the North and South.

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Silver hake – Last survey update (2017)

5 10 15 20 25 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

Survey Weight (Kg/tow) Year

North

Annual 3 yr Avg. fFall survey Target (6.42 kg/tow) Threshold (3.21 kg/tow)

0.0 1.0 2.0 3.0 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

Year

South

3 yr Avg. fFall survey Target (1.65 kg/tow) Threshold (0.825 kg/tow) Annual

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Northern Silver Hake – Stratum 30

  • In Fall of 2018, the survey did not cover stratum 30
  • Applied the Ratio approach to develop a raising factor to impute

missing stratum 30

  • Raising factor was based on the Bigelow fall survey for years 2009-2017
  • Stratum 30 only constitute of 3% of the total stock Area (NE Geo.Bank)
  • Time Series average contribution of Stratum 30 by weight ~3%
  • Imputation had miniscule effect
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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003 2007 2011 2015

Ratio [(All Strata)/(All strata-Str30)]

Fall Survey

(Expanded catch in weight All Strata)/(Expanded Catch in Weight w/out Stratum 30)

Northern Silver Hake – Relative Contribution of Stratum 30

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1967 1968 1969 1976 1996 2014

0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 0.0 1.5 3.0 4.5 6.0 7.5 9.0 10.5 12.0 13.5 15.0 16.5 18.0 19.5 21.0 22.5 24.0 25.5

Ratio [(All Strata)/(All strata-Str30)]

Biomass (weight /tow) Heterogeniety in the pattern of biomass vs. "contribution" from Stratum 30

Does stratum 30 depend on biomass. i.e. increase or decrease at low or high stock? No Strong pattern

Northern Silver hake

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100,000 200,000 300,000 400,000 500,000 600,000

1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017

Expanded Catch Weights (kg)

Fall Survey Expanded Catch in Weight

Stratum 30 All Strata W/out Stratum 30

Northern Silver hake

1963 – 2017 : TS average contribution of stratum 30 ~ 3% 2009 – 2017: also ~ 3%

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5 10 15 20 25 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018

Survey Weight (Kg/tow) Year Annual 3 yr Avg. Fall Survey Target (6.42 kg/tow) Threshold (3.21 kg/tow) 2018_adj.

Northern Silver hake: Survey update through 2019

Year kg/tow 2018_unad 13.25 2018_adj 13.15 Imputing is inconsequential for the northern stock. 38% decline in the survey biomass since 2016 from 21.5kg/tow to 13.25kg/tow Three year mean also has declined in the recent three years but is still 5 times above the thresholds

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Northern Silver hake: Size Composition 2009-2018

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Mean 1-20cm 60.31 51.26 44.18 61.92 65.08 53.36 70.61 61.86 82.93 87.55 63.91 % from Prev Yr

  • 15%
  • 14%

40% 5%

  • 18%

32%

  • 12%

34% 6%

Recruitment (1-20cm) Above recruitment average in 2016-2017.

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Southern Silver Hake – Fall 2017

  • No Coverage in SNE and MA region
  • Seven of 35 survey strata was covered and only in the S.Geo.Bank region
  • Missing strata 1-12 and 61-76 constitute 75% of the total Mgt. Area
  • On average (1967-2016), these missing strata contribute to 72% of total

catch for the Mgt. area

  • Imputation of fall survey 2017 value is likely going to be unreliable owing to

a significant fraction of missing strata from the Mgt. Area.

  • An alternative approach is to treat fall survey 2017 as a missing value
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Southern Silver hake Relative Contribution of Strata 1-12 & 61-76

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

1967 1971 1975 1979 1983 1987 1991 1995 1999 2003 2007 2011 2015

Ratio [(All Strata)/(All strata - Missing strata)]

Fall Survey

(Expanded catch in weight All Strata)/ (Expanded Catch in Weight w/out Missing Strata:1-12 and 61-76.)

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Southern Silver hake

1979 1985 1999 2009 2010 2011 2012 2013 2014 2015 2016

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Ratio [(All Strata)/(All strata-Str30)]

Heterogeniety in pattern of biomass vs. "contribution" from Missing strata (1-12, 61-76)

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Southern Silver hake

20,000 40,000 60,000 80,000 100,000 120,000 140,000

1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015

Expanded Catch Weights (kg) Fall Survey Expanded Catch in Weight Missing Strata 1-12 and 61-76 All Strata W/out Mising Strata

On average missing strata constitute 65- 72% by weight.

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Southern Silver hake

y = 0.7876x + 45346 R² = 0.0534

0.00 20,000.00 40,000.00 60,000.00 80,000.00 100,000.00 120,000.00 140,000.00 0.0 5000.0 10000.0 15000.0 20000.0 25000.0 30000.0 35000.0

All Strata All Strata-Missing Strata

All Strata vs All Strata Excl. Missing Strata Expanded Catch Wts 1967-2016

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Southern Silver hake

y = 3.1513x - 1054.5 R² = 0.4318

0.00 20,000.00 40,000.00 60,000.00 80,000.00 100,000.00 120,000.00 0.0 5000.0 10000.0 15000.0 20000.0 25000.0 30000.0

All Strata All Strata-Missing Strata

All Strata vs All Strata Excl. Missing Strata

Expanded Catch wts 2009-2016

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0.0 1.0 2.0 3.0 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018

Survey Weight (Kg/tow) Year Annual 3 yr average Fall biomass Target (1.65 kg/tow) Threshold (0.825 kg/tow) Ratio - 3yr avg Regression - 3yr avg.

Southern Silver hake: Survey update through 2018

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Southern Silver hake: Size Composition 2009-2018

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Silver hake Summary

  • Northern Silver: Influence of stratum 30 is miniscule and inconsequential

to the scaling of the survey and biomass stock status determination. Imputation is not necessary.

  • Stock declined in recent three years but remains above the biomass

threshold and target.

  • Southern Silver: Large proportion of strata missing in 2017. Missing strata

constitute a large proportion of the total catch in the southern management area. Suggest to treat 2017 as a missing value given the limited coverage and available data to conduct a reliable imputation.

  • Recent survey estimates (2016 and 2018) show a general increase since
  • 2015. Three year average remains about the threshold but below the

target.