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 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

NEFSC Survey Strata Map for Red and Silver hake

Northern Strata:20-30, 36-40Missing strata in 2018 Str. 30 (3% stock Area)

Southern Strata:01-19, 61-76Missing Strata in 2017Str. 1-12 and 61-76 (75% stock Area)

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

Surv

ey W

eigh

t (Kg

/tow

)

Year

North

3-yr. avgTarget (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 SpringSurveyTarget(1.01kg/tow)

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

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

Surv

ey W

eigh

t (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

Northern Red hake: Size Composition 2010-2019

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Mean3-21cm 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.

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

Surv

ey W

eigh

t (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

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

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.

Silver hake – Last survey update (2017)

0

5

10

15

20

25

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

Surv

ey W

eigh

t (Kg

/tow

)

Year

NorthAnnual3 yr Avg. fFall surveyTarget (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 surveyTarget (1.65 kg/tow)Threshold (0.825 kg/tow)Annual

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

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

[(Al

l Str

ata)

/(Al

l str

ata-

Str3

0)]

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

Northern Silver Hake –Relative Contribution of Stratum 30

1967

1968

1969

1976

19962014

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

[(Al

l Str

ata)

/(Al

l str

ata-

Str3

0)]

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

0

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

Expa

nded

Cat

ch W

eigh

ts (k

g)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%

0

5

10

15

20

25

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

2016

2018

Surv

ey W

eigh

t (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/tow2018_unad 13.252018_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

Northern Silver hake: Size Composition 2009-2018

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Mean1-20cm 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.

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

Southern Silver hakeRelative 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

[(Al

l Str

ata)

/(Al

l str

ata

-Miss

ing

stra

ta)]

Fall Survey(Expanded catch in weight All Strata)/

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

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

[(Al

l Str

ata)

/(Al

l str

ata-

Str3

0)]

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

Southern Silver hake

0

20,000

40,000

60,000

80,000

100,000

120,000

140,00019

67

1969

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

2009

2011

2013

2015

Expa

nded

Cat

ch W

eigh

ts (k

g)

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.

Southern Silver hake

y = 0.7876x + 45346R² = 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 S

trat

a

All Strata-Missing Strata

All Strata vs All Strata Excl. Missing Strata

Expanded Catch Wts 1967-2016

Southern Silver hake

y = 3.1513x - 1054.5R² = 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 S

trat

a

All Strata-Missing Strata

All Strata vs All Strata Excl. Missing Strata

Expanded Catch wts2009-2016

0.0

1.0

2.0

3.0

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

2016

2018

Surv

ey W

eigh

t (Kg

/tow

)

Year

Annual3 yr average Fall biomassTarget (1.65 kg/tow)Threshold (0.825 kg/tow)Ratio - 3yr avgRegression - 3yr avg.

Southern Silver hake: Survey update through 2018

Southern Silver hake: Size Composition 2009-2018

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.