Analysis of ancillary survey data and surfclam fishery tow data for ...
Updated Survey Indices for Silver and Red hake through 2019...Survey Weight (Kg/tow) Year North...
Transcript of Updated Survey Indices for Silver and Red hake through 2019...Survey Weight (Kg/tow) Year North...
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.