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Stock Assessment for Central Southern Management Area (CSMA) Striped Bass Stocks
Marine Fisheries Commission Business Meeting
February 11, 2011
Overview
• Available Data• Methods• Results• Conclusions• Research Recommendations
Assessment Review
• Internal Review• External Peer Review
Available Data• Fishery-independent
– NCWRC Spawning Grounds Surveys• Catch rates• Scales (Tar River)
– NCDMF Program 915• Catch rates
Available Data
• Fishery-dependent– Trip ticket program (landings)– Creel survey– Biological samples not used (too few
samples)
Data Limitations• The input data limitations for these
analyses are twofold: – Limitations inherent in the surveys
collecting the data• Examples: Lack of defined spawning areas,
use of multispecies survey
– Analytical limitations resulting from data that are not complete or that were not collected• Examples: Incomplete age data by system, lack
of system specific life history parameters
Methods
• Despite data limitations, multiple methods were applied to attempt to determine stock status– Trend analysis– Catch curves
• Ultimately, none of the methods were able to determine stock status reliably
Trend Analysis• Catch-per-unit-effort (CPUE)
– NCWRC Spawning Grounds Survey: number of striped bass collected per hour of sampling effort
– NCDMF Program 915: number of striped bass collected per 160 sets in a year (12 hr net set of 240 yds)
• Examined CPUE by age (cohort) over time
CPUE Ages 3 to 6 Neuse River-Spawning Grounds, 1994-2009
CPUE = number of fish per electrofishing hr
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
CP
UE
Year
Age-3 Age-4 Age-5 Age-6
CPUE Ages 3 to 6 Neuse River-Program 915, 2003-2009
CPUE = number of fish in 160 gill net sets
0
20
40
60
80
100
120
140
2003 2004 2005 2006 2007 2008 2009
Ca
tch
wit
h U
nif
orm
Eff
ort
(N
um
be
rs o
f Fis
h)
Year
Age-3 Age-4 Age-5 Age-6
CPUE Ages 3 to 7 Tar/Pamlico River-Spawning Grounds, 1996-2009
CPUE = number of fish per electrofishing hr
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
CP
UE
Year
Age-3 Age-4 Age-5 Age-6 Age-7
CPUE Ages 3 to 7 Tar/Pamlico River-Program 915, 2003-2009
CPUE = number of fish in 160 gill net sets
0
50
100
150
200
250
2003 2004 2005 2006 2007 2008 2009
Ca
tch
for
Un
ifo
rm E
ffo
rt (
Nu
mb
ers
of F
ish
)
Year
Age-3 Age-4 Age-5 Age-6 Age-7
Catch Curves• Used to estimate mortality from catch or
survey age data• Total mortality (Z) is the sum of fishing
(F) and natural (M) mortality
Z = F + M
Catch Curves
-6
-4
-2
0
2
4
6
8
0 2 4 6 8 10 12
ln C
PUE
Age
Used Unused Linear (Used)
Annual Total Mortality (Z) Neuse River-Spawning Grounds
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
Tota
l Mo
rta
lity
Year
Z Lower CI Upper CI
Annual Total Mortality (Z) Neuse River-Program 915
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
2003 2004 2005 2006 2007 2008 2009
Tota
l Mo
rta
lity
Year
Z Lower CI Upper CI
Annual Total Mortality (Z) Tar/Pamlico River-Spawning Grounds
-0.50
0.00
0.50
1.00
1.50
2.00
2.50
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
Tota
l Mo
rta
lity
Year
Z Lower CI Upper CI
Annual Total Mortality (Z) Tar/Pamlico River-Program 915
0.00
0.50
1.00
1.50
2.00
2.50
2003 2004 2005 2006 2007 2008 2009
Tota
l Mo
rta
lity
Year
Z Lower CI Upper CI
Size Distribution
• Changes in length and age distribution can be indicative of stock trends– Expanding distribution rebuilding– Truncated distribution declining
Neuse River Commercial Length Frequency
0%
5%
10%
15%
20%
25%
30%
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46
Pe
rce
nt
at
Le
ng
th
Length (inches)
1997-2002 2003-2009 Sample Sizes1997-2002: 602003-2009: 424
Neuse River Spawning Grounds Survey Length Frequency
0%
5%
10%
15%
20%
25%
30%
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46
Pe
rce
nt
at
Le
ng
th
Length (inches)
1994-2004 2003-2009 Sample Sizes1994-2002: 1,8392003-2009: 1,362
Neuse River Program 915 Length Frequency
0%
5%
10%
15%
20%
25%
30%
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 39 41 43 45 47
Pe
rce
nt
at
Le
ng
th
Length (inches)
Sample Size1,559
Pamlico River Commercial Length Frequency
0%
5%
10%
15%
20%
25%
30%
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46
Pe
rce
nt
at
Le
ng
th
Length (inches)
1995-2002 2003-2009 Sample Sizes1995-2002: 7972003-2009: 803
Tar/Pamlico River Spawning Grounds Survey Length Frequency
0%
5%
10%
15%
20%
25%
30%
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46
Pe
rce
nt
at
Le
ng
th
Length (inches)
1996-2002 2003-2009 Sample Sizes1996-2002: 4,6732003-2009: 3,657
Pamlico River Program 915 Length Frequency
0%
5%
10%
15%
20%
25%
30%
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 39 41 43 45 47
Pe
rce
nt
at
Le
ng
th
Length (inches)
Sample Sizes2,055
Conclusions• Total mortality (Z) estimates vary
without trend providing little information for stock status determination
• Length distributions provide no substantial evidence of a viable stock
• The size and age distributions, low abundance, and the absence of older fish support continued management efforts to promote enhancement of the striped bass fisheries in each system
Research Recommendations• Since the 2004 FMP, significant efforts
were made to fill CSMA data gaps, but critical data are still needed– Life history parameters– Additional fishery-dependent data– Improved fishery-independent data
• Above data necessary to perform a reliable, quantitative assessment – Funding and staff needed to collect needed
data