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