comparative selectivity on length at maturity among alaskan sockeye salmon fisheries neala kendall...
TRANSCRIPT
Comparative selectivity on length at maturity among Alaskan sockeye
salmon fisheries
Neala KendallTom Quinn
School of Aquatic and Fishery SciencesUniversity of Washington
Seattle, WA, USA
M. Bond
Need for evaluating harvest selection
Life history traits are changing over time (Darimont et al. 2009 PNAS)
Need for quantifying harvest selection
Life history traits are changing over time (Darimont et al. 2009 PNAS)
Importance of quantifying harvest selection (Carlson et al. 2007 Ecology Letters, Edeline et al. 2007 PNAS)
Need for quantifying harvest selection
Life history traits are changing over time (Darimont et al. 2009 PNAS)
Importance of quantifying harvest selection (Carlson et al. 2007 Ecology Letters, Edeline et al. 2007 PNAS)
Evaluating implications of selection (Olsen et al. 2004 Nature, Heino and GodØ 2002 Bulletin of Marine Science)
Difficult to quantify fishery selection
Hutchings, Nature 2005
Fish caught
Length
Fishery selectivity curve
?
Alaska salmon: good model to study fishery selection
Semelparous Anadromous Length and age at maturity
easy to measure Know population size and
structure Long-term gillnet fisheries Large, long term data set
J. Carter
Research questions
Does fishery selection vary by fish length and sex?
J. Carter
Research questions
Does fishery selection vary by fish length and sex?
Are fish length at age changes over time correlated with fishery selection?
J. Carter
Alaska sockeye salmon fisheries
Bristol Bay
Upper Cook Inlet
Alaska
Methods
Yearly historical fishery reconstruction
Characterize annual length distributions in catch, escapement (not caught), and total run
Estimate:
1) Length-specific vulnerability
2) Selection differentials
Length frequency histogram example
Females
Males
-
100,000
200,000
300,000
450 500 550 600 650
Length (mm)
Num
ber o
f fis
h
Total run
Catch
Escapement
-
100,000
200,000
300,000
400,000
400 450 500 550 600 650
Length (mm)
Nu
mb
er
of f
ish
Total runCatchEscapement
Vulnerability profiles by length
Females
Males
199000
.20
.40
.60
.81
400 450 500 550 600 650
Upper Cook Inlet males
Body length (mm)
Vu
lne
rab
ility
1994
Body length (mm)
Vu
lne
rab
ility
1999
400 450 500 550 600 650
Body length (mm)
Vu
lne
rab
ility
2002
Body length (mm)
Vu
lne
rab
ility
2003 00
.20
.40
.60
.81
400 450 500 550 600 650
Body length (mm)
Vu
lne
rab
ility
199000.2
0.40.6
0.81
400 450 500 550 600 650
Upper Cook Inlet males
Body length (mm)
Vulnerability
1994
Body length (mm)
Vulnerability
1999
400 450 500 550 600 650
Body length (mm)
Vulnerability
2002
Body length (mm)
Vulnerability
2003 00.2
0.40.6
0.81
400 450 500 550 600 650
Body length (mm)
Vulnerability
1990 1994 1999 2002 2003
400 650 400 650 400 6500
10
1
Selection on length: SSDs
SSD
Larger fish are escaping to
spawn than are getting caught
+-
Smaller fish are escaping to
spawn than are getting caught
Standardized selection differential =
lengthescapement – lengthtotal run
std. deviation of lengthtotal run
0
0.1
0.2
0.3
-0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6
Standardized selection differential
Pro
po
rtio
n f
req
ue
nc
y
Male
Female
J. Carter
Female SSDs more consistently negative than male SSDs
Female average
Male average
Fishery selection on Bristol Bay sockeye salmon and length at age changes over time
Differential fishery selection on ocean age 2 fish
Pro
po
rtio
n f
req
ue
nc
y
Pro
po
rtio
n f
req
ue
nc
y
Standardized selection differential
Standardized selection differential
Nushagak
0.0
0.1
0.2
0.3
0.4Male
Fem ale
Naknek-Kvichak
0.0
0.1
0.2
0.3
0.4
Egegik
0.0
0.1
0.2
0.3
0.4
-0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4
Ugashik
0.0
0.1
0.2
0.3
0.4
Togiak
0.0
0.1
0.2
0.3
0.4
-0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4
P < 0.001P = 0.143
0.0
0.1
0.2
0.3
0.4Male
Fem ale
0.0
0.1
0.2
0.3
0.4Male
Fem ale
0.0
0.1
0.2
0.3
0.4Male
Fem ale
0.0
0.1
0.2
0.3
0.4Male
Fem ale
P < 0.001P < 0.001
P < 0.001P = 0.002
P < 0.001
P = 0.051
P = 0.010P = 0.756
Nushagak
Naknek-Kvichak
Egegik
Ugashik
Togiak
Nushagak
Naknek-Kvichak
Ugashik
Togiak
1960 1970 1980 1990 2000 2010Year
NushagakMale
Female
Naknek-Kvichak
Egegik
1960 1970 1980 1990 2000 2010Year
Average length of ocean age 2 fish has decreased over time
Ave
rag
e le
ng
th (
mm
)
slope=-0.60
slope=-0.64
slope=-0.26
slope=-0.31
slope=-0.16
slope=-0.05slope=-0.19
slope=-0.21
slope=-0.16
slope=-0.21
450
550
450
550
Ave
rag
e le
ng
th (
mm
)
450
550
450
550
Egegik
Ugashik
Togiak
Nushagak
Naknek-Kvichak
slope: P = 0.003
slope: P = 0.033
slope: P = 0.005
slope: P = 0.218
slope: P = 0.869
SSDs somewhat correlated with decreasing length at age over time
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
-0.20 -0.15 -0.10 -0.05 0.00
Standardized selection differential
Slo
pe
of
oc
ea
n a
ge
2
len
gth
ov
er
tim
e
Conclusions
Are larger than average fish more vulnerable to being caught?
YESFish caught
ConclusionsConclusions
Males
Does the fishery harvest different lengths of males than females?
YES
Length
Females
Conclusions
Are fish length at age changes over time correlated with fishery selection?
YES Fishing districts that harvest
larger fish show a greater decline in fish length at age
over time
Conclusions
Mary Beth Loewen and Matt Foster, ADFG Mark Willette and Terri Tobias, ADFG Tim Baker, ADFG Jeff Hard, NOAA Fisheries Alaska Salmon Program, UW Funding:
School of Aquatic and Fishery Sciences Alaska Sustainable Salmon Fund National Science Foundation Gordon and Betty Moore Foundation
Acknowledgements
J. Bennis J. Carter
Bristol Bay—100% gillnets
Chignik—100% purse seines
Alitak—mixed purse seines/gillnets
Vulnerability differs by length & sex example
Females
J. Carter
Males
0
0.2
0.4
0.6
0.8
1
450 500 550 600 650
Length (mm)V
uln
era
bilit
y
0
0.2
0.4
0.6
0.8
1
430 480 530 580 630
Length (mm)
Vu
lne
rab
ilit
y
0
0.2
0.4
0.6
0.8
1
Vu
lne
rab
ility
Females
Vulnerability curves differ among years
J. Bennis
Length (mm)
1980 1991 2002
420 620420 620 420 620
J. Carter
Vulnerability profiles
1989
00
.20
.40
.60
.81
400 450 500 550 600 650
Body length (mm)
Vu
lne
rab
ility
1990
Body length (mm)
Vu
lne
rab
ility
1991
400 450 500 550 600 650
Body length (mm)
Vu
lne
rab
ility
1992
Body length (mm)
Vu
lne
rab
ility
1993
400 450 500 550 600 650
Body length (mm)
Vu
lne
rab
ility
1994
Body length (mm)
Vu
lne
rab
ility
1995
Body length (mm)
Vu
lne
rab
ility
1996
Body length (mm)
Vu
lne
rab
ility
1997
Body length (mm)
Vu
lne
rab
ility
1998
00
.20
.40
.60
.81
Body length (mm)
Vu
lne
rab
ility
1999
00
.20
.40
.60
.81
Body length (mm)
Vu
lne
rab
ility
2000
400 450 500 550 600 650
Body length (mm)
Vu
lne
rab
ility
2001
Body length (mm)
Vu
lne
rab
ility
2002
400 450 500 550 600 650
Body length (mm)
Vu
lne
rab
ility
2003
Body length (mm)
Vu
lne
rab
ility
Chignik female
Vulnerability profiles
Chignik male
1989
00
.20
.40
.60
.81
400 500 600
Body length (mm)
Vu
lne
rab
ility
1990
Body length (mm)
Vu
lne
rab
ility
1991
400 500 600
Body length (mm)
Vu
lne
rab
ility
1992
Body length (mm)
Vu
lne
rab
ility
1993
400 500 600
Body length (mm)
Vu
lne
rab
ility
1994
Body length (mm)
Vu
lne
rab
ility
1995
Body length (mm)
Vu
lne
rab
ility
1996
Body length (mm)
Vu
lne
rab
ility
1997
Body length (mm)
Vu
lne
rab
ility
1998
00
.20
.40
.60
.81
Body length (mm)
Vu
lne
rab
ility
1999
00
.20
.40
.60
.81
Body length (mm)
Vu
lne
rab
ility
2000
400 500 600
Body length (mm)
Vu
lne
rab
ility
2001
Body length (mm)
Vu
lne
rab
ility
2002
400 500 600
Body length (mm)
Vu
lne
rab
ility
2003
Body length (mm)
Vu
lne
rab
ility
Vulnerability profiles
Upper Cook Inlet female
198900
.20
.61
450 550 650
Body length (mm)
Vu
lne
rab
ility
1990
Body length (mm)
Vu
lne
rab
ility
1991
450 550 650
Body length (mm)
Vu
lne
rab
ility
1992
Body length (mm)
Vu
lne
rab
ility
1993
450 550 650
Body length (mm)
Vu
lne
rab
ility
1994
Body length (mm)
Vu
lne
rab
ility
1995
Body length (mm)
Vu
lne
rab
ility
1996
Body length (mm)
Vu
lne
rab
ility
1997
Body length (mm)
Vu
lne
rab
ility
1998 00
.20
.61
Body length (mm)
Vu
lne
rab
ility
199900
.20
.61
Body length (mm)
Vu
lne
rab
ility
2000
Body length (mm)
Vu
lne
rab
ility
2001
Body length (mm)
Vu
lne
rab
ility
2002
Body length (mm)
Vu
lne
rab
ility
2003
Body length (mm)
Vu
lne
rab
ility
2004
450 550 650
Body length (mm)
Vu
lne
rab
ility
2005
Body length (mm)
Vu
lne
rab
ility
2006
450 550 650
Body length (mm)
Vu
lne
rab
ility
2007
Body length (mm)
Vu
lne
rab
ility
Vulnerability profiles
Upper Cook Inlet male
198900
.20
.61
400 500 600 700
Body length (mm)
Vu
lne
rab
ility
1990
Body length (mm)
Vu
lne
rab
ility
1991
400 500 600 700
Body length (mm)
Vu
lne
rab
ility
1992
Body length (mm)
Vu
lne
rab
ility
1993
400 500 600 700
Body length (mm)
Vu
lne
rab
ility
1994
Body length (mm)
Vu
lne
rab
ility
1995
Body length (mm)
Vu
lne
rab
ility
1996
Body length (mm)
Vu
lne
rab
ility
1997
Body length (mm)
Vu
lne
rab
ility
1998 00
.20
.61
Body length (mm)
Vu
lne
rab
ility
199900
.20
.61
Body length (mm)
Vu
lne
rab
ility
2000
Body length (mm)
Vu
lne
rab
ility
2001
Body length (mm)
Vu
lne
rab
ility
2002
Body length (mm)
Vu
lne
rab
ility
2003
Body length (mm)
Vu
lne
rab
ility
2004
400 500 600 700
Body length (mm)
Vu
lne
rab
ility
2005
Body length (mm)
Vu
lne
rab
ility
2006
400 500 600 700
Body length (mm)
Vu
lne
rab
ility
2007
Body length (mm)
Vu
lne
rab
ility
Using estimated selectivities, model ideal
length and age at maturity under different
harvest scenarios (JØrgensen et al. 2009 Evol.
Apps.)
Calculate maturation reaction norms for
spawning populations
J. Bennis J. Carter
Future work, extensions
J. BennisJ. Bennis