the 2015 stock assessment of common snook, …data sources life history stock identification...
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The 2015 stock assessment of
Common Snook, Centropomus undecimalis
Robert Muller, Alexis Trotter, and Philip Stephens
13 January 2016
Florida Fish and Wildlife Conservation Commission
Fish and Wildlife Research Institute
Orlando, FL
Data sources
Life History
Stock identification Tringali et al. 2008
Cold kills Stevens et al. In review
Spawning Lowerre-Barbieri et al. 2014, Young 2014
Age-specific natural mortality Lorenzen 2005
Growth, maturity
morphometrics, Taylor et al. 2000
Fishery
Landings and releases MRFSS/MRIP
Lengths of fish landed Fish Bio Snook samplers ,
MRFSS/MRIP and Everglades National Park
(Gulf), anglers logbooks
Lengths of released fish Angler logbooks
Ages of landed fish Fish Bio Snook samplers
Ages of fish in population FIM samplers
Abundance indices FIM, MRFSS, ENP on Gulf
Environmental factors
Red Tide cell counts FWRI Harmful Algal Bloom program
Temperature National Buoy Data Center (Venice pier)
Gulf Atlantic
Microsatellite DNA analysis with 24 loci of Florida snook collected
from both coasts (total n = 1,396 fish)
Tringali et al. (2008) found two highly structured groups with
individuals being faithfully assigned to the Atlantic or Gulf stock
Stock identification
Reviews in Fisheries Science:116:111-116 Fig. 2.2
Lo
ci
Age - growth
FWRI Fishery
independent sampling
Length is not a good
indicator of age 0 5 10 15 20
04
00
80
01
20
0
Age(yr)T
ota
l le
ng
th (
mm
)
0 5 10 15 20
04
00
80
01
20
0
Age(yr)
To
tal l
en
gth
(m
m)
0 5 10 15 20
04
00
80
01
20
0
Age(yr)
To
tal l
en
gth
(m
m)
0 5 10 15 20
04
00
80
01
20
0Age(yr)
To
tal l
en
gth
(m
m)
Atlantic Females Males
Gulf Females Males
N = 2,031 N = 6,727
N = 4,086 N = 7,3066 yr old Common Snook
Fig. 2.6
Natural mortality Age-specific natural mortality rates
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1 2 3 4 5 6 7 8 9
10
11
12
13
14
15
16
17
18
19
20
+
Nat
ura
l mo
rtal
ity
per
yea
r
Age (yr)
Atlantic
Gulf
The higher natural mortality for the Gulf coast reflects more cold kills
plus red tides.
Maturity Snook are protandrous hermaphrodites (fish hatch as males and then most
males transition to females).
Spawning occurs in May-September depending upon coast in inlets, on
beaches, and nearshore.
Because females come from mature males, the sex ratio by age can be
used as the female maturity schedule (Taylor et al. 2000); however, recent
acoustic tagging has revealed that snook may remain in the rivers and skip
spawning (Trotter et al. 2012, Young et al. 2014).
Fishery Bulletin 98:612-624, Trans Am Fish Soc 141:1016-1025, MEPS 505:227-240
0.00
0.20
0.40
0.60
0.80
1.00
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Pro
bab
ilit
y o
f be
ing
fem
ale
Age (yr)
AtlanticObs
Pred
P =e-1.578-0.705Coast+0.307Age/(1+ e-1.578-0.705Coast+0.307Age)where Atlantic coast = 1 and Gulf coast= 0
0.00
0.20
0.40
0.60
0.80
1.00
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Pro
bab
ilit
y o
f be
ing
fem
ale
Age (yr)
GulfObs
Pred
Landings and releases
Note: the vertical axes differ by
coast.
Fig. 3.2.3
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
19
81
19
83
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85
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91
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93
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95
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97
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99
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01
20
03
20
05
20
07
20
09
20
11
20
13
Nu
mb
er o
f fi
sh
Year
AtlanticReleased alive
Landings
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
19
81
19
83
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85
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20
09
20
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Nu
mb
er o
f fi
sh
Year
GulfReleased alive
Landings
On either coast, most of
the snook are released.
Total harvest
A series of 23 experiments
estimated the release mortality
rate at 2.13% (Taylor et al. 2001)
Total harvest = Landings +
2.13% * Releases
North American Journal of Fisheries Management 21:70-75 Fig. 3.2.4
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
19
81
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83
19
85
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20
01
20
03
20
05
20
07
20
09
20
11
20
13
Nu
mb
er
of
sno
ok
Year
Died subsequent to release
Landings
Atlantic
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
19
81
19
83
19
85
19
87
19
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19
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93
19
95
19
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99
20
01
20
03
20
05
20
07
20
09
20
11
20
13
Nu
mb
er
of
sno
ok
Year
Died subsequent to release
Landings
Gulf
Fishing effort
Source: National Marine Fisheries Service, Marine
Recreational Information Program (MRFSS/MRIP)
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
19
81
19
83
19
85
19
87
19
89
19
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19
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19
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19
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19
99
20
01
20
03
20
05
20
07
20
09
20
11
20
13
Sno
ok
trip
s
Year
Atlantic
Gulf
Fig. 3.3.1a
Lengths of snook landed in recent
years under minimum size limit
(1986-1998, 24 in one fish
greater than 34 in) and two slot
limits (1999-06, 26-34 in and
2008-2014, 28-32 in on the
Atlantic coast and 28-33 in on the
Gulf coast).
Sizes of retained fish
0.00
0.05
0.10
0.15
0.20
0.25
12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46
Pro
po
rtio
n
Total length (in)
Atlantic 1986-1998
1999-2005
2008-2014
0.00
0.05
0.10
0.15
0.20
0.25
12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46
Pro
po
rtio
n
Total length (in)
Gulf 1986-1998
1999-2005
2008-2014
Fig. 3.4.1
Source: FWRI Snook program
and MRFSS/MRIP
Sizes of released fish
Angler logbooks contain the numbers
and the lengths of the fish caught and
whether the fish was kept or released.
In 2010, the Snook and Gamefish
Foundation initiated its Angler Action
online program for anglers to provide
similar information regarding their
trips. The proportions shown here are
2008-2014 average lengths. n = 35650.00
0.02
0.04
0.06
0.08
0.10
<=12
14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44+
Pro
po
rtio
n
Total length (in)
Atlantic
0.00
0.02
0.04
0.06
0.08
0.10
<=12
14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44+
Pro
po
rtio
n
Total length (in)
Gulf N = 3,278 fish
N = 6,233 fish
Ages of snook sampled in recent
years under two slot limits (1999-
05, 26-34 in and 2008-2014, 28-
32 in. on the Atlantic coast and 28-
33 in on the Gulf coast).
Ages of retained fish
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Pro
po
rtio
n
Age (yr)
Atlantic 1999-2005 n=2,454
2008-2014 n=2,550
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Pro
po
rtio
n
Age (yr)
Gulf 1999-2005 n=4,870
2008-2014 n= 786
Ages of released fish
Ages were assigned with year- and
coast-specific age-length keys. The
first step was to use fishery dependent
ages and then age the remaining
lengths with fishery independent age-
length keys. The figures are 2008-
2014 averages.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Pro
po
rtio
n
Age (yr)
Gulf
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Pro
po
rtio
n
Age (yr)
Atlantic
Abundance indices Fishery independent monitoring
with a 183-m haul seine.
326570 623
699681
664
662718 670 668
655
639658
654
652654
674
683
643
0.00
0.25
0.50
0.75
1.00
1.25
1.50
19
96
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97
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19
99
20
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20
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20
12
20
13
20
14
Nu
mb
er p
er s
ein
e h
aul
Year
Gulf
428
462456
443
564666 713
712699 650
681
631
594
704 752
647604 618
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.801
99
6
19
97
19
98
19
99
20
00
20
01
20
02
20
03
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04
20
05
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20
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20
11
20
12
20
13
20
14
Nu
mb
er
pe
r se
ine
hau
l
Year
Atlantic
Fig. 4.1.1.1
Abundance indices
There is general agreement
among the indices used for
guiding the model. All of the
indices showed a marked
decrease in 2010.
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.501
98
6
19
88
19
90
19
92
19
94
19
96
19
98
20
00
20
02
20
04
20
06
20
08
20
10
20
12
20
14N
um
ber
cau
ght
per
set
or
inte
rvie
w
Year
FIM
MRFSS/MRIP
Fig.4.1.3
Atlantic
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
19
81
19
83
19
85
19
87
19
89
19
91
19
93
19
95
19
97
19
99
20
01
20
03
20
05
20
07
20
09
20
11
20
13N
um
ber
cau
ght
per
set
or
inte
rvie
w
Year
FIM
MRFSS/MRIP
ENP
Gulf
Assessment model
Snook configuration of Age-Structured Assessment Program Version 3.0.17 (ASAP,
NMFS Toolbox, Legault and Restrepo 1998)
Recreational fishery
Releases were linked to the directed fishery and the release mortality was 2.13%
Three abundance indices indices on Atlantic coast and four indices on the Gulf
Model is fit to: Landings and releases
Abundance indices
Age composition of indices, landings, and releases
ICCAT WORKING DOCUMENT, SCRS 98/58
Benchmarks
Transitional spawning potential
ratios are calculated using the
estimated historical fishing
mortality rates and are not in
equilibrium. The stock on the
Atlantic coast was very near the
40% objective and the stock on the
Gulf coast exceeded the objective.0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.801
98
61
98
71
98
81
98
91
99
01
99
11
99
21
99
31
99
41
99
51
99
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99
71
99
81
99
92
00
02
00
12
00
22
00
32
00
42
00
52
00
62
00
72
00
82
00
92
01
02
01
12
01
22
01
32
01
4
Tran
siti
on
al s
paw
nin
g p
ote
nti
al
rati
o
Year
2015 Assessment
2013 assessment
2012 Assessment
2006 Assessment
40% SPR
Atlantic
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
19
86
19
87
19
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19
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90
19
91
19
92
19
93
19
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20
07
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20
14
Tran
siti
on
al s
paw
nin
g p
ote
nti
al
rati
o
Year
2015 Assesssment
2013 Assessment
2012 Assessment
2006 Assessment
40% SPR
Gulf
Fig. 4.2.2.4.8.1.2
0/
/
F
FF
RSSB
RSSBtSPR
676584
559
306
0.00
1.00
2.00
3.00
4.00
Nu
mb
er o
f sn
oo
k p
er h
aul s
ein
e se
t
Bay system
Regional comparisons
6531
3003
1459
1019
5344
0.00
1.00
2.00
3.00
4.00
Nu
mb
er p
er t
rip
Region
FIM
MRFSS/MRIP
Fig. 4.5.2
The two data sources agree. On
average the regions with highest
and the lowest catch rates were
on the Atlantic coast and the
regions on the Gulf coast were in
between.
Regional comparisons
195 266
267
302
286284
278352
314312
291287
293
288
282304
310
320
265
0.00
2.00
4.00
6.00
8.00
10.001
99
6
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
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06
20
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Nu
mb
er o
f sn
oo
k p
er h
aul s
ein
e
Year
259262 244 239
236 239 291270
242248
254 251256
344 410 311 268 2760.00
2.00
4.00
6.00
8.00
10.00
19
96
19
97
19
98
19
99
20
00
20
01
20
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Nu
mb
er o
f sn
oo
k p
er h
aul s
ein
e
Year
137
200
192192
189
192
196
241
254
200
222
176 141
160146
144 144
148
0.00
2.00
4.00
6.00
8.00
10.00
19
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19
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20
00
20
01
20
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Nu
mb
er o
f sn
oo
k p
er h
aul s
ein
e
Year
135208 230
210
224
208216
216214
208
210
205207
204
212
206206
206 206
0.00
2.00
4.00
6.00
8.00
10.00
19
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19
97
19
98
19
99
20
00
20
01
20
02
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03
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Nu
mb
er o
f sn
oo
k p
er h
aul s
ein
e
Year
Fishery independent haul seine catch
rates by region
Tampa Bay Indian River
Charlotte Harbor Tequesta
Fig. 4.5.3
Environmental effectsTwo environmental factors that are
known to effect snook are
temperature and red tides.
Howells and Sonski (1990) found
that sub-adult snook (265-380 mm
TL) ceased feeding at 14oC and died
at 9oC.
Bennett (2006) estimated the impact
of the 2005 red tide on snook in
Sarasota Bay as part of his thesis.
Northeast Gulf Science 11:155-158 M.S. Thesis, University of Florida
0.00
0.02
0.04
0.06
0.08
0.10
0.12
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
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19
98
19
99
20
00
20
01
20
02
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03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
20
14
Pro
po
rtio
n o
f h
ou
rs b
elo
w 1
4oC
Year
0.00
0.50
1.00
1.50
2.00
2.50
3.00
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
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06
20
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20
08
20
09
20
10
20
11
20
12
20
13
20
14
Log 1
0(C
ells
per
lite
r)
Year
Temperature
Red tide
Environmental effects
0.00
0.10
0.20
0.30
0.40
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Pro
po
rtio
n
Age (yr)
For red tide, we used the age composition
from 286 snook otoliths collected by Mote
Marine Laboratory personnel on 15 July
2005 from Lido Key and New Pass. Lengths
were 350-910 mm TL and ages 2-14 years .
For cold kills, we used the age composition
from 75 snook otoliths collected by
Everglades National Park personnel on
18,19, and 24 January 2010 from cold killed
snook. Lengths were 168 – 1045 mm TL
and ages 1-10 years.
We don’t know how many snook die when
these events occur.
Red Tide
Cold kill
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1 2 3 4 5 6 7 8 9 10
Pro
po
rtio
n
Age (yr)
Cold kill
Environmental effects
0.00
0.50
1.00
1.50
2.00
2.5019
8619
8719
8819
8919
9019
9119
9219
9319
9419
9519
9619
9719
9819
9920
0020
0120
0220
0320
0420
0520
0620
0720
0820
0920
1020
1120
1220
1320
14
Fish
ing
mo
rtal
ity
per
yea
r (a
ge-7
)
Year
Base
Environment
0
500
1,000
1,500
2,000
2,500
3,000
19
86
19
88
19
90
19
92
19
94
19
96
19
98
20
00
20
02
20
04
20
06
20
08
20
10
20
12
20
14
Rec
ruit
me
nt
(nu
mb
er o
f ag
e-1
fis
h,
tho
usa
nd
s)
Year
Base
w/Environmental effects
w/Environmental effects (half)
0
200
400
600
800
1,000
1,200
1,400
1,600
19
86
19
88
19
90
19
92
19
94
19
96
19
98
20
00
20
02
20
04
20
06
20
08
20
10
20
12
20
14
Spaw
nin
g b
iom
ass
(mt)
Year
Base
w/Environmental effects
w/Environmental effects (half)
After Fig. 4.2.2.4.8.2.3
0.00
0.50
1.00
1.50
2.00
2.50
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
2014
Mo
rtal
ity
per
yea
r (a
ge-7
)
Year
Fishing mortality
Natural mortality
Environmental effects
0
100
200
300
400
500
600
7001
98
61
98
71
98
81
98
91
99
01
99
11
99
21
99
31
99
41
99
51
99
61
99
71
99
81
99
92
00
02
00
12
00
22
00
32
00
42
00
52
00
62
00
72
00
82
00
92
01
02
01
12
01
22
01
32
01
4
Spa
wn
ing
bio
ma
ss (
mt)
Year
Atlantic Age-12+
Age-11
Age-10
Age-9
Age-8
Age-7
Age-6
Age-5
Age-4
Age-3
Age-2
Age-1
SSB 40%SPR
0
200
400
600
800
1,000
1,200
1,400
1,600
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
20
14
Spa
wn
ing
bio
ma
ss (
mt)
Axis Title
Gulf Age-12+
Age-11
Age-10
Age-9
Age-8
Age-7
Age-6
Age-5
Age-4
Age-3
Age-2
Age-1
SSB 40%SPR
Spawning biomass by age
Note: the spawning biomass on
the Gulf with the environmental
effects shows the truncated
age structure after the cold kill.
Environmental effects
The unfished SSB/R illustrates
the impact of the environmental
effects.
Fig. 4.2.2.4.8.2.4
SSB/RF=0
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Kilo
gram
s p
er r
ecru
it
Age (yr)
Unfished
F40%SPR
SSB/RF
SSB/RF=0
0/
/
F
FF
RSSB
RSSBtSPR
0.00
1.00
2.00
3.00
4.00
5.001
98
6
19
88
19
90
19
92
19
94
19
96
19
98
20
00
20
02
20
04
20
06
20
08
20
10
20
12
20
14
Fis
he
d s
pa
wn
ing b
iom
ass p
er
recru
it
(kg)
Year
Base
Enviromental effects
0.00
1.00
2.00
3.00
4.00
5.00
19
86
19
88
19
90
19
92
19
94
19
96
19
98
20
00
20
02
20
04
20
06
20
08
20
10
20
12
20
14
Un
fish
ed
sp
aw
nin
g b
iom
ass p
er
recru
it (
kg)
Year
Base
Enviromental effects
Environmental effects benchmark
Fig. 4.2.2.4.8.2.3
0.00
0.20
0.40
0.60
0.80
1.00
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
20
14
Tra
nsit
ion
al sp
aw
nin
g p
ote
nti
al ra
tio
Year
Base
Enviromental effects
40% SPR
Benchmarks
0.00
0.25
0.50
0.75
1.00
1.25
1.50
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
F ra
tio
(F g
m/F
40
%SP
R)
SSB ratio (SSB2014/SSB40%SPR)
Atlantic
0.00
0.25
0.50
0.75
1.00
1.25
1.50
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
F ra
tio
(F g
m/F
40
%SP
R)
SSB ratio (SSB2014/SSB40%SPR)
Gulf
Including environmental effects
When the cold kill and the uncertainty
in the snook response are considered,
the spawning biomass took a severe
hit and is recovering.
0.00
0.25
0.50
0.75
1.00
1.25
1.50
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
F ra
tio
(F g
m/
F 40
%SP
R)
SSB ratio (SSB2014 / SSB40%SPR)
Gulf
Questions?