Download - # STT/STJ Yellowtail Fishing Trips
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Population Size, Growth, Mortality and Movement Patterns of Yellowtail
Snapper (Ocyurus chrysurus) in the U.S. Virgin Islands
CRP Funded Project NMF4540114Funding :
Federal=$132,850CFMC=$20,000
STFA in-kind=$11,200
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# STT/STJ Yellowtail Fishing Trips
1997-98
1998-99
1999-00
2000-01
2001-02
2002-03
2003-04
2004-05
2005-06
2006-07
0
200
400
600
800
1,000
1,200
1,400
1,600
0
50
100
150
200
250
300
Line Fishing TripsSeine Fishing Trips
Line
Fis
hing
Trip
s
Sein
e Fi
shin
g Tr
ips
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Yellowtail lbs/Trip
0
20
40
60
80
100
120
140
160
Seine Fishing Trips
Line Fishing Trips
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Yellowtail Snapper Annual STT/STJ Landings# lbs
1997-98
1998-99
1999-00
2000-01
2001-02
2002-03
2003-04
2004-05
2005-06
2006-07
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000Trap Fishing lbs.Seine Fishing Lbs.Line Fishing Lbs
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Annual Yellowtail Landings # Fish
1997-98
1998-99
1999-00
2000-01
2001-02
2002-03
2003-04
2004-05
2005-06
2006-07
0
20,000
40,000
60,000
80,000
100,000
120,000Trap Fishing # Fish
Seine Fishing # Fish
Line Fishing # Fish
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Average Monthly Handline & SeineTrips (1997-2008 Average)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec70
75
80
85
90
95
100
8
9
10
11
12
13
14
15
16
Line TripsSeine Trips
# H
andl
ine
Trip
s
# Se
ine
Trip
s
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Yellowtail per Trap /Haul
1 2 3 4 5 6 7 8 9 10 11 120.00
0.02
0.04
0.06
0.08
0.10
0.12
f(x) = 0.0000102021 x⁶ − 0.000342536 x⁵ + 0.00422758 x⁴ − 0.0233757 x³ + 0.0566732 x² − 0.0509065 x + 0.0536458R² = 0.831780854529242
Month
Fish
/Tra
p Ha
ul
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Pit Tags
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Scanner for Port Sampling
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Weight Calculations
200 250 300 350 400 450 500 550 6000
500
1,000
1,500
2,000
2,500
3,000
f(x) = 4.07311784274785E-05 x^2.83389025365432R² = 0.92811483610145
Length (mm)
Wt (
gms)
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Study StatusTagging Trips # Fish Total Lbs Average
Hand line 27 2023 2431 1.23Traps 10 99 113 1.15Total 36 2122 2544 1.21
Port Sampling 208 15,119 20,103 1.33
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Port Sample Locations
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Length at First Reproduction (FISHBASE) 188 mm Male, 224 mm Female
CFMC Size Limit 304.8 TL, 244.7 FL
Length at First Capture (FL in mm)
Traps 228 mm
Hand Line 208 mm
Nets 198 mm
Length at Full Recruitment
Traps 270 mm
Hand Line 290 mm
Seine Nets 260 mm
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Calculation of Total Mortality Rate (Z)
Where: is the number of fish at time (t) and Z is the rate of total mortality.
An age specific instantaneous rate of Z was calculated by solving the Von Bertalanffy growth equations for t (median age of the size class in the frequency distribution.*
Where: is the length (in mm) at age (t). is the asymptotic length at which growth is zero. t0 is included to adjust the equation for the initial size of the organism and is defined as age at which the organisms would have had zero size.
Solving equation for t (age) allows for calculation of the age (in years) of each size class.
2005=0.1742011-12=0.249
*Manooch, C.S. III. and C.L. Drennon, 1987. Age and growth of yellowtail snapper and queen triggerfish collected from the U.S. Virgin Islands and Puerto Rico. Fish. Res. 6:53-68. Otolith analysis.
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Hand line Size Frequency
220240
260280
300320
340360
380400
420440
460480
500520
540560
580600
0.0%
2.0%
4.0%
6.0%
8.0%
10.0%
12.0%
14.0%
Fork Length (mm)
#
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220240
260280
300320
340360
380400
420440
460480
500520
540560
580600
0.0%2.0%4.0%
6.0%8.0%
10.0%12.0%14.0%
16.0%
Project Yellowtail Snapper
Fork Length (mm)
#Age 4 5 6 7 8
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190
50100150200250300350400450500
Age (yrs)
Fork
Len
gth
(mm
)
𝒍_((𝒕))=𝑳_∞ (𝟏−𝒆^(−𝒌(𝒕−𝒕_𝟎 ) ) )𝑳_∞=510𝒌=0.139𝒕_𝟎=-.96
Manooch, C.S. III. and C.L. Drennon, 1987. Age and growth of yellowtail snapper and queen triggerfish collected from the U.S. Virgin Islands and Puerto Rico. Fish. Res. 6:53-68.
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Fish Trap Size Frequency
200230
260290
320350
380410
440470
500530
560590
620650
6800%
5%
10%
15%
20%
25%%
of T
otal
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Tagging/Port Sampling Summary
Sep-11
Oct-11
Nov-11
Dec-11
Jan-12
Feb-12
Mar-12
Apr-12
May-12
Jun-12Jul-1
2
Aug-120
500
1000
1500
2000
2500
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
Total Tags
Survivors
Port Samples/Tag
# Ta
gs/S
urvi
vors
Port
Sam
ples
/Tag
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Summary of Mortality• 2005 Size/Frequency Distribution=0.174 (0.0154/month)• 2011-12 Size/Frequency Distribution=0.249
(0.0208/Month)• Coral World
– Initial “Fishing/Transport” Mortality=9.6%Heavy stress from transport to tanks analogous to additional mortality from predators.
– Tag Loss= 1.6%– Pre “Catastrophic” Mortality=2.1% (matches 2011-2012 rate)
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Gear Selectivity
Where:S is Selectivity and and are calculated iteratively via nonlinear regression. From the non-linear model (Proc NLIN in SAS) with known values of size class and percent of the sampled population for that size class. The output was estimates of both parameters, which were then used within the selectivity equation to estimate size selectivity for each size class and particularly the size class at which selectivity peaked.
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Selectivity Analysis: Fish TrapsYellowtail snapper (Ocyurus chrysurus) [Traps]
Size Class
220 230 240 250 260 270 280 290 300
Sel
ectiv
ity
0.0
0.2
0.4
0.6
0.8
1.0
1.2
ObservedPredicted
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Selectivity Analysis: Hand LineYellowtail snapper (Ocyurus chrysurus) [Handline]
Size Class
200 220 240 260 280 300 320
Sel
ectiv
ity
0.0
0.2
0.4
0.6
0.8
1.0
1.2
ObservedPredicted
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• Assess rate of tag loss (1.7%)• Assess mortality
– 9.6% initial “fishing/transport” mortality– Mortality following initial mortality almost exactly
that indicated from size/frequency analysis.– Catastrophic mortality after 3 weeks.– Necropsy revealed that 60% had small livers when
compared to fish from market and 69% had liver fluke infestation.
Coral World Studies
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Survivorship at Coral World
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 300%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
"3/18 All Tagged"
"5/27 Tagged"
"5/27 No Tag"
"7/27 No Tag, Octogon"
"7/27 No Tag, Quarantine"
Days
% S
urvi
vors
hip
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Recaptures• None so far• Comparison with Rick Niemeth’s tagging. All tagging
done on aggregation site. To date Niemeth has tagged – 751 Nassau (2004-2010) and have recaptured 187 back on
the aggregation site. In addition 3 have been captured by fishermen and reported to UVI by STFA members (0.5/year).
– 661 yellowfin grouper and recaptured 25. All tags and recaps were on the aggregation site.
– 3644 red hind (1999-2006) and recaptured 99. 47 Red hind were recaptured off the aggregation site (6.7/year).
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Next Steps• Finish Coral World Studies• Double Tagging with Floy and Pit tags.
Started 8/15)• Floy Tagging of remainder• Continue Port Sampling.• Data from DFW.