Transcript Summary of Research on Spiny Dogfish in North Carolina by

Summary of Research on Spiny
Dogfish in North Carolina
by Rulifson and Colleagues,
1997-2003
• Mark-recapture, with population estimate for 19972000 exploitable stock.
• Population estimate for spiny dogfish south of Cape
Hatteras, NC during winter 1999 using “area
swept” method.
• Biological characterization of overwintering
dogfish north and south of Cape Hatteras, 1998-99.
Spiny Dogfish, Squalus acanthias
Spiny Dogfish Tagging Studies
~15,106 over 6-7 years
•
•
•
•
Hickman et al. (2000)
Thorpe and Beresoff (2000)
Rulifson et al. (2000)
SEAMAP Winter Tagging Cruises
– 1997, 1998, 1999, 2000, 2002, 2003
• Canada – Nova Scotia 1996
16th Annual Cooperative Winter
Tagging Cruise Cooperators
•
•
•
•
•
•
•
U.S. Fish and Wildlife Service
NOAA Fisheries
Atlantic States Marine Fisheries Commission (ASMFC)
NC Division of Marine Fisheries
MD Department of Natural Resources
South Atlantic Fisheries Management Council
East Carolina University
R/V Oregon II
• Owned by NOAA
• Commissioned in
1967
• 170 ft. long, 34 ft
wide, 14 ft draft.
• 950 gross tons
• 17-18 Crew
• 12 Scientists
Internal
anchor
tag
Single-barb dart tag with canula
2003-Spiny Dogfish
8,940 measured, sexed
2,986 tagged & released
(33.4%)
Witnessing the
birth of a spiny
dogfish pup
1500
n = 103
1250
1000
Distance (km)
Recaptures
as a function
of distance
from NC
tagging sites
(through
2000)
750
500
250
0
0
30
60
90
120
150
180
210
Calendar day
240
270
300
330
360
Distance from NC Release Site vs Days at Large
1400
1200
1000
Distance (km)
Longest time for
at-large is
currently 2,350
days from
Canada release
(’96) and
recapture (’03)
800
600
400
200
0
0
200
400
600
800
Days at large
1000
1200
1400
1600
Recaptures by Lat.-Long.
45
43
Latitude
41
39
37
35
33
-78
-76
-74
-72
-70
Longitude
-68
-66
-64
Recapture Mode
• Gill net 73%
–
–
–
–
–
–
–
7.0 inch (10%)
6.5 inch (35%)
6.0 inch (35%)
4 3/8 inch
4.0 inch
3 inch
“croaker net”
•
•
•
•
•
Trawl
Rod and reel
Longline
Handline
Dropnet
11.1%
7.4%
6.2%
1.2%
1.2%
Release Mode – Recapture Rate
Release
mode
Number
released
Percent
Recapture
Gill net
8,126
0.48
Trawl
2,018
2.38
US East Coast Overwintering Release Sites
Figure 1. Mark and release
locations of spiny dogfish captured
off the North Carolina Outer Banks
during the 1997-98 and 1998-99
winter commercial fishing seasons.
The range of Seamap Cruises in
1997 and 1998 are marked with
C97-1 and C97-2, and C98-1 and
C98-2, respectively and fish were
caught by trawl. Fish collected
during the FRG studies were
collected by sink gillnet (red-lined
area).
Scientific Sink Gillnet Locations
Winters 1997-8, 1998-9
Spiny Dogfish Population Estimate –
Cape Hatteras to Cape Fear, NC
(Newman, Moore, and Rulifson 2000)
• Sonar and Loran (GPS)
survey to identify
aggregations of spiny
dogfish.
• Experimental gillnets
deployed for 45 minutes
within the aggregation.
• Outline of aggregation
marked with Loran
coordinates.
“Area Swept” Method Using Scientific Gill Net Sets
Figure 4. Area of a spiny dogfish aggregation located in Raleigh Bay during Set 8, between
Core Banks and Cape Lookout Shoals, March 10, 1999. Estimated area = 15,138.49 hec; scale
= 1:458,824.
Figure 5. Area of a spiny dogfish aggregation located in Long Bay during Set 2,
between Frying Pan Shoals and Shalotte Inlet, February 16, 1999. Estimated area
= 1,634.22 hec; scale = 1:365,000.
Figure 6. Area of spiny dogfish aggregation located in Onslow Bay during Set 4, between
Topsail Island and Carolina Beach Inlet, February 18, 1999. Estimated area = 30,521.47
hec; scale = 1:445,462.
Figure 7. Area of a spiny dogfish aggregation located in Onslow Bay during Set 5,
between Beaufort Inlet and Bogue Inlet, February 19, 1999. Estimated area = 5,505.42
hec; scale = 1:279,683.
Assumptions
1.
2.
3.
4.
5.
6.
7.
8.
All nets fished at 100% efficiency;
All nets were set for approximately the same time;
Dogfish were uniformly distributed within the cluster;
Fish were not highly mobile during the study, remaining in
the same general cluster area;
Only those dogfish within 25-50 yds (i.e., 5,000 – 10,000
yds2) of the net were captured;
None of the fish captured and released was recaptured in
subsequent samples (i.e., 100% bycatch mortality as per
NMFS designation); and
Estimated surface area of the dogfish aggregation
accurately described the cluster size.
Fish leaving from natural mortality and entering the
commercial fishery were equal and stable during this
period.
Spiny Dogfish Population Size
Table 2. Effort, catch per effort, and population estimation of spiny dogfish aggregations south of Cape Hatteras in Raleigh, Long
and Onslow bays, North Carolina during February-March 1999.
Assuming
Assuming
Total
Total
Average Minimum
100x100 yds
100x50 yds
% of total
Cluster
Total effort-catch effort-all catch - aggregation
capture
capture
population
number Date catch
nets
nets
catchnets size (ha) Pop. Estimate 1
Pop. Estimate 2 Estimate 1 Estimate 2
Raleigh Bay
1
8
2/15/1999
3/10/1999
0
496
0
14
28
21
2
0
2
0
150
249
312
235
1444
35.4
15,138.49
641,437
1,282,875
54.7
58.8
28
21
1.0
1,634.22
1,954
3,909
0.0
0.2
39
20
26
15
49
21
35
21
3.8
12.5
12.0
15.7
30,521.47
5,505.42
9,217.67
4,905.09
140,395
81,974
132,288
91,906
280,789
163,949
264,576
183,811
14.3
10.0
12.6
8.4
12.9
7.5
12.1
8.4
116
224
66,922.36
1,089,954
2,179,909
100.0
100.0
Long Bay
2
3
2/16/1999
2/17/1999
Onslow Bay
4
5
6
7
2/18/1999
2/19/1999
3/8/1999
3/9/1999
Totals
Dogfish Summary Data –
South of Cape Hatteras
Table 3. Summary of body measurements for male and female spiny dogfish
captured south of Cape Lookout, NC to the North Carolina-South Carolina state
line during the winter of 1999 onboard the Captain Dell. SD = 1 standard
deviation from the mean.
Total length (cm)
Mean + SD
Range
Fork length (cm)
Mean + SD
Range
Female
81.6 + 6.5
59 - 103
71.5 + 6.1
50 - 91
2.3 + 0.7
0.5 - 4.6
Male
76.5 + 4.1
64 – 86
67.1 + 3.8
56 - 76
1.5 + 0.3
0.6 - 2.0
Sex
Body weight (kg)
Mean + SD
Range
Dogfish Lengths South of Cape Hatteras
Table 4. Mean total lengths (cm) + SD and range of spiny dogfish captured in seven
mesh sizes (inches) of a scientific sink gill net south of Cape Lookout, NC to the North
Carolina-South Carolina state line during the winter of 1999 onboard the Captain Dell.
Mesh size
(inches)
n
Males
Mean TL + SD
n
Females
Mean TL + SD
TL range (cm)
TL range
3.0
2
75.5 + 3.5
73 - 78
91
78.0 + 4.7
68 - 93
4.0
20
75.2 + 4.2
64 - 82
238
77.5 + 5.8
64 - 92
4.5
14
75.6 + 3.1
73 - 84
399
81.3 + 6.4
59 - 103
5.0
10
77.9 + 5.6
69 - 86
314
81.8 + 5.9
67 - 98
5.5
4
76.5 + 1.7
74 - 78
117
83.7 + 5.8
68 - 99
6.0
1
75
143
85.3 + 5.4
72 - 101
6.75
0
79
88.6 + 5.2
79 - 100
1381
81.6 + 6.5
59 - 103
Total
51
76.5 + 4.1
64 - 86
Dogfish Reproductive Stage South of Cape Hatteras
Table 5. Number of female dogfish within each embryonic development stage of
the gestation period captured south of Cape Lookout, NC to the North CarolinaSouth Carolina state line during the winter of 1999 onboard the Captain Dell.
Embryonic
development
stage
Number of females
Percent number
of females
1
80
26
2
75
24
3
92
30
4
2
1
5
57
18
6
3
1
Total
309
100
Table 1. Number of spiny dogfish and bycatch fish species collected in scientific
sink gill nets south of Cape Lookout to the North Carolina-South Carolina state
line during the winter of 1999 onboard the Captain Dell.
Bycatch in
Scientific Sink
Gillnets, Cape
Hatteras to SC
Common name
Scientific name
Number captured
Percent of total
Spiny dogfish
Squalus acanthias
1,444
87.2
Atlantic menhaden
Brevoortia tyrannus
83
5.0
Smooth dogfish
Mustelus canis
60
3.6
American shad
Alosa sapidissima
12
0.7
Atlantic croaker
Micropogon undulatus
11
0.7
Sandbar shark
Carcharhinus milberti
11
0.7
Summer flounder
Paralichthys dentatus
9
0.5
Weakfish
Cynoscion regalis
9
0.5
Butterfish
Peprilus triacanthus
4
0.2
White mullet
Mugil curema
4
0.2
Searobin
Family – Triglidae
3
0.2
Pinfish
Lagodon rhomboides
2
0.1
Clearnose skate
Raja eglanteria
1
<0.1
Black sea bass
Centropristis striata
1
<0.1
Mullet
Mugil sp.
1
<0.1
Bluefish
Pomatomus saltatrix
1
<0.1
1,656
100
Total fish captured
Are the Overwintering Populations
in North Carolina North and South
of Cape Hatteras two Separate
Populations, or One Extended
Population?
14
Population Size Class Structure
% freq Females
Hatteras-SC, Feb-Mar
1999
Hatteras-Kitty Hawk, 98-99
20
14
16
10
% Frequency of fish
% frequency of fish
FEMALES
FEMALES
12
Mean - 81.3 cm
Standard deviation - 6.6 cm
Minimum - 62 cm
Maximum - 106 cm
n = 1133 fish
8
6
4
Mean - 81.6 cm
Standard deviation - 6.5 cm
Minimum - 59 cm
Maximum - 103 cm
2D
n - 1382
fishGraph 1
12
8
4
2
0
0
20
30
40
50
60
70
80
90
100
110
60
65
% Frequency of fish
16
10
Mean - 75.3 cm
Standard deviation - 6.4 cm
Minumum - 28 cm
Maximum - 87 cm
n - 103 fish
8
6
70
75
80
85
90
95
100 105 110
MALES
MALES
12
55
20
14
% frequency of fish
% freq males
X Axisin
50
4
2D Graph 2
Mean - 76.5 cm
Standard deviation - 4.1 cm
Minimum - 64 cm
Maximum - 86 cm
n - 52 fish
12
8
4
2
0
0
20
30
40
50
60
70
80
90
100
110
Total length (cm)
Figure 4: Percent total length (cm) frequency of male and female spiny dogfish captured
inshore from Hatteras to Kitty Hawk, North Carolina during the winter of 1998-99 onboard
the Bout Time.
50
55
60
65
70
75
80
85
90
95
100 105 110
Total length (cm)
Figure 10. Length frequency (TL, %) of male and female spiny dogfish
captured in coastal waters south of Cape Hatteras, North Carolina to the
North Carolina-South Carolina state line by the Captain Dell during the winter
of 1999.
Population Age Class Structure
Hatteras-Kitty Hawk, 98-99
Hatteras-SC, 2D
Feb-Mar
1999
Graph 5
30
40
FEMALES
FEMALES
35
25
Percent frequency
n = 318 fish
mean age = 24 years
age range = 12 - 38 years
30
Frequency
f-ag
25
20
15
n = 222 fish
age range = 9 - 34 years
mean age = 21 years
20
15
10
10
5
5
0
0
40
30
X Axis
MALES
MALES
35
25
Percent frequency
n = 100 fish
mean age = 19 years
age range = 3 - 29 years
30
Frequency
2D Graph 4
25
20
15
n = 39 fish
age range = 8 - 22 years
mean age = 15 years
20
mAGE-fre
15
10
10
5
5
0
0
0
5
10
15
20
25
30
35
40
45
Age (years)
Figure 8. Age frequency of male and female spiny dogfish captured from
Kitty Hawk to Cape Hatteras, North Carolina during the winter of 1998-99
onboard the Bout Time.
50
0
5
10
15
20
25
30
35
Age (years)
Figure 13. Age frequency (%) of male and female spiny dogfish
captured in coastal waters south of Cape Hatteras to the North CarolinaSouth Carolina state line by the Captain Dell during winter 1999.
40
Von Bert Growth Estimations
Hatteras-Kitty Hawk, 98-99
Hatteras-SC, Feb-Mar 1999
120
110
90
100
Lt = 95(1 - e-0.12(t - 2.6))
n = 318 fish
80
Total length (cm)
Total length (cm)
FEMALES
FEMALES
FEMALES
100
70
60
50
40
30
20
n = 318FEMALES
fish
mean age = 24 years
age range = 12 - 382D
years
Graph
80
60
3
Lt = 92(1 - e-0.17(t - 1.9))
n = 222 fish
n = 318 fish
mean age = 24 years
age range = 12 - 38 years
40
20
10
0
0
X Axis
120
110
MALES
100
90
Lt = 81(1 - e
n = 100 fish
80
MALES
MALES
100
-0.17(t - 1.9)
)
Total length (cm)
Total length (cm)
MALES
2D
Graph 2
70
60
50
40
30
20
n = 100 fish
mean age = 19 years
age range = 3 - 29 years
Plot 2
MAGES v Col 7
80
n = 100 fish
mean age = 19
L =years
82(1 - e-0.24(t - 2.1))
age range = 3 t- 29 years
n = 39 fish
60
40
20
10
0
0
0
5
10
15
20
25
30
35
40
Age (years)
Figure 10. The von Bertalanffy growth equations for male and female spiny
dogfish captured from Kitty Hawk to Cape Hatteras, North Carolina during the
winter of 1998-99 onboard the Bout Time. Bar represents 1 standard deviation
from the mean.
0
5
10
15
20
25
30
35
40
Age (years)
Figure 14. The von Bertalanffy growth equations of male and female spiny dogfish
captured in coastal waters south of Cape Hatteras to the North Carolina-South
Carolina state line by the Captain Dell during winter 1999. Bar = one standard
deviation from the mean.
Age to Maturity
120
110
100
90
80
70
60
50
40
30
20
10
0
110
50% Maturity = 82 cm total length
n = 1189 fish
100
50% Maturity = 2.2 kg
n = 305 fish
90
50% Maturity = 2.6 kg
n = 1176 fish
80
50
60
70
80
90
100
110
Female total length (cm)
110
70
2D Graph 2
60
WT v Col 12
WT v Col 13
50
40
100
50% Maturity = 2.6 kg weight
n = 1176 fish
90
Percent Mature
Hatteras-SC, Feb-Mar 1999
Percent mature
Percent mature
Hatteras-Kitty Hawk, 98-99
30
80
20
70
60
10
50
40
0
30
0
20
10
1
2
3
4
5
Female total weight (kg)
0
0
1
2
3
4
5
Female total weight (kg)
Figure 11. Total length (cm) and weight (kg) at 50% maturity for female spiny
dogfish captured from Kitty Hawk to Hatteras, North Carolina onboard the
Bout Time during the winter of 1998-99.
6
Figure 15. Length (TL, cm) and weight (kg) at 50% maturity of female spiny dogfish
captured in coastal waters south of Cape Hatteras to the North Carolina-South Carolina
state line by the Captain Dell during winter 1999.
Fecundity
2D Graph 4
Hatteras-Kitty Hawk, 98-99
Hatteras-SC, Feb-Mar 1999
log(NP) = 0.78log(TMW) + 0.24
r2 = 0.18
n = 562 fish
Range of pups per female = 2 - 11 pups
Average # of pups per female = 4.45 pups
10
log(NP) = 0.33log(TMW) + 0.51
n = 152
range of pups per female = 1 - 10 pups
average # of pups per female = 4.75 pups
10
Number of Progeny
8
Number of progeny
Weight v Total pups
Plot 4 Regr
12
12
6
4
8
6
4
2
2
0
0
1
2
3
4
5
6
7
8
Total maternal weight (kg)
Figure 12. Number of progeny (NP) in relation to the total maternal weight
(TMW)(kg) for fecundity of female spiny dogfish captured from Kitty Hawk
to Hatteras, North Carolina onboard the Bout Time during the winter of 1998-99.
0
1
2
3
4
5
6
7
8
Total maternal weight (kg)
Figure 16. Number of progeny (NP) in relation to the total maternal weight (TMW)
(kg) of female spiny dogfish captured south of Cape Hatteras onboard the Captain
Dell during the winter of 1999.
Supporting Mark-Recapture
Information
• Dogfish tagged off Cape Hatteras to Kitty Hawk
and north have been recaptured at the northern end
of the range (Gulf of Maine).
• Dogfish tagged south of Cape Hatteras have been
recaptured at the northern end of the range (Gulf
of Maine).
• One dogfish tagged during SEAMAP cruise (north
of Cape Hatteras) was recaptured near Wilmington
(south of Cape Hatteras)
Spring migration, summer
habitat
Fall migration
Overwintering
Second “unit stock”?
First “unit stock”
Unsampled extension
Conclusions about North
Carolina Dogfish
• Overwintering migratory stock of the U.S. Eastern
Seaboard
• Dogfish aggregations south of Cape Hatteras
represent a small but important part of the
overwintering population
– Similar demographics
– Tag return confirmation
• Tag returns suggest that Cape Cod shelf area is the
northern terminus for U.S. eastern Seaboard stock;
minimal mixing between U.S. and Canadian dogfish.