1
Supporting Information
2
Movements of subadult and adult female lemon sharks in Florida and The Bahamas
3
Fig. 1 provides a synthesis of tag-recapture on the long distance movements of
4
subadult and adult female lemon sharks in Florida and The Bahamas compiled from the
5
National Marine Fisheries Cooperative Tagging Program (NMFS-CTP) database, some
6
of which has already been published elsewhere. We supplemented this with unpublished
7
information on the movements of adult female lemon sharks fitted with internal acoustic
8
transmitters and remotely tracked using passive acoustic telemetry. Here, we provide
9
additional details of this ongoing study.
10
Adult lemon sharks were targeted at Jupiter, Florida, one of the few known places
11
in the region where this life-stage occurs in large, predictable aggregations. Individuals
12
were captured at ca 25-30 m depth in the winter months (January to March) from 2005 to
13
2009. Sharks were collected using drift lines with single baited 20/0 circle hooks. All
14
sharks were fitted with a coded acoustic transmitter (Vemco® V16H) internally implanted
15
into the coelom. Nominal battery life for the tags was 84 months. Intervals for the coded
16
signals were randomized between 90 and 360 seconds. All sharks were released after the
17
hook was removed, with a typical at-vessel handling time of less than 15 minutes. Long-
18
range movements of sharks carrying acoustic transmitters were determined from
19
transmitter detection strings on underwater Vemco receivers that were deployed by us
20
and others. Approximately 165 Vemco acoustic receivers are deployed by the Florida
21
Atlantic Cooperative Tracking (FACT) research group, spanning a total of 310 km of
22
coastline between Delray Beach and Cape Canaveral. The Atlantic Coastal Telemetry
23
(ACT) array research group has approximately 1,000 monitors deployed in various
24
locations along the U.S. eastern seaboard north of the FACT array (pers. comm.
25
Dewayne Fox – ACT coordinator). Long distance movements were also detected through
26
tag returns from commercial fishing operations.
27
Lemon sharks fitted with acoustic transmitters at Jupiter were detected on local
28
receivers for a few months after tagging, after which they all dispersed from the local
29
area. After correcting for two sharks known to have been killed by fishermen within a
30
year of tagging, 33 of 41 individuals (80.5%) returned to the tagging site in subsequent
31
years (Supplementary Table 1). Sharks were detected on receivers or captured by
32
fishermen hundreds of kilometers away along the U.S. coast, ranging from the Dry
33
Tortugas, Florida (dispersal distance from tagging site ~ 515 km) to the Santee River
34
Mouth, South Carolina (~ 720 km from tagging site, Fig. 1). Sharks were also detected on
35
receivers deployed in Altamaha Sound Georgia, (~ 515 km, Fig. 1) and Cape Canaveral,
36
Florida, (~ 225 km, Fig. 1). All of these movements represent minimum dispersal given
37
that the majority of the coast, especially south of Jupiter, is not under receiver
38
surveillance. The average dispersal of adult females was 299.8 km and ranged from 225
39
km to 715 km.
40
41
42
43
44
45
Supplementary Table 1. Maximum-recorded dispersal distances (km) and years of return to tagging site for adult lemon sharks fitted
46
with acoustic transmitters and acoustic transmitters off Jupiter, Florida. “Max distance recorded” is the coastal distance between the
47
shark’s tagging location off Jupiter and either (a) a receiver it was detected on (“Acoustic detection” under “Detection type and shark
48
fate”), (b) a location provided by a fishermen who caught the shark (“Tag return”) and either harvested the animal or released it alive
49
or (c) from the pop-off location of a pop-off satellite archival tag (PSAT). “Return years” refers to winter periods (January to April)
50
when the individual was detected by receivers off Jupiter, indicative of philopatry.
51
52
Shark ID
34
36
2140
2141
2143
2145
2146
2147
2148
2151
7949
7950
Date
tagged
Total
length (cm)
Sex
23-Feb-07
24-Feb-07
27-Feb-07
254
255
236
M
M
M
5-Feb-08
26-Feb-07
8-Feb-08
15-Feb-08
9-Feb-08
15-Feb-08
9-Feb-08
22-Feb-08
26-Feb-08
251
245
231
237
231
232
238
248
268
M
M
M
M
M
M
M
M
F
Max distance
recorded (km)
2008
720
512
512
720
275
225
915
505
512
607
512
715
Y
Y
Y
N/A
N
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Return years
2009
2010
Y
Y
Y
N
N
Y
Y
Y
Y
Y
Y
Y
N/A
N/A
N/A
N
N/A
Y
Y
N
N
Y
N
Y
2011
Detection type and shark
fate
N/A
N/A
N/A
N/A
N/A
N/A
N
N/A
N/A
N/A
N
N
Acoustic detection
Acoustic detection
Acoustic detection
Acoustic detection
Tag return released
Acoustic detection
Tag return released
Acoustic detection
Acoustic detection
Tag return released
Acoustic detection
Acoustic detection
7955
7956
7959
7960
7961
7966
7967
13038
52494
52993
52994
52995
55114
55115
55116
55121
55122
55123
55124
55125
55126
55127
63424
63425
63427
63429
63430
63431
25-Feb-08
11-Mar-08
25-Feb-08
25-Feb-08
12-Mar-08
11-Mar-08
6-Sep-08
6-Sep-08
8-Feb-12
22-Feb-09
22-Feb-09
8-Mar-09
21-Feb-09
14-Feb-09
21-Feb-09
21-Feb-09
21-Feb-09
21-Feb-09
22-Feb-09
14-Feb-09
21-Feb-09
13-Feb-09
1-Mar-10
1-Apr-10
29-Jan-10
20-Feb-10
1-Apr-10
1-Apr-10
229
255
242
262
235
263
257
257
240
265
280
274
247
242
240
247
276
279
293
255
242
260
260
264
284
245
260
237
F
M
M
F
F
M
M
M
M
F
F
F
F
F
M
F
F
F
F
F
M
F
F
F
F
M
F
F
225
96
512
225
225
225
230
340
1020
518
225
225
225
715
225
225
225
225
225
225
225
500
225
225
225
505
225
225
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Y
N
Y
Y
Y
Y
Y
Y
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Y
N
N
N
Y
Y
Y
Y
N/A
Y
Y
Y
N
Y
N
Y
Y
Y
Y
Y
Y
Y
N/A
N/A
N/A
N/A
N/A
N/A
N
N
N
N
N
N
N
Y
N/A
Y
Y
N
N
Y
N
N
N
Y
N
Y
N
Y
N
N
Y
Y
Y
N
Acoustic detection
Sat Tag
Acoustic detection
Acoustic detection
Acoustic detection
Acoustic detection
Tag return harvested
Acoustic detection
Acoustic detection
Sat Tag
Acoustic detection
Acoustic detection
Acoustic detection
Acoustic detection
Acoustic detection
Tag return harvested
Acoustic detection
Acoustic detection
Tag return harvested
Acoustic detection
Acoustic detection
Tag return harvested
Acoustic detection
Tag return harvested
Acoustic detection
Acoustic detection
Acoustic detection
Acoustic detection
63433
63435
63436
63437
323622
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
29-Jan-10
23-Feb-10
19-Feb-10
28-Jan-10
26-Feb-08
266
280
220
278
265
F
F
F
F
M
225
225
225
225
230
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Y
N
Y
y
N/A
Acoustic detection
Acoustic detection
Acoustic detection
Acoustic detection
Tag return harvested
75
How many of the tagged 1993-1998 sharks are likely to have survived to adulthood?
76
To put individual detections of natal philopatry in context it is useful to have
77
some understanding of how many of the females we tagged from 1995-1998 were
78
probably still alive in 2008-2012 and would have matured and had their first litters before
79
2012. Many parameters are needed to make such an estimate. We stress that what we
80
present is the only approximation that we can make with the available data, and it should
81
be viewed as providing a very general idea of likely number of survivors.
82
The probability of each tagged female surviving to have its first litter was
83
calculated by multiplying the annual survival rates for each year from when it was last
84
observed until the age of first reproduction, and excluding those that would have pupped
85
for the first time after 2012. The expected number of females to survive to pup was the
86
sum of these individual probabilities. A Monte Carlo simulation was used to estimate the
87
uncertainty in the estimate (Cortes 2002, Babcock et al. 2013). For Monte Carlo
88
simulation, each parameter (survival age 1-4, survival age 5+, age at reproduction) is
89
given a probability density function representing the uncertainty in the estimate; random
90
values of the three parameters are drawn from their probability density functions, and the
91
number of individuals that survive to pup is recalculated for each set of parameter values.
92
The 95% confidence interval of the number of survivors is calculated from the 2.5 and
93
97.5 percentiles of the distribution in estimated number of survivors.
94
The annual survival fraction from age 1-4 was drawn from a triangle distribution
95
between 0.43 and 0.85, corresponding to the range of survival values obtained during a
96
previous study of lemon sharks conducted at Bimini from 1995-2000 (DiBattista et al.
97
2007). The annual survival from age 4 and higher, after the sharks have left Bimini, was
98
drawn from a triangle distribution between 0.86 and 0.91, the same distribution used by
99
Cortes (2002), based on longevity data. The age at maturity was selected randomly with
100
equal probability from age 12, 13 and 14, so that the females would return to pup at age
101
13, 14 or 15. The smaller value is taken from previous studies (Brown and Gruber 1988);
102
the larger values reflect the fact that the females in this study made their first return at
103
later ages. For each of 10,000 Monte Carlo simulations, for each tagged shark, values of
104
survival between age 1-4, survival age 4+, and age at maturity were drawn. The survival
105
in each year, from the age when the shark was last captured (age 1 to 3) to its age at first
106
pupping were multiplied to produce a total survival probability for each shark. For some
107
individual sharks, the age at last capture was recorded as a range (e.g. 1-3), in which case
108
an age was drawn randomly with equal probability from ages 1, 2 and 3, for each of these
109
sharks in each Monte Carlo draw. The expected number of tagged females in each
110
simulation to survive to produce their first litter was the sum across all tagged sharks of
111
their survival probabilities, excluding those whose age at maturity implied that they
112
would have their first litter after 2012. The analyses were conducted in R, version 2.15.2
113
(Carnell 2011; R Core Team 2012). We enumerated juvenile females that were tagged in
114
Bimini from 1995-1998 that survived beyond the age of 2 years based on recapture
115
information (N=128). Monte Carlo simulations estimated that only 15 of these
116
individuals are likely to have survived to deliver their first litters up to 2012 (95% C.I.=
117
8-25).
118
Alternative nursery habitat
119
120
Lemon shark nursery habitat in the region is characterized as being shallow (< 1
m depth), close to shore, and occurring over sand and seagrass substrates, often near
121
mangroves (Morrissey and Gruber 1993; Gruber et al. 2001). We used the habitat-layered
122
map in The Bahamas GIS viewer (Mumby 2012) to calculate the percentage of available
123
coastline and near shore benthos with these characteristics within a 200 km radius of
124
Bimini, a conservative estimate of the dispersal range of adult female lemon sharks based
125
on compiled tagging and telemetry data above (Supplementary Table 1). Given this
126
dispersal range, GIS analysis suggests that Bimini constitutes ~ 2.4% of the nursery
127
habitat available to them, assuming that this entire potential nursery habitat is actually
128
used. As a preliminary assessment of lemon shark use of this potential nursery habitat we
129
conducted a hook-and-line survey in this habitat at two locations in Andros Island and
130
two locations in the Berry Islands from May 27-June 6, 2013. We observed large
131
numbers of juvenile lemon sharks in all four locations and captured 18 individuals < 90
132
cm TL in Andros and 11 in the Berry Islands (Supplementary Figure 1). These
133
preliminary validation efforts suggest that GIS analysis provides a useful approximation
134
of realized nursery habitat for lemon sharks within a 200 km radius of Bimini. Assuming
135
that the habitat we monitored at Bimini is 2.4% of the potential nursery habitat for 8-25
136
possible tagged returnees, then if female sharks chose nursery areas locations randomly
137
out of the available habitat the probability that an individual female would choose the
138
Bimini nursery would be 0.024. The probability of six or more of the surviving 8-25
139
Bimini females giving birth at Bimini under the null hypothesis of randomly choosing
140
nursery habitat would be less than 0.0001 (calculated from the binomial distribution with
141
probability 0.024 and sample size 8-25).
142
143
Supplementary Figure 1: Islands with lemon shark nursery habitat on the Great Bahama
144
Bank, Bahamas. Areas in yellow boxes on left panel are shown on the upper right (Berry
145
Islands) and lower right (Andros Island). Red boxes outline the area that was surveyed
146
for lemon sharks. Red circles show capture locations of juvenile lemon sharks (< 90 cm
147
TL) at each site (N = 11 at the Berry Islands; N= 18 at Andros). Size of circle is
148
proportional to the number of individuals captured at each site.
149
150
151
152
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153
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Carnell R (2011) Triangle: Provides the standard distribution functions for the triangle
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Gruber SH, De Marignac JRC, Hoenig JM (2001) Survival of juvenile lemon sharks
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Morrissey JF, Gruber SH (1993) Home range of juvenile lemon sharks, Negaprion
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