hard clams and other suitable species are considered. Published by Elsevier Science B.V.
Keywords
:
GIS; Hard clam; Mercenaria; Aquaculture; Lease site selection
1. Introduction
Considerable effort has been expended on the development of suitable tech- niques for the effective culture and marketing of a variety of aquatic animal and
plant species, including for example various algae, invertebrates such as clams and shrimp, and a host of vertebrate fish species e.g. Rosenthal et al., 1995. In
contrast, much less effort has been expended to assist in the crucial process of selecting a site suitable for field grow-out of the chosen species e.g. Kapetsky et
al., 1987, 1988; Meaden and Kapetsky, 1991; Ross et al., 1993; Fridley, 1995; Kapetsky and Nath, 1997; Aguilar-Manjarrez and Nath, 1998; Parker et al.,
1998; Rubec et al., 1998. As a result, a substantial database is available that describes appropriate feeds, expected growth rates, reproductive seasonality, and
rates of mortality for a lengthy list of potentially aquaculture-suitable species. Unfortunately, much of that information has been derived under laboratory or
controlled conditions, and even the information that has been obtained from field grow-out is site-specific and may have little applicability at other sites. Such
information is adequate for animals that are cultured exclusively under controlled conditions. However, field grow-out is essential to obtain the production scales
and economic returns necessary to fulfil the promise of aquaculture and to adequately supplement marine capture fisheries Meaden and Kapetsky, 1991.
Successful large-scale aquaculture therefore requires the selection of a grow-out site that will provide rates of economic return predicted under laboratory and
controlled grow-out situations. Until recently, that process of site selection has largely been ignored, especially in the marine environment Aguilar-Manjarrez
and Ross, 1995.
In Florida, USA, the economic potential of aquaculture is recognized both by individual citizens migrating into the industry and by local and state governmental
entities responsible for management of this emerging economic sector. Aquaculture is fully supported by state government in Florida Florida Statutes, 1996, and that
support has led to the development of successful ventures particularly in the tropical fish, alligator, catfish, and in the marine environment shellfish industry
subsectors. The hard clam Mercenaria spp. has emerged in the last decade as one of the most economically important aquaculture species in the marine environment.
Hard clam aquaculture in Florida has expanded from an essentially non-existent industry B 1 of total 1993 commercial clam landings in Florida to an industry
with annual landings approaching 4.6 million \ 55 of total 1997 commercial clam landings in Florida. The development of the Florida hard clam aquaculture
industry has not occurred without controversy, however, particularly with respect to the requirement for final grow-out of cultured product on publicly-owned
sovereign submerged lands. The challenge has been to provide clam culturists with
adequate and suitable nearshore habitat within which to produce clams, while minimizing conflict with other user-groups demanding access to these extremely
resource-rich shallow coastal waters. Multiple criteria must be considered when determining the suitability of a site for
hard clam aquaculture Berrigan, 1996. The State of Florida requires that hard clam leases be located in areas containing natural densities of less than five clams
per m
2
to avoid conflict with the fishery for naturally occurring clams, and in areas that are essentially devoid 1 coverage or less of rooted aquatic vegetation to
avoid negative impacts on this important natural resource. For harvesting purposes, the lease must be located within an Approved or Conditionally Approved shellfish
harvesting zone Table 1; Berrigan, 1996, with Approved zones being most desirable and Conditionally Approved zones being least desirable. To avoid inter-
ference with vessel traffic, the lease borders must be located a minimum of 30 m from the nearest recognized navigational channel. Finally, from the perspective of
the culturist, sites located in water depths less than 1.8 m are most desirable for ease of maintenance and because the clams grow faster in shallower water Arnold et al.,
1991. The culturist also desires a site that is located in close proximity to a boat ramp to facilitate site access and product transport, although not so close as to
experience negative impacts from boating traffic. Finally, it is useful to identify areas that have been historically characterized by water quality suitable for the
Table 1 Shellfish harvesting area classifications for Florida waters Rodriguez, 1998
Classification Criteria
Approved Dangerous concentrations of fecal material, pathogenic microorganisms,
and poisonous or deleterious substances are not present. Conditionally Approved The area meets Approved area classification criteria. Bacterial pollution is
intermittent, and conditions associated with the release, persistence, and distribution of bacterial pollution are known. A management plan is
available for closing and reopening the area that includes the administrative procedures to implement those actions.
The area is not so contaminated with poisonous or deleterious substances Restricted
that consumption of shellfish after relaying or controlled purification would be hazardous. Shellfish harvesting from Restricted areas is allowed
only by special license and requires State approved monitors. Conditionally Restricted The area will meet Restricted area classification criteria. The area is not
so contaminated with poisonous or deleterious substances that consumption of shellfish after suitable purification would be hazardous. A
management plan is available for closing and reopening the area that includes the administrative procedures to implement those actions.
Fecal material, pathogenic microorganisms, or poisonous or deleterious Prohibited
substances are consistently or unpredictably present in dangerous concentrations. Alternatively, surveys identify actual or potential pollution
sources of high magnitude which may affect the shellfish harvesting area. Unclassified
A comprehensive shellfish harvesting survey is not available for the area. Shellfish harvest is prohibited from Unclassified waters.
Table 2 List of stations used in the determination of minimum salinity and dissolved oxygen D.O. in Shellfish
Harvesting Area C SHA C of the Indian River lagoon
a
End year Minimum salinity ppt
Minimum D.O. mgl Station no.
N Start year
98 13.0
27 4.0
53 96
61 87
98 13.2
1.1 91
98 13.9
64 1.5
54 93
98 14.2
94 4.5
66 34
94 46
98 12.9
4.0 68
98 13.2
69 0.6
65 93
98 13.4
93 0.3
57 70
87 152
98 13.3
0.5 71
98 13.4
72 0.5
163 87
97 12.9
87 4.6
69 74
93 63
98 6.8
0.7 76
98 14.4
77 4.6
33 96
98 13.4
94 1.7
55 78
94 36
98 14.2
1.8 79
98 12.9
80 2.0
37 94
98 12.0
87 0.5
82 158
87 164
98 13.3
0.4 84
98 13.1
85 0.4
180 87
98 15.3
93 0.5
32 88
87 180
98 13.0
0.3 91
87 183
98 13.3
0.3 92
98 12.4
87 0.4
94 174
93 54
98 11.5
0.6 96
98 12.0
97 0.7
47 94
98 12.6
94 0.6
58 99
94 35
98 12.8
1.7 100
98 13.3
101 0.5
166 87
98 13.0
87 0.6
102 153
87 127
98 11.9
0.6 103
98 13.9
104 0.7
58 94
98 12.7
87 3.5
105 111
87 150
98 12.9
1.9 112
87 171
98 13.5
0.8 114
98 13.4
92 0.3
84 121
92 64
98 13.3
0.4 122
98 14.4
123 0.5
56 92
98 13.3
92 0.5
71 124
92 84
98 12.8
0.5 127
92 83
98 13.2
0.4 128
98 13.3
94 0.8
131 50
92 53
98 13.0
0.7 132
92 53
98 13.0
0.8 133
a
See Figs. 5 and 6 for locations of water quality sampling stations. N = number of samples collected at that station during the sampling interval.
Table 3 List of stations used in the determination of minimum salinity and dissolved oxygen D.O. in
Charlotte Harbor
a
End year Minimum salinity ppt
Minimum D.O. mgl Station no.
N Start year
59 23.1
0.3 86
G1 98
2.2 17.0
G10 102
98 85
19.4 123
1.2 85
98 G20
1.2 G24
100 85
98 24.0
2.7 18.9
86 114
98 G25
8.2 94
2.3 89
98 G26
98 19.3
1.7 G30
89 85
11.6 108
1.8 85
98 G110
1.7 23.2
G130 79
96 85
15.2 80
3.6 85
96 G140
137 6.6
2.5 85
G160 98
4.0 6.9
121 85
G170 98
14.3 98
4.0 86
98 G180
98 13.5
1.1 G190
135 85
11.6 94
1.4 85
98 G200
3.2 0.5
M10 123
98 84
0.5 111
1.3 84
98 M20
0.5 120
2.2 84
98 M40
3.2 1.0
85 135
98 M50
0.7 138
3.2 85
98 M60
98 0.2
2.3 M70
135 85
98 0.5
2.9 M110
122 84
2.8 0.8
98 M111
87 131
98 3.0
0.4 160
M130 84
1.2 0.8
84 140
98 M150
0.4 48
4.2 84
98 M161
98 0.4
3.3 M163
79 84
2.4 137
0.4 84
98 M170
3.0 0.2
M180 117
98 84
0.4 115
3.0 84
98 M190
0.1 109
3.4 84
98 M200
2.4 0.1
84 112
98 M210
0.0 84
1.8 86
98 M211
98 0.4
3.4 M212
58 86
98 0.0
4.0 M213
82 89
1.1 3.4
98 P20
85 86
P30 9.3
75 85
98 13.1
4.1 24.1
41 85
P40 98
13.4 72
1.2 85
98 P50
98 22.6
1.4 P51
58 86
16.7 45
4.8 88
98 P52
3.9 18.2
P53 66
98 85
21.6 74
2.4 88
98 P54
98 24.0
1.3 P57
85 72
4.0 26.5
98 88
P58 25
25.4 80
0.5 85
98 P59
P60 2.9
75 85
98 22.5
0.6 98
88 22.5
60 P61
Table 3 Continued End year
Minimum salinity ppt Minimum D.O. mgl
N Station no.
Start year 98
21.5 0.4
P62 51
85 2.2
18.5 98
P70 85
70 98
23.7 3.9
P80 68
85 5.3
11.3 33
85 P90
97 22.8
78 2.5
85 98
P130 98
13.5 2.4
P300 74
85 13.1
76 2.9
85 98
P310 3.6
12.4 P311
77 98
85 12.4
79 4.3
85 98
P320 13.0
65 2.3
85 98
P321 2.7
12.1 98
P360 85
42 3.4
83 2.1
88 98
P370 1.9
4.1 85
85 P380
98 9.6
38 1.7
85 98
P390 98
11.7 3.1
P400 43
85 2.1
P420 73
86 98
10.7 2.0
5.7 85
84 98
P430 3.2
85 2.6
85 98
P440 98
2.9 1.6
P470 77
85 98
2.3 1.2
P490 85
85 2.6
0.8 98
P500 85
48 97
11.2 2.0
P501 26
87 2.9
26.5 9
89 F77
98 28.8
16 6.2
89 98
F143 98
26.5 4.6
F197 20
89 98
27.8 5.5
F289 89
15 3.5
27.2 F665
53 98
89 26.4
41 4.7
89 98
F1016 13.1
51 4.7
89 98
F1169 2.0
15.9 98
F1369 89
51 98
2.5 2.4
F2226 89
50
a
See Figs. 11 and 12 for locations of water quality sampling stations. N = number of samples collected at that station during the sampling interval. The letter preceding the station number indicates
the Shellfish Harvesting Area SHA from which the data were collected G, Gasparilla Sound; M, Myakka River; P, Pine Island Sound; F, FMRI Fisheries Independent Monitoring Program.
growth and survival of the target organism throughout the 10-year life of the aquaculture lease Berrigan, 1996.
A Geographic Information System GIS-based methodology is here described that is effective in assisting with the identification and quantification of sites
suitable for shellfish aquaculture, can be used to identify information needs applicable to the identification of additional sites, and may considerably alleviate
many of the user-group conflicts that plague industry development. Similar tech- niques have been previously applied in both developing e.g. Aguilar-Manjarrez and
Nath, 1998 and developed e.g. Kapetsky et al., 1990 countries, and to both coastal marine e.g. Ross et al., 1993 and inland freshwater e.g. Kapetsky and
Nath, 1997 fisheries. These applications are extended to a coastal marine inverte- brate, the hard clam Mercenaria spp., and the capabilities of GIS techniques in
providing a user-friendly approach to selecting individual lease sites that may be only several hectares in areal extent are emphasized.
2. Methods
