GIS and Aquaculture: Soft-Shell Clam Site Assessment
285
plan. These issues are address by descriptive and prescriptive queries within ArcView™
and the Spatial Analysis module (ESRI, 1996).
Preparation of the clam biology data for analysis included the calculation of
clam densities as well as an estimate of the total biomass for each area. The attribute
clam length was subdivided into 4 classes and they are:
1)
2)
3)
4)
Juvenile - length < 35 mm (LT 35 mm)
Pre-Recruits - length >= 35 and < 50 mm (GE 35 to LT 50 mm)
Recruits - length >= 50 mm and < 63.5 mm (GE 50 to LT 63.5 mm)
Brooding Stock - length >= 63.5 mm (GE 63.5 mm)
A Query Summarize function in ArcView™ (Fig. 6) was used to summarize by
GEOCODE, the total number of clams for each size class. Thus each 100 x 100 m grid
in the recruit
group represents the market clam population. The procedure for calculating clam
densities involved the addition of the four clam size class fields (attributes) to the clam
biology point databases. For each record a value of 1 was assigned to a size class
attribute if the clam length value was within the specified class interval otherwise the
value was set to 0. The study area is assigned a total count for each clam size class.
Given that the sampling occurs in a 0.25/m sq. area at the center of each grid, the
density for each size class was calculated as: n/area, where n is the total number of
285
plan. These issues are address by descriptive and prescriptive queries within ArcView™
and the Spatial Analysis module (ESRI, 1996).
Preparation of the clam biology data for analysis included the calculation of
clam densities as well as an estimate of the total biomass for each area. The attribute
clam length was subdivided into 4 classes and they are:
1)
2)
3)
4)
Juvenile - length < 35 mm (LT 35 mm)
Pre-Recruits - length >= 35 and < 50 mm (GE 35 to LT 50 mm)
Recruits - length >= 50 mm and < 63.5 mm (GE 50 to LT 63.5 mm)
Brooding Stock - length >= 63.5 mm (GE 63.5 mm)
A Query Summarize function in ArcView™ (Fig. 6) was used to summarize by
GEOCODE, the total number of clams for each size class. Thus each 100 x 100 m grid
in the recruit
group represents the market clam population. The procedure for calculating clam
densities involved the addition of the four clam size class fields (attributes) to the clam
biology point databases. For each record a value of 1 was assigned to a size class
attribute if the clam length value was within the specified class interval otherwise the
value was set to 0. The study area is assigned a total count for each clam size class.
Given that the sampling occurs in a 0.25/m sq. area at the center of each grid, the
density for each size class was calculated as: n/area, where n is the total number of