ponds. There is significant variation across production intensities in pond area, type,
cultivation methods, stocking density, and number of crops cultivated per year. Pond
preparation for intensive aquaculture requires digging, aeration equipment, and installing a
water exchange system, whereas little pond preparation is necessary for extensive
aquaculture. And, while all farmers stock their ponds, either from a mix of fish, crab, or
shrimp found in local water bodies or with bought fingerlings, stocking density varies
greatly (between 4 head/m2 and between 40 and 100 head/m2
). Table 4 highlights key
characteristics of pond aquaculture at the various production intensities found across our
data set (see Baluyut 1989, Edwards 1998 for a detailed analysis of production intensity).
Those practicing extensive aquaculture follow the lunar calendar, harvesting crab and
black tiger shrimp twice per month during low tides. Farmers are selective in their harvesting,
prioritizing larger-sized crab and shrimp to enable juveniles to further fatten.
Stocking takes place when needed or if species are found from the wild, enabling farmers
to take advantage of market prices. Harvest levels per hectare are linked to salinity, soil
conditions, water quality, and weather. Intense heat can be an issue, particularly in the dry
season when the earth cracks and water is scarce. As one extensive fish farmer commented:
‘‘we put the crab and shrimp into the pond and they then just disappear. This has happened
a few times now. Maybe because of the weather?’’ (Ca Mau Jan. 2014). Households
respond to environmental change in many ways, including an intensification of effort on
their shrimp and fish farms