Agriculture and Environment: Shrimp

Environmental Impacts of Production: Pollution from Effluents

Pollution from effluents comes from many sources in shrimp production. Perhaps the most important is the feed. Semi-intensive and intensive production systems require about 2 kilograms of feed to produce 1 kilogram of shrimp. This feed averages from 15-35% fish meal by weight, and from 20-40% protein by weight.

Leftover food in shrimp ponds
Consequently, feed is a major cause of water quality deterioration in shrimp ponds. This problem is accentuated because as much as 33% of the food is not even consumed by the shrimp.

Shrimp farmers cannot know precisely how many shrimp are alive in their ponds, so feeding is guesswork. The main problem with nutrient loading in local water systems occurs during the shrimp harvest.

Nutrient loading during pond draining
Shrimp are harvested by draining the ponds, and it is estimated that 90% of all the nutrients that are produced in a shrimp pond are released during the last 25% of pond draining. No one has yet found a way to harvest shrimp efficiently without draining the ponds.

The effluents from individual ponds or single operations may fall within reasonable standards. However, too many farms in one area may well exceed the carrying capacity of the ecosystem to assimilate nutrients.

Credits

Extracts from "World Agriculture & Environment" by Jason Clay - buy the book online from Island Press

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