PDC Day 11: Aquaculture

The previous day’s discussion of ponds in the landscape segued easily into looking at what can be grown in them. Many of us got rather inspired by the idea of raising multiple species of fish and plants in a pond.

Muscovy duck

Bodies of water being three-dimensional, they can be enormously productive. Some of the basic permaculture principles for land production apply: the productivity of edge, where an irregularly-shaped pond provides a wide variety of habitats for both aquatic and terrestrial species; the integration of plant and animal culture, such that ducks, for example, contribute to the nutrients available to fish and aquatic plants and vice-versa; the stacking of different levels from waterfowl to floating plants to mid-water species such as prawns to bottom feeders such as catfish.

It is very important to use native species in an open system. Tilapia, a warm water fish, can be grown in a closed hydroponic system with tanks, but if a few eggs escape – e.g. on the feet of birds – they can devastate the local ecology downstream.

Blueberries and wild rice are among possible species to grow along the edge of a pond.

Duckweed

Duckweed, a tiny floating green plant, ¬†fixes nitrogen and is high in protein. It’s invasive or abundant, depending on your point of view. Duckweed can be used in both wastewater treatment and biofuel production – at the same time.

Smoked fish is another high-value product we could produce with our own smokehouse.

Fish farming near Port Mouton, NS

Ocean fishing is broken. By taking the biggest fish, we have forced an unnatural selection for smaller and smaller fish and shellfish. Trawlers routinely dump huge loads of bycatch (species they aren’t licensed to harvest) that end up in decaying piles at the bottom of the ocean.¬†Raising huge monocultures of salmon in crowded aquaculture cages near the shore requires feeding them food they would never normally eat, and treating them with drugs that cannot possibly stay within the cages.

But humanity does not have to stop eating fish. It is possible to grow fish sustainably on a small, local scale using the lessons of permaculture.

 

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