Mai Po

Overview

Gei Wai

© WWF Hong Kong

In Asia, people living in coastal areas have many hundreds of years of experience producing shrimps using ponds located adjacent to bays or estuaries. In Hong Kong, knowledge of how to do this did not arrive until the mid-1940's, when a wave of immigrants from China came into the Hong Kong SAR. These ponds were known as gei wai (literally meaning a pond enclosed by a bund) and were mainly for shrimp production but fish, oysters, algae and brackish water sedges were also harvested.

Each of the Mai Po gei wai covers an area of approximately 10 ha and are now recognised as good examples of how coastal wetlands can be managed sustainably, i.e. so that they can be of benefit to local communities, with minimal adverse impact to the environment. This is because traditional gei wai shrimp production relies on the natural productivity in the adjacent bay. At Mai Po, the ponds are stocked by flushing in young shrimps from Deep Bay in autumn, and the shrimps feed on naturally occurring organic matter, e.g. dead mangrove leaves, on the bottom of the pond. As a result, fishermen protected the stands of mangroves inside the pond as a source of food for the shrimps and fish. The shrimp of main commercial importance is Metapenaeus ensis (gei wai shrimp) but fish, such as Mugil cephalus (Grey mullet) are also present.

The original managers of Mai Po, the gei wai shrimp pond operators, used to completely drain down their gei wai to harvest the fish inside the pond when the shrimp-harvesting season has ended. This starts from early winter.

When the gei wai is drained, the areas of shallow water or exposed mud on the pond floor provide feeding and roosting habitats for hundreds of fish-eating birds, particularly herons, egrets and the endangered Black-faced Spoonbill. Since this traditional form of gei wai management adds to the ecological value of the area, WWF Hong Kong has continued to drain down the gei wai on a rotational basis. One gei wai is drained every two weeks from November to March, in order to provide feeding habitat for the migratory waterbirds that are passing through, or winter in Deep Bay.

In order to provide the best views for visitors of the many waterbirds in the draining gei wai, a net-screen will be placed across the Closed Area Fence Road end of the gei wai when they are drained, so that visitors can see the impressive numbers of herons, egrets and Black-faced Spoonbills feeding and roosting in the draining pond.