Mai Po Wildlife

Fish

Species of Interest - Common Mud-skipper Boleophthalmus pectinirostris

© WK Leung / WWF Hong Kong

Physical Description

The Common Mud-skipper is brown in colour with irregular spots and markings on its body. Adults are typically 6-10cm in length. Its head is round-shaped with a pair of protruding eyes above to help locate potential predators. Muscular and strong pectoral fins and tails enabling this fish to skip and hop on the mud surface (hence its name). The pelvic fin has also evolved into a sucking disc which allows it to grip to mangrove trunks and roots.

Global Status and Distribution

The Common Mud-skipper is widely distributed throughout coastal areas of the Northwest Pacific region and South China Sea, including Korea, Japan and Taiwan.

Habitat destruction, pollution and hunting pose the greatest threats to Common Mud-skipper. The main habitat for which they depend for survival, coastal mudflat, is under heavy development pressure in many countries. Throughout China they are served as food and are also kept as pets in some countries.

Local Status

This is the most abundant mud-skipper species in Hong Kong and can be found in almost all estuarine and mudflat areas. It is not a protected species, but those inside the Mai Po Inner Deep Bay Ramsar Site receive protection under the Wild Animal Protection Ordinance.

Basic Ecology

Common Mud-skipper inhabit estuarine and mudflat areas, especially at the fringe of the inter-tidal mangrove towards the higher to middle tidal zone. In order to adapt to water level changes, the Mud-skipper has developed special physical and behavioural characteristics.

Their gills enable them to breathe in open air and they can also breathe through their skin and the lining of their mouth and throat as long as the fish remains moist. This allows the mudskipper to survive out of water on the mudflat until the tide rises once again, something other fish can not do.

Common Mud-skipper create borrows on the mud surface for roosting and nesting which they retreat into when the mudflat is not covered with water or when danger is nearby. The male mud-skipper can be seen frantically defending his territory around the burrow during the mating season (March-September). Females lay eggs in the burrow of the mate and the male is responsible for guarding the eggs until they hatch and the offspring become independent.

The main food items are small invertebrates such as insects and crabs. However, the mud-skippers are themselves an important food source for many resident and migratory waterbirds.