Between Water and Land: Mudskipper Context Clues

A Fish on the Mud

1Along some warm coastlines, mangrove trees grow beside broad, muddy flats. The tides change this habitat throughout the day. At high tide, much of the mud is submerged beneath the water. Later, the same ground becomes exposed, with no water covering its surface. A mudskipper, a fish that spends time out of water, can use both versions of this changing home.

2As the tide begins to recede, water drains away from the mangrove roots. Puddles become smaller, and wider strips of mud appear between them. Mudskippers can move onto these newly uncovered areas to search for food. Small animals living on the mud provide meals for these unusual fish.

3Moving over mud requires different tools from swimming. A mudskipper presses its strong front fins against the ground to propel itself forward. Each push sends its body a little farther across the surface. These fins work somewhat like a person's crutches, supporting the body while helping it move from one spot to another.

4A mudskipper's eyes are elevated. Like a lookout on a raised platform, they sit above much of the surrounding scene. Many fish have eyes on the sides of their heads, but a mudskipper's eyes project from the top. This position helps it watch the area while its body stays low.

5Sun and wind can quickly dry the surface of an uncovered mudflat. When a mudskipper leaves the water, it must retain moisture, or its skin will become too dry. Water can enter a cloth and then evaporate, leaving the cloth dry; the fish, however, needs to keep moisture around. Its moist skin and mouth lining help it take in oxygen from the air.

6Many mudskippers dig burrows in the soft ground. When danger approaches, a nearby burrow can serve as a refuge. A fish may dash inside instead of remaining out in the open. On bare mud, it is vulnerable: a hunting bird has a clear view and can approach it more easily. Inside the burrow, the fish is harder to reach.

7Even outside a burrow, many mudskippers can be surprisingly inconspicuous. Their brownish or grayish coloring resembles the mud around them rather than standing out like a bright flag. An observer may look directly at a patch of ground without noticing the fish until it moves. Blending into the background can make a small animal difficult to spot.

8Compared with a mudskipper, a fish that cannot breathe air is at a disadvantage on an exposed mudflat. Without water covering its gills, that fish may struggle to get enough oxygen. The mudskipper has useful ways to meet the challenges of a place that changes between water and land.