Finding Food in Seagrass Beds
The sandy plains and seagrass beds that exist in coral lagoons and in the spaces between large coral heads are home to a variety of invertebrates, including mollusks, worms, and shrimps. Some of these animals seek shelter by hiding beneath the sand at certain times throughout the day, away from the attentions of their predators. But as far as some fish are concerned, out of sight is not necessarily out of mind. Quite a few fish species, including goatfish, cowfish, and many wrasses, use some ingenious tactics to seek out hidden prey.
How does the goatfish find its prey?
Goatfish use a pair of barbels on the chin to dig into the sandy substrate in pursuit of buried prey. The barbels themselves are covered with chemosensory cells, so that as the fish sifts through the sand, it is able to taste what it cannot see. Foraging goatfish kick up large clouds of fine sand as they root around on the seabed and this attracts a crowd of other fish, which hang around in the hope of picking up a free meal in
the shape of a disturbed creature from below.
What other kinds of fish forage in the lagoons?
Seahorses are usually found among seagrass beds in lagoons, holding onto the vegetation with their prehensile tails and snapping at passing invertebrates in the water column. The bizarrely shaped cowfishes also occupy the calmer waters of the lagoon. Like their relatives, the puffers and the triggers, they use the remarkable technique of blowing jets of water at the substrate to uncover buried benthic invertebrates.
Snake eels lie buried in the sand itself, with only the tip of their snout showing. In this position they can keep a lookout for any prey that crawls or swims too close. If the prey comes within range, the eel explodes from its hiding place and captures its victim before it can react. Lizardfish, too, can be found on these sandy plains and hunt in a similar way to the snake eels, although they do not burrow into the sand. Instead, they rely on patience and camouflage to conceal them from their fish and invertebrate prey.
How else can fish uncover hidden prey on the seabed?
Although the remarkable jet-blowing tactics used by the puffers and their relatives to uncover hidden, buried prey probably takes the prize for ingenuity, there are other ways of reaching prey beneath the sand. One method involves taking in a large mouthful of sand and sifting through it, spitting out the sand or ejecting it through the gills, and retaining the animals that were sheltered within it. This approach is taken by hogfish, among others. Wrasses are extremely active foragers and will make great efforts to secure a meal, including moving or upturning stones on the seabed to expose the selection beneath.