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 Natures Fast Feeder - The Frogfish - first published in the Nassau Guardian June 1981
Yellow Frogfish

 

The little fish was slowly patrolling the edge of the reef, picking at the tiny animals that form its food, when it disappeared. One second it was there, and the next, it was gone. All that remained was a disturbance in the water and a slight movement from a weed covered brown rock.

The brown rock is not a rock, nor is the fluttering shrimp-like animal above it, a shrimp. The two constitute the obvious and less obvious parts of one of the most highly adapted and efficient predatory fish of the reef.

There are seven species of frogfish or anglerfish in the Bahamas, none of which grow very large. The smallest is the Smallspot Frogfish, which attains a maximum size of two inches, while the giant of the family the Ocellated (eyed) Frogfish, reaches a mighty 15 inches.

The frogfishes are masters of camouflage, their bodies squat, lumpy and decorated with protuberances resembling weed, and their colour - drab and irregular, mimicking precisely the stones and rocks they inhabit. 

The foremost spine of the dorsal fin has moved forward, to the upper lip and become amazingly modified to resemble a shrimp or small fish, not only in its appearance, but also by its movements.  The strategy of the frogfish is to play a waiting game and interest passers-by in its lure. When the curious fishes come too close, the frogfish strikes. By expanding its mouth at an incredible speed it creates a suction that engulfs its prey before it knows what is happening. A frogfish can expand the volume of its mouth by 12 times in less than six-thousandths of a second, making it one of the fastest feeding vertebrates known to science. Of course, in so doing, the fish swallows a lot of water as well as its prey, but this is ejected as soon as its supper is in its stomach. Movement of prey from the mouth into the stomach is achieved in little more than time than that required catching the prey in the first place. Sargassumfish

These fish also have the ability to ingest fish longer than themselves. Like many deep-water predators, their mouths and stomachs are gigantic in proportion to the rest of the animal.

While most Bahamian frogfish are bottom-dwellers, the Sargassum Fish (Histrio histrio) inhabits floating rafts of Sargassum weed. Growing to a length of around six inches, it stalks its prey in the weed rather than waiting for its prey to come to it, relying on its superb cryptic colouration, and its ability to propel itself by forcing water through the reduced gill openings. The pectoral fins of the Sargassum fish are actually prehensile, and can grasp strands of Sargassum weed like tiny hands as it slowly makes its way through the Sargassum raft. This species is not particular about its food and will even consume members of its own kind. One dissected Sargassum Fish held sixteen smaller Sargassum Fish in its stomach!

Most anglerfish eat other fish, although any shrimp that comes within range is fair game. The Goosefish (Lophius americanus) of North American waters grows to four feet in length and has been reported to eat Seagulls and Cormorants a not too inconsiderable task in view of its huge mouth and fearsome dentition.

Few of us will ever see a frogfish in its own habitat, but boaters may be interested in looking for the Sargassum fish. If a mass of floating weed is netted and shaken out into a bucket of water, a variety of marvelously adapted Sargassum inhabitants can be observed. Fish, crabs and shrimps all with the mottled brown colouration of the weed in which they live will appear.

Within, the fish order Pediculati the Frogfish and their kin, can be seen some of the most amazing adaptations of the animal world. From the greatest depths to the shallows of the reefs, they lie in wait or cunningly stalk their supper, their activities known only to themselves and to their bewildered and unsuspecting prey - the latter for only the shortest time!.

 

R. Attrill 2006