Creatures of the Deep: Tripod Fish

By Dylan Howell (unedited)

As many people know, the deep sea is full of fantastical creatures that seem like they couldn't possibly exist. Some may even look like aliens. However, sometimes these creatures can look pretty silly. One such creature is the Tripod Fish.

This creature has evolved three, elongated pelvic and caudal fins that it uses to "stand" on the sea floor, hence the name. They live anywhere from 900m to 4,700m down on the abyssal plain of the Pacific, Atlantic, and Indian oceans. This fish has an interesting hunting method consisting of standing on the sea floor, facing into the current, and waiting for prey to drift within reach.

Since sight is a virtually useless sense in the depths, this fish uses the sensitive rays of their pectoral fins to detect nearby prey. When something gets close enough, they will use these fins almost like hands to guide the food towards their gaping mouth. Their diet includes things like zooplankton, planktonic crustaceans, and other small organisms. Another interesting fact is how they swim.

When hunting, the pelvic fins become rigid to provide support, but when the fish swims, they become soft and flexible to allow for fluid movement. Scientists theorize that this is caused by a controlled flow of fluid to and from the fins. When the fluid is directed into them, the fins stiffen, but when directed away, they become flexible. Tripod Fish are typically bronze colored with gray markings on the head and belly. The largest one on record is 37 centimeters in length, but the average specimen is about 30 centimeters long with fins about 1 meter in length.

Until recently, the technology did not exist to dive down and study these creatures, so much is still unknown about them. Nevertheless, Tripod Fish are fascinating and quite comedic looking creatures.

Image credit: Bahamas Deep-Sea Coral Expedition Science Party, NOAA-OER