Pipefish are distinctive little fish that resemble seahorses stretched out straight. Like seahorses they snap up their prey using a long tubular snout, have a body covered in bony plates and brood their young using a pouch on the abdomen of the male. There are about 200 species found around the world, although here in New England there is only one, the Northern Pipefish (Syngnathus fuscus).
Like seahorses, pipefish are lacking some of the fins typically found on other kinds of fish. The pelvic fins are gone entirely and there is only a single dorsal fin on the animal’s back. For most fish the dorsals are used for balance, but for the pipefish it is the primary appendage used for locomotion. By undulating this fin the fish moves slowly forward through the water. Again like seahorses, the pectoral fins look like little ears placed far up on the head. Pectorals are the wing-like fins found on the sides of nearly all fish and are used primarily for steering and breaking. For pipefish they are also used to help out the dorsal fin as the fish swims.
At first glance it would appear that the pipefish also lacks a tail fin, but it’s there, usually folded up tightly so that the end of the body appears to come to a point. (This diary on seahorses goes into more detail about the fins of this family of fishes.) When the fish needs a quick burst of speed this caudal fin snaps open like a Japanese fan. You can see the expanded tail fin on the African species below:
Pipefish are shallow water fish, rarely growing more than a foot or so in length. They rely on camouflage both for protection and to conceal themselves as they wait for small shrimp and other prey to come close enough to be snapped up by the mouth. The long, thin body is ideal for camouflaging the fish in seaweed and eelgrass plants. They can often be found hovering among these weeds and allowing themselves to be swayed back and forth with the currents. Like many camouflage fish, pipefish have a knack for color change, ranging from black, tan, green and red depending on the type of weeds it is hiding in.
Although it seems as though the pipefish is so well-adapted to living among weeds that it would only be found in this type of habitat, its actual range is surprisingly varied. It can be found in nearly any shallow area including muddy bottoms (where it turns black and lies flat on the mud), rocky bottoms and even at the mouths of rivers where they sometimes travel into freshwater. It is one of the few saltwater fish able to do so.
Pipefish have excellent vision, important for spotting the small prey it feeds on. It shows an interesting habit of moving each eyeball independently, often with one facing forward and the other looking behind it. Being a "lying-in-wait" predator, rather than actively chasing prey it patiently waits for unsuspecting animals to move close to it. The long tubular snout acts like a vacuum cleaner, sucking up tiny fish and crustaceans with the small, toothless mouth located at the tip. To create the suction the fish snaps its mouth open quickly. Both water and prey gets sucked into the tube, the food is pressed against the roof of the mouth while the water is expelled through the gills, and then the prey is swallowed. A six-inch pipefish can eat up to fifty shrimp a day using this method.
Pipefish breed from April to September, usually having multiple clutches each season. Again like seahorses, the role of carrying the eggs is reversed. The male has a long brood pouch under the body where the eggs are held and incubated until they hatch. When empty the pouch looks like a deflated fold of skin lying flat against the body. But after the female injects the hundred or so eggs into it, using an egg-laying structure called an oviduct to avoid spillage into the surrounding water, the pouch swells like a balloon. Just before hatching the eyes of the babies can sometimes be seen through the thin, stretched skin of the brood pouch. While seahorses are monogamous, forming pair bonds each season, and in some cases for life, most species of pipefish practice polyandry, meaning each female mates with multiple males.
The eggs have no yolk but are instead fed by the inner lining of the male’s pouch, which accounts for the thinning as the eggs age. Eggs hatch in about two weeks and the juveniles look like this:
Other diaries in this series can be found here.