Pipefish - cryptic beauties
Observant scubadivers diving over eelgrass meadows but also over sandy bottom from shallowest regions to several meters depth can presently find common and, with a little luck, less frequent representatives of a bizarre and fascinating group of bony fishes - pipefish
Pipefish belong to the Syngnathiformes, a bizarre group of bony fishes that also comprises seahorses, weedy and leafy sea dragons. All Syngnathiformes have several physical features in common, a fused jaw and a partly reduced body musculature – species of this group mostly use pectoral and dorsal fins for locomotion. Within this group, pipefish belong to the family Syngnathidae. They are mostly planktivorous, i.e. the prey upon plankton organisms like copepods and fish fry. Pipefish inhabit coastal zones and the high seas of all oceans from subpolar regions to the tropics. In the western Baltic, five out of more than 320 pipefish species can be encountered. Apart from their fascinating looks allowing them to be perfectly camouflaged in their environment (a reason why many specimens simply are easily missed during diving!) pipefish also display a surprising reproduction behavior: Indeed the male pipefish becomes “pregnant”! After a courtship characterized by synchronous choreographed displays by both fishes, the female fish deposits eggs species-specific into a specialized brood pouch on the underside of the male or attaches them to a spongy part of skin in that region. At that time, the eggs are fertilized by the male. A special mucous membrane in the brood pouch region then surrounds and nourishes the eggs. After a comparatively long incubation time of about 4 weeks, the fry hatch. Juveniles remain for a certain time in the safety of the brood pouch before they are “released” by the male as miniature copies of their parents. Thus, juvenile pipefish experience an effective way of brood care. Species living on or above the seafloor display the highest extent of such brood care by the development of a longitudinal brood pouch by a groove and two skin folds on the belly of the male fish. Many pipefish species are monogamous, i.e. male and female fish remain together for live. In domestic species, a male willingly “hatches” eggs of several female fishes – or considered different and labeled with a biological term: a female pipefish deposits eggs at several males (polyandry).
In the western Baltic pipefish species of the genus Syngnathus and “snake pipefish” species of the genus Nerophis and Entelurus are common. All have a distinctly elongated, snake like, straight body without conspicuous fins in common. A closer look nevertheless reveals features that facilitates assignment of the discovery to one of the genera mentioned above. The genus syngnathus unlike the genera Nerophis and Entelurus has developed pectoral and caudal fins. Especially the pectoral fins are hard to distinguish, the triangular caudal fin at the tail end however is relatively easy to discern.
So: caudal fin present?
Yes – "pipefish" (Syngnathus)
No- "snake pipefish" (Nerophis or Entelurus)
Once the Genus “Syngnathus” is identified, one has to go further into details: Have a closer look at the tubular snout. If the snout is laterally compressed at the mouth end and clearly higher than the eye diameter, you have encountered a broad-nosed pipefish (Syngnathus typle). This species is often associated with eelgrass and perfectly camouflaged in this environment by green coloration. The underside of the body additionally often resembles color and structure of eelgrass blossoms. But also in pipefish the exception proves the rule: Broad-nosed pipefish are also common over sandy bottom and throughout the littoral and can be encountered in darker, brownish colors.
Broad-nosed pipefish (Syngnathus rostellatus). Foto: R. Rathke
If the terminal tubular snout is not compressed but round and its diameter is not bigger than the eye diameter, the species encountered is either the lesser pipefish (or Nilsson´s pipefish, Syngnathus rostellatus) or the greater pipefish (Syngnathus acus). Both inhabit structured regions in the littoral and are also common beneath eelgrass meadows. Distinguishing the exact species is really difficult apart from by maximum size. Generally, this has to be done by counting longitudinal ridges of the dermal skeleton between the head and the dorsal fin – a task impossible to accomplish while scubadiving. However, in the majority of cases one will have the lesser pipefish in front of the mask as the greater pipefish is really uncommon in the western Baltic and inhabits rather the North Sea and adjacent regions.
Lesser pipefish or Nilsson´s pipefish (Syngnathus rostellatus)
Photo: R. Rathke
If the search for a caudal fin remained unsuccessful and thus led to the “snake pipefish”, a further identification should be no major problem. The straight-nose pipefish (Nerophis ophidion) dwells between algae threads and above all between eelgrass halms. Due to its mostly greenish color its perfectly camouflaged. It is easily distinguished by the fact that it uses its (we recall: caudal fin lacking) tail to latch to eelgrass etc. (by the way another distinct identification feature: no other pipefish species in the Baltic Sea attaches to the substrate in this way).
The snake pipefish or ocean pipefish (Entelurus aequoreus) is a very large and conspicuous species actually uncommon in the Baltic Sea. Females attain a maximum size of up to 60cm. Due to its bright, yellowish to brownish color with distinct bluish rings along the body and an additional brown band on height of the eyes on both sides of the head, this species can not be confused with others. It inhabits eelgrass meadows and the total littoral but is also common in oceanic regions of the high seas. In the last years, this species displayed some sort of population explosion in the North Sea and adjacent regions, presumably owing to changed ambient conditions due to climate change. In the Baltic Sea the number of catches and sightings also continuously increased. The snake pipefish or ocean pipefish thus can no longer accounted as uncommon in Baltic Sea. An encounter with this fascinating species nevertheless can be regarded as a highlight of a Baltic dive that should be noted in the dive-log and of course in the TaMOs protocol.
NDR 1 Welle Nord: TaMOs feature
