Filetail catshark - Parmaturus xaniurus
Filetail catshark Parmaturus xaniurus on sandy bottom.
Body structure, features & anatomy
The Filetail catshark Parmaturus xaniurus is a small catshark from the family Pentanchidae. WoRMS lists the name as accepted; on Haitauchen the species is within Selachii, Galeomorphi, Carcharhiniformes and the genus Parmaturus.
Shark-References traces the first description back to Gilbert in 1892. The German name refers to the rough, file-like structure in the tail area that distinguishes these deep-water catsharks from many shallower catsharks.
How to recognize the species
The species remains small, reaching about 55 centimeters in length according to the references used. The body is slim, the head is relatively short, and the eyes are adapted to living close to the ground in subdued deep light.
The combination of small body size, deep-water habitat, catshark shape and tail characteristics counts for identification. This species is not normally a sighting target for divers, but rather an example of the little visible deep-sea diversity of catsharks.
Distribution & habitat
FishBase describes for Parmaturus xaniurus a distribution area in the eastern Pacific from California to the Gulf of California. The type is therefore included in Haitauchen USA, Mexico and that Pacific Ocean linked.
The habitat is on the outer continental shelf and on the upper continental slope. The depth information used ranges from approximately 88 to 1250 meters and clearly shows that this is not a typical reef or snorkeling area.
Depth, structure and local visibility
The depth range is more important than a broad country map. The species uses soft to mixed bottoms in deeper coastal and slope zones where normal recreational diving does not take place.
A distribution map was therefore not included. For this public profile page, the textual classification makes more sense: eastern Pacific, deep shelf and slope areas, hardly any direct encounters with divers.
Life history, diet & reproduction
FishBase classifies the Filetail catshark as a bottom-hugging, deep-water fish. The diet includes small fish and invertebrates that live in or above the bottom of the shelf and slope zone.
Like other catsharks Parmaturus xaniurus egg-laying. Embryos develop in egg capsules that provide protection for the offspring until the young hatch as small, independent sharks.
Bottom life instead of open water
The way of life suits a poorly lit, structurally quiet deep-water habitat. Large gill openings, ground-level movement and small body size are more important than speed for this ecological niche.
There is significantly less publicly available information about behavior, growth and precise population dynamics than for known coastal sharks. This makes the species scientifically interesting, but difficult to plan for direct shark observation.
Threats & conservation status
IUCN Red List evaluated Parmaturus xaniurus global as Least Concern, according to Haitauchen as not endangered. However, this classification does not mean that deep-water habitats are free of pressure.
Possible points of contact with humans arise primarily through bottom trawling or deep fishing, in which small catsharks can occur as bycatch. Targeted use is not the focus of this type.
What the classification means
The current assessment is comparatively reassuring, but should be read with caution. Deeper-dwelling species are often observed less frequently, and local changes in fishing pressure or habitat quality are not always immediately noticeable.
To protect such species, clean catch data, bycatch monitoring and responsible deep fishing are more important than classic reef protection measures. For most people, the Filetail catshark becomes visible primarily in data, not under water.
Filetail catshark & humans
Applies to people Parmaturus xaniurus, the Filetail catshark, as harmless. Its small size, deep-water habitat and bottom-hugging lifestyle make encounters with divers virtually unlikely.
If the species does appear in fisheries, it is more likely to be bycatch than a target species. This is precisely why correct species recording and feedback from deep fishing are important so that stocks do not disappear in the noise of data.
Respectful classification
For Haitauchen, this species represents a different view of sharks: not every shark species is an encounter animal. Many species are small, deep-dwelling and ecologically specialized, but are still part of the shark diversity of a marine area.
Those who study this species learn above all how closely taxonomy, deep-sea ecology and fishing data are related. This is less spectacular than a reef encounter, but just as important for a complete picture of the sharks.
Profile
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Taxonomy
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