Trachyrincus scabrus

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Trachyrincus scabrus
Trachyrincus scabrus, drawing from "Oceanic Ichthyology" by George Brown Goode and Tarleton H. Bean.

Trachyrincus scabrus , drawing from "Oceanic Ichthyology" by George Brown Goode and Tarleton H. Bean .

Systematics
Paracanthopterygii
Order : Cod-like (Gadiformes)
Family : Grenadier fish (Macrouridae)
Subfamily : Trachyrincinae
Genre : Trachyrhynchus
Type : Trachyrincus scabrus
Scientific name
Trachyrincus scabrus
Risso , 1810

The Trachyrincus scabrus is a little researched fish that occurs mainly in the deep sea and feeds on predatory fish .

features

The most striking feature of Trachyrincus scabrus is its very large head. The head length is 25 to 32% of the body length. The eyes are very large, the horizontal eye diameter is about a third of the length of the head. The eye is oval in shape, which is why the horizontal diameter is larger than the vertical. The muzzle is long and pointed and makes up 38 to 45% of the length of the head. The mouth is underneath and horseshoe-shaped and there are numerous fine teeth in both jaws. The first dorsal fin (dorsalis) has 11 to 12 soft rays, of which the second fin ray is the longest. The second dorsalis starts directly behind the first, is set a little deeper and a little longer than the anal fin (analis). At the end it merges with the caudal fin (caudalis) as well as the analis, which is a little shorter and deeper than the second dorsalis. The pectoral fins (pectoralia) each have 20 to 22 fin rays, while the pelvic fins (ventralia) only consist of seven (rarely six) fin rays. The ctenoid scales of Trachyrhynchus trachyrhynchus usually have three teeth, so-called denticles, and are formed from cycloid scales during ontogenesis . In the head region, the scales form a coherent shell and on both sides of the base of the dorsal and anal fin there is a row of these scales, which are provided with a crest. This comb is also serrated in adult animals. The fish is usually gray-brown in color and has a total length of over 50 cm in the adult state.

Mouth of Trachyrincus scabrus

Occurrence

The distribution area of Trachyrincus scabrus stretches north in the Atlantic to the Irish continental shelf , across the western Mediterranean to the southernmost point, Cape Verde. Trachyrincus scabrus is the most common species in the Mediterranean among the grenadier fish . Rafinesque (1810) describes this species for the first time from samples from Nice as Oxycephys scabrus, at the same time Risso (1810) also describes this species as Lepidoleprus trachyrhynchus. Vaillant (1888) found this animal on the coasts of Morocco , Sudan and Cape Verde. Koehler (1896) discovered the fish in the Gulf of Gascogne . Richard (1904) fishes this species again in Morocco from a depth of approx. 1215 m and Johnsen (1927) found specimens in the larval stage in the area of ​​Gran sol. IA Trunov pulled this species out of the water in the southwest Atlantic in 1972. This species is often fished in undeveloped areas at a depth of over 500 m. Trachyrincus scabrus occurs at depths between 300 and 1500 m and is very well adapted to the prevailing conditions there. With a constant water temperature of 13 ° C, increased salinity and little light and oxygen, its growth and reproduction are slowed down, and its metabolic rate is lowered.

nutrition

The pelagic fish Trachyrincus scabrus feeds mainly on hover shrimp and copepods . It also eats small fish such as crabs (Crustacea), cephalopods (cephalopods), polychaetes (polychaetes) or snails (Gastropoda).

Reproduction and development

Trachyrincus scabrus shows a strongly seasonal reproduction pattern and the different stages of development of the fish take place at different depths of the sea. Microscopic examination of the gonads in the female revealed six different ovarian stages. Mature females can be found in fall and winter. In autumn, the females are in the development and spawning stages, and they spawn actively in winter. After hatching, the juvenile animals live at a depth of between 300 and 400 m. In the second year of life they migrate to a depth between 400 and 500 m. In the third and / or fourth year of life, they become sexually mature and migrate again to a depth between 600 and 800 m. The adults can then be found at a depth between 900 and 1400 m, with the largest specimens found at a depth between 900 and 1050 m.

Parasites

The parasitic infestation is not uncommon in fish, so also is Trachyrincus scabrus often a subclass of the flukes (trematodes), the so-called digeneans infested. The parasitism was discovered by Constenla et al. (2011) described in more detail. Bathycreadium elongatum sits preferentially in the pyloric blind sac or in the intestine of the fish and affects approximately 75% of all individuals. Sometimes parasites are also found in the stomach or in the vicinity or in the mesentery . The parasitic infestation leads to nodular lesions in the pyloric blind sac, which, on histological examination, show granulomatous inflammation. The comparison of the 28S rRNA of the parasites from the nodules and those that occur freely in the pyloric blind sac showed 100% agreement. Bathycreadium elongatum lives freely in the mesentery in spring and summer and lays its eggs in the nodules. After the larvae hatch, the nodules degenerate in autumn. Mostly juvenile animals can be found in winter and spring. In summer the number of juvenile and adult animals is almost the same and in autumn it shifts to a higher number of adults and senescent animals.

Relationship with people

The species is very sensitive to environmental changes. Due to the massive shrimp fishery, the animals do not have enough time to reach full size. As a common bycatch, they are processed into fish meal and oil.

Taxonomy and systematics

Synonyms are: Trachyrincus scabrus , Oxycephas scabrus , Trachyrhynchus scabrus , Trachyrincus anonyme , Lepidoleprus trachyrincus , Trachyrincus trachyrincus and Macrurus trachyrhynchus .

literature

  1. ↑ a b Geistdoerfer, P .: Macrouridae . In: Whitehead PJP, Bauchot M.-L., Hureau J.-C-, Nielsen J. & Tortonese E. (Eds.): Fishes of the North-Eastern Atlantic and the Mediterranean . tape 2 . UNESCO, Paris 1986, ISBN 92-3002308-6 , pp. 644-676 .
  2. ↑ a b c d e Risso A .: Ichthyologie de Nice, ou Histoire Naturelle des Poissons du département des Alpes Maritimes. F.Schoell, Paris 1810.
  3. ^ A b c d Cohen, DM, T. Indada, T. Iwamoto and N. Scialabba: Gaiform fishes of the world. Accessed October 2017 .
  4. ↑ a b c d e Fernandez-Arcaya, U., Recasens, L., Murua, H., Ramirez-Llodra, E., & Rotllant, G .: Population structure and reproductive patterns of the NW Mediterranean deep-sea macrourid Trachyrincus scabrus (Rafinesque, 1810) . In: Marine Biology . tape 159 , 2012, p. 1885-1896 , doi : 10.1007 / s00227-012-1976-8 .
  5. ↑ a b c d Rafinesque CS: Carattèri di alcuni nuovi generi e nuove specie di animali (principalmente di pesci) e piante della Sicilia, con varie osservazioni copra i mesmidi. 1810.
  6. ^ Vaillant, L: Poissons . In: A. Milne-Edwards (ed.): Expéditions scientifiques du 'Travailleur' ​​et du 'Talisman' pendant les années 1880-1883. G.Masson, Paris 1888.
  7. ^ Koehler R .: - Results Scientifiques de la campagne du "Caudan" dans le Golfe de Gascogne . In: Annales de'l Université de Lyon . tape 26 . Masson et Cie, Editeurs, Paris 1896.
  8. ↑ a b c d Ibañez, M .: Notas Ictiologicas IV. Contribución al Estudio de la Biología y Crecimiento de un pez Batibéntico Trachyrincus scabrus (Risso) en el Mediterráneo y Atlántico NE. In: Munibe . tape 29 , 1977, pp. 213-230 .
  9. ^ Richard J .: Campagne scientifique de la "Princesse Alice" en 1904. In: Bulletin de Musée Océanografique de Monaco . tape 41 , 1905.
  10. ^ Johnsen S .: On some bathypelagic stages of the Macrourid fishes . In: Nyt Magazin for Naturvidenskaberne . tape 65 , 1927, pp. 221-242 .
  11. ↑ Constenla, M., Carrassón, M., Moyà, CM, Fernàndez-Chacón, A., Padrós, F., Repullés-Albelda, A., & Montero, FE: Parasitisation by Bathycreadium elongatum (Digenea, Opecoelidae) in pyloric caeca of Trachyrincus scabrus (Teleostei, Macrouridae). In: Diseases of aquatic organisms . tape 96 , 2011, p. 239-247 , doi : 10.3354 / dao02393 .
  12. ^ Giorna, ME: Mémoire sur des poissons d'espèces nouvelles et de genres nouveaux. Plus: Suite et conclusion du mémoire (pp. 177-180). Mémoires de l'Académie impériale des sciences, littérature et beaux-arts, Turin, Sér. Sciences Physiques et Mathématiques. 1809.