Blackmouth catshark

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Blackmouth catshark

Least Concern  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Carcharhiniformes
Family: Scyliorhinidae
Genus: Galeus
Species:
G. melastomus
Binomial name
Galeus melastomus
Range of the blackmouth catshark
Synonyms

Pristiurus melanostomus Lowe, 1843
Pristiurus souverbiei LaFont, 1868
Scyllium artedii Risso, 1820
Scyllium melanostomum Bonaparte, 1834
Squalus annulatus Nilsson, 1832
Squalus delarochianus* Blainville, 1816
Squalus prionurus Otto, 1821

* ambiguous synonym

The blackmouth catshark (Galeus melastomus) is a

caudal fin
. It reaches lengths of 50–79 cm (20–31 in), with sharks in the Atlantic growing larger than those in the Mediterranean.

Slow-swimming but active, the blackmouth catshark is a

Least Concern
, as there is no indication that its numbers have declined despite fishing pressure.

Taxonomy and phylogeny

Ma).[5]

Distribution and habitat

The blackmouth catshark is widely distributed in the northeastern Atlantic Ocean, from southwestern

continental slope, at depths of 150–1,400 m (490–4,590 ft). However, it has been documented from water as shallow as 20–25 m (66–82 ft)[6] in Norway, and as deep as 2,300–3,850 m (7,550–12,630 ft) in the eastern Mediterranean.[7] The depths at which it is most common vary between regions, for example 300–500 m (980–1,640 ft) in the Bay of Biscay,[8] 400–800 m (1,300–2,600 ft) off Portugal,[9] 500–800 m (1,600–2,600 ft) in the Strait of Sicily,[7] 1,000–1,400 m (3,300–4,600 ft) in the Catalan Sea,[10] and 1,500–1,830 m (4,920–6,000 ft) in the eastern Mediterranean.[11] Water temperature does not appear to be an important factor in determining the distribution of this species.[7]

Found on or near the bottom, the blackmouth catshark favors a muddy habitat.[12] There is little evidence for segregation by sex.[9][13] A number of studies in the northern and western Mediterranean have reported that adults occur deeper than juveniles.[10][12][13][14] Other studies though have found no such pattern. It is possible that areas such as the waters off southern France offer a habitat suitable for sharks of all ages.[15] Another explanation with some scientific support is that adults are most common at intermediate depths, while young sharks are restricted to shallower water and both adults and juveniles are found in deeper water. If true, the age-depth inconsistencies observed from previous research could have resulted from incomplete depth sampling.[7]

Description

Early illustration of a blackmouth catshark, showing its ornate dorsal color pattern.

The reported maximum lengths attained by the blackmouth catshark varies from 67 to 79 cm (26 to 31 in) for Atlantic sharks and 50 to 64 cm (20 to 25 in) for Mediterranean sharks; a length record of 90 cm (35 in) may be dubious. Females attain a larger ultimate size than males.

pectoral fin bases.[16][17][18]

The two

dermal denticles. There is a prominent row of enlarged denticles, resembling saw teeth, along the upper edge of the caudal fin.[16] The body is grayish-brown above, with 15–18 dark, rounded saddles, blotches, and/or spots that run onto the tail; each marking is highlighted by a paler border. The underside is white, as are the tips of the dorsal and caudal fins. The inside of the mouth is black.[17][19]

Biology and ecology

Within its range, the blackmouth catshark is one of the most abundant sharks over the upper and middle continental slope.

tapeworm Ditrachybothridium macrocephalum and the protist Eimeria palavensis.[24][25]

Feeding

The blackmouth catshark has well-developed eyes and ampullae of Lorenzini for finding prey.

The blackmouth catshark is an active,

sharks and rays and smaller members of the same species. The importance of cephalopod prey across ages differs between regions.[8][10][27] The stomachs of some blackmouth catsharks have found to contain pieces of animals too large for a single shark to overwhelm, suggesting that it may sometimes attack in groups. Scavenging has been infrequently documented, including of human refuse.[1][10]

When foraging, the blackmouth catshark swings its head from side to side to employ its senses more effectively. It likely relies mainly on vision and

lens and cone cells of its eyes are large, allowing smaller or farther objects to be discerned from the background. The rod cells of its eyes are most sensitive to the wavelengths emitted by bioluminescence, which is exhibited by most of the organisms it hunts. For electroreception, the blackmouth catshark has a high number of ampullae of Lorenzini that are evenly arranged, which enhances spatial resolution and is best suited for localizing fast-moving prey.[28][29]

Life history

Unlike most members of its genus, the blackmouth catshark exhibits multiple oviparity, in which more than one egg can mature within each oviduct simultaneously. Females may contain up to 13 developing eggs, though 1–4 per oviduct is typical.[7][16] The number of eggs laid annually per female has been estimated at between 60 and 100, increasing with female size.[13] Only the right ovary is functional in mature females. The egg case is vase-shaped and bears a slight flange along the lateral margins; the anterior end is squared off, with a pair of stubby, coiled horns at the corners, while the posterior end is rounded. The surface of the case is somewhat translucent, smooth, and glossy. The case is a golden brown color when first laid, and becomes dark brown in sea water.[4] Egg cases produced by Atlantic sharks measure 3.5–6.5 cm (1.4–2.6 in) long and 1.4–3.0 cm (0.55–1.18 in) across. Those produced by Mediterranean sharks tend to be smaller at 4.2–5.5 cm (1.7–2.2 in) long and 1.7–2.5 cm (0.67–0.98 in) across. Larger females produce slightly larger egg cases.[9]

Mating and egg-laying proceeds year-round; reproductive activity is highest in winter and summer, though not all studies have found such a seasonal pattern.[9][13][14] The eggs are deposited on muddy substrates in relatively shallow water.[7][30] Maturation size varies between geographical regions, and is generally larger in the Atlantic than in the Mediterranean. Lengths at maturity for males and females have been variously reported from 48 to 79 cm (19 to 31 in) and 56 to 79 cm (22 to 31 in) respectively in the Atlantic,[9][13] and from 42 to 55 cm (17 to 22 in) and 39 to 61 cm (15 to 24 in) respectively in the Mediterranean.[13][15]

Human interactions

Harmless to humans and of little economic value,

fisheries. In particular, it is among the most commonly bycaught sharks in trawls targeting deepwater lobsters and shrimps (Nephrops norvegicus, Parapenaeus longirostris [es], Aristeus antennatus, and Aristaeomorpha folicea), operating off Portugal and in the Mediterranean. Most captured sharks are discarded, probably with heavy mortality. Some fisheries, such as those off Portugal and Italy, retain and utilize a small subset of the largest individuals for human consumption fresh or dried and salted, and for leather; the fishing fleet of Viareggio, Tuscany reported landing 700 kg (1,500 lb) in 2005. In the northeastern Atlantic, this shark is being increasingly targeted by fishers following the decline of other deepwater shark species.[1][9][12][14]

Off

Least Concern. In the waters of the European Commission, fishing for this species is managed as part of the Total Allowable Catch (TAC) for deepwater sharks.[1]

References

  1. ^
    doi:10.2305/IUCN.UK.2021-2.RLTS.T161398A124477972.en
    . Retrieved 19 November 2021.
  2. ^ Rafinesque, C.S. (1810). Caratteri di alcuni nuovi generi e nuove specie di animali e piante della Sicilia: con varie osservazioni sopra i medesimi (in Italian). Palermo: Per le stampe di Sanfilippo. p. 13. Caratteri di alcuni nuovi generi e nuove specie di animali e piante della Sicilia: con varie osservazioni sopra i medesimi.
  3. ^ a b c Froese, Rainer; Pauly, Daniel (eds.) (2010). "Galeus melastomus" in FishBase. October 2010 version.
  4. ^ a b Iglesias, S.P.; M.H. du Buit & K. Nakaya (2002). "Egg capsules of the deep-sea catsharks from the eastern North Atlantic, with first descriptions of the capsule of Galeus murinus and Apristurus aphyodes (Chondrichthyes: Scyliorhinidae)" (PDF). Cybium. 26: 59–63. Archived from the original (PDF) on 2010-12-28.
  5. ^ Cigala Fulgolsi, F. (1986). "A deep water elasmobranch fauna from a lower Pliocene outcropping (Northern Italy)". In Uyeno, T.; R. Arai; T. Taniuchi; K. Matsuura (eds.). Indo-Pacific Fish Biology: Proceedings of the Second International Conference on Indo-Pacific Fishes. Ichthyological Society of Japan, Tokyo. pp. 133–139.
  6. ^ "Tor Jan Sevaldsen on Instagram: "Flott Hågjel ved Bremsneskaia på dagens dykk."". Instagram. Retrieved 2015-12-25.
  7. ^
    doi:10.12681/mms.122
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  11. doi:10.3354/meps251075
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  12. ^ a b c Rinelli, P.; T. Bottari; G. Florio; T. Romeo; D. Giordano & S. Greco (2005). "Observations on distribution and biology of Galeus melastomus (Chondrichthyes, Scyliorhinidae) in the southern Tyrrhenian Sea (central Mediterranean)" (PDF). Cybium. 29 (1): 41–46. Archived from the original (PDF) on 2010-12-27.
  13. ^ a b c d e f g Capapé, C. & J. Zaouali (1977). "Biology of Scyliorhinidae from Tunisian coasts 6 G. Galeus melastomus Rafinesque, 1810: bathymetric and geographical distribution, sexuality, reproduction, fecundity". Cahiers de Biologie Marine. 18 (4): 449–463.
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  17. ^ a b Day, F. (1884). The Fishes of Great Britain and Ireland, Volume 2. London: Williams and Norgate. p. 314.
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  20. ^ Alves, D.M. Behaviour and patterns of habitat utilisation by deep-sea fish. Analysis of observations recorded by the submersible Nautilus in "98" in the Bay of Biscay, NE Atlantic. M.Sc. Thesis, University of Tromsø, June 5, 2003.
  21. ^ Pascal, L., L. Daniel, and S. Bernard (2000). Observations of chondrichthyan fishes (sharks,rays and chimaeras) in the Bay of Biscay (North-eastern Atlantic) from submersibles. Proceedings of the 3rd European Elasmobranch Association Meeting, Boulogne-sur-Mer, 1999.
  22. doi:10.1111/j.1095-8649.1982.tb03916.x. Archived from the original
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  25. ^ Marquès, A. & C. Capapé (2001). "Eimeria palavensis n. sp. (Apicomplexa: Eimeriidae) from the Blackmouth Catshark, Galeus melastomus (Chondrichthyes: Scyliorhinidae)". Acta Adriatica. 42 (2): 65–70.
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  27. doi:10.1111/j.1439-0426.2008.01112.x
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  28. doi:10.1111/j.1095-8649.2001.tb00190.x
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  30. ^ Tursi, A.; G. D’Onghia; A. Matarrese & G. Piscitelli (1993). "Observations on population biology of the blackmouth catshark Galeus melastomus (Chondrichthyes, Scyliorhinidae) in the Ionian Sea". Cybium. 17 (3): 187–196.
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