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Prionace glauca:   (click for more)

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Synonyms
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  • ? Squalus adscentionis  Osbeck, 1765
  •  
  • ? Squalus rondeletii  Risso, 1810
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  • Squalus caeruleus  Blainville, 1825
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  • ? Galeus thalassinus  Valenciennes, in Cuvier, 1835
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  • ? Thalassorhinus vulpecula  Valenciennes, in Müller & Henle, 1839
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  • Thalassinus rondelettii  Moreau, 1881
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  • Carcharias pugae  Perez Canto, 1886
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  • Carcharias gracilis  Philippi, 1887
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  • ? Carcharias aethiops  Philippi, 1896
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  • Prionace macki  Phillipps, 1935
    FAO Names
    En - Blue shark, Fr - Peau bleue, Sp - Tiburón azul.
    3Alpha Code: BSH     Taxonomic Code: 1080200401
    Scientific Name with Original Description
    Squalus glaucus  Linnaeus, 1758, Syst. Nat., (10) 1: 235. Placed on the Official List of Specific Names in Zoology by the International Commission on Zoological Nomenclature (Opinion 723.4d, 1965, name no. 2058). Holotype: none. Type Locality: "Habitat in Oceano Europaeo".
    Diagnostic Features
    fieldmarks: Dorsal coloration dark blue, bright blue on sides and abruptly white on the undersides, usually slender body, long snout, large eyes, gill raker papillae, long, narrow, pointed pectoral fins, short labial furrows, first dorsal fin on back but closer to the pectoral bases than the pelvics, second dorsal less than a third size of first but about opposite it, a weak keel on the caudal peduncle, and a narrow-lobed caudal fin with a long ventral lobe.

    Body rather slender. Head narrow, only moderately depressed, not trowel-shaped; snout narrowly parabolic in dorsoventral view, very long, with preoral length greater than internarial space and mouth width; eyes large, without posterior notches; spiracles absent; unique papillose gill rakers present on internal gill openings; nostrils small, internarial space about 2.5 to 3 times the nostril width; anterior nasal flaps very short and broadly triangular, not tubular; labial furrows very short with uppers shorter than lowers and with their ends falling far behind eyes;  teeth well differentiated in upper and lower jaws; upper and anteroposteriors with broad, triangular, curved erect to oblique, serrated cusps but with no blades or cusplets (except in very young specimens); lowers with slender cusps, no blades or cusplets, and variable serrations; cusps of lower teeth not prominently protruding when mouth is closed; 24 to 31/25 to 34 rows of teeth.  Interdorsal ridge absent; low dermal keels present on caudal peduncle; upper precaudal pit transverse and crescentic.  First dorsal origin well behind pectoral rear tips, its midbase much closer to pelvic than to pectoral bases, and free rear tip slightly anterior to pelvic origins; second dorsal fin much smaller than first, its height 1/2 of first dorsal height or less; its origin slightly posterior to anal insertion; pectoral fins very narrow and somewhat falcate, pectoral length from origin to free rear tip 1/2 or less of pectoral anterior margin; pectoral origins varying from under interspace between third and fourth gill slits to under fourth gill slits; anal slightly larger than second dorsal, with short preanal ridges and a deeply notched posterior margin.  Colour intense deep blue above, white below, without a colour pattern. Large sharks, adults possibly reaching 4 m or more. 
    Geographical Distribution
    Distribution Map
    Oceanic and circumglobal in temperate and tropical waters (probably the widest ranging chondrichthyan):Western Atlantic: Newfoundland to Argentina. Central Atlantic. Eastern Atlantic: Norway to South Africa, Mediterranean. Indo-West Pacific: South Africa and southern Arabian Sea to Indonesia, Japan, Australia, New Caledonia and New Zealand. Central Pacific. Eastern Pacific: Gulf of Alaska to Chile.
    related Launch the Aquatic Species Distribution map viewer
    Habitat and Biology
    A wide-ranging, oceanic-epipelagic and fringe-littoral shark, occurring from the surface to at least 152 m. depth. Although an offshore species it may venture inshore, especially at night, and often in areas with a narrow continental shelf or off oceanic islands.In temperate waters blue sharks occasionally venture to the edges of kelp forests or sufficiently far inshore to be caught in pound nets. The blue shark is often found in large aggregations, not tightly organized schools, and often close to or at the surface in temperate waters.It prefers relatively cool water at 7 to 16°C but can tolerate water at 21°C or even more; it ranges far into the tropics but shows tropical submergence and occurs at greater depths there. In the tropical Indian Ocean the greatest abundance of blue sharks occurs at depths of 80 to 220 m, with temperatures about 12 to 25°C.  The blue shark is often seen cruising slowly at the surface, with its large pectoral fins outspread, and its first dorsal fin and terminal caudal lobe out of the water.  [more...]

    Viviparous, with a yolk-sac placenta; number of young 4-135 per litter. The number of young varies considerably among females, more so than any other livebearing shark, and may be partially dependent on size of the female. In the Indian Ocean sex ratios of fetuses were in aggregate 1:1, though individual females often have slightly more of one sex than another. The gestation period is 9 to 12 months, and possible maximum age at least 20 years. Off the Western North Atlantic most female blue sharks are immature at 0 to 4 years old, adolescent at 4 to 5 years, and adult from 5 to 6 years and beyond. Males mature at about 4 to 5 years old.  [more...]
      The blue shark feeds heavily on relatively small prey, especially bony fishes and squid, though other invertebrates, small sharks, and mammalian carrion is readily taken and seabirds occasionally are caught at the surface of the water. Much of the prey of the blue shark is pelagic, though bottom fishes and invertebrates figure in its diet also.  [more...]
    Squid are a very important prey of these sharks;  [more...]
    Size
    Maximum size 383 cm on reasonably good evidence, though unconfirmed reports of larger individuals up to 4.8 to 6.5 m are mentioned in the literature; males maturing between 182 and 281 cm, and reaching at least 311 cm, females adolescent at 173 to 221 cm, adult at 221 to at least 323 cm; size at birth about 35 to 44 cm. A length/weight equation for the blue shark (Strasberg, 1958) is: Log Wt(lbs) = -5.396 + 3.134 log TL (cm).
    Interest to Fisheries
    This common oceanic shark is usually caught with pelagic longlines but also hooks and lines, pelagic trawls, and even bottom trawls near coasts. Catches for the blue shark have been reported to FAO only from area 27 (Northeast Atlantic); countries reporting, since 1978, are mainly France (with a peak of 358 t in 1994) and Denmark (only a few metric tons). The total catch reported for this species to FAO for 1999 was 3 199 t. The countries with the largest catches were Spain (2 233 t) and New Zealand (593 t).
    It is utilized fresh, smoked, and dried salted for human consumption; its hides are used for leather; fins for shark-fin soup base; and also for fishmeal and liver oil. This shark is also considered a game fish and taken by sports anglers with rod and reel.

    The blue shark is the most widespread oceanic shark and has a great overall abundance. It is a very common bycatch in high-seas longline and driftnet fisheries but it is not a very valuable shark, so mostly only the fins are taken. However, there are some countries that readily consume blue sharks such as Spain, Brazil, Italy, and France (Bonfil 1994, Stevens in press c). This species is the most popular shark in sport fisheries in the US (Hoff and Musick 1990) and is likely taken by recreational fishermen throughout the world. There are no reliable statistics for the catches (directed or incidental) of blue sharks around the world and this makes difficult to understand the impact of fisheries on the stocks. Bonfil (1994) made some rough calculations based on reported catch rates in the literature and estimated that the high-seas longline and driftnet fisheries of the late 1980s could have taken some 6.2-6.5 million blue sharks annually. Matsunaga and Nakano (1996) compare changes over time of CPUE data in two areas of the Pacific (0-10° N and 10-20° N) and find no significant changes in blue shark abundance. Nakano (1996) detected a 20% decrease in Japanese longline CPUE for blue sharks in the North Pacific but no trend in other areas of the world. The only known assessment of the impact of high seas fisheries on blue shark stocks was done by Nakano and Watanabe (1992). These authors concluded that the catch levels in the late 1980s had no significant impact on the blue shark populations of the North Pacific. However, other authors (Anon. 1992, Wetherall and Seki 1992) consider that appropriate information is lacking for such an assessment. In the United States, blue sharks were an important bycatch during the development of the California swordfish/thresher shark driftnet fishery but the total numbers killed were relatively low (Cailliet et al 1993). Off the U.S. Atlantic coast, blue shark catch rates from pelagic longline logbook data decreased sharply in the first 3 years of data available but remained without trend since 1989 (Cramer 1998). In contrast to this, standardised catch rates for the sport fishery of Virginia-Massachusetts showed an increasing trend over the same period (Brown 1998). This conflicting information suggests likely errors in the above data. Canada started an experimental fishery for blue sharks off its Atlantic coast in the early 1990s. This fishery has a 225 t TAC (Mooney-Seus and Stone 1996).

    Conservation Status : The blue shark is a prolific species with an intrinsic rebound potential that is above the average of 26 species analysed by Smith et al. (1998). The IUCN Red List classifies blue shark as a Lower Risk/Near Threatened species at the world level (Camhiet al. 1998). The high abundance and worldwide distribution of this species offers a relative buffer against extinction. However, some discrete stocks might become threatened in the future if bycatch in high seas fisheries does not come under strict monitoring and control. Fortunately, efforts towards alleviating the lack of monitoring data are currently being taken by multiple regional tuna fisheries organisations around the globe.
    related Additional information from IUCN database
    related Additional information from CITESdatabase
    Remarks
    Threat to humans: A dangerous species, with several attacks on people and boats on record. Spearfishing divers have been harassed by these sharks, and have had to fend them off with spears to keep from being bitten. Sometimes these sharks will slowly circle divers, possibly out of curiosity, and sometimes for a quarter hour or more. An odd 'sport' for divers off Southern California is swimming with blue sharks that have been baited into the vicinity of a boat, possibly as a test of virility on the part of the mostly male divers. The blue shark is not strongly aggressive under such circumstances of contact with people underwater, but on the other hand is not very timid. A slowly approaching shark of this species should be handled with caution, as it may bite (possibly in test-feeding) after circling for some time.
    Source of Information
    FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 2 - Carcharhiniformes.Compagno, L.J.V. 1984.  FAO Fish. Synop., (125) Vol.4, Part 2
    Bibliography
    Bass, d'Aubrey & Kistnasamy, (1975)
    Bigelow & Schroeder, (1948)
    Cadenat & Blache, (1981)
    Casey, (1979)
    Clarke & Stevens, (1975)
    Compagno, (l979, 1981)
    Compagno & Vergara, (1978)
    Feder, Turner & Limbaugh, (1974)
    Fourmanoir, (1961)
    Garrick & Schultz, (1963)
    Gubanov & Grigor'ev, (1975)
    Pratt, (1979)
    Randall, (1963)
    Sciarotta & Nelson, (1979)
    Stevens, (1973, 1974, 1975, 1976)
    Strasberg, (1958)
    Tricas, (1979)
     
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