| 词条 | Scalloped hammerhead |
| 释义 |
| name = Scalloped hammerhead | image = Scalloped hammerhead cocos.jpg | image2 =Sphyrna lewini Gervais.jpg | status = EN | status_system = IUCN3.1 | status_ref = [1][2] | genus = Sphyrna | species = lewini | authority = (E. Griffith & C. H. Smith, 1834) | synonyms = Sphyrna couardi Cadenat, 1951 | range_map = Sphyrna lewini distribution map.svg | range_map_caption = Range of the scalloped hammerhead }} The scalloped hammerhead (Sphyrna lewini) is a species of hammerhead shark, and part of the family Sphyrnidae. Originally known as Zygaena lewini, its genus name was later changed to its current name. The Greek word sphyrna translates into "hammer" in English, referring to the shape of this shark's head. The most distinguishing characteristic of this shark, as in all hammerheads, is the 'hammer' on its head. The shark's eyes and nostrils are at the tips of the extensions. This is a fairly large hammerhead, though is smaller than both the great and smooth hammerheads. This shark is also known as the bronze, kidney-headed, or southern hammerhead. It primarily lives in warm, temperate, and tropical coastal waters all around the globe between latitudes 46°N and 36°S, down to a depth of {{convert|500|m|abbr=on}}. It is the most common of all hammerheads. TaxonomyThe scalloped hammerhead was first named Zygaena lewini and then renamed Sphyrna lewini by Edward Griffith and Hamilton Smith in 1834. It has also been named Cestracion leeuwenii by Day in 1865, Zygaena erythraea by Klunzinger in 1871, Cestracion oceanica by Garman in 1913, and Sphyrna diplana by Springer in 1941. Sphyrna comes from the Greek and translates into hammer.[3] It is a sister species to Sphyrna gilberti, differing by the number of vertebrae.[4] Though once considered a distinct species, McEachran and Serret synonymized Sphyrna couardi with Sphyrna lewini in 1986.[5] DescriptionOn average, males measure {{convert|1.5|to|1.8|m|ft|abbr=on}} and weigh about {{convert|29|kg|lb|abbr=on}} when they attain sexual maturity, whereas the larger females measure {{convert|2.5|m|ft|abbr=on}} and weigh {{convert|80|kg|lb|abbr=on}} on average at sexual maturity.[6] The maximum length of the scalloped hammerhead is {{convert|4.3|m|ft|abbr=on}} and the maximum weight {{convert|152.4|kg|lb|abbr=on}}, per FishBase.[7] A female caught off of Miami was found to have measured {{convert|3.26|m|ft|abbr=on}} and reportedly weighed {{convert|200|kg|lb|abbr=on}}, though was in a gravid state at that point.[8] These sharks have a very high metabolic rate, governing behavior in acquiring food. These sharks occupy tertiary trophic levels.[9] The scalloped hammerhead shark, like many other species, uses the shore as a breeding ground.[9] Due to high metabolic rates, young scalloped hammerhead sharks need a lot of food, or they will starve. Distribution and habitatThe scalloped hammerhead is a coastal pelagic species; it occurs over continental and insular shelves and in nearby deeper water. It is found in warm temperate and tropical waters, worldwide from 46°N to 36°S. It can be found down to depths over {{convert|500|m|abbr=on}}, but is most often found above {{convert|25|m|abbr=on}}.[10] During the day, they are more often found close to shore, and at night, they hunt further offshore. Adults are found alone, in pairs, or in small schools, while young sharks occur in larger schools.[3] BehaviorSchoolingThese sharks are often seen during the night,day, and morning in big schools, sometimes numbering hundreds, most likely because large groups can obtain food easier than singles or small groups, especially larger and trickier prey, as commonly seen. The younger the sharks, the closer to the surface they tend to be, while the adults are found much deeper in the ocean. They are not considered dangerous and are normally not aggressive towards humans. Sexual dimorphismThe female scalloped hammerheads undergo migration offshore at a smaller size than males[11] because the larger classes of the hammerhead, such as those from 100 to 140 cm long, travel deeper down.[11] Males and females differ in that males are observed to stay deeper than female sharks in general. Sexual maturity generally occurs once the scalloped hammerhead attains 240 cm in total or longer. Physically, the mature females have considerably wider uteri than their maturing counterparts. A lack of mating scars has been found on mature females.[12] Unlike females, males reach sexual maturity at a much smaller size. The male-to-female ratio of the scalloped hammerhead is 1:1.29.[12] Females probably are capable of giving birth annually.[12] usually in the summer. This species does not seem to attack each other even in periods of starvation. In addition, scalloped hammerheads have migratory behaviors. As a result, deprivation results from migration and young growth. While the Taiwan scalloped hammerhead seems to have an earlier maturity rate, it is still reported to be slow to mature.[18] DietThis shark feeds primarily on fish such as sardines, mackerel, and herring, and occasionally they feed on cephalopods such as squid and octopus. Larger specimens may also feed on smaller species of shark such as the blacktip reef shark, Carcharhinus melanopterus. Human interactionAs of 2008, the scalloped hammerhead is on the "globally endangered" species list. In parts of the Atlantic Ocean, their populations have declined by over 95% in the past 30 years. Among the reasons for this drop off are overfishing and the rise in demand for shark fins. Researchers attribute this growth in demand to the increase in shark fins as an expensive delicacy (such as in shark fin soup) and are calling for a ban on shark finning, a practice in which the shark's fins are cut off and the rest of the animal is thrown back in the water to die. Hammerheads are among the most commonly caught sharks for finning.[19] See also{{Portal|Sharks}}
References1. ^{{Cite web|url=https://www.iucnredlist.org/species/39385/10190088|title=The IUCN Red List of Threatened Species|website=IUCN Red List of Threatened Species|access-date=2018-10-27}} 2. ^{{cite press release |title=More oceanic sharks added to the IUCN Red List |publisher=IUCN |date=2007-02-22 |url=http://www.iucn.org/en/news/archive/2007/02/22_pr_sharks.htm|archiveurl=https://web.archive.org/web/20080706152000/http://www.iucn.org/en/news/archive/2007/02/22_pr_sharks.htm|archivedate=2008-07-06|accessdate=2007-02-25 |quote= The status of scalloped hammerhead shark was heightened from Near Threatened to Endangered. }} 3. ^1 {{cite web | title=Scalloped Hammerhead|publisher=Florida Museum of Natural History | url=http://www.flmnh.ufl.edu/fish/Gallery/Descript/ScHammer/ScallopedHammerhead.html}} 4. ^{{Cite journal | last1 = Quattro | first1 = J. M. | last2 = Driggers | first2 = W. B. I. I. | last3 = Grady | first3 = J. M. | last4 = Ulrich | first4 = G. F. | last5 = Roberts | first5 = M. A. | title = Sphyrna gilberti sp. Nov., a new hammerhead shark (Carcharhiniformes, Sphyrnidae) from the western Atlantic Ocean | doi = 10.11646/zootaxa.3702.2.5 | journal = Zootaxa | volume = 3702 | issue = 2 | pages = 159 | year = 2013 | pmid = | pmc = }} 5. ^Martin, R. Aidan. (February 24, 1998). Recent Changes in Hammerhead Taxonomy. ReefQuest Centre for Shark Research. Retrieved on October 18, 2008. 6. ^FLMNH Ichthyology Department: Scalloped Hammerhead. Flmnh.ufl.edu. Retrieved on 2013-05-23. 7. ^Sphyrna lewini, Scalloped hammerhead : fisheries, gamefish. Fishbase.org (2012-07-03). Retrieved on 2013-05-23. 8. ^Castro, José I. (2011) The Sharks of North America. Oxford University Press. {{ISBN|978-0-19-539294-4}} 9. ^1 {{cite journal|title=Estimation of daily energetic requirements in young scalloped hammerhead sharks, Sphyrna lewini |date=2006-08-01 |doi=10.1007/s10641-006-9016-5 |volume=76 |issue=2–4 |journal=Environmental Biology of Fishes |pages=139–149|last1=Duncan |first1=Kanesa May }} 10. ^{{cite book|editor1=Froese, Ranier|editor2=Pauly, Daniel |title=Sphyrna lewini|publisher=FishBase|accessdate=10 December 2008|url=http://www.fishbase.org/Summary/SpeciesSummary.php?id=912}} 11. ^1 {{cite journal |title=The determinants of sexual segregation in the scalloped hammerhead shark, Sphyrna lewini |date=1987-01-01 |doi=10.1007/BF00002325 |volume=18 |journal=Environmental Biology of Fishes |pages=27–40|last1=Klimley |first1=A. Pete }} 12. ^1 2 {{cite journal |title=Aspects of Reproductive Biology of the Scalloped Hammerhead Shark, Sphyrna lewini, off Northeastern Brazil |date=2001-06-01 |doi=10.1023/A:1011040716421 |volume=61 |issue=2 |journal=Environmental Biology of Fishes |pages=151–159|last1=Hazin |first1=Fabio |last2=Fischer |first2=Alessandra |last3=Broadhurst |first3=Matt }} 13. ^1 2 {{cite journal|title=Highly directional swimming by scalloped hammerhead sharks, Sphyrna lewini, and subsurface irradiance, temperature, bathymetry, and geomagnetic field |date=1993 |doi=10.1007/BF00346421 |volume=117 |journal=Marine Biology |pages=1–22|last1=Klimley |first1=A. P. }} 14. ^{{cite journal |title=Scalloped hammerhead shark Sphyrna lewini, uses deep-water, hypoxic zone in the Gulf of California |doi=10.1111/j.1095-8649.2009.02230.x |volume=74 |issue=7 |journal=Journal of Fish Biology |pages=1682–1687|year=2009 |last1=Jorgensen |first1=S. J. |last2=Klimley |first2=A. P. |last3=Muhlia-Melo |first3=A. F. }} 15. ^{{cite journal|doi=10.2989/025776198784126610|title=Cephalopods in the diets of four shark species (Galeocerdo cuvier, Sphyrna lewini, S. Zygaena and S. Mokarran) from Kwa Zulu-Natal, South Africa|journal=South African Journal of Marine Science|volume=20|pages=241–253|year=1998|last1=Smale|first1=M. J.|last2=Cliff|first2=G.}} 16. ^1 {{cite journal|title=Age, growth and reproductive biology of the silky shark, Carcharhinus falciformis, and the scalloped hammerhead, Sphyrna lewini, from the northwestern Gulf of Mexico |date=1987-07-01 |doi=10.1007/BF00005346 |volume=19 |issue=3 |journal=Environmental Biology of Fishes |pages=161–173|last1=Branstetter |first1=Steven }} 17. ^1 2 {{cite journal |title=Global phylogeography of the scalloped hammerhead shark (Sphyrna lewini) |doi=10.1111/j.1365-294X.2006.02933.x |pmid=16780437 |volume=15 |issue=8 |journal=Molecular Ecology |pages=2239–2251|year=2006 |last1=Duncan |first1=K. M. |last2=Martin |first2=A. P. |last3=Bowen |first3=B. W. |last4=De Couet |first4=H. G. }} 18. ^{{cite journal |url=http://scholarspace.manoa.hawaii.edu/handle/10125/1267| last1 = Chen | first1 = CT | last2 = Leu | first2 = TC | last3 = Joung | first3 = SJ | last4 = Lo | first4 = NCH | year = 1990 | title = Age and growth of the scalloped hammerhead, Sphyrna lewini, in northeastern Taiwan waters | journal = Pacific Science | volume = 44 | issue = 2| pages = 156–170 }} 19. ^{{cite web | title=Hammerhead Shark Makes Endangered Species List | publisher= redorbit.com | url=http://www.redorbit.com/news/science/1259813/hammerhead_shark_makes_endangered_species_list/ |date=February 19, 2008|author=Savage, Sam }} External links{{Commons category|Sphyrna lewini}}
4 : Sphyrna|Pan-tropical fish|Fish described in 1834|Species endangered by use as food |
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