Alosa

Alosa<ref>Alosa Linck, 1790 ITIS</ref> is a genus of fish, the river herrings, in the family Alosidae. Along with other genera in the subfamily Alosinae, they are generally known as shads.<ref>Alosinae ITIS</ref><ref name=FAO>Subfamily AlosinaeTemplate:Dead linkTemplate:Cbignore FAO Fisheries Bulletin</ref> They are distinct from other herrings by having a deeper body and spawning in rivers. Several species can be found on both sides of the Atlantic Ocean and the Mediterranean Sea. Also, several taxa occur in the brackish-water Caspian Sea and the Black Sea basin.<ref name=Coad/> Many are found in fresh water during spawning and some are only found in landlocked fresh water.

Fossil record

These fishes lived from the Eocene to Quaternary (from 55 million years ago to now). Fossils have been found in Canada, the United States, Greece, Kazakhstan, Azerbaijan, Hungary, Romania, and Italy.<ref>Paleobiology Database</ref>

File:Clupeidae - Alosa elongata.JPG

Fossil of Alosa elongata

Appearance

Alosa species are generally dark on the back and top of the head, with blue, violet, or greenish tints.<ref name=Coad/> Some can be identified as having a grey or green back.<ref name=Coad/> Spots are commonly found behind the head, and the fins may vary from species to species or individually.<ref name=Coad/> Most species of Alosa weigh Template:Convert or less, with A. pontica and A. fallax weighing up to 2 kg, and A. alosa can exceed 3–4 kg.<ref name=Coad/>

Biology

Shads are thought to be unique among the fishes in having evolved an ability to detect ultrasound (at frequencies above 20 kHz, which is the limit of human hearing).<ref name="Mann">Mann, D. A.; Higgs, D. M.; Tavolga, W. N.; Souza, M. J.; and Popper, A. N. (2001). Ultrasound detection by clupeiform fishes. Journal of the Acoustical Society of America 109:3048–3054</ref> This was first discovered by fisheries biologists studying a type of shad known as blueback herring, and was later verified in laboratory studies of hearing in American shad. This ability is thought to help them avoid dolphins that find prey using echolocation. Alosa species are generally pelagic.<ref name="Greek">Template:Cite journal</ref> They are mostly anadromous or semianadromous with the exception of strictly freshwater landlocked species.<ref name=Greek/> Alosa species are generally migratory and schooling fish.<ref name=Greek/> Males usually mature about a year before females; they spawn in the late spring to summer.<ref name="travis">Template:Cite thesis</ref><ref name="Bianco">Template:Cite journal</ref> Most individuals die shortly after spawning.<ref name=travis/><ref name=Bianco/> Alosa species seemingly can change readily to adapt to their environments, as species are found in a wide range of temperatures and waters.<ref name="Bianco"/>

Lifecycle and reproduction

As Alosa species are generally anadromous, they face various obstacles to survival.<ref name="Lochet">Lochet, A., S. Boutry, and E. Rochard. Estuarine Phase during Seaward Migration for Allis Shad Alosa Alosa and Twaite Shad Alosa Fallax Future Spawners. Ecology of Freshwater Fish 18 (2009): 323-35.</ref> They may have to pass through numerous barriers and waters to get to either their spawning grounds or normal habitats (the sea in most cases).<ref name=Lochet/> Estuaries are a major factor in numerous Alosa species' migrations.<ref name=Lochet/> Estuaries can be highly variable and complex environments contributing to fluctuating biological interactions,<ref name=Lochet/> with shifts in osmolarity, food sources, predators, etc.<ref name=Lochet/> Since many adult Alosa species die after spawning, only the young generally migrate to the sea from the spawning grounds.<ref name=Lochet/> Duration of migration varies among fish, but can greatly affect survival.<ref name=Lochet/>

Reproduction varies by species.<ref name="Coad">Template:Cite journal</ref> Studies done on Alosa in Iranian waters have shown that spawning varies in time, place, and temperature of the waters they inhabit.<ref name=Coad/> Fecundity may also vary.<ref name=Coad/> Species are known to spawn as early as April or as late as August.<ref name=Coad/> Temperatures range from about 11 to 27 °C.<ref name=Coad/> Fecundity can range from 20,000 to 312,000 eggs.<ref name=Coad/> Eggs are pelagic.<ref name=Coad/> Geography and temperature are important environmental factors in egg and young-of-year development.<ref>Template:Cite journal</ref>

The lifespan of Alosa species can be up to 10 years, but this is generally uncommon, as many die after spawning.<ref name=Coad/>

Systematics

The systematics and distribution of Alosa shads are complex. The genus inhabits a wide range of habitats, and many taxa are migratory. A few forms are landlocked, including one from Killarney in Ireland, two from lakes in northern Italy, and two in Greece. Several species are native to the Black and Caspian Seas. Alosa species of the Caspian are systemically characterized by the number of rakers on the first gill arch.<ref name="Malkin">Malkin, E. M., and S. B. Andrianova. Biology and Traits of the Formation of Stock of Big-eyed Shad Alosa Saposchnikowii. Journal of Ichthyology 48.6 (2008): 443-51.</ref> They are classified as being "multirakered", "medium-rakered", or "oligorakered".<ref name=Malkin/> The multirakered are primarily plankton feeders, the oligorakered have large rakers and are predators, and the medium-rakered generally consume a mixed diet.<ref name=Malkin/> Most current species of the genus Alosa in North America can be found in Florida, whereas the distribution of most of them is broader.<ref name=McBride>Richard S. McBride (2000). Florida's Shad and River Herrings (Alosaspecies): A Review of Population and Fishery Characteristics. Florida MAR8INE Research Institute Technical Reports: Technical Report TR-5, Florida Fish and Wildlife Conservation Commission. St. Petersburg, Florida.</ref>

Morphology is notoriously liable to adapt to changing food availability in these fish. Several taxa seem to have evolved quite recently, making molecular analyses difficult. In addition, hybridization may be a factor in shad phylogeny.<ref name="Faria">Faria, R.; Weiss, S.; and Alexandrino, P. (2006). A molecular phylogenetic perspective on the evolutionary history of Alosa spp. (Clupeidae). Molecular Phylogenetics and Evolution 40(1): 298–304. {{#invoke:doi|main}} (HTML abstract).</ref> Nonetheless, some trends are emerging. The North American species except the American shad A. sapidissima can probably be separated in a subgenus Pomolobus. Conversely, the proposed genus (or subgenus) Caspialosa for the Caspian Sea forms is rejected due to paraphyly.<ref name=Faria/>

Species by geographical origin

North America

• Alosa aestivalis (Mitchill, 1814) (blueback herring) File:Blueback herring fish (white background).jpg
• Alosa alabamae D. S. Jordan and Evermann, 1896 (Alabama shad)
• Alosa chrysochloris (Rafinesque, 1820) (skipjack shad) File:Skipjack herring fish alosa chrysochloris (white background).jpg
• Alosa mediocris (Mitchill, 1814) (hickory shad) File:Hickory shad (Duane Raver).png
• Alosa pseudoharengus (A. Wilson, 1811) (alewife) File:Alewife fish (white background).jpg
• Alosa sapidissima (A. Wilson, 1811) (American shad) File:American shad fish alosa sapidissima (white background).jpg

Western Europe and the Mediterranean

• Alosa agone (Scopoli, 1786) (agone)
• Alosa algeriensis Regan, 1916 (North African shad)
• Alosa alosa (Linnaeus, 1758) (allis shad) File:Alosa alosa.jpg
• Alosa fallax (Lacépède, 1803) (twait shad)
• Alosa killarnensis Regan, 1916 (Killarney shad)

Caspian Sea, Black Sea, the Balkans

• Alosa braschnikowi (Borodin, 1904) (Caspian marine shad)
• Alosa caspia (Eichwald, 1838)
  • A. c. caspia (Eichwald, 1838) (Caspian shad)
  • A. c. knipowitschi (Iljin, 1927) (Enzeli shad)
  • A. c. persica (Iljin, 1927) (Astrabad shad)
• Alosa curensis (Suvorov, 1907) (Kura shad)
• Alosa immaculata E. T. Bennett, 1835 (Pontic shad)
• Alosa kessleri (Grimm, 1887) (Caspian anadromous shad)
• Alosa macedonica (Vinciguerra, 1921) (Macedonia shad)
• Alosa maeotica (Grimm, 1901) (Black Sea shad)
• Alosa saposchnikowii (Grimm, 1887) (Saposhnikovi shad)
• Alosa sphaerocephala (L. S. Berg, 1913) (Agrakhan shad)
• Alosa tanaica (Grimm, 1901) (Azov shad)
• Alosa vistonica Economidis and Sinis, 1986 (Thracian shad)
• Alosa volgensis (L. S. Berg, 1913) (Volga shad)

Recreational fishing

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Commercial fishing

Commercial capture production of wild shad in tonnes.<ref>FAO (2006) Yearbooks of Fishery Statistics Summary Tables</ref><ref>FAO (2014) Yearbook - Fishery and Aquaculture Statistics, no. 24.</ref>
1999	2000	2001	2002	2003	2004	2005	2008	2010	2011	2012	2013	2014
788,770	860,346	665,284	589,692	524,800	569,160	605,548	588,978	645,977	611,371	604,842	628,622	636,678

Management

Shad populations have been in decline for years due to spawning areas blocked by dams, habitat destruction, pollution, and overfishing. Management of shad has called for more conservative regulations, and policies to help the species have lower fishing mortality.<ref name="asmfc-shad">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Political significance

Shad serve a peculiar symbolic role in Virginia state politics. On the year of every gubernatorial election, would-be candidates, lobbyists, campaign workers, and reporters gather in the town of Wakefield, Virginia, for shad planking. American shad served as the focal point of John McPhee's book The Founding Fish.<ref>"American Shad - Fish Reference Library - RedOrbit." RedOrbit - Science, Space, Technology, Health News and Information. 3 Apr. 2007. Web. 27 Nov. 2011. <http://www.redorbit.com/education/reference_library/science_1/fish/2579052/american_shad/index.html>.</ref>

Culinary use

File:Shad roe.jpg

Shad roe

The roe, or more properly the entire engorged uterus of the American shad—filled with ripening eggs, sautéed in clarified butter and garnished with parsley and a slice of lemon—is considered a great delicacy, and commands high prices when available.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

See also

• The Shad Foundation

References

• {{#invoke:Cite taxon|main|fishbase|genus=|species=|subspecies=}}

External links

• Tastes of the Region: Shad An article celebrating shad's cultural importance to the Hudson Valley
• Lambertville NJ Shad Festival
• Science Cheerleader - Shad: Our Pollution vs. Their Resolution.