Alosa

Alosa species are generally dark on the back and top of the head, with blue, violet, or greenish tints. Some can be identified as having a grey or green back. Spots are commonly found behind the head, and the fins may vary from species to species or individually. Most species of Alosa weigh or less, with A. pontica and A. fallax weighing up to 2 kg, and A. alosa can exceed 3–4 kg. ==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). 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. They are mostly anadromous or semianadromous with the exception of strictly freshwater landlocked species. Most individuals die shortly after spawning. Alosa species seemingly can change readily to adapt to their environments, as species are found in a wide range of temperatures and waters. ==Lifecycle and reproduction==

As Alosa species are generally anadromous, they face various obstacles to survival. 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). Studies done on Alosa in Iranian waters have shown that spawning varies in time, place, and temperature of the waters they inhabit. The lifespan of Alosa species can be up to 10 years, but this is generally uncommon, as many die after spawning. == 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. They are classified as being "multirakered", "medium-rakered", or "oligorakered". 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. 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. • †Alosa aralensis Chisara, 1977 - Oligocene of Russia • †Alosa avcilarensis Rückert-Ülkümen, 1994 - Miocene of Turkey • †Alosa baykali Rückert-Ulkümen, 1965 - Miocene of Turkey • †Alosa elongata Agassiz, 1843 - Late Miocene of Italy, Greece and Algeria (=A. crassa Sauvage, 1873, A. numidica Sauvage, 1873, A. renoui Sauvage, 1873) • †Alosa fortipinnata Rückert-Ulkümen, 1965 - Miocene of Turkey • †?Alosa ganolytoides David, 1946 - mid-late Eocene of California [scale] (taxonomy uncertain) • †Alosa genuina Daniltshenko, 1960 - Miocene of North Caucasus, Russia • †Alosa latissima Heckel, 1853 - Oligocene of Italy, potentially Miocene of Turkey • †Alosa paulicrenata Bratishko et al. 2015 - Middle Miocene of Kazakhstan [otolith] • †Alosa pinarhisarensis Rückert-Ulkümen, 1965 - Miocene of Turkey • †Alosa sagorensis (Steindachner, 1863) - Oligocene of Hungary & potentially Poland, Miocene of Turkey • †Alosa sculptata (Weiler, 1920) - Miocene of Germany • †Alosa spinosa (Rückert-Ulkümen, 1965) - Miocene of Turkey • †Alosa weileri Rückert-Ulkümen, 1960 - Miocene of Turkey The former fossil species A. ovalis Rückert-Ulkümen, 1965 is now placed in Clupeonella as Clupeonella ovalis. ==Recreational fishing==

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. ==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. ==Culinary use==

The American shad’s egg sacs, known as shad roe, are a seasonal springtime ingredient traditionally sautéed in butter and served with lemon and parsley. Due to their short availability and unique, rich texture, they are considered a specialty, commanding higher prices in early spring when the female fish migrate up rivers to spawn. These delicate, lobe-shaped, or ribbon-like, sets are typically cooked carefully to maintain their structure, resulting in a savory, mild flavor that is often paired with bacon or other rich ingredients. ==See also==