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shad-owing

Shad

[shad]

The shads or river herrings comprise the genus Alosa, fishes related to herring in the family Clupeidae. They are distinct from others in that family by having a deeper body and spawning in rivers. The several species frequent different areas on both sides of the Atlantic Ocean and in the Mediterranean Sea. The shad fry live for a year or two in fresh water.

The American or Atlantic shad (A. sapidissima) is a valued food fish. It was especially important in the 1700s; however, many of the rivers where it was common now suffer from pollution. Traditionally it was caught along with salmon in set nets which were suspended from poles driven into the river bed reasonably close to shore in tidal water. It weighs between 3 and 8 pounds and has a delicate flavour when cooked. Though bony, it is worth the effort, and indeed many esteem it above the famous Atlantic salmon. It is considered flavourful enough to not require sauces, herbs or spices. It can be boiled, filleted and fried in butter or baked. Traditionally a little vinegar is sprinkled over it on the plate. In the eastern United States roe shad (females) are prized because the eggs are considered a delicacy.

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.

Biology

Shads are unique among the fishes in having evolved an ability to detect ultrasound (sound at frequencies above 20 kHz, which is the limit of human hearing). This was first discovered by fisheries biologists studying 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.

Systematics

Systematics of shads are extremely complex. The genus inhabits a wide range of habitats, and many taxa are migratory. There are also a few land-locked forms, one from Killarney in Ireland and two from lakes in northern Italy. There are species native to the Black Sea and Caspian Sea, as well as the Persian Gulf.

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, it appears as if hybridization is a factor to be reckoned when researching shad phylogeny.(Faria et al. 2006)

Nonetheless, some trends are emerging. The North American species except the Atlantic shad can probably be separated in a subgenus (or even genus) Pomolobus. On the other hand, the proposed genus (or subgenus) Caspialosa for the Caspian Sea forms is rejected due to paraphyly.(Faria et al. 2006)

References

  • (2006): A molecular phylogenetic perspective on the evolutionary history of Alosa spp. (Clupeidae). Molecular Phylogenetics and Evolution 40(1): 298–304. (HTML abstract)
  • The Founding Fish (2002) ISBN 0-374-10444-1

External links

pl: Aloza

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