Alosa sapidissima
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Alosa sapidissima |
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| ( A. Wilson , 1811) |
Alosa sapidissima ( Syn .: Clupea sapidissima ), known in the USA as American shad or Atlantic shad , is a fish from the herring family ( Clupeidae ). It is distributed on the east coast of the United States from Newfoundland to Florida and is also found as an introduced species on the northern Pacific coast . Alosa sapidissima is not particularly closely related to the other North American shads . It even seems that itcomesfrom a "European" Alosa line.
Alosa sapidissima has been called "the fish that fed the founders of the American nation". Adult animals weigh between 1.4 and 3.6 kg. They have a delicate aroma when cooked. In the eastern United States, roe shad (females) are particularly valued as the eggs are a popular delicacy .
features
Alosa sapidissima are elongated fish with silvery scales. They are often referred to as "freshwater tarpon ". They are on average 30–50 cm, a maximum of 80 cm long and can weigh up to 3 kg. The current world record set in Massachusetts is 5.1 kg. They become sexually mature at the age of 3 to 6 years.
Way of life
The fish spends most of its life in the Atlantic and only returns to freshwater to spawn. The populations in the north are occasionally iteroparous (they survive the act of spawning and return several times), while in the southern populations the animals usually die after spawning ( semelparitia ). In the sea the fish live in schools . Often a thousand of them come to the surface. In winter they retreat to greater water depths and begin their ascent into the spawning waters when the water temperature in the rivers rises to 13-18 ° C. Fish have been caught in the sea at depths of up to 65 fathoms (119 m).
Like other types of herring, Alosa sapidissima feeds primarily on plankton , as well as pelagic shrimp and fish eggs. They also rarely eat small fish.
The sexually mature fish move into the spawning waters in early summer. Spawning is delayed at temperatures below 10–13 ° C. Correspondingly, the spawning season shifts into summer the further north the spawning area is. In Georgia it starts in January; in March in the tributaries of the Pamlico Sound and the Albemarle Sound ; in April in the Potomac River ; and in May and June in the northern currents between Delaware and Canada .
In large rivers, such as the Connecticut River , the fish move far upstream. The greatest distance from the sea they apparently reach in the St. Johns River in Florida , a very gently rising river (1.5 cm per km) that repeatedly forms large lakes; fish were caught there 600 km inland.
The fish choose shallow, sandy or gravelly places where they lay their eggs between sunset and midnight. The females release their eggs in packets of approx. 30,000 eggs, with large fish up to 156,000 eggs should be laid. A female can lay 200,000–600,000 eggs in a year. In rivers north of Cape Fear , the exhausted fish return straight to the sea. Further south, most of the fish die after they lay eggs.
The eggs are transparent, tinged pink or amber in color. They are semi-transparent and not sticky. They roll with the water along the bottom of the river. The fry hatch within 12 to 15 days at a temperature of 11 ° C, between six and eight days at a temperature of 17 ° C. These are the usual times on the rivers between Maine and the Bay of Fundy .
The larvae are approx. 9-10 mm long. Juvenile fish remain in the rivers until autumn, then they move into the salt water. With a length of 38–114 mm, they resemble adult animals in shape.
Nutritional values
Like most types of herring, Alosa sapidissima contains a lot of omega-3 fatty acids , twice as much as wild salmon. Plus, they usually contain very few toxins such as PCBs , dioxins , and mercury . Therefore Alosa sapidissima is a valuable food fish.
Hazard and protection
The stocks have been declining steadily since the beginning of the 20th century. Traditionally, the fish were caught along with salmon in set nets near the estuaries. Many of the rivers in which the fish were once common are now heavily polluted, but the relatively short residence time in the corresponding water sections reduces their exposure to environmental toxins. For example, research by fisheries science has shown that fish do not stay in the Hudson River long enough to ingest PCBs and other toxins. Nevertheless, catching Alosa sapidissima in the Hudson River and the surrounding marine area is now prohibited. However, pollution could primarily harm the juvenile fish.
Many of the rivers are now heavily blocked by weirs and dams, so that a whole part of the spawning grounds is lost. In the Merrimack River, for example, the number of fish caught decreased from 900,000 in 1789 to 0 in 1888 and this appears to be related to major dam projects that cordoned off the river during that time. It is only recently that this situation has started to be improved. Among other things, the Chesapeake Bay Program is trying to reintroduce the fish. Fishing has almost no measurable impact on the population, but the fish are threatened by overfishing, so the stocks are looked after by the US Fish and Wildlife Service , the National Marine Fisheries Service and the state fisheries authorities. The Atlantic States Marine Fish Commission serves as the coordinator of conservation efforts.
Launch in the North Pacific
Alosa sapidissima was planted in the San Francisco Bay / Sacramento River in California around 1800. Since then it has spread to many river systems along the west coast of North America. There is now a large population in the Columbia River . In recent years, between two and five million fish have been counted annually at Bonneville Dam and The Dalles Dam . Spawning fish enter the Columbia River in May and June and migrate into the Snake River via the Lower Granite Dam and into the Upper Columbia River via the Priest Rapids Dam . In contrast to many other neozoa , no negative effects on ecosystems have been observed so far .
Occasionally, Alosa sapidissima appears on the northwest coast of the Pacific , for example in Kamchatka , Russia .
Shad fishing
Shad are valued as fishing prey , which have a complex and difficult to understand feeding behavior during the spawning season. In contrast to the salmon species, they are able to take up food even in fresh water. Their eating behavior is influenced by various factors, such as cloudiness and water temperature. Anglers use both spinning tackles and fly fishing lures. Usually they bite best in the main flow or the deepest part of the river bed. In the north, between April and June, the most productive times are when the water temperatures rise above 14 ° C and improve when the water becomes warmer.
Cultural meaning
Shad have significant symbolic significance in the region. In years of state government elections, many candidates, supporters, and journalists gather for shad planking in Wakefield, Virginia . The Connecticut communities of Essex and Windsor hold annual Shad festivals, and New Jersey hosts Lambertville on the Delaware River.
Individual evidence
- ↑ a b c d e Alosa sapidissima on Fishbase.org (English)
- ↑ Faria, R .; Weiss, S. & Alexandrino, P. (2006): A molecular phylogenetic perspective on the evolutionary history of Alosa spp. (Clupeidae). Molecular Phylogenetics and Evolution 40 (1): 298-304.
- ^ "The fish that fed the (American) nation's founders". Wheeler, Timothy B .: Once nearly wiped out, shad stage an uneven comeback in the Chesapeake Bay . In: Baltimore Sun , May 8, 2015. Retrieved May 10, 2015.
- ^ "Grass Shad - Another Fine Bait - Southeastern King Mackerel Club - King Mackerel Fishing in Southeastern North Carolina." Southeastern King Mackerel Club - King Mackerel Fishing in Southeastern North Carolina-. Web. December 15, 2011. online ( Memento from April 26, 2012 in the Internet Archive )
- ↑ a b American shad at RedOrbit.com science news ( April 10, 2016 memento in the Internet Archive ).
- ^ Wheeler, Timothy B .: Once nearly wiped out, shad stage an uneven comeback in the Chesapeake Bay . In: Baltimore Sun , May 8, 2015. Retrieved May 10, 2015.
- ^ New York State Freshwater Fishing 2010-2011 Official Regulations Guide
- ^ Hudson River Maritime Museum Kingston Shad Festival . Hudson River Maritime Museum. August 2006. Archived from the original on August 20, 2006.
- ↑ A. sapidissima (Wilson, 1811) - американский шэд Позвоночные животные России. sevin.ru