Microgadus tomcod
| Microgadus tomcod | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Microgadus tomcod |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Microgadus tomcod | ||||||||||||
| Walbaum , 1792 |
Microgadus tomcod is a fish from the cod family. The species is native to coastal waters of the North American east coast, from the US state of Virginia in the south to the southern Canadian Labrador coastincluding the Saint Lawrence River .
In the range the species is called in English Atlantic tomcod , frostfish or winter cod . Their common French names are Poulamon atlantique , Poisson des chenaux , Loche , Petite morue and Poisson de Noël .
features
.jpg)
The appearance of this fish is similar to other cod: it has three dorsal fins and a barb on the lower jaw. The body color consists of brown and olive brown tones, the belly is lighter and light gray. The skin has small scales and dark spots. The greatest documented length of a specimen is 38.1 cm.
Distribution area
The habitat of the species is in the Nearctic . The animals inhabit the coastal waters of the North American east coast without venturing into particularly great depths: They have been proven to a depth of 69 meters. They are found farthest south off Virginia , northward they reach Canadian waters off Labrador . The species also thrives in brackish water and colonizes fresh water, so that it belongs to the fauna of the St. Lawrence River and also occurs in some lakes without access to the sea.
nutrition
The demersal species that lives near the seabed feed on small animals. Crustaceans form an important part of the menu, and worms and small fish such as smelt and herrings are also eaten.
Reproduction
Spawning occurs in winter over sandy or gravelly soil, the eggs sink to the bottom and adhere to the substrate. Mainly tidal rivers and estuaries, sometimes also places far upstream, are used as waters. The reproduction takes place in fresh and brackish water: marine populations move up the rivers to reproduce and return to the sea after the spawning business.
Ecological feature
The population in the Hudson River was severely damaged by waste water containing PCBs . The chemicals were introduced into the water system by General Electric at Fort Edward and Hudson Falls between 1947 and 1977 . An average lifespan of up to seven years is typical for the species, with a main focus on the age distribution of three to four year old specimens. In 1983, however, 97% of the specimens in the Hudson River population were at most one year old and only 3% of the fish were two years old. Many had tumors, the livers were greatly enlarged and discolored.
Since then, however, the age pyramid has changed again in the direction of a species-typical distribution. A genome change is assumed to be the cause of the increased resistance to environmental toxins. In the Hudson River population, a greatly increased likelihood of a mutation - a loss of six base pairs in the AHR2 gene (AHR: aryl hydrocarbon receptor ) - was observed: 99% of the animals examined had this, compared with only 10% of a comparison group occurred from uncontaminated biotopes. The protein encoded by AHR2 binds to molecules such as PCB and dioxins and transports them into the cell lumen, where the harmful effects of the toxins then occur. The mutation reduces and makes this transport more difficult. Hudson River Tomcod embryos are about a hundred times more resistant to these long-lived organic pollutants than comparative specimens from populations from unpolluted waters.
Use as food fish
Microgadus tomcod is not particularly important for commercial fisheries, and the species is not an object of targeted pursuit. Possible catches are landed and marketed. Sport fishermen like to chase M. tomcod . In the French-speaking part of Canada, especially in the maritime provinces , ice fishing is a popular winter pastime. In Sainte-Anne-de-la-Pérade , this so-called pêche aux petits poissons des chenaux has the character of a folk festival; in winter 2008/2009 over 130,000 participants were counted.
Web links
Individual evidence
- ↑ a b c d Microgadus tomcod on Fishbase.org (English)
- ↑ a b IUCN : IUCN Red List, Atlantic Tomcod ( EN ) IUCN. 2013. Accessed January 8, 2019.
- ↑ a b Ronald J. Klauda, Thomas H. Peck, Gary K. Rice: Accumulation of polychlorinated biphenyls in Atlantic tomcod (Microgadus tomcod) collected from the Hudson River estuary, New York . In: Bulletin of Environmental Contamination and Toxicology , Volume 27, Number 1, July 1981, pp. 829-835, doi : 10.1007 / BF01611103 .
- ^ CE Smith, TH Peck, RJ Klauda, JB McLaren: Hepatomas in Atlantic tomcod Microgadus tomcod (Walbaum) collected in the Hudson River estuary in New York . In: Journal of Fish Deseases . Volume 2, Number 4, July 1979, pp. 313-319, doi : 10.1111 / j.1365-2761.1979.tb00173.x .
- Jump up ↑ Isaac Wirgin, Nirmal K. Roy, Matthew Loftus, R. Christopher Chambers, Diana G. Franks, Mark E. Hahn: Mechanistic Basis of Resistance to PCBs in Atlantic Tomcod from the Hudson River . In: Science . Volume 331, number 6022, 2011, pp. 1322-1325, doi : 10.1126 / science.1197296 .
- ↑ Jennifer Welsh: Fish Evolved to Survive GE Toxins in Hudson River ( EN ) Live Science. February 17, 2011. Retrieved January 8, 2019.
- ^ Anne Minard: Hudson River Fish Evolve Toxic PCB Immunity ( EN ) National Geographic . February 19, 2011. Retrieved January 8, 2019.
- ↑ lespetitspoissons.ca - Historique ( FR ) Retrieved January 8, 2019.