Large numbers of salmon are killed by parasites, finds new study
provided by EOL authors
On Phys.org:
The study, published today in Proceedings of the Royal Society B, involved experts at the University of St Andrews and is the first evidence of the full impact of sea lice on salmon mortality levels.
Read more at:http://phys.org/news/2012-11-large-salmon-parasites.html#jCp
Seine River Benthopelagic Habitat
provided by EOL authors
This taxon is one of a number of benthopelagic species, whose habitat includes the Seine River system of Western Europe. Benthopelagic fish are found near the bottom of the water column, feeding on benthos and zooplankton The Marne and Yonne exhibit the greatest torrential flows, due to the percentage of their courses underlain by impermeable strata, in combination with the river gradients. Although the Loing manifests the highest percentage of impermeable strata of all the tributaries, its low gradient mitigates against torrential velocities. Thus the majority of the Seine and its tributaries exhibit a relaxed generally even flow rate. Seine water pollutant loads of heavy metals, nutrients, sediment and bacteria are relatively high, especially influnced by wastewater and surface runoff from Paris and its suburbs. Parisian pollutant loadings are noted to be particularly high during periods of high rainfall, not only due to high runoff, but also from the inadequate sewage treatment facilities in periods of high combined wastewater/stormwater flow. Heavy metal concentrations at Poses weir reveal the following levels: copper, 1.9 milligrams per liter; cadmium, 32 mg/l; and lead, 456 mg/l. Concentrations of zinc are also quite high, making the Seine Estuary one of the most highly contaminated estuaries in the world with respect especially to lead and cadmium. Significant amounts of toxic pollutants are also attached to sediments deposited in the Seine during the last two centuries, including mercury, nickel, chromium, toluene, DDT and a variety of herbicides and pesticides. Downriver from Paris, significant quantites of ammonium are discharged into the Seine from effluent of the Achères wastewater treatment plant. There are a total of 37 fish species inhabiting the Seine, and another two taxa that are known to have been extirpated in modern times. Two of the largest aquatic fauna known to have lived in the Seine are now locally extinct: the 500 centimeter (cm) long sturgeon (Acipenser sturio) and the 83 cm long allis shad (Alosa alosa). The largest bentho-pelagic species occurring in the Seine are: * the introduced 105 cm silver carp (Hypophthalmichthys molitrix); * the native 120 cm barbel (Hypophthalmichthys molitrix); * the native 150 cm Atlantic salmon (Salmo salar); and, * the native 500 cm Wels catfish (Silurus glanis).
