Yangtze River Demersal Habitat
This taxon is one of a number of demersal species in the Yangtze River system. Demersal river fish are found at the river bottom, feeding on benthos and zooplankton.
The upper Yangtze basin consists chiefly of Paleozoic limestone and terrigenous sedimentary rock, with some granitic material. The most downstream element of the upper Yangtze basin is often termed the Sichuan Basin; here the Yangtze cuts through Triassic and Permian material before entering the Three Gorges. The Three Gorges area is a stretch of the Yangtze that runs approximately 660 kilometers, terminating at the site of the Three Gorges Dam. Prior to construction of the dam, the Three Gorges area was a site of exceptional natural beauty; after dam construction the gorge areas were filled with approximately 100 meters in depth of Yangtze water, and considerable amounts of the watershed were graded.
The lower Yangtze basin consists of anabranching river structures and Pleistocene coastal terraces. Prior to development of the Three Gorges Dam, the Yangtze Delta was replenished with a copious sediment load reaching the river mouth; however, the dam has now severely limited the natural flow and deposition of sediment to the delta region. Consequently, the integrity of the delta is been compromised, with scouring exceeding deposition, and the very stability of the delta is endangered.
Lower and middle basins of the Yangtze carry heavy pollutant loads. In the lower Yangtze basin nitrate levels are high, measuring at about 1000 tons per day at Datong; these levels accrue from high applications of chemical fertilizer applied and also considerable loadings of untreated sewage due to the large human population of the basin, with correspondingly little infrastructure for sewage treatment.
Heavy metal concentrations are also high in the lower Yangtze, with measurements of dissolved lead at 0.078 microgram/liter; cadmium (0.024 microgram/liter), chromium (0.57 microgram/liter), copper (1.9 microgram/liter), and nickel (0.50 microgram/liter). Levels of dissolved arsenic have been measured at 3.3 microgram/liter) and zinc at 1.5 microgram/liter), both notably higher by factors of 5.5 and 2.5 respectively than other typical large world rivers. In Yangtze River suspended sediment, arsenic comprises 31 microgram/gram, lead comprises 83 microgram/gram, and nickel comprises 52 micrograms/gram of sediment content
There are several large native demersal fish found in the Yangtze River, chiefly the 250 centimeter (cm) long endangered Yangtze sturgeon (Acipenser dabryanus), the 120 cm Chinese sturgeon (Acipenser sinensis), the 200 cm Giant mottled eel (Anguilla marmorata), the 122 cm black carp (Mylopharyngodon piceus), the 300 cm Chinese paddlefish (Psephurus gladius), and the 100 cm Silurus meridionalis. Furthermore, there are a few exceptionally large native benthopelagic fishes found in the Yangtze, namely, the 105 cm Silver carp (Hypophthalmichthys molitrix), the 200 cm Wuchang bream (Megalobrama amblycephala), the 200 cm yellowcheek (Elopichthys bambusa), the 145 cm common carp (Cyprinus carpio carpio), the 122 cm Mongolian redfin (Chanodichthys mongolicus), the 102 cm predatory carp (Chanodichthys erythropterus) and the 100 cm snakehead (Channa argus argus).. The demersal fish Silurus meridionalis also is found as a Yangtze River endemic species.