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Posey County, Indiana

Information provided for informational purposes only

Note: This information is provided for reference purposes only. Although the information provided here was accurate and current when first created, it is now outdated.

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Freshwater Mollusks

Table of Pesticide Active Ingredients

Active IngredientCode
1mWithin the shaded area shown on the map and 1/2 mile up all streams that join the shaded area, do not apply this pesticide within 20 yards from the edge of water for ground applications, nor within 100 yards for aerial applications.

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Freshwater Mollusks [Unionidae]

Freshwater mollusks found in this area include the Fat pocketbook. This mussel is in the family Unionidae, a family restricted to North America. A far larger percentage of this family is imperiled than any other taxonomic (species) group. The United States used to have a major industry harvesting freshwater mussels for mother of pearl buttons, freshwater pearls, etc,. There still may be a little harvesting, but not much.

Freshwater mussels can live up to 50 years. After hatching, the young mussel larvae attatch themselves to the gills of a fish. In this parasitic stage of the mussel lifecycle, the larvae are dependent upon the fish for nutrients and mobility. However, only a few host fish are known. After larvae have grown and begun to develop a shell, they detach from the fish. Mature mussels bury themselves in riffles and shoals of watersheds and feed by siphoning phytoplankton and other plant matter from the water. Reverse siphoning is used to expell undigestible particles from the shell. Silt in the water clogs these feeding siphons.

Major factors affecting mussel populations are alterations in temperature, changes in waterflow, and siltation; all caused by stream damming and channeling. Agricultural runoffs and industrial practices have also affected mussel habitat by degrading water quality and causing siltation. In addition, because mussels are filter feeders, the effects of pollution are intensified due to the large quantities of water drawn through their siphons in the feeding process. Another significant threat to native mollusks is the widespread and rapid population growth of the introduced zebra mussel. The zebra mussel not only competes with native species, but also attatches to them (or anything hard) adding so much weight that the native species cannot open to feed.

Matthews, J.R. (ed.), The Official World Wildlife Fund Guide to Endangered Species, Beacham Publishing Inc, Washington, DC. Vol II, pp. 955-956.

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