fish that take many months or years to build up. Potential sources of 

 ammonia or nitrogen, besides sewage plants and anaerobic sediments, 

 include industrial plants (especially refineries and munitions plants), 

 feedlots, and agricultural fields. 



Although a general recovery does seem to be beginning in the 

 Illinois River, with the return of fingernail clams in some areas where 

 they have been absent at least 30 years and appearance of largemouth 

 bass throughout the Illinos River proper, the pace and permanence of 

 recovery still appears to be threatened by ammonia, even if the problem 

 now turns out to be episodic instead of chronic. Reports of fingernail 

 clam and mussel die-offs in the Upper Mississippi River and other rivers 

 (Wilson et al . submitted; Blodgett and Sparks 1987; Neves 1987) indicate 

 that drastic population declines in macroinvertebrates that burrow in 

 sediments are not unique to the Illinois River. 



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