Considering the remarkable migration of the eel, and the present ob- 

 stacles to its movement, it is not surprising that it is rare. Eels 

 spend most of their lives in freshwater streams and rivers. When they 

 are approximately a dozen years old, 2% to 4 ft long, 3% to 6 lb in 

 weight, they migrate downstream to the sea. They spawn in certain parts 

 of the Sargasso Sea, between the West Indies and the Azores, then die. 

 The young swim and drift back to continental waters, then ascend the 

 Mississippi River system. Physical or chemical barriers such as naviga- 

 tion dams and effluents may hinder the migration of eels. 

 Skipjack herring (Alosa chrysochloris) 



Skipjack herring were taken sporadically throughout the river. 

 Large numbers apparently moved up the Illinois River during the spring 

 flood of 1973, and sport fishermen were catching them on minnows at 

 Havana. 

 Gizzard shad (Dorosoma cepedianum) 



Gizzard shad were abundant in collections in all pools of the river. 

 The numbers and pounds reported in Table 7 do not begin to reflect the 

 actual abundance of the species for the following two reasons: (1) small 

 gizzard shad are stunned only momentarily by the electric shock and usu- 

 ally get away before they can be netted; and (2) so many gizzard shad 

 usually appear that it is futile to try to net them all, and so netting 

 efforts were concentrated on other species. 



Gizzard shad are neither a commercial nor a game species, but small 

 shad are valuable forage for largemouth bass, crappies, and even species, 

 such as drum, that ordinarily prefer mollusks when they are available. 



Shad are sensitive to low dissolved oxygen and probably sensitive 

 to cold temperatures. Die-off s of gizzard shad as a result of low dis- 

 solved oxygen levels sometimes occur in the bottomland lakes and back- 

 waters in mid-summer and usually occur in winter because of low tempera- 

 tures and perhaps low oxygen levels also. Nevertheless, because of 

 their high reproductive capacity, gizzard shad populations do not seem 

 to be much affected by these die-offs. 



2] 



