peak years. Collections in 1975 and 1976 indicate that mussels a^-e 

 not abundant in Pools 24, 25, and 26 (Perry, in press: 6). 



Species Composition Cha^ a. species composition of ^ 

 mussel fauna of the Mississippi River has changed little from the pre- 

 dam era (Table 8 ) , but the relative abundance of certain species has 

 been reduced. tt,«~ 



„. u Th6re are few data °n the species changes 



that have occurred in Pools 24, 25, and 26 of the river. 



Evidently, the ebony ghell mnssel (Fusconala ebena) 



was once very abundant in Pools 24, 25, and 26 as well a71h7e^ir7~ 

 river (Townsend, 1902: 707; Cohen, 1921: 22; Nord, 1967: 191) A 

 shell sample from the Mississippi River at Grafton, Illinois, in 1912 

 consisted of 32 percent ebony shells (Danglade, 1914: 25) mis 

 mussel was an important commercial species, taken for the pearl button 

 industry (Smith, 1899; Townsend, 1902: 707; Coker, 1921: 41; Nord 1967- 

 193). The known fish host for this mussel is the skipjack herring 

 (Alosa chrysochlori s), a fish that is supposedly migratory (Coker et 

 al., 1921: 153; Starrett, 1971: 289). It appears that the construc- 

 tl0n ° f dams on the Mississippi River inhibited the 



movements of this fish (Coker, 1914: 23, 26; Barnickol and Starrett 

 1951: 323) and in doing so reduced the survival of the ebony shell mussel. 

 By 1926 the skipjack was no longer found above Keokuk Dam (Carlander 

 1954: 48) and Barnickol and Starrett (1951: 323) report that skipjack 

 herring were only taken occasionally in their collections from the 

 river between Caruthersville, Missouri, and Warsaw, Illinois, in 1944. 

 Nord summarizes: 



The importance of the three-ridge in today's fishe-y 



claT™ W ti0D °J J" 6 Ch3ngeS that have occurred In'the 

 clam Population of the Mississippi River over the years. 



SduJtrTw II s th£ eb ° ny She11 W3S the backb °ne of the 



t^fisIerT (1967: P 19 C 3) S "" "** ^ ^'^ f ™ 



The UMRCC survey (Perry, in press: 8) classified the ebony shell as 

 uncommon in the river. 



49 



