259 



DRAFT 



'And even though the shad is primarily a plankton feeder, the overlap of 

 beruhic prey in its diet and in the diets of other juvenile salmonids, such 

 as Chinook salmon, coho salmon, and steelhead trout, provides ample 

 evidence that competition is occurring, ..." 



This statement is not true. No conclusion can be drawn from overlap (it is unknown if 

 food is limiting). 



The discussion of competitive interactions between American shad and anadromous 

 salmonid juveniles is largely a hypothesis that the authors do not substantiate with 

 scientific research. The major weakness in this argument is that the authors fail to 

 document the extent of spatial and temporal overlap in estuary rearing habitat between 

 these species, or demonstrate that food availability is limiting juvenile salmonid 

 production in the Columbia estuary. The authors also fail to note that juvenile shad are 

 a prey source of juvenile salmonids in rivers and estuaries (Emmett et al. 1991). An 

 alternate hypothesis of this fact could conclude that the increased abundance of juvenile 

 shad should have caused increased salmonid production because of an increased food 

 supply (assuming that food supply is limiting salmonid production). 



Reduced Population Size 



Why is this subheading presented in the American Shad section? 



A-53 



