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xi <br />15 C. It can be inferred from this study that razorback suckers made <br />a spawning migration, but the data are insufficient to draw any <br />conclusions about the pervasiveness of this phenomenon. There was <br />no evidence that flannelmouth or bluehead suckers made a spawning <br />migration. <br />Fecundity of razorback suckers was variable and ranged from 24,490 <br />for a fish 529 mm in total length (TL) to 76,576 eggs for a fish 485 mm <br />TL. The youngest razorback sucker that was collected during this study <br />was age IV; all razorback suckers were mature. Flannelmouth suckers <br />first matured at age IV and most fish were mature by age VII. <br />Flannelmouth sucker fecundity ranged from 4,000 eggs (450 mm TL) to <br />40,000 eggs (500 mm TL). Bluehead suckers produced as few as 4,000 <br />(340 mm TL) and as many as 20,000 eggs (430 mm TL). Bluehead and <br />flannelmouth suckers from the Colorado River produced significantly <br />greater numbers of eggs than fish of equivalent lengths from the Green <br />and Yampa Rivers. <br />Razorback and flannelmouth suckers collected in 1974-76 attained <br />a maximum age of nine years. Razorback suckers from the Colorado <br />River were significantly longer than fish of the same age from the <br />Green and Yampa Rivers. Flannelmouth suckers from the Colorado River <br />were significantly heavier than fish of equivalent lengths from the <br />Green and Yampa Rivers. The differences in fecundity and growth rates <br />for fish from the two locations can probably be attributed to <br />differences in temperature between the rivers. <br />(116 pages)