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<br />Table 7. Density estimates at Sevens, Yampa River, 1998 to 2003,
<br />
<br />YAMPA RIVER Density estimate in fish per hectare
<br />SEVENS no/ha no/ha No/ha no/ha no/ha
<br />Species 1998 1999 2000 2001 2003
<br />Total fish 179.4 179,1 122.1 104,7 215,8
<br />FJannelmouth sucker 63.2 60,5 47.4 42,3 31,0
<br />Bluehead sucker 42.8 36,9 46,9 17,9 1,6
<br />Roundtail chub 10,6 6,0 6.4 3,7 3,5
<br />White S, + hybrids 30,4 29,2 16.7 20,8 82,7
<br />Channel catfish 14,8 19,8 2,0 7,5 7.7
<br />Carp 9,1 12,6 4.1 5.6 16,0
<br />Smallmouth bass 2.4 5,6 0,5 5,8 68.2
<br />Northern pike 3,6 4,6 0,3 0,4 1,1
<br />
<br />Channel catfish were about half the density and biomass in the dry years (2000,2001
<br />and 2003) compared to 1998 and 1999 (Table 8). The lowest year for catfish density and
<br />biomass was in 2000, but its abundance rebounded in the 2001 and 2003 sample, Northern
<br />pike were much more common in 1998 and 1999 than the later years,
<br />
<br />Flannelmouth sucker mean length did not vary much between years (Table 9), In
<br />each year very few individuals less than 20 cm were caught. This was also observed in 2003
<br />(Figure AI-8), Mean length of blue head sucker was less in the three dry years compared to
<br />the baseline years (Table 9). Also bluehead sucker less than 20 cm were rarely collected
<br />(Figure AI-I). Mean length of round tail chub was less in 2003 (Table 9) than earlier years,
<br />This was due to the increased presence of fish less than 31 cm compared to prior years
<br />(Figure A 1-13),
<br />
<br />Table 8, Biomass estimates at Sevens, Yarnpa River 1998 to 2003.
<br />
<br />YAMPA RIVER
<br />SEVENS Kg/ha Kg/ha Kg/ha Kg/ha Kg/ha
<br />Species 1998 1999 2000 2001 2003
<br />Total fish 162,2 165,4 98,4 87,5 129,0
<br />Flannelmouth sucker 66,1 66,1 50,0 39,2 35,9
<br />Bluehead sucker 17,2 14,5 14,8 5,0 0.6
<br />Roundtail chub 6.3 3,9 3.9 2,0 1,8
<br />While S. + hybrids 22,9 23.2 14.4 12,3 24,6
<br />Channel catfish 21,5 22,4 3,2 10,2 11,9
<br />Carp 25.4 30,8 11,6 17,0 42,7
<br />Smallmouth bass 1,2 1,9 0,2 0.9 11,1
<br />Northern pike 1,4 2,6 0.4 0,8 0,5
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