7194 - Laserfiche WebLink

Home Browse Search

= ....1 PESULTS 9 e !.J.gr.:.::'?:.1 Drift-net samples were collected from July 3 through August 16; 1985; resulting in 204 total samples~ Nine fish species from four families were collected (Table 11~ Bluehead sucker (CatostoffiuS discobolusl was the dominant species collected, constituting 48% of the total catch and oc:cur'l~ i ng in 40% of the '";amp}, (,~~,>" eh <3.nnc~1 c,J.t.f j. ~;h (1f;..L~:~J U.i.:J,.15.~. f2.I:L8j;.t~}t.u. ~2.) Co lor .=':l.do ~:;qu.a~o.jf i sh (f.::j;.':.<s.:r!.9s;.t]g):.1~:~.;:;. .L!.,J.f;j..l:L;i.); .9.nd f 1 ,3.nn2 1 mou.t.h sue k'~I~ (Catostomus latipinni~) ~~ere the next most abundant species, accounting for 32; 10 and 7 percent of the total catch, and occurring in 42, 22; and 28 percent of the samples, respectively. Other species collected included mu.ch smaller numbers of speckled dace (Phinirhthvs osculusl; Gila spp.; san d ~5 h i n e ~- ( t~_g t I::-S:P.i.::2. "2..tr.::i~1l.L!:.l.f.:?'~,L5.), .f .3, the .9. d m inn 0 ~.! EJ..ill.~.P.t~.:.~.l..~~I~ p-r.:.f~tm e 1 E.~. 1 ; an d mot t.1 ed sc u 1 pin (h.gtt!;;:~2 [:;!.:~!:...tr.:.9...U. The six native species dominated the drift sample, constituting 68% of the 4,589 fish collected, and occurring in 67% of the samples, Similarly, native species collected in the drift samples in 1983 and 1984 accounted for 65% of the 1,509 and 2;711 fish sampled in each year, respectively (Haynes et al. 1985). Similar to past years, channel catfish was the major non-native species collected in the drift with bluehead sucker representing the major nat.ive species. C qL!;;lJ::_;~l: d 0 _..1:LCllLs:.:t.::J.:Lt2.h Larval Colorado squawfish were -first collected on July 9, six days after sampling began (Table 2). Thereafter, they were present in the drift samples each week through to termination of sampling on August 16. Seventy percent of the larval squawfish ~~ere collected during July 9-12, with a smaller peak representing 18% of the total sample collected on August 6-8. The 455 larval Colorado squawfish collected during this study represents the largest single collection of this species by drift-net alone or in combination with seine samples for the Yampa River. The overall drift density for larval Colorado squawfish in 1985 was 4.0 individuals /lOOOm3. Drift densities in 1983 and 1984 were 1.2 and 0.9 individuals /1000m3, respectively. Size of the larval squawfish collected in 1985 ranged from 7.9 to 10mm, compared to 7.2 to 9.5mm for 1983-84 (Haynes et a1: 1985). Over the six weeks in which larval Colorado squawfish were captured, mean lengths ranged from 8.5 to 9.0mm with maximum-minimum length intervals per sample ranging only from 1,2-1.5mm (T.a.ble 3). Using the length data and the age-growth equations, larval squawfish collected in 1985 were estimated to be 12-20 days old post-spawning (Table 2): The post-spawning age range for larval squawfish collected in 1983-84 was 8-18 days. The estimated post-spawning ages for larval Colorado squawfish in 1985 indicate spawning occurred at least from June 23 through August 1 (Fig.2!. It is possible that more spawning and production of larvae occurred later than August 1, since larval Colorado squawfish were still being collected at termination of sampling on August 16. Peak spawning was estimated to have occurred during June 25-29, accounting for 671. of the larvae collected. Two minor spawning peaks are also evident during July 3-5 and July 23-26, accounting for another 7 and 15 percent, respectively, of the larvae sampled.