WSP09970 - Laserfiche WebLink

Home Browse Search

,fl, fJ111!U!~' .U U-~-~ <l ,. " Brown trout population estimates have consistently increased between 1985 and 1987 at the Almont to Lost Canyon Resort Bridge while they have fluctuated up and down at the Lost Canyon to Rocky River Resort section. Wild rainbow estimates have increased dramatically in 1987 over the 1985-86 estimates for both sections. Catchable rainbow stocking on the Almont to Lost Canyon Resort Bridge section has been an on-going management practice through 1987 as this section is either on public land or open to public angling by virtue of a stocking agreement between the CDOW and private landowners. The HCC strain rainbows stocked in August-September 1985 were found in abundance in September 1985 during the population estimation period. However, ,they were almost totally gone from both sections by September 1986. Onlyll remained of the 10,000 stocked, for an estimated survival of O.Oll%. Similarly, of the 10,000 BELL, strain rainbows stocked in late-summer 1986, an estimated 251 remained in September 1987, for an estimated survival, of 2.5%. Both plants were adipose-clipped. The HCC strain averaged l6.5 cm in length and the BELL strain averaged l2.4 cm in length at stocking. Thus, both strainscwere certainly large enough at stocking to survive the rigors of stream life"assuming the genetic material and "wildness" was present in those strains. It will be 1988 or 1989 before we begin to see any potential survival for the 1986 and 1987 plants of CRR rainbows showing up in the, population estimates as these cohorts were both under 5 cm average size at stocking. However, we did collect some of both the CRR and TAS strain rainbows during our September 1987 population estimation procedures. Rio Grande River The stocking records for numbers, sizes, strains, and dates for the three study areas on ,the Rio Grande 'River are presented in Table ll. During the current segment of the study, a third study area was added to this investigation. The new area, the Rio Grande Fisherman Area,,(RGFA), is approximately 19hectares in area and 6 km (3.7 miles) long, ,located just upstream of the U.S.F.S. Marshall Park Campground near Creede, Colorado. The other two study areas are the State Bridge (SB) section near Del Norte and the Coller Wildlife Area (CWA) near South Fork. Rainbow and brown crout population and biomass estimates for the SB section of the Rio Grande River from 1981 through 1987 are given in Table 10. Stocking of CRRfingerlings began in October 1984 and has continued since then. The increase in rainbow density and biomass estimates since 1985 has been dramatic. Examination of the rainbow life table data (Table ll) clearly indicates the dramatic increases in rainbow year-class,strength. since 1984. ' Survival of the 1984 and 1985 plants 2 years after stocking has been very good. It appears, heavy mortality occurs between the fry (age 0+) and juvenile (agel+) life stages. Minimum survival at age l+ for the 1984 and 1985 cohorts is 4.7% and l2.4%, respectively. We stocked l2,500 CRR fingerlings in September 1986'that averaged 5.l cm in length. The 1986 rainbow cohort estimate was 544, for a minimum survival estimate of 4.35%. The term minimum survival is used, since there are no restrictions on emigration out of the section either upstream or downstream. Survival of the 1984 and 1985 cohorts at age 2+ was estimated at 4.07% and 5.7%, . ; 00002404