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were given a relative abundance ratinq. Other families of importance, but <br />not collected in significant numbers in sample areas are: Crustaceans and <br />Mayflies. Table 9 presents N.F.R.I. collected specimens and their relative <br />abundance ratings. <br />As table 7 indicates, the agricultural drain system in the Grand Valley <br />have extreme variations in both flows and water chemistry. N.F.R.I. selected <br />drains and sampled them as representative of the majority of drains in the <br />Grand Valley. <br />Results of sampling as presented in Table 7 show the species of fish and <br />eneral families of macroinvertebrates. Only 2 native species of fish were <br />collected in the drains, the balance are in+rndolced species and are (JeneNally <br />considered as tolerant to a high T.D.S. Several species of macroinverts also <br />have adapted to or tolerate the conditions found in these drains. <br />These agriculture drains are important to the fishery particularly from <br />early summer to late fall because of the large amounts of food contributed by <br />irrigation runoff. The major food organism is the earthworm. The upper <br />stretches of these drains seem to be a nursery area for most of the species <br />listed. N.F.R.I. feels the irrigation return flows as they are now constituted, <br />contribute significantly to the fishery in the Grand Valley. <br />8 C; s h llec-T ?'n? <br />l+ds`rableAis presented as a summary ofd effort in selected areas during <br />the years 1974-76. The netting effort during 1974-1975 way during the author's <br />employment with the Colorado Division of Wildlife. The 1976 work was as N.F.R.I. <br />under contract with the Bureau of Reclamation. The data as presented shows a <br />marked reduction in catch of fish per unit of effort in 1976. This table <br />also shows a downstream distribution throughout the study area where suitable <br />habitat is present, with no apparent intolerance to high TDS. <br />(24)