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Index of Threat = (1- C) * P, where... P =prevalence =the number of ponds containing species A divided by the number of ponds in which the most prevalent fish species (X) occurs, so P = #A / #X; we divide by the most prevalent species to scale P to a maximum of 1, realizing that some ponds are fishless C =control =the number of ponds in which species A occurred that have received a control treatment (poison, screen, etc.), divided by the number of ponds in which species A occurs, so C = #Acontrolled / #A ~I Example: if species A is present in 20 ponds, and species X (the most prevalent species) is present in 40 ponds, the prevalence of species A is calculated as P = ZO,~'/ 40 or 0.5. Further, if 10 of the 20 ponds containing species A have been treated to effectively control nonnative fish abundance or escapement, the relative control of species A is C = 10 / 20 or 0.5. Therefore, the overall threat of species A (the proportion of uncontrolled ponds containing species A multiplied by it's prevalence in the study area) is Index of Threat = (1- 0.5) = 0.5 or 0.25. Comparatively speaking, if the number of ponds treated to control nonnative fish increases, and some or all of these ponds also contain species A, the Index of Threat will decline. If the number of ponds containing species A increases due to additional sampling, invasion or stocking, the index will increase. Now two examples will briefly show the integrity of the Index of Threat by defining the endpoints. Theoretically, if effective control has occurred in all ponds that contained species A, then C = 20 / 20 = 1; therefore, the Index of Threat = (1-1) * 0.5 =ZERO. So, as expected, no threat is perceived if control in complete. Also, if species A exists in all ponds and control is zero, C = 0 / 40 = 0; P = 40 / 40 = 1; therefore Index of Threat = (1 - 0) * 1 = 1. Thus, as expected again, the maximum threat to critical habitat would be perceived by a prevalent nonnative fish species occurring in all ponds, and no control measures have been applied. Pre- and Post-Regulation Fish Stocking Data The goal of this effort was to compile data on nonnative, nonsalmonid fish stocking in western Colorado for the years 1998 to 2001. It was decided that 1998-1999 would serve aspre- regulation data, and 2000-2001 would represent post-regulation data. Although new stocking regulations were adopted early in 1999, it was understood that the remainder of the year would be required to make the private sector, vendors and purchasers of nonnative, nonsahnonid fishes, aware of these new restrictions. Available data was sought or acquired from five categories of records believed to document stocking activity. 1) Vendor sales receipts 2) CDOW private stocking permits 3) CDOW importation permits 4) CDOW private and commercial lake licenses 5) CDOW stocking records for public waters 6 1 J v 1 L~ f i