USING MARK-RECAPTURE METHODS TO ESTIMATE FISH ABUNDANCE IN SMALL MOUNTAIN LAKES

The majority of lacustrine fish populations in the western USA are loc ated far from the nearest road. Although mark-recapture techniques are widely accepted for estimating population abundance, these techniques have been broadly ignored for fisheries surveys in remote mountain la kes because of restricted access and associated logistical constraints . In this study, mark-recapture experiments were used to estimate fish population abundance in nine small (< 7 ha) lakes of the North Cascad es National Park Service Complex. Fish in the mark sample were collect ed by angling, fin-clipped, and immediately released; fish were recapt ured with variable mesh monofilament gill nets. A single-census Peters en estimator was used to calculate abundance in each lake, and assumpt ions for unbiased estimates appeared to be satisfied in most cases. Po st-release mortality of angler-captured fish was low. The small size o f these lakes in conjunction with the brief period of rime allotted fo r each individual experiment apparently reduced the probability of une qual vulnerability and mortality for marked and unmarked fish. Single- census mark-recapture experiments appeared to provide reasonable estim ates of population abundance in these mountain lakes. Resulting estima tes furnish a substantial increase in information when compared to mor e ubiquitous assessments of relative abundance, but the logistical req uirements are modest. We believe that this technique may useful for su rvey purposes in other small, remote lakes.