9636 - Laserfiche WebLink

Home Browse Search

data," random surveys to locate individual signals were made throughout the pond at various times of day and night, nominally in evening just prior to sunset and in morning just after sunrise. A directional hydrophone was used to determine the presence and general direction of a signal, while the omni- directional hydrophone was used to pinpoint the location of sedentary fish (or tags). Finally, during 2004 only, a fixed listening station was established using an anchor and buoy placed near the geographic center of the pond. That station was manned periodically using both types of hydrophones to ascertain general fish or tag location, and an attempt then was made to establish a precise location using adirected-random survey. Directional Data Analysis. Compass bearing data were sorted and correlated so that only temporally paired, simultaneous observations were retained, and all values were rounded to the nearest 5 degrees: Data were entered into an Excel spreadsheet that showed all corresponding intersections for the two listening stations, and data then were corrected for geographic declination at Cibola HLP relative to true north by subtraction of 13 degrees. An ArcView "project" was created to accommodate the paired directional data and, the Cibola NW digital orthographic quarter quadrangle (DOQQ) was downloaded from the Arizona Regional Image Archive (ARTS) and added to the project. Next, a lake poly file to represent the Cibola HLP was created from the Cibola NW DOQQ. Global Positioning System (GPS) coordinates were used to create two point files, one representing the two listening stations and the other representing 26, 5-m wide "zones" that were designated along'the high levee (see Point Data Analysis, below). An array of $00 m-long radial lines representing each individual bearing observation was created from the stations point file for each listening station, and these were separated into individual shape files based on the listening station from which they were created (i.e., high levee or low [river] levee). The "intersections to points" theme from ESRI then was used to create a single point for each intersection of the radial lines, and these in turn were used to create x-y coordinate fields in an intersection data table. Fish data were added to the ArcView project, and fields showing bearing data for low and high levee stations were inserted. The point intersection shapefile table and the fish data were joined, based upon common station/bearing criteria, and exported as a new table of individual joined data. Finally, a fish shapefile was created from the fish table by converting the fish event theme to a shapefile, and the fish table was summarized based on the low- high levee bearings field. The final result was a graphic that shows which fish were located within each at each two-dimensional space (defined by the intersection of radiating bearings), and the number of occurrences of each fish within each space. All intersections that fell within the 800 m radius were plotted in ArcView and the remainder was removed from consideration as uninformative. Paired data were 3