| Summary: | Eleven sequential size-based hydroacoustic surveys conducted with a 200 kHz split-beam transducer during the summers of 2011 and 2012 were used to quantify seasonal declines in fish abundance in a boreal reservoir in Manitoba, Canada. Fish densities were sufficiently low to enable single target resolution and tracking. Target strengths converted to log2-based size-classes indicated that smaller fish were consistently more abundant than larger fish by a factor of approximately 3 for each halving of length. For all size classes, in both years, abundance (natural log) declined linearly over the summer at rates that varied from -0.067.day-1 for the smallest fish to -0.016.day-1 for the largest (R2 = 0.24–0.97). Inter-annual comparisons of size-based abundance suggested that for larger fish (>16 cm), mean winter decline rates were an order of magnitude lower (-0.001.day-1) and overall survival higher (71%) than in the main summer fishing season (mean loss rate -0.038.day-1; survival 33%). We conclude that size-based acoustic survey methods have the potential to assess within-season fish abundance dynamics, and may prove useful in long-term monitoring of productivity and hence management of boreal aquatic ecosystems. LDBS1_All_ST Acoustic survey data (exported single target detections) from Lac du Bonnet, Manitoba, on July 26th, 2011. LDBS2_All_ST Acoustic survey data (exported single target detections) from Lac du Bonnet, Manitoba, on August 2nd, 2011 LDBS3_All_ST Acoustic survey data (exported single target detections) from Lac du Bonnet, Manitoba, on August 3rd, 2011 LDBS4_All_ST Acoustic survey data (exported single target detections) from Lac du Bonnet, Manitoba, on August 15th, 2011 LDBS5_All_ST Acoustic survey data (exported single target detections) from Lac du Bonnet, Manitoba, on August 18th, 2011 LDBS6_All_ST Acoustic survey data (exported single target detections) from Lac du Bonnet, Manitoba, on August 27th, 2011 LDBS7_All_ST.csv Acoustic survey data (exported single target detections) from Lac du ...
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