Hydroacoustic target strength validation using angling creel census data

Validation of hydroacoustic in-situ target strength is problematic in large, deep lowland rivers, which cannot be sampled easily by conventional methods such as netting or electric fishing. A sampling programme involving three different techniques (split beam sonar, angling census and post-angling competition data collection) was conducted to examine methodologies suitable for target strength validation. This combination of techniques also assessed the relative merits of each method for best describing fish populations and the stocks exploited in a recreational coarse fishery. The sonar estimated the greatest number of fish of the three techniques, with a strong positive size correlation with the other two methods. The angling census and post-competition census accounted for more larger fish, >26 cm, than were detected acoustically, indicating a stratification of species that were exploited by angling but not detected by horizontal sonar. The combined techniques demonstrated a suitable, cost-effective, hydroacoustic validation method for large UK rivers, which supports recreational coarse fisheries management, with the added advantage of species identification.