We started with the Beaglebone Black with a custom shield that used a MCP3008 ADC converter and a instrumentational op-amp to pick up the signals and then feed the signal through a op-amp to amplify it further . We decided to use a Beaglebone due to its high processing rate and its Linux OS. The shield included a speaker to notify the researchers if a fish is near, and to sample the signal at 100k Hz and store the data on a SD card.
The probe was made out of a 3 1/2" long , 1/4" thick PVC pipe with a 3 wire audio cable. I used hot glue to hold everything in place, and to make sure the probe is waterproof.
After a signal is received we store it on the Sd card in hexdecimal format with a header that included the date and time of recording.