Not really, the "easy" way is to hook up an enormously expensive multi-beam sonar to a surface vessel. A more difficult but inexpensive way to start would be t

Not really, the "easy" way is to hook up an enormously expensive multi-beam sonar to a surface vessel. A more difficult but inexpensive way to start would be to take a single-channel Ping2 transducer: https://bluerobotics.com/store/sensors-sonars-cameras/sonar/ping-sonar-r2-rp/ https://bluerobotics.com/store/sensors-sonars-cameras/sonar/... and hook it up to a pan/tilt system and datalogger. Low-power sonar shouldn't hurt fish. At only 0.2W, even with a 10ms pulse width increasing the instantaneous power output to 20W, that ultrasound pulse is probably not even perceptible to fish. Lots of studies have shown that "fish finders" are not perceptible to fish, and humans typically can't hear them either. On the other hand, military sonar can have power levels of many kilowatts and sound pressure levels that are literally off the charts, generating forces of 235 dB that cannot be replicated in air at atmospheric pressure. These are known to kill whales, dolphins, and other wildlife! They are even powerful enough to kill or maim humans who happen to be swimming too close to the ship or submarine; navies will use this to deter/repel boarders when docked in potentially hostile locations.