Verifying data quality and troubleshooting hydroacoustics

How to verify data quality after deploying sensors.

Step 1: Sensor Placement and Installation

Ensure that sensors are placed according to EN Installation on Cage | STEP 5: Cage Duo Sensors

Step 2: Initial Data Verification

After the installation, a preliminary check of the echograms are performed to ensure that there are no obvious problems with sensor positioning or obstacles in the water.
If the echograms appear clean, this suggests a successful installation.

Step 3: Meal time data verification.

Verify that fish behavior is consistent with what you expect during mealtime.
If possible verify with cameras.

Troubleshooting echograms

Fish is outside of the measurement volume, that is below 25 meters or along the edges.

Empty Cage / No relevant signals

Fish taken out of cage, while equipment still operative. Inspector scales echograms by looking at the typical echostrenghts in the last 24 hours. Consequently, right after the cage has been emptied, the echogram is black as expected.

However, the day after, the echogram in the bottom sensor looking up here is very noisy. This is because, the lack of physical objects in the water column leads to very little echo and a normalization scale which will enhance electrical + acoustic noise. It is likely that this will manifest itself in the upward looking beam. Simply because the coverage volume is smaller (due to surface cropping ~25m) and hence more likely to be empty than the top sensor looking down (~50m).

Sensor is up from the water

Unknown

Echosunders entangled with equipment (Laser node)

Echograms are not showing small fish.

Image1: One color on the Fa3 echogram is not visible on the graph.

Image2: With google chrome dark mode, you can see an additional color nuance in grey, which is invisible otherwise.

Echograms show a weird stripe pattern.

27.Sept.23 - Western norway.

Symptoms: Echograms seens as ‘weird’ showing apparently artificial data on fish behavior on both Inspector and FA3(images).

Hypothesis: Seems like it is missing data from the accelerometer for some reason. Could be that the MCU is not getting the proper responses from the sensor.

Solution: Power cycling the echosounder.

Echograms show many small outage data on FA3

27.Jan.24 - Nothern norway.

Symptoms: Echograms shows red stripes on FA3 that does not seem to stabilize.

Probable cause: Very bad weather/storm at the site.

Solution: Wait until the weather gets better.

Mitigation: Use up facing beams in Inspector, as they are less affected by harsh weather.

Tuna entagled with echosounder cable

16.Sep.22 - Western norway.

Symptoms: Surface detection fails on echograms and then data looks bad on Inspector, affecting the deep sensor(up-facing).

Cause: There was a predator(yellowfin tuna) inside the cage that got its tail tangled with our cable and eventually died.

Solution: Staff from the site took it out.