Automatic Bluefin Tuna Sizing with a Combined Acoustic and Optical Sensor

Area of Science:

• Marine Biology
• Acoustic and Optical Sensing Technology
• Fisheries Science

Background:

• Accurate fish sizing is crucial for fisheries management and stock assessment.
• Traditional methods for measuring fish size can be labor-intensive and may stress the fish.
• Developing non-invasive, automated systems for fish measurement is a key research area.

Purpose of the Study:

• To propose and validate a novel underwater sensor system for automatic sizing of juvenile bluefin tuna.
• To combine acoustic and optical data for accurate Snout-Fork Length (SFL) and width measurements.
• To improve the efficiency of automated fish sizing compared to existing methods.

Main Methods:

• Development of an underwater sensor integrating acoustic (echogram) and optical (video) devices.
• Application of image processing for identifying fish traces in acoustic data and fitting ventral silhouettes in video frames.
• Verification of correspondence between acoustic and optical data for accurate fish sizing.

Main Results:

• The combined acoustic-optical sensor successfully provided automatic and accurate measurements of juvenile bluefin tuna SFL and width.
• The proposed system demonstrated a 7.2-fold increase in samples per hour compared to stereoscopic vision methods.
• Measurement accuracy was maintained without compromise, even with a high density of fish (77 juveniles).

Conclusions:

• The study validates the efficacy of combining acoustic and optical data for automated fish sizing.
• This integrated sensor represents a significant advancement towards autonomous, real-time fish measurement systems.
• Future work will focus on optimizing electronics and processing for a fully autonomous embedded sensor.