Sound recordings of the Patagonian king crab (Lithodes santolla)

Hydroacoustic techniques are the most suitable means for the remote sensing of the aquatic environments. Passive acoustics is the action of receiving sounds originated by different sources in the surrounding medium. The sound waves produced by a source are captured by a hydrophone and can be used to identify its origin. When an array of hydrophones is used, the position of the sound source can also be determined. Many aquatic organisms are able to produce sound with different purposes. Crustacean species, such as crabs and lobsters, produce sounds by means of pincer movements and also due to friction between shells, enabling scientists to study their behavior by using acoustic receivers of the appropriate frequency bandwidth and receiving sensitivity. In this work we proposed the use of passive acoustics in order to study the performance of crab fishing gear. The determination of the time of entrance into the fishing pots and the period of their residence were of particular interest. In order to test this hypothesis, we registered sounds amplitudes from different fishing pots by means of low cost, homemade self-contained hydrophone recorders. We were able to register the exact time of cages settlement on the bottom and the moment when the first crab entered the pot. We recorded an increasing sound level due to the incremented number of captured organisms. These results will be useful to adjust current models used for crab abundance assessment and it is expected to achieve a greater accuracy.