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Sharks

Explanations, unusual event

Results Explained

This figure shows a short portion of the data record from the mini-PAT we deployed on the very first shark we ever caught, tagged, and released in Resurrection Bay. Since we physically recovered this tag, we were able to access all recorded data, including data from a tri-axial accelerometer that shows changes in the orientation of the tag.

 

This revealed that this particular shark likely died a violent death, presumably the result of the attack by a predator, which occurred at a depth of around 270m. As we are looking into what happened here, we will fill in additional details on this event. 

PSS-1-event broad
Data recovered from a miniPAT deployed on a 2.8m immature female shark. Dark blue trace = depth; Light Blue, Red and Black traces are the three different axes of the accelerometer. Through the early part of this record there is always some movement detected by the accelerometers, but no major change in orientation of the externally attached tag. This is apparent from the observation that the relative signal strength of the three axes does not change. In the middle of the data segment shown, all of a sudden the axis with the strongest signal repeatedly changes, which indicates multiple rapid inversions, lasting over a period of about 5min. Then most motion seems to cease.
Vertical movement
Conclusions

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