Movements in the deep: Using deep-sea loggers to track longline movements on the seabed.

Dr Tabitha Pearman, Vulnerable Marine Ecosystems Project

Figure 1. View of longline weight static on the seabed. Image courtesy of consolidate fisheries limited.

With the assistance of the crew from the CFL Hunter the Vulnerable Marine Ecosystems (VME) Project has been deploying loggers onto longlines to measure longline movement on the seabed. The ability to measure longline movement is very exciting because it gives us our first ever insight into how Spanish trotlines behave whilst on the seabed. Understanding exactly how the longlines move while on the seabed is important in calculating how much of the seafloor fishing gear contacts, a metric known as the ‘fishing footprint’. As part of the VME Project, fishing footprints are mapped and compared to the predicted spatial distribution of VMEs in order to help inform a VME strategy.

Figure 2. Deep-sea loggers that measure acceleration are attached to longlines to track their movements during fishing. The loggers are 10 cm in length and can withstand depths of 3000m! However, for our research they are only deployed to a maximum depth of ~1500 m.

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