Visualising fishing effort / by Francisco Blaha

Global Fishing watch.jpg

Global Fishing Watch is the product of a technology partnership between SkyTruth, Oceana, and Google that is designed to show all of the trackable fishing activity in the ocean.

This interactive web tool – currently in prototype stage – is being built to enable anyone to visualise the global fishing fleet in space and time. Global Fishing Watch will reveal the intensity of fishing effort around the world, one of the stressors contributing to the precipitous decline of our fisheries.

The tool uses a global feed of vessel locations extracted from Automatic Identification System (AIS) tracking data collected by satellite, revealing the movement of vessels over time. The system automatically classifies the observed patterns of movement as either “fishing” or “non-fishing” activity.

The prototype visualisation contains 300 million AIS data points covering over 25,000 unique vessels. For the initial fishing activity map, the data is limited to 35 million detections from 3,125 vessels that we were able to independently verify were fishing vessels. Global Fishing Watch then displays fishing effort in terms of the number of hours each vessel spent engaged in fishing behaviour, and puts it all on a map that anyone with a web browser will be able to explore.

However, it may seems that the scale of each vessel image projected on the maps significantly overstates the spatial presence of each vessel and is therefore misleading. For example round the NZ EEZ the EEZ appears to be lit up most of the time. The actual number of vessels fishing with AIS (or VMS) deployed would be fewer than 70 and that in the fourth largest EEZ in the world with a physical area larger than Australia.

The implied scale of each vessel position must be several tens of square kilometres and is visually misleading.  Australia appears to lack much fishing inside its EEZ simply because most Australian vessels are small and don't operate AIS (only vessels 24 mt plus are required to have it), hence the system may not provide information on the true scale of globall fishing as most of it is within EEZs and coastal waters and done by small vessels without any electronic monitoring.

Would be good to see the real size of the vessel position and the tracks, which i'm sure will be equally impacting, but technically more correct

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