"Considering these points, I perceived that if the problem were to be solved in anything like a satisfactory manner it would be necessary to ascertain, not only where the youngest larvae were to be found, but also where they were not."

Johannes Schmidt, 1922.

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What are satellite tags and why use them?

Pop off satellite tags, or PSATs are widely used to track the movements of large pelagic animals (those that live in the upper few hundred metres of ocean and that typically travel hundreds or thousands of miles) that are difficult to follow or sstudy by any other means. The PSATs are mounted on the animal and stores data (temp, depth and light) while attached to the animal. At a predetermined time, the tags initiates an onboard release mechanism and pops off the animal. The tag is buoyant and rises to the surface where it relays its stored data to the ARGOS satellites. The data can then be downloaded via the ARGOS system. Unfortunately, the size of most PSATs limits the number of species they can be used on- especially in the case of eels. photo: Pop off satellite tags or PSATs

The very recent development of small PSATS has opened up new horizons for marine biologists. In particular, the small PSAT tags now available are small enough to attach to European eels, albeit the very largest ones (90 cm and above). Recent pilot studies of trans-oceanic eel migrations using pop-off satellite tags on eels tagged as part of the GALATHEA 3 expedition; has proved the concept of tagging eels in this way. In the eeliad project, silver eel migrations will be studied by implementing a large-scale tagging programme on silver eels at the Atlantic boundary zone.

The eeliad project will contribute to efforts funded under the auspices of the Census of Marine Life (CoML) project ( and by being associated with the EUTOPIA initiative. The goal of this initiative is to implement studies of oceanic-scale animal movements in a similar way to the TOPP programme. By association with the European CoML programme, eeliad will focus attention on European efforts to make breakthrough scientific discoveries about eel migrations.

line drawing of an eel