We have now been back from the Sargasso Sea for some weeks and have reflected a bit on the outcome. One of the main projects on the expedition was to get an impression on the amount of eel larvae out there and, in this way, get an indirect measure of the amount of adults (that must have been there to spawn the eggs).
I was onboard Dana on the first part of the expedition, where we covered the 3 most westerly transects. As you might remember I reported quite low catches of eel larvae and hoped that the spawning area had shifted a bit to the east. This turned out not to be the case. Also on the more eastern transect the catches were quite low.
Thus we have to conclude – preliminary – that the amount of adult eel coming to the spawning area has unfortunately not increased substantially. Therefore, the improvement in the amount of glass eel coming to Europe in the most recent 3 years is more likely to be due to better ocean currents and the like than to sufficient management in Europe of the eel stock in Europe.
Seen from a scientific point of view, one very good discovery on the expedition was that the eel larvae are very evenly distributed in the Sargasso Sea. It was not the case that in a few hauls we caught thousands of larvae and in others only a handful. We caught a few in most hauls and never more than 65 eel larvae. This means that it is possible to monitor on a routine basis, say every 2nd year, the amount of spawners in the eel stock and in that way keep track of the eel management in Europe - does it work or not?
My judgment is that a three-week survey in the area will give a precise picture of the situation. It could be done as a European cooperation with USA and Canada because the American eel species is also spawning in the Sargasso Sea.
Scientifically, the expedition went extremely well I think. The entire ecosystem was investigated from physical-chemical features, bacteria, nana-plankton, etc all the way up to the top predators. The energy requirements and swimming speed of eel larvae, bacteria on fish egg surfaces and eel genetics were also covered. There was hectic activity on the deck and in the laboratories 24/7. A lot of data and samples have been collected and almost all went very well. I am sure that when all this is worked up and analyzed it will represent a large step forward for the science of the Sargasso Sea ecosystem and for the ocean phase of eel especially.
The eel larvae fishing positions in the Sargasso Sea and beyond.