Climate change and passive transport of European eel larvae

One hypothesis to explain the large decline in the recruitment of the European eel (Anguilla anguilla) from the 1980s onwards is that a change in ocean circulation has influenced the drift of eel larvae, resulting in lower recruitment. To test this hypothesis, a simple Lagrangian model was constructed to simulate a passive drift from the spawning area in the Sargasso Sea to the European shelf. The simulation utilised the velocity data from a reanalysis of ocean climate, the Simple Ocean Data Assimilation (SODA 2.1.6), for the period 1958-2008 covering the time of regime shift in eel recruitment. The average drift time and latitudinal distribution of the arrival of eel larvae were explored for a range of constant depth levels and instantaneous mortalities. The model showed that the proportion of eel larvae carried by the North-East Atlantic Current to northern latitudes of arrival was greater before 1970, whereas there was an increase in amount of larvae being entrained into the southbound current branches after this time. The overall success of drift from the spawning area to the East Atlantic was not affected and clearly contradicts that this could explain the observed recruitment decline.