Does the Invasive Predator Mnemiopsis leidyi A. Agassiz, 1868 Control Copepod Abundances in the Seine Estuary?

The indigenous ctenophore Pleurobrachia pileus (O.F. Müller, 1776) was common in the coastal waters of English Channel early 1990s and showed very abundant populations downstream part Seine estuary. In 2005, non-indigenous Mnemiopsis leidyi A. Agassiz, 1868, a species native to Western Atlantic, reported for first time Europe Norwegian fjords Le Havre harbour (Seine estuary, France). More recently, 2017, both were recorded during suprabenthos zooplankton sampling estuary along downstream-upstream transect. Both show more May than September. Conversely, copepods spatial distribution depending on distribution, with low copepod abundances being associated high abundances, while are where ctenophores absent or display abundances. We propose that intense predation is related changes hydrological conditions over two last decades. This may explain dramatic decline abundance which could have negative effect its nursery role.