In the Irish Sea, the role of scyphomedusae is of primary interest
as there has been an increasing trend in the mean overall jellyfish
biomass in the western part of the region since at least 1994 (Lynam
et al., 2011). The Irish Sea is a semi-enclosed sea between Ireland
and Great Britain (Fig. 1). Based on its bathymetry, it can be subdivided
into two regions. The region east of the Isle of Man is
relatively shallow with depths less than 50 m, and is influenced by
major estuarine inputs with the existence of a salinity front in
Liverpool Bay (Dickson and Boelens, 1988). Conversely, the region
west of the Isle of Man is characterised by a channel 100e150 m
deep (running along a northesouth axis), and which becomes