The Irish Sea West Nephrops stock (FU15) is in ICES Subarea 7 and comprises ICES rectangles: 35E3-E5, 36E3-E5, 37E3-E5, and 38E4 within 7a. The FU 15 Nephrops fishery was first developed in the late 1950s. The environment in the Western Irish Sea is very suitable for Nephrops, with a large mud patch and a gyre that retains the larvae over the mud patch, thus ensuring good recruitment. The ground can be characterized as an area of very high densities of small Nephrops. (ICES 2020)

Differences in N. norvegicus population demographic structure among geographical sectors and in total mortality appear to be highly related to different exploitation levels. (Abelló et al. 2002)

Low levels of differentiation were found between Norway lobster populations and there were no signs of an Atlantic–Mediterranean divide or of an isolation-by-distance scheme of differentiation (Stamatis et al. 2004).

The perception in the Irish Sea is that the growth rates in the eastern Irish Sea are similar to those in the western Irish Sea but the mean sizes (CLmm) in each fishery are markedly different, with the eastern Irish Sea Nephrops being the larger (ICES 2016).

Stocks are assessed at a Functional Unit (FU) level. Each FU corresponds to a specific habitat area. However, the units are managed at the ICES Division level. Thus, Nephrops management areas fall within the TAC regime of the European CFP, although allocated TACs do not coincide totally with the Functional Units (ICES 2023).

There is an EU multiannual plan (MAP) that has been agreed for this stock (EU 2019) and it is considered to be precautionary when implemented at the FU level. There is no agreement between the EU and the UK regarding this plan, and it is not used as the basis for the advice for this stock. ICES provides catch scenarios consistent with the F_MSY ranges in the MAP.