There are only 6 species of euphausiids that reside permanently and breed in the North Atlantic, north of 40" N. These are: Thysanopoda acutifrons HOLT & TATTERSALL, Nyctiphanes couchii (BELL), Meganyctiphanes norvegua (M. SARS), Thysanoessa inermis ( KRØYER), T. longicaudata (KRØYER) and T. raschii (M. SARS). A further 8 species occur fairly commonly in southern regions of the North Atlantic and are occasionally caught in more northern areas; these are Bentheuphausia amblyops G. O. SARS, lhysanopoda microphthalma G. 0. SARS, Euphausia krohnii (BRANDT), Thysanozssa gregaria G. O. SARS, Nematoscelis megalops G. O. SARS, Nematobrachion boopis (CALMAN), Stylocheiron elongatum G. O. SARS, S. longicorne G. O. SARS, S. maximum HANSEN, and S. abbreviatum G. O. SARS. These species are all included in the key presented here.
Occasional individuals of other species have been recorded in the sea area lying between southern Ireland and 40' N (see MAUCHLINE & FISHER, 1969) but these species have not been included in the key. If a species is not identified by the key given here then recourse should be made to the fuller key and to the sources of original descriptions of species given in MAUCHLINE & FISHER (1969).
Published under the auspices of the following ICES Steering Group or Committee