Gammarus marinus (Leach, 1815)

Norway by Tulkki (1963) in the outermost Hardangerfjord. Later Synonyms: Gammarus marinus View in CoL auct; Chaetogammarus once found in the Oslofjord (C. Christophersen, pers. comm.) and marinus auct; Echinogammarus marinus auct. a few places between Hardanger and the outer Trondheimsford Description and illustrations: Stephensen 1935 -42, p. 340, ( Vader 1969), in all cases close to the open coast, as is also the figs 45-46pp; Sexton & Spooner 1940, p. 638, figs 1-2; Lincoln case in Britain ( Spooner 1957). Not yet found further north than 1979, pp 265, 267, figs 122a, 123 ( Chaetogammarus m.). the Trondheimsfjord, but may well occur there. Ecology and habitat: This is the most euryoecious of the Marinogammarus species. Usually it is to be found under stones in the upper half of the intertidal. In places with some freshwater H. The Relictogammarus group flow, or where M. obtusatus and/or? M. finmarchicus for some This consists of only the small species R. stoerensis , which reason are absent, it may occur lower down. M. marinus tolerates according to the studies of Hou & Sket (2016) should be more sediment in the substrate than the other species, and it also considered the sister group to all other Gammaridae . occurs in brackish waters. In estuaries it occurs far into the mesohalinicum (den Hartog 1964). In the fjords in W. Norway it penetrates very far: in Hardanger until Osafjorden (Brattegard 17. Relictogammarus stoerensis ( Reid, 1938) 1966), in the Sognefjord far into the Lusterfjord ( Vader 1977a). Distribution in Norway: Very common everywhere in Synonyms: Gammarus stoerensis Reid, 1938 ; southern Norway. Its distribution is insufficiently known in Marinogammarus stoerensis auct.; Chaetogammarus stoerensis northern Norway: it is not rare around Tromsø, but we know of auct.; Echinogammarus stoerensis auct. no reliable records east of the North Cape. Description and illustrations: Stephensen 1935 -42, p.

346. fig. 49 ( Marinogammarus st.); Sexton & Spooner 1940, p.

662, fig. 8 ( Marinogammarus st.); Lincoln 1979, p. 271, fig. 125 ( Chaetogammarus st.).

Ecology and habitat: Intertidal, under stones and in gravel, coarse mud-intermixed sand or other mixed fine substrate, at places where lesser amounts of freshwater flow out. The vertical distribution covers almost the entire intertidal, down from MHWN; higher up it is often replaced by Gammarus duebenii . R. stoerensis tolerates much brackish water; in the Sognefjord the first author ( Vader 1977a) found them at Dale in the Lusterfjord, where the fjord is ice-covered several months each winter. In the inner fjords R. stoerensis may be almost dominant some places (cf Skadsheim 1983) and it is there, where the salinity is very variable during the year, much less confined to freshwater trickles.

Distribution in Norway: Probably common along the entire Norwegian coast, but absent from Svalbard. There are as yet few records from N. Finnmark ( Vader 1971), but the species also occurs in the Murmansk region ( Segerstråle 1948).