INTRODUCTION ^49 



shelf waters sampled in November 1936. The fact that the temperatures diminish as one proceeds 

 offshore supports this view. There should be an earlier tendency towards establishment of a thermo- 

 cline, favouring earlier onset of the main diatom increase, under the warmer conditions prevailing 



'"'itTs^thus probable that over the area of the trawling surveys the times of maximal production of 

 phytoplankton are only slightly later than in corresponding latitudes in European waters, and not so 

 much later as in the oceanic sub-Antarctic waters beyond the edge of the shelf. , , , . 



The effect upon fishes of a slightly later timing of this basic element in the 'plankton-calendar of 

 the locality is likely to be a corresponding shift in their own dispositions, in so far as these are affected 

 by the plankton, for it is generally true that zooplankton maxima follow the maximal ' standing crop 

 of phytoplankton. Some of the evidence on this point has recently been well summarized by Bogorov 



^' One of the most striking features of the zooplankton of the region is the swarming of lobster-kriU 

 (the Grimothea post-larval pelagic stages of Munida gregaria\ which occurs most frequently during 

 the summer months. The aduhs of this anomuran also swarm at the surface occasionally. The swarms 

 of post-larvae are often thick enough to impart a reddish appearance to the surface of the sea, observed 

 by many of the earliest navigators of these waters (Matthews, 1932, P?" 479-8;, several references) 

 The later phases of this species are limited to coastal areas round the Falkland Islands and along the 

 mainland coast, within our area (Rayner, X935, %• 18). A closely allied iorr.M. suhrugosa, is even 

 more widespre;d and abundant on the shelf (Rayner, i935, P- ^38, fig- ^D- The later stages of this 

 species are more strictly bottom dwellers. Munida spp. are of great importance in the ecology of the 

 region, as a staple food of whales (Matthews, 1932, PP- 481-3)- seals (Hamilton, 1934. p. 295), bird 

 and fihes M. gregarra is also found fulfilling a similar role in New Zealand waters (numerous 

 eferences quotef by Matthews). Other allied species of Anomura are equally -P-^-^/^^^^^^ Jf^^ 

 Pacific off Mexico and southern California (information supplied by Capt. Fagerh and by Dr Waldo 

 L Schmidt of the Smithsonian Institute, quoted by Matthews, 1932, p. ^']^). 



Rayner's detailed work on the growth of the Falkland species of M...W. shows that they are c-- 

 paratLly long-lived (5 years or more of post-larval life in M. subrugosa) and are sexually matu e 

 rom the'end of the first year of post-larval life. The Antarctic krUl, EupH..^a ^^P^rt^;^^^^^^ 

 a less specialized group, and pelagic throughout its life history, lives for a much shorter time^ The 

 di St X differences in pelagic life of the two regions may be affected by this difference in the If 

 histo" of their respective key-industry animals, as well as by the more obviously important physical 



^' Euphausians are quite important constituents of the macroplankton over the shelf, but are obviously 

 les! important than'm the Antarctic. None have been observed to form ^^nse -rms^ ^^^^^^^^^^^ 

 the surface of the sea, as E. superha commonly does in the Antarctic, and as Meganychphanes 

 tZtallT^ inermis) more rarely do in north European waters. Two or more 



Southern p ies of Thysanoessa are to be found over the shelf, and of these T. gregana is the mo 

 rindant From Tohn^s (1936) work we know that of the genus Euphausia, E. vallenUm is the most 

 wilpread Z.^My the Ust numerous species around the Falkland Islands and in our southern 

 lion £ ZL E. Lus, E. longrrostris and E. triacantha also occur. Judging by its general dis 

 Sion tough^ut the sub- Antarctic Zone, E. luce, may be the most important species on the shelf 

 farther north but quantitative data are not yet available. , . if ^ fi^I. wprP 



The ub nu ,ous hyperid amphipod Para,hen.hio gaudichaudii is abundant on .he shelf, and fi h were 

 faqundy found .o'have been'feeding upon h. Numerous -'anoid copepods oecur and „^a - 



dance of large Scyphomedusae is frequendy referred to m the log books. The general 



