250 DISCOVERY REPORTS 



zooplankton is indeed not unlike that of north European waters, but important differences may be 

 expected to appear, especially in the times of maximum abundance of the different groups, when the 

 material is fully worked up. As already explained, however, this must wait upon the completion of 

 taxonomic revision of the groups. Moreover, the environmental features of an area of this size, both 

 physical and biological, present almost unlimited scope for further investigation. In general we may 

 say that most of the more important macroplanktonic forms have a wide, often a circumpolar distri- 

 bution within the sub-Antarctic Zone. They are noticeably less restricted than the benthos in their 

 latitudinal range also, including a higher proportion of species that may extend into the distinct water- 

 masses both to the south and to the north of the sub-Antarctic Zone. Among microplankton forms 

 this wide tolerance is even more marked ; many of them are cosmopoHtan. 



METHODS OF PRESENTATION 

 It has not been considered advisable to attempt to publish the biometric data on fishes in full, for the 

 raw data alone in manuscript form weigh over i cwt. These papers will be stored by the Discovery 

 Committee, and it is hoped that much information may still be gleaned from them. 



Full details of the station positions are appended, with some of the abstracted data on the most 

 important.fishes. The numbers of fishes recorded are shown with station numbers only, in the general 

 distributional accounts of each species. Wherever it has been found profitable to consider length and 

 weight measurements these are given in the form of summarized tables and diagrams with legends 

 which It is hoped contain sufficient explanation. The data relating to different species varies so much 

 that It IS obviously impossible to adopt uniform treatment throughout. 



Such simple statistics as have been ventured upon relate mainly to length-frequency distributions 

 and mean lengths. Where mean lengths have been used to compare or contrast catches from difl^erent 

 stations or groups of stations I have included sufficient information as to dispersion to enable the 

 significance of the differences to be determined. Simpson and Rowe's book (1939) has been a great 

 help m dealing with the numerical data. 



The systematic arrangement and taxonomy of the fishes follow Norman's report (1937) throughout 

 In discussing bionomics of the fishes I have stressed differences and resemblances between Patagonian 

 species and those most nearly allied to them that have already been studied on better-known fishing 

 grounds elsewhere. I believe that it is easier for readers without experience of this particular area to 

 visualize the conditions if they are presented in this way. Since hake are the most important species 

 on the shelf, I have tested out the theories developed by Hickling during his prolonged work on the 

 iiuropean species, m so far as our scantier data on the Patagonian species permit. With the possible 

 exceptions of cod, haddock, herring and plaice, Hickling's work on hake probably constitutes the most 

 complete picture we have of the life history of any marine fish. Consequently all members of the 

 Discovery staff who have been concerned in this work have studied Hickling's work intensively 



Iwo conventions have been used to facilitate general descriptions offish distribution, and to ensure 

 that seasonal comparisons should be kept roughly comparable: . 



First, the whole area has been arbitrarily subdivided into ' northern ', ' intermediate ' and ' southern ' 

 regions, according to latitude. The interval chosen was 4° of latitude, so that the northern region 

 includes all trawling survey stations north of 46° S, the intermediate region all those between 46 and 

 50 b, and the southern region all those south of 50° S. This subdivision has already been indicated 

 mtig. 2. It IS an arbitrary division introduced solely for the purpose of reducing the data to manage- 

 abe proportions, but it approaches a natural division inasmuch as the physical conditions that change 

 with latitude afl^ect the flora and fauna. Provided that large-scale migrations in a north and south 



