236 DISCOVERY REPORTS 



large stones and boulders. It was found that this area extended over the 200 m. line for some distance 

 beyond the immediate coastal shelf investigated during the previous survey. 



Mr John concluded his preliminary report (which has not been published) with the statement that 

 Mr Marr emphatically agreed with his opinion that ' any decision on a commercial fishery in and near 

 the waters of the Falkland Islands must depend on a greater knowledge of the seasonal variations of 

 the hake of the locality, and of waters farther north, and a full knowledge of what is known concerning 

 hake in other waters '. 



The preliminary results of the first two surveys have been treated at some length to show how 

 great was their value when the third survey was planned. Several of the pioneers (notably Mr John) 

 were engaged upon other studies after finishing their share of the field work, and the value of their 

 efforts should be recognized. The third, most extensive and important survey, was carried out by 

 Gunther himself with the assistance of Mr G. W. Rayner. The results form a large part of the main 

 substance of this report. In this section, therefore, I have referred to the field observations only where 

 they modified the general picture previously gained of the conditions. The longer period available, 

 and increased experience, permitted improvements in working methods which must first be made 

 clear. 



THE THIRD SURVEY 



At Dr Kemp's suggestion the plan of the third survey was designed to include five lines of stations 

 spaced at regular intervals over the shelf between 44 and 54° S. Rough ground was to be avoided 

 when possible, but eflForts made to keep the stations uniformly spaced. Each line was planned on a 

 course of 111° — roughly normal to the coast. The isotherms here run almost parallel to the coast, 

 and the value of observations upon temperature and salinity is much increased if they can be made as 

 nearly as possible at right angles to the isotherms, as our hydrologists have frequently pointed out. 

 After the two northernmost lines of stations had been completed, permission was obtained still further 

 to extend the scope of the survey. Gunther did this by interpolating four lines of more closely spaced 

 trawling stations, and by making many additional observations, including a north-south line that pro- 

 vided valuable evidence of the effect of latitude. This tends to be masked (in the absence of such 

 evidence) by seasonal movements, the effects of increased depth, and so forth. 



As finally carried out the programme included vertical hauls of the Gran international net (N50V) 

 with water samples from surface and bottom at all stations. The vertical nets provide evidence on 

 the distribution of fish eggs and phytoplankton, the water samples gave temperatures and salinity 

 determinations. The trawling stations were of three types : 



(i) On the lines A, B, C, D and E (those of the original plan) the stations were 60 miles apart and 

 the procedure the same as on previous surveys, with the addition of the N50V. 



(2) On the intermediate lines W, X, Y and Z, the stations were 30 miles apart, and in addition to 

 the normal routine the trawl was shot for a further period of four hours whenever fish seemed plentiful. 



(3) On the additional lines the trawl was shot for one hour at stations 60 miles apart, the conical 

 dredge was not used and no repeat hauls were made (see Figs, i c, d). 



Russell's bottom-net, with plankton nets towed obliquely on the same wire, was fished on six rather 

 irregular lines during passages to and from the trawling stations, and on two more lines of additional 

 observations where a small beam trawl was also used. 



The observations made included some important additions to the standard practice of the first two 

 surveys. Among the essential routine observations the sorted fish were weighed in addition to being 

 sexed and measured, and the larger species of invertebrates were also weighed in addition to being 

 counted and listed. At selected stations whenever possible the important fishes, after being sexed and 



