HORIZONTAL DISTRIBUTION, GROWTH AND DYNAMICS OF DISPERSAL 313 



larvae recorded at each station is also shown. The diagram is based practically throughout on observa- 

 tions where the total surface catch was large or very large, at sixteen of the stations shown it being 

 of the order of loo-iooo or above, at the remaining two (Stations 368, 369) of the order of 50-100. 

 Stations at which the total catch was less than 50 have not been included. On this basis the graphical 

 expression of the stage frequency presented here may be said to carry the maximum significance our 

 data permit. 



Taking first then the position in February and March, if the larvae were spreading from a major 

 locus of spawning in Weddell West eastwards into Weddell Middle entirely in the surface stream, as 

 they manifestly appear to be doing in Figs. 74 and 75, we should expect to find that, since they 



LONGITUDE 



DtX OF MONTH 



STATION 



FURCILIA 



SECTOR 



and 

 MONTH 



60W 



CALYPTOPIS 



WEDDELL WEST 

 FEBRUARY 



30W 



47° 44° 



IS IS 

 I96S 618 



40° 



19 



620 



34° 

 17 

 VI4 



30° 



25 



361 



30° 



25 



362 



DEEP LARVAE 213 24 



WEDDELL MIDDLE 

 MARCH 



WOE 



27° 

 2 

 365 



27° 



8 



358 



27° 



9 



369 



26° 23° 



12 4 



1994 1142 



18° 



5 



1144 



Seal, per c^" =° "° r^^, r^7„„ I I 



213 24 24 - - - I - - - II 30 661 I - - - - 1141 



WEDDELL EAST 

 APRIL 



30E 



OI° OI° 01° 04° 19° 20° 



14 IS 16 30 27 26 



2316 2318 2320 1353 2346 2344 



SECTOR 



and 

 MONTH 



LONGITUDE 

 DAY OF MONTH 

 STATION 

 6 FURCILIA 

 5 

 4 

 3 

 2 

 I 



3 CALYPTOPIS 

 2 

 I 

 DEEP LARVAE 



Fig. 76. Developmental condition of surface larvae in the Weddell drift, showing evidence of eastward dispersal partly in 

 the surface stream and partly in the cold bottom water. For further explanation and details of construction see text. 



would be feeding and growing and moulting as they went, as the season advanced the swarms would 

 become progressively and conspicuously older as they travelled towards the east. Contrary, however, 

 to expectation we find that in Weddell Middle, for instance, the older swarms are in the west and the 

 younger, indeed conspicuously younger, in the east, the youngest of all at Station 1144 (repre- 

 sented in Fig. 75 by the large black and white plot almost half-way between 30° W and 0°) being 

 in fact the most easterly. While it seems clear enough that the swarms encountered between 34° and 

 27° W (Stations ¥14,^ 361, 362, 365, 368 and 369), being conspicuously older than those farther west, 

 did in fact originate in larval risings that took place somewhere to the west of where they were 

 recorded, subsequently being carried eastwards to 30° W and beyond in the surface drift, the swarms 

 still farther east (Stations 1994, 11 42 and 1144) are obviously too young to have had a similar history. 

 On the contrary, it seems they must originally have reached the surface in situ, or if not actually in situ 

 at any rate somewhere not very far to the west of where they were found. In other words, unless these 

 easterly Weddell Middle swarms were derived from some local oceanic spawning, which although 

 possible does not (p. 296) appear very likely, it seems they must have got carried to their easterly 

 situation through the spreading of eggs and nauplii in the bottom water flowing from the west. To 

 invoke deep transport to account in part at least for the eastward spreading of the larvae is not after 

 all unreasonable, for we know that the bottom water is moving to the east and have some reason to 

 think (p. 100) that all along its path from west to east very young larvae are rising out of it, upwards 

 and into the surface stream, at Station 11 44, it would seem, in very large numbers. 



It is equally clear, turning to the position in March and April, that the April swarms in Weddell 

 East just eastward of 0° (Stations 2316, 2318 and 2320) are much too young to be explained in terms 

 of transport in the surface stream from an original locus of spawning so far away as Weddell West. 

 Clearly they must originally have come to the surface much nearer at hand and having regard to their 

 age they could very well it is suggested have done so, in the First Calyptopis stage, somewhere in the 

 1 One of the stations worked from the Norwegian whale factory ' Vikingen'. 



36 DM 



