390 



Fart III. — Tirentieth Annual Eej^ort 



67 mm. 



91 mm. 



and last year. In the haul on 18th October, for example, the fifty- 

 two smallest whitings, measuring from 67 

 to 89 mm., formed a pretty distinct group 

 by themselves, as represented in the adjoin- 

 ing figure, but the steepness of the upward 

 slope of the large curve (a) show^ed that 

 they belonged to the same series, and that 

 a portion of the somewhat larger (but still 

 small) fishes were absent, and perhaps had 

 risen from the bottom. If the fish were in 

 their second year they would have lived 

 through two summers, a supposition con- 

 tradicted by the proved rate of growth ; 

 and, moreover, no small whitings to repre- 

 sent such a hypothetical series w^ere ob- 

 tained in winter, spring, or early summer 

 — not until July — either on the bottom or 



in midwater, although the large otter-trawl wdth the finest-meshed net 

 was employed. 



The young whitings taken in the deep water oS Aberdeen also showed 

 a considerable increment in length, the mean size, computed from the 

 measurements, increasing from 105"1 mm. on 3rd September to 143*3 

 mm. on 15th January, an increase of 38 '2 mm. (1| inches), with a falling 

 temperature. The particulars are given in the following Table, and it will 

 be seen that the average size in the deep water in January was consider- 

 ably greater than in Aberdeen Bay. This may be partly owing to the 

 temperature in the former place being somewhat higher, but an 

 examination of the curves for the two localities shows that it is for the 

 most part caused by the larger fishes moving off from the shallow water 

 in winter in greater proportion than the smaller fishes. The next older 

 series (see Table, p. 431), i.e., over one year, are fairly abundant in the bay 

 in the summei', and they move offshore in September and October as the 

 smaller wdiitings come in, the larger of these again moving off in winter. 

 This is the main reason, as the curves indicate, of the actual diminution 

 of the mean-size for the winter in Aberdeen Bay, although growth then is 

 likewise retarded. 



