180 Part II1I—Twenty-fourth Annual Report 
series of papers in the Annual Reports of the Board.* The numbers of 
the various species measured for this work, and already dealt with, are as 
follows :— 
Plaice, = = 17,950 | Gurnard, — -— 5,495 
Common Dab, — 26,230 | Norway Pout, - 7,192 
Flounder, — — 231 Hake, LS 571 
Lemon Dab, —- 2,201 Herring, - -— 19,806 
Witch, - — §,422 Sprat, —- -— 6,473 
Long Rough Dab, 20,261 | Grey Skate, - 432 
Turbot, =~.= 212 Angler, - = 722 
Brill, - = 807 Armed Bullhead, 1,312 
Cod, = =) ATO Lesser Weever, 417 
Haddock, - - 28,760 Lumpenus = 738 
Whiting, - -— 58,164 | 
Numerous measurements of other forms, as halibut, megrim, ling, pollack, 
coalfish, tusk, catfish, have also been made, and will be dealt with later. 
Most of the fish were measured on board commercial steam-trawlers, 
engaged either in trawling investigations in territorial waters or in 
commercial fishing in the North Sea. 
MetuHops. 
In a previous papert I gave a full account, with illustrations, of the 
method adopted in collecting and measuring the fishes. Besides this 
method, there is no doubt that much may be learned by keeping 
fishes in confinement, and measuring and weighing them from time 
to time, for comparison with those obtained on the fishing grounds, and 
this has been done. Another method, referred to above—viz., labelling 
the fish—has also in certain cases given good results, most, perhaps, with 
flat-fishes. Recently a fourth method has been employed, especially in 
Germany, by the examination of the markings on the scales, otoliths or 
ear-stones, and bones. It has also been used in the international investi- 
gations in this country by Garstang and Wallace, with reference particularly 
to the growth of the plaice, and the results agree with those obtained by 
a study of the measurements.t 
CoMPARISON BEerwEEN DIFFERENT SPECIES. 
While one general result of the investigations on the rate of growth of 
fishes has been to show that they do not grow so fast as was generally 
believed, it has been made clear that different species may increase at 
different rates, apart from differences in size. In fishes which undergo a 
marked metamorphosis, growth is sometimes, and perhaps always, slow, 
especially at early periods, It is thus with the plnice and other flat-fishes, 
with the eels, and with the herring and sprat. Among round fishes, as 
the cod, the haddock, and the whiting, on the contrary, growth is com- 
paratively rapid. A young haddock grows many times faster than a 
plaice. 
With regard to the age at which fishes attain mature size and begin to 
reproduce, similar differences exist. So far as the investigation has gone, 
*19th, 20th, 2st, 22nd. 
| Twentieth Annual Report, Part IlI., pp. 226-334, 
+ North Sea Fisheries Investigation Committee. Report (No. 2, Southern Area) on 
Fishery and Hudrographical Investigations in the North Sea and Adjacent Waters. 
