of the Fishery Board for hicotland. 347 



it might be called a smaller race. The same is true of the common 

 dab. 



The presence of the first series of small plaice on the beaches in 

 summer, and scarcely ever present in my hauls made on board travelers, 

 was also shown by the use of the push-net in a foot or two of water at 

 low tide. The collections in this case were made for the most part in 

 Loch Fyne, but it is unnecessary to detail here the averages, since they 

 varied considerably, and were usually too low for the particular 

 season, owing, as the curves show, to the proportion of the smaller fishes 

 being unduly large. At the end of December a fairly good curve 

 included sixty-three small plaice from 4(5 to 87 mm., the average size 

 being 64-9 mm. The next series was represented by a few from 94 to 

 116 mm., and a third series by three, measuring 176, 194, and 202 mm. 



I now turn to the investigations on the East Coast made on board 

 trawlers. In them, as already mentioned, the first series was entirely 

 absent, and the second series only occasionally represented, and then 

 almost always by only a few specimens. This was due to the circum- 

 stances that the plaice of different series have a special distribution and 

 thai; the fishing was conducted within a certain range of depth. 

 The successive groups or generations of plaice exhibit a more or less 

 perfect rotation or succession from the margin of the beach out into 

 moderately deep water, so that a given generation or series, speaking 

 broadly, inhabits a particular zone or range of depth — with a certain 

 amount of overlapping. This relationship to depth, or segregation of 

 series, 'is, however, more or less disturbed in stormy weather, by 

 seasonal (temperature) change, and in the case of the adults by the 

 migratory movements associated with spawning. In winter I have 

 observed that plaice that normally inhabit several fathoms may be 

 found, notwithstanding the diminished temperature, sometimes iri-egu- 

 larly in shallow water, and are even caught in the push-net on the 

 bench ; this wandering may be due to storms or to the search for food 

 at a season when food is scarce. 



The steam trawlers cannot work very close to the shore, and hence, 

 the normal distribution of the series being such as I have deso'ibed, the 

 smaller fishes were rarely taken. Another impei-fection may be 

 alluded to — viz., that in the hauls of the trawlers the older series, 

 inhabiting usually deeper water, were also, as a rule, imperfectly 

 represented. The trawlers worked for profit, and only incidentally for 

 scientific purposes, and they fished in the places and depths at which the 

 best catches of plaice for the market could be obtained, i.e. most medium- 

 sized fish. It thus happens that in most of my hauls only one or two 

 series or gcn3rations of plaice were well represented, those, namely, living 

 within the depths at which the net was worked, and it was often a 

 matter of much difficulty to ascertain the true features of the measure- 

 ments. In one case, for example, a series might contain an undue 

 proportion of large fish belonging to it, and the average size of the 

 group would consequently be high, while the same series, at a later date, 

 might contain a large proportion of small individuals and the average 

 size would be lower, showing an apparent diminution instead of increase 

 of growth. Difficulties of this kind were common, but when the limits 

 of the groups were ascertained with some certainty, comparison of the 

 medium ordinates of each gave a clue to the real growth. 



The hauls were made in Aberdeen Bay and the Moray Firth, and in 

 several cases, from the circumstances referred to, the measurements of the 

 plaice did not give satisfactory results. The sexes, moreover, were not 

 at first separately distinguished. The particulars of various of these 

 hauls are given in the appended Tables, and some of the features 

 may be here described. 



