8 Part III. — Tiventij-sixth Annual Report 



be measured or to be separated from the fluctuations due to other 

 causes, whether natural or artificial. An exception was the case 

 of the introduction of the shad to the waters of the Pacific by the 

 United States Commission. Fry of this fish, which did not exist 

 there, were brought from the Atlanric coast between 1873 and 

 1880, the total number being comparatively small, viz., 619,000. 

 From these colonies the shad increased to such an extent that in 

 1895 it was reported to be one of the most abundant fishes of 

 California, and had extended along 2700 miles of coast line. With 

 the view of ascertaining the effect of the liberation of the fry of 

 plaice, considerable numbers of them were transferred to Loch 

 Fyne from the hatchery of the Fishery Board in the years 1896- 

 1901, and a few months later the abundance of the young plaice 

 to be found in certain localities in the loch was tested by fishing 

 with a push-net on the beach. In the six years 1908-1908 no fry 

 were placed in the loch, and the push-nettings were continued at 

 the same places and at corresponding times in order to determine 

 the abundance of the young fish in the same way. The total 

 number of the year's plaice which were obtained was 13,068, the 

 collective results in the two periods being as follows : — 



Thus, in the first period, when plaice fry were being put into the 

 loch, the average number of young plaice taken was 87'7 per hour, 

 whereas in the second period, when no plaice fry were added, the 

 average number taken per hour was 397, or less than half. The 

 average at each of the five stations where collections were made 

 was less in the second period than in the first, the decrease per 

 hour ranging from 19'2 to 1047. The collections were made in 

 the months of June, July, August, and September, and 

 the mean number of young plaice taken per hour was 

 less in each month in the second period than in the 

 first, and, with one or two exceptions, this was true of 

 each of the stations considered separately. As shown in the 

 accompanying Table, the fluctuations from year to year were very 

 considerable, the mean annual average ranging in the first period 

 from 24 to 174, and in the second period from 8 to 112. When 

 the average was high at one station or in one month it was also, 

 with few exceptions, high at the other stations and in the other 

 months, and so when it was low, and thus the numbers represent 

 approximately an actual abundance or scarcity of the young plaice 

 in Loch Fyne in the particular years. 



