278 PLANKTON STUDIES IN RELATION TO 



fishing, and during the latter part of tlie period considered there is no 

 reason to suppose that the number of boats has greatly altered. The 

 fluctuation, as shown by the official figures, in consideration of the 

 usual fair-weather conditions during this month, is less liable to 

 be influenced by causes other than the greater or less extent of 

 migration. 



On reference to the above table it will be seen that in May, 1906, 

 the landings touched a minimum for the seven years ; whereas, al- 

 though the figures in no way compare with those of 1905, the May 

 landings for 1907 are suggestive of a good season. The good May 

 fishing of 1907 as opposed to the bad of 1906 forms a useful compari- 

 son when we come to consider plankton conditions of the same period 

 in these two years. 



From an examination of the daily market reports published in the 

 Fish Trades Gazette, it woiild appear that in 1906 the fishery was 

 gradually improving throughout May until the last week, when, after 

 a short period of improved conditions, it began rapidly to decline, and 

 remained depressed until the end of the season. 



In 1907, from information derived from the same source, and from 

 observations taken at Xewlyn by Mr. W. Bygrave, it appeared that 

 heavy landings of mackerel took place during the first and second 

 weeks in May. The market was several times glutted ; and there is 

 every reason to suppose that, had not a short spell of bad weather 

 intervened, in which the men temporarily lost sight of the shoals, the 

 landings would have been considerably greater than they appear to be 

 from the official statistics. However, despite the unfavourable com- 

 parison between the figures for May, 1905, and those of 1907, from all 

 accounts there is every reason to consider the latter year to have been 

 an excellent season. 



In reviewing the plankton conditions generally, it should first be 

 pointed out that throughout May, 1906, phytoplankton was present in 

 fair quantity in every sample taken during the month on the fishing 

 grounds (see Table I). In 1907, on the other hand, it had almost 

 completely disappeared, and as may be seen from the Plankton Tables 

 (Table II), zooplankton was represented by merely a few species of 

 Copepods in extreme abundance. The comparative symbol , " cc " 

 shown on the tables for certain samples (Nos. 52, 53, 54, 55) 

 hardly sufficiently indicates the large quantities of the species 

 occurring in the sample. 



In comparing the plankton conditions during May of these tw^o 

 years, it may be mentioned that a far greater number of observations 

 were taken in 1907 than in 1906. It is desirable, therefore, in draw- 



