21 



portion to the numbers caught, in other words, that in good years 

 a large percentage of fish were recorded as empty. If therefore a 

 comparison were made with the experiments of past years, isolated 

 years of plenty could be pointed out which were in no worse con- 

 dition than this year. This year, however, is far below the average 

 of our records of food, and the food used is different. This may 

 be illustrated in the following manner. The first line in each case 

 gives the order of preference of food in the pre-war experiments 

 and the second line the order in 1920. 



PLAICE : — Mollusca, Fish, Worm, Crustacea, 



Fish, Worm, Crustacea, Mollusca. 



DAB : — Crustacea, Mollusca, Fish, Worm, 



Fish, Crustacea, Mollusca. 



FLOUNDER:— Mollusca, Fish, Crustacea, Worm, 

 Fish. 



The other species are practically unchanged, feeding mainly 

 on fish, and fish in our tables means nearly always sandeels. The 

 dab appears to be more adaptable to changes in food supply than 

 the plaice and flounder. 



Seeking for an explanation of the peculiarities of 1920 one 

 naturally recalls the reports which repeatedly were made of the 

 inshore surface waters being covered with oil, and on one or two 

 occasions so thickly that guillemots, gulls and other birds of 

 similar habits were entangled in the oil. It is obvious that the 

 presence of oil at the surface would have a disastrous effect on 

 pelagic life and on the pelagic stages of demersal life. When 

 the first submarine was sunk off the Fames in 1915 the oil was 

 observed on the surface from Holy Island to the Coquet. The 

 rocks of the Fames were covered with oil between tide marks, 

 and seabirds were picked up on the beach, dead or helpless from 

 the effect of the oil on their feathers. Early in 1918 a large part 

 of the southern region of the Northumberland coast was 

 heavily charged with oil, and the effects were the same on the 

 bird life, large numbers perishing. In this connexion it may 

 be remarked that Despott writing on the decrease of certain of 

 the inshore fish of Malta stated that the oil from the ships was one 

 at least of the causes of the decrease 



