SEA-FISHERIES LABORATORY. 221 



We see, at once, some interesting relationships. It is 

 clear, in the first place, that the variations of fat and water in 

 the muscle substance of the fish are very closely complementary 

 to each other.* The scale for the water contents has been 

 reversed so as to show this relationship the more clearly. It 

 is very apparent in the case of the Manx herrings, and much 

 more so in the case of the Welsh herrings. As the fat-content 

 increases, the water-content decreases, and vice versa. Now 

 this is what one would expect. Carbohydrates are practically 

 absent in most sea fishes ; not even in the liver of well-fed 

 herrings can these substances be detected. f The proportion of 

 protein we may suppose, without evidence to the contrary, 

 will tend to remain constant, so that it must be the water in 

 the flesh which undergoes seasonal variations. This is not 

 quite the case, as the graph shows, and there must be an 

 appreciable variation in the percentage of protein in the 

 muscle substance. Nevertheless the variation is slight 

 compared with that of the water and fat. 



To a certain extent the latter variation is similar, in its 

 progress, to that of the sea-temperature. The latter cannot 

 be exactly estimated, since the positions of the herring shoals 

 were not ascertained when the samples were forwarded to us. 

 Further these positions were, no doubt, variable, being nearer 

 to the land at one time than at others, and this would make 

 an appreciable difference in the temperature curve. The 

 sea-temperature is, therefore, that at Carnarvon Bay Light 

 Vessel, a position where the land hardly influences the annual 

 variation of temperature, and which may be taken as generally 

 representative of the water in the open sea round the south 

 end of Isle of Man. There is a general relationship between 



* This confirms Milroy's results of analysis of herrings rnado for the 

 Scottish Fishery Board (see 24th Ann. Rept. Fishery Board for Scotland, 1905 

 (1906), Pt. Ill, pp. 83-107. Also 25th Ann. Rept., 1900 (1908), Pt. Ill, pp. 

 197-208. 



t See Stirling, 2nd Ann. Rept. Fishery Hoard for Scotland, Appdx. P., 

 No. I. pp. 31-40, Plates 1 and 11, 1883 (1884). 



