SEA-FISHERIES LABORATORY. 91 



be the case (and this is what the Mersey statistics indicate) 

 that the years 1920-22 represent a natural maximum of abun- 

 dance, while the years 1914-15 represent a minimum. 



Investigations in the Solway Firth. 



The special grant for plaice investigation made by the 

 Ministry of Agriculture and Fisheries has enabled us to investi- 

 gate, for the first time, the fishery in the Solway. The upper 

 reaches of the Firth are a typical small-fish region while fairly 

 large plaice occur, in the autumn months, just north and south 

 of St. Bees' Head. At the entrance to the Solway lies an 

 important plaice spawning ground, and ripe fish with clear, 

 running eggs were taken there at the end of February. The 

 shoals just south-west of Maughold Head, in Isle of Man, are a 

 good plaice ground during the first months of the year, but 

 later the larger fish leave there to spawn at the mouth of 

 the Firth. These investigations are m progress, and I hope 

 that we may be able to study this very interesting region 

 during 1921. In the meantime Mr. W. C. Smith has made a 

 provisional report on the Solway to the Ministry of Agriculture 

 and Fisheries. 



Work on the Mussel. 



Mr. Daniel has now nearly completed a year's observations 

 on the seasonal changes that are undergone by the common 

 mussel. The investigation has been rather difficult since none 

 of the ordinary methods of chemical estimation of the " proxi- 

 mate food principles," proteid, fat and carbohydrate, can be 

 strictly adapted to this shellfish. Modifications in the known 

 methods have to be elaborated in order that the investigation may 

 be as precise as possible. It has been found that the common 

 mussel is a very abundant source of the rare and expensive 

 substance, glycogen, the proportion of which in mussel flesh is 

 connected, in some way, with the spawning act of these shell- 

 fish. This investigation is far from being complete, and, so 

 far, a complete spawning cycle has not been studied. A 



