SEA-FISHERIES LABORATORY. 147 



outside. We can ascertain the range of sizes of fish 

 caught in nets of particular mesh only by using each by 

 itself. 



Very few hauls by nets of mesh other than 6 inches 

 have been made; they are all recorded in the tables on 

 pp. 163-165. Captain Eccles used nets of |-inch mesh 

 (p. 163), 4-inch mesh (p. 164), 6-inch mesh and 7-inch 

 mesh (p. 165). The results are rather few yet for 

 statistical treatment, and one must remember that the 

 range of sizes of plaice taken in the nets will be affected 

 by various factors. Thus an unusually large proportion 

 of invertebrates, say large jelly-fishes or star-fishes, in 

 the catch will be associated with a larger proportion of 

 smaller fish ; while a difference in the speed at which the 

 net is dragged must also aifect the catch. I do not 

 suppose that a 4-inch net dragged from a steamer would 

 give the same range of sizes as the same net dragged over 

 the same ground by a sailing boat. Probably two fisher- 

 men working the same boat and net over the same ground 

 would not get similar catches. In order to obtain reliable 

 measures for the catching powers, with regard to the size 

 of fish, of trawl nets of different meshes it would be 

 necessary to make a large number of trials on the same 

 ground and by the same boat and fishermen. I should 

 think that a dozen hauls by nets of 6 and 7 inch mesh 

 during the same month, on a ground where fish were 

 abundant during the whole period, and arranged so that 

 so many comparison hauls were made on alternate days, 

 would give fairly reliable results. Of course it might 

 be objected that the fish population had changed during 

 the interval, and that it would be difficult to trawl over 

 precisely the same ground each time, but these objections 

 appear to me to be cavilling rather than real criticism. 

 At any rate, no other practicable means of investigation 

 can be suggested. 



