SEA-FISHERIES LABORATORY. 167 



After October the growth, ceases until the following April, when 

 it begins rather slowly, increases up to about the middle of 

 July, then falls off and finally ceases again about the middle 

 of October. 



Now the growth is very variable. Even in the same season 

 some fish of the same age grow more rapidly than others. 

 Plaice reared in Port Erin tanks showed this to a remarkable 

 extent, some (of the same year's spawning) being actually 

 twice as long as others : this is individual variability. There 

 is seasonal variability : thus, fish of, say, two years of age 

 may grow more rapidly in one year than do the fish of two years 

 of age in another year. Finally, there are local variations : 

 thus, the English workers obtained the well-known result that 

 plaice grow about twice as long, in the same period of time, 

 on the Dogger Bank than they do just off the Dutch coast. 



The following table (No. 14) gives the results of the 

 measurements of 7,724 plaice, all caught on the nursery grounds 

 and on the inshore grounds, and mostly within the territorial 

 limits. The table, therefore, represents very well the kind of 

 plaice to which regulations, restrictions, and prohibitions, of any 

 kind, would apply. 



A few words of explanation are necessary : 



These are all plaice caught by shrimp-trawls (of 2-inch 

 mesh) and fish-trawls (of 6-inch mesh). Now a shrimp-trawl 

 will, in theory, catch plaice up to any length, but if it does take 

 a fish of over about 25 cms. long, say, there is always the 

 chance that the latter may swim out again through the mouth 

 of the net : this is because there is not a very great " draught " 

 of water through the very narrow and close meshes of a shrimp 

 trawl-net. Therefore the latter tends to under -sample the 

 larger fish that are on the ground over which it is dragged. 

 On the other hand the 6-inch meshed fish-trawl will not catch 

 many plaice less than 10 cms. in length, and this is because 

 most plaice less than that length, and many of those between 



