SEA-FISHERIES LABORATORY. 103 



too ether, that is, we have to find the " dispersions " before 

 the information is of much use. 



4"-mesh 

 6"-mesh 

 7"-mesh 



6f" 8J' 



8" 101" 



These dispersions are shown above. Half of all the fish 

 caught by the 7" mesh, for instance, were 8" to 10J" in length, 

 and half of all the fish taken by the 6" mesh were 6f " to 8-J" in 

 length. If we had considered a dispersion of one- third we 

 should have found that the two catches (6" and 7") did not 

 overlap. Then we could have said that the chance that all 

 the plaice caught by a 7" mesh were bigger than all the fish 

 caught by a 6" mesh was about 1 in 3. 



The Migrations of Plaice. 



All the data obtained in the past have been considered. 

 Of the experiments made, those made near the Nelson Buoy 

 summer plaice fishing- grounds give the most interesting results. 



These results are charted as a series of nine charts showing 

 the migrations from month to month throughout the year. 



Attempts have been made to show how these migrations 

 depend on the sea-temperature and its variation from month 

 to month. But the hydrographic data are not full enough to 

 make this connection more than probable. 



