SEA- FISHERIES LABORATORY . 



Figure 2 represents the Shortest Half-Ranges. 



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Fig. 2. Graph showing the variations in the abundance of plaice. 

 The heights of the columns represent shortest half -ranges. 



The two graphs show essentially the same conditions, 

 but obviously Fig. 1 exaggerates the variability. We must 

 conclude that the latter is real, that is, represents changes that 

 actually occurred in the sea, because the general form of the 

 graphs is the same, no matter how the figures are dealt with. 

 The method of taking shortest half-ranges subdues the rather 

 violent changes indicated by taking averages ; thus the 

 cusps are lower in Fig. 2. They are high in Fig. 1 because 

 of the influence of the several exceptionally large hauls. 



Taking the results of the catches made by the fish trawl 

 net, we see that there must have been a minimum somewhere 

 before 1892, and later minima about 1905 and 1915. There 

 are maxima about 1896-8 and in 1910-11. The results of the 

 fishing by the shrimp trawl show very much the same variations, 

 but there are indications in Figs. 1 and 2 that the various 

 maxima and minima occur earlier in the cases of the shrimp 

 trawl catches than they do in the cases of the fish trawl ones. 

 This is as one would expect, since on such grounds as those 



