134 SALT-WATER FISHES 



fish. This will better enable us to understand the otherwise 

 seemingly capricious journeyings up the coast. This phrase, 

 by the way, must be used with caution, for much may depend 

 on whether it is meant to signify the progress of shoals actually 

 working their way along, for example, our south coast, from 

 west to east, in a course approximately parallel to the shore, or 

 whether it indicates merely their successive appearance at 

 points on the coast from west to east. 



The importance of the foregoing distinction will be obvious 

 when we bear in mind the extent to which modern enquiry has 

 tended to explain fish migrations as comparatively restricted 

 journeys between the deep and shallow water — i.e. in a direction 

 either oblique or at right angles to the shore. There is a wide 

 gap between the ichthyology of the end of the Victorian era 

 and that of its dawn, when the first edition of Yarrell was 

 published. We can now, for instance, distinguish with some 

 reason between the motives of the spring and autumn move- 

 ment of the mackerel, the first having for its object the arrival 

 on suitable spawning-grounds, the second being rather con- 

 nected with the movements of larval fishes upon which, in the 

 fall of the year, mackerel are wont to feed. This distinction 

 is confirmed by the examination of the stomachs of mackerel 

 caught at the two seasons, those of spring mackerel being 

 comparatively empty, while a large proportion of those captured 

 in autumn are crammed with the young of rocklings, 

 sand-eels, and other shore-dwelling species. The practical end 

 and aim, over and above the intrinsic interest attaching to the 

 elucidation of such mysteries, of these enquiries into the 

 migrations of mackerel must obviously be the discovery of the 

 whereabouts of the shoals when absent from our coasts. 

 Possibly, if biological investigation does eventually throw 

 lio-ht on the exact whereabouts of the shoals during the three 

 months of winter, the fish will be found in a locality and at a 

 depth such as to bring them conveniently within the operations 

 of the nets ; and whether, even if the shoals were so located, 



