BIOLOGISTS' WORK FOR THE INDUSTRY 197 



lected, and a considérable part of the work on this was done, 

 although it will require considérable time to even preliminarily 

 complète the work. Some points are, however, already clear, 

 The mackerel (as was foreshadowed in the expédition of 1915) 

 certainly shed only a very few eggs along the Atlantic coast of 

 Nova Scotia, and there is no indication that any of thèse sur- 

 vive to produce young mackerel. However, the conditions found 

 at the head of St. Margaret's bay are such that the eggs of 

 fishes like the blue perch or cunner, the witch, and the plaice 

 develop successfully and produce large numbers of the young 

 of those fishes. As thèse eggs develop successfully with those of 

 the mackerel in the GuK of St. Lawrence, it is reasonably certain 

 that if mackerel ever spawn at the head of St. Margaret's bay, 

 (which spawning may occur in some years), the eggs would 

 develop successfully. Elsewhere along the coast the conditions 

 are in large part, or whoUy, unsuitable for such development, 

 chiefiy because of the low température. It is also clear that 

 St. Margaret's bay and adjacent waters form an important and 

 successful breeding ground for the lobster because of the higher 

 température there. The greater abundance of smallish lobsters 

 in those waters indicates this. 



The Shad Problem 



The decrease in the catch of shad has been a cause for com- 

 plaint for many years and has brought about first of ail the esta- 

 blishment of hatcheries (later abandoned) and latterly of the 

 institution of a close season of a period of years. Comparatively 

 little has been known of the life of shad both in its fresh-water 

 and marine stages, so that it has been very doubtful as to what 

 means would be best to bring about an increase in the catch 

 without interfering too much with the fishery. Mr. A, H. Leim, 

 of Toronto, has been studying the life of the shad on the Shubena- 

 cadie river and in Minas channel and intermediate waters. He 

 finds that in the river mentioned the great majority of the eggs 

 spawned per'sh owing to the natural acidity of the water being 

 too great. It is not unexpected, therefore, that he finds the shad 



