16 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



quite unexpected, and in part probably confirmatory of conclusions 

 stated in a previous part of this report. 



The inshore waters of Casco Bay have been generally supposed to be 

 one of the most important spawning-grounds of the mackerel on our 

 coast. If this opinion be well grounded, one would expect to find large 

 numbers of mackerel eggs on the surface, and I was consequently much 

 surprised at the almost utter barrenness of the collections in this 

 respect. Although other pelagic eggs of at least twelve species were 

 found, some of them in very great abundance, most of the surface speci- 

 mens yielded no mackerel eggs at all, or but two or three were detected 

 among thousands of the eggs of other species. An unidentified species 

 of egg, which in its early stages, could scarcely be distinguished from 

 the mackerel, was found in some abundance, but, when developed, pro- 

 duced a larva having very different characteristics. The only occasions 

 on which any considerable number of mackerel eggs were obtained was 

 during the prevalence of south and southeast winds, which blew within 

 the scope of our observations the offshore surface waters, a fact indi- 

 cated by an increased density. One is, therefore, probably justified in 

 concluding that during the season of 1897 only a very few mackerel 

 spawned inshore in the vicinity of Casco Bay, and that spawning for 

 the most part was accomplished at a greater or less distance out at 

 sea. This conclusion, of course, does not necessarily invalidate former 

 conclusions that the vraters of Casco Bay constitute an important 

 breeding-ground for this species, but simply establishes the fact that 

 certain conditions, not at present definitely known, sometimes cause 

 most of the mackerel to spawn farther off shore. It may be added 

 that the literature of the mackerel coutains much evidence confirmatory 

 of this opinion. 



Of the mackerel eggs obtained by surface towings, all were in early 

 stages of development, the oldest containing embryos having 12 or 13 

 myotomes and extending about halfway around the egg; that is, they 

 were in stages that are reached under the artificial conditions of propa- 

 gation during the third day of development. Now, of the eggs of 

 various other species of fishes, as of the dinner, sea bass, and scup, 

 which habitually spawn inshore, those obtained under similar condi- 

 tions exhibited many examples in later stages of development, and 

 one would expect, if the mackerel egg remained similarly afloat until 

 hatched, that among the 200 or 300 eggs collected at the surface some 

 of the later stages would be sure to occur. The absence of such stages 

 seems to confirm the observation that in water of the comparatively 

 low density obtained here the eggs of this species will not float during 

 the later stages of development. It is possible that the eggs of the 

 mackerel are usually deposited so far out at sea that the density of 

 the water to which they are subjected is sufficient to float them during 

 the entire period of development. It may also be suggested that large 

 numbers of them may be carried by winds or currents to the open 

 ocean, and there find the conditions best suited to their welfare. 



