672 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



process I observed several years ago. In the beginning of July the roe of* 

 the mackerel begins to loosen, and about the middle of July most of 

 them have done si)awmug. The spawning period may, therefore, as a 

 general rule, be placed about the fir.st half of July. By gently pressing 

 the sides of mackerel caught during this time, mature roe may be pro- 

 cured for investigations. It comes out of the genital opening of the 

 mackerel in the shape of small beads, clear as crystal, which when 

 placed in a vessel containing sea-water keep floating near the surface 

 as long as the roe is fresh. The grains of roe or the eggs are of about 

 the same size as those of the codfish (or a little larger), but are distin- 

 guished from these, as a closer examination will show, by a large and 

 very distinct and clear oil-bladder near the upper pole (that side of the 

 ef!;g which is uppermost). By this peculiar oil-bladder, which is invari- 

 ably found in every egg, the roe of the mackerel can easily be distin- 

 guished from that of most other fish. Impregnated and developed roe 

 may be obtained in a very simple manner by dragging a tine net along 

 the surface of the water, especially during westerly or southerly wind 

 when the current goes toward the coast. I have in this manner obtained 

 as much as I desired, and have been enabled to follow its whole develop- 

 ment, which, in all essential points, agrees entirely with what on former 

 occasions I have stated concerning the development of the roe of the 

 cod. I also succeeded in hatching young fish from roe obtained in the 

 above-described manner, but was not able to keep them alive for any 

 length of time. When coming out of the egg they are comparatively 

 less developed than the young codfish, entirely transparent and clear as 

 water with the exception of a little sulphur-colored spot on each side of 

 the neck. Mackerel which have been recently hatched may easily be 

 recognized, not only by these spots, but also by the same bright oil-blad- 

 der which characterized the individual grains of roe. This oil-bladder, 

 which formerly occupied the top part of the egg, is now inclosed in the 

 back part of the belly in the residue of yolky matter. 



I was unfortunately prevented from following up the further develop- 

 ment of the young mackerel. This summer was very unfavorable to 

 such observations, as the mackerel spawned at an unusually great dis- 

 tance from the coast, and as a constant land-wind drove the roe and 

 the young fish far out into the sea. Both this year, however, and on for- 

 mer occasions, 1 have about the same time or somewhat later observed 

 small mackerel, measuring about a finger's length, on the surface of the 

 water and invariably at a considerable distance from the coast. These 

 young mackerel, which had already assumed the definite shape and color 

 peculiar to the mackerel, are doubtless one-year-old fish. In the Chris- 

 tiania fish-market one may see large quantities of these one-year-old 

 mackerel, every year somewhat later in the season ; and besides these 

 a somewhat larger kind, the so-called " spir" or small mackerel, about 

 the size of a common herring, which must therefore be about two years 

 old. When a mackerel is three years old I consider it capable of spawn- 



