232 



RATE OF GEOWTH OF SOME SEA FISHES. 



majority were ripe males ; there was not a single ripe female among 

 them, but a few unripe. It may be concluded from this that the 

 males continue feeding when ripe, but the females do not. In the 

 evening we shot the drift-nets, and, on hauling them next morning, 

 got about 150 mackerel, among which were many ripe and many 

 spent. The males were more numerous than the females in this lot 

 also. Of the seven I took for examination six were selected as the 

 smallest of the catch, and the other as a specimen of the larger sort. 

 The condition and dimensions of these specimens were — 



Thus the smallest ripe female taken on this occasion was 29*5 cm. 

 long (ll'G inches) and 7j oz. in weight. The female of 5| oz. was 

 not shotten and apparently would not have spawned that season, 

 the ovaries being quite undeveloped. The first question to be 

 considered is, assuming about 11 inches to be the length of the 

 smallest mature female, whether this size is usually reached in one 

 year. We have no reason at present to suppose that the mackerel 

 reaches maturity more rapidly than the herring, and I have, therefore, 

 estimated the age of these mackerel, 29*5 cm. to 32'8 cm. in length, 

 at two years. On June 10th, during the spawning period, six 

 specimens were taken of 22'2 to 23"5 cm. in length, and whose 

 weight did not exceed 3| oz. These must have been one year old 

 at least ; they showed no signs of sexual maturity, and I have pro- 

 visionally estimated their age at one year only. Then we have the 

 specimens taken in the anchovy nets in November. I was at first 

 inclined to conclude that these came from the spawning of the 

 previous June or July. But this would make the growth extra- 

 ordinarily rapid. Mr. Dunn, of Mevagissey, has seen young 

 mackerel of this size in November, and it is his opinion that they 

 are only five months old. The account of the growth given by Day, 

 on Dunn's authority, is that the young are plentiful in the bays in 

 August and September, when they are about 3 inches long, reaching 

 6 or 7 inches in November ; then they leave for the deep sea and 

 reappear the following June, when they are 8 or 9 inches long. 

 According to this reasoning they would increase 3 or 4 inches in 

 length in the two months October and November, and only 2 inches 

 in the seven months between November and June. This is manifestly 

 improbable, and there are various considerations to support the con- 



