236 RATE OF GROWTH OF SOME SEA FISHES. 



mean a doubling of the weight ; unfortunately the weight of the 

 fish does not enter into his calculations^ but I have no doubt he is 

 perfectly right in his conclusion. 



In another paper published separately in octavo in 1878, under 

 the title " Biological Observations made in the Artificial Bearing of 

 Herring of the Western Baltic/' Meyer records the increase in size 

 of some larval herrings which were hatched in captivity and kept 

 alive till they were five months old. Some increase in length took 

 place in the first two days, when the largest larvae measured 9*2 to 

 9*3 mm. After the eleventh day the number of the larvae began to 

 be diminished rapidly by death, and the growth was retarded. On 

 the forty-seventh day after fertilization, the young fish measured 

 only 1*2 cm., while according to the observations of the free specimens 

 in the Schlei the length should have been 1*7 cm. The water was 

 now supplied unfiltered and abounding in Copepoda and other small 

 pelagic animals, whereupon the young fish began to grow with very 

 great rapidity, and at the end of five months were as large as their 

 free-living brethren in the Schlei. The lengths observed in the 

 free and the captive specimens were as follows : 



Thus it will be seen that the young fish in captivity, when they 

 obtained suitable food in abundance, made up for lost time, and at 

 the end of five mouths were as large as the fish living under natural 

 conditions. From the remarkable rapidity with which these young 

 herrings, after being stunted for a time by want of nourishment, 

 caught up in growth with the free-living fish of the same age, 

 Meyer draws the conclusion that the rate of growth in the herring 

 depends largely on the quantity of food available, and as the latter 

 must be greater in summer than in winter, the rate of growth of 

 the fish must vary at different seasons of the year and in different 

 years, so that only an average rate of growth can be determined. 



At Plymouth I have only once seen a number of half-grown 

 herring captured. This was on May IGth, 1889, when I watched a 

 ground-seine being hauled on the south shore of the Cattewater. 

 Some hundreds of herring were brought on shore, and I secured a 

 sample of twenty-four, which measured 11 to 14 cm. (4'3 to 5'5 

 inches) in length. Now the spawning of herring at Plymouth takes 

 place principally in Bigbury Bay in January and February. I 



