164 



Part III. — Twenty -second Annual Report 



Among the seven whitings the growth in the first hundred days when 

 the mean temperature was 4*5 C. (40*1 F.) was not great, the increase in 

 different fishes, as will be seen from the Table, varying from 12 to 21mm., 

 the mean increase being 16mm., and the mean for each ten days on the 

 average being 1*6 mm. The fishes were of different sizes as shown, and 

 the increase per ten-day period varied from 1*2 to 2-1 mm. In the 

 succeeding 55 days when the mean temperature of the water was 9*3 C. 

 (48*7 F.) the actual increment of length in different fishes ranged from 

 9mm. to 19mm., the mean per ten days ranging from 1'64 to 3*45mm. 

 The average increment was lS'SGmm. and the mean for the lot per ten- 

 day period was 2*5 2mm. Over the whole period of 155 days, the mean 

 temperature being 6*5 C. (43*7 F.), the actual increments varied from 

 24mm. to 40mm. (from about one inch to an inch and nine sixteenths) the 

 mean increase was 29 , 86mm., or about 1^- inches, and for the ten-day 

 period the mean increase was l'93mm. There is no doubt that the 

 greatest amount of growth was in the latter part of the second period, 

 when the temperature was highest ; at this time it was a common remark 

 how fast the fish were growing, but for the reason above stated they were 

 not more frequently measured. The whitings, it may be said, appeared 

 to be in good condition and health. 



The codlings grew more rapidly than the whitings. One of them 

 (No. 2) which grew fastest during the first period developed a diseased 

 growth or tumour in the second period when its rate of increase was 

 therefore very slow. It has been accordingly left out of the calculations 

 of the means in the second period, and the other four fishes have been 

 also dealt with separately throughout. In the first hundred days the 

 increments varied from 34 to 41mm. (1| to 1| inches), the means for the 

 ten days being from 3*4 to 4-1 mm. ; the mean increase was 37*4mm., and 

 the ten days' mean 3 '7 4mm. In the second period of fifty-five days the 

 actual amount of growth was a little greater, so that under the difference 

 of temperature indicated the codlings grew about twice more rapidly. 

 Omitting the diseased fish the increments varied from 34 to 41mm. — 

 precisely the same as in the first period— the average was 37*8mm. and 

 the mean for 10 days 6 -8 7mm. Over the whole time of 155 days the 

 amount of growth in the four healthy fishes was respectively 79, 79, 71, 

 71mm., the average being 75*7mm., or about 3^ inches — a very con- 

 siderable rate considering the temperature of the water. On the other 

 hand the fishes were supplied with abundance of food, and the codlings 

 were the greediest of them all, and no doubt got more food in a given 

 time than they would under natural conditions in the sea. With the 

 exception of the one referred to they all remained healthy throughout 

 the experiment. 



The growth of the single haddock was also fairly rapid for the 

 temperature. In the first hundred days its increase amounted to 27mm., 

 or a little over an inch, the mean for ten days being 2*7. In the second 

 period, like the codlings, the actual growth was about the same, although 

 the time was only about half ; it amounted to 28mm. (I! inch), the ten- 

 day mean being 5 'lmm. Over the whole period the actual increase in 

 length was 55mm. (2 T 3 ^ inches), the average for the ten-day period being 

 3'55mm. 



The growth of the single common dab in this tank was slow and 

 presented a contrast to the round fishes ; it was an adult female. The 

 increase in the first period was only 6mm. (§ inch), the mean for ten days 

 being 0"6mm. In the second period it did not increase at all. Two 

 circumstances may have affected this, the first that four spawning 

 flounders were put into this tank early in the second period, and it is 

 possible that the greater competition for food prevented the dab getting 



