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Part III. — Twenty -fourth Annual Report 



The difference referred to may be brought out by the following 

 diagram, showing in proper relation the annual growth of the long rough 

 dab and whiting up to sexual maturity, and of the herring according to 

 Meyer and Jenkins up to the same period. 



1 2 



j I | Herring (Meyer) 



1 2 3 

 I | j | Herring (Jenkins). 



1 2 

 I ! | Whiting. 



12 3 

 I | j | Long Rough Dab. 



Meyer's methods of determining the size of the herrings living 

 naturally in the sea were unsatisfactory, and were unlikely to furnish a 

 just estimate of the average size or of the true rate of growth, and his 

 experiments are subject to important reservations, since only selected 

 results are given, and not full details or numbers ; and, moreover, too 

 much stress was laid on the amount of growth in the summer months as 

 a factor in computing the amount of growth for the whole year. 



Thus, the growth of the herrings in the Schlei, as determined by him 

 for comparison with his later rearing experiments, amounted to only 

 48-54mm. inches) over the five summer months, or an average of 



just 10mm. per month, aud the herrings which he reared grew to a 

 similar extent over the period. But the temperature in these months is 

 the highest in the year, the means ranging from 51 2 F. for May to 67*2 

 F. for August, and in no other month, except May, was it under 61 5 F. 

 Then, again, in the best of his experiments, in which the young herrings 

 were kept in a floating box for 50 days, the growth was at the mean rate 

 of 9*6mm. (§ of an inch) per month, but the months were at the end of 

 June and July, the mean temperature in the latter month beiug 66*2 F. 



Compare these reasonable results with his results in winter, derived ■ 

 from the comparison of herrings from the sea, as shown in another Table. 

 We find that from the end of November to the end of March (when with 

 many fishes growth is quite arrested and always very slow) the indicated 

 growth in the four months, December to March, amounted to 48mm., or 

 12mm. a month, which is higher than in summer, a result that is 

 obviously fallacious. And yet the average size when a year old is placed 

 at 135mm., a size which appears to have been inferred from five months' 

 growth at 10mm. per month and seven months' growth at 12mm. per 

 month. 



In point of fact, as shown in my various papers on the rate of growth 

 of fishes, as in the one in the present report, growth in summer greatly 

 exceeds the growth during the rest of the year, while it is extremely 

 small in the period from October-November to February-March.* 



*Here are a few examples. The growth of young haddocks from 31st July to 10th 

 September (41 days) amounted to 38 •6mm., or at a rate of *94mm. per day, or 29mm. 

 per month ; from 31st July to the 18th October (79 days) they increased by 61'lmm., or 

 at a rate of - 77mm. per day, or about 24mm. per month ; over part of winter, from 28th 

 November to 15th January (48 days) the increase was 37mm., or at a rate of 'OSmm. per 

 day, or 2 - 4 per month. Another series increased by 28 - 6mm. in the 41 days from 24th 

 July to 3rd September, the rate being '7mm. per day, or 21mm. per month. Overwinter 

 and spring another series increased in 164 days, from 18th December to 30th May, by 

 33 9mm., or at a rate of - 2mm. per day, or 6*4mm. per month, and the period included 

 April and May, which is one of the most favourable months. 



With the'young whiting, whose habitat more nearly resembles that of the young herring, 

 the retardation in winter and the rapid growth in summer are marked. From June to the 

 middle of September one set of observations shows a growth of -5mm. per day, or 15 '8mm. 



