214 Part HI. — Twenty-fourth Annual Report 



zones of the vertebrae, he says " one may count three at one time, and at 

 the next attempt there seem to be four or five, and the total number 

 always remains doubtful and uncertain." He found that tranverse slices 

 of the otoliths showed the markings much better, and he chiefly used 

 them in determining the age of the specimens of cod he studied. Here 

 are some of the results, though doubt is expressed as to the certainty of 

 the determination in some cases : — 



Caught 9th November. 



Caught 9th March. 



Len 



gth. 



Probable Age. 



Length. 



Probable Age. 



Cm. 



Inches 





Cm. 



Inches. 





47 





about 2h years 



24-3 



10 



2 years 



54 



21 1 



3£ „ 



30-5 



121 



I " 



64 





31- „ 



30-7 



A 



2 „ 







possibly 2J 



335 



13f 



2 



73 



291 



3* „ 



44-3 



m 



3 a 





45-6 



18J 



3 „ 









67-5 



27 



4 „ 



According to these later results, Mr. Cunningham says, the cod at two 

 years of age is 10 to 13 or 14 inches in length, at three years 17 to 19 

 inches, at four years 27 inches ; but, he adds, it would require the 

 examination of a large number of specimens to ascertain the average and 

 range of sizes at these ages. So far as these results go, they are in 

 agreement with my own derived from the method of measuring the fishes. 



Lately Dr. S. Strodtmann published a paper on the spawning and migra- 

 tions of fish in the Baltic, which contains some observations on the growth 

 of young cod, taken in Travemiinder Bucht* 



A series numbering 555, taken on 15th October, 1904, measured from 

 5cm. to 16cm. (2-6| inches), the average being 10"0cm., or barely 4 

 inches. A month later, November 14th, 743 ranged from 5cm. to 15cm., 

 the average being 10 "5cm. On December 12th, 333 measured from 7cm. 

 to 19cm (2|-7| inches), the average being 1 3 5, or 5§ inches. At the 

 beginning of March in the following year they ranged from 9cm. to 

 17cm., and numbered 75, the average size being 12'8cm., and at the 

 beginning of April 123 ranged from 9cm. to 17cm., the average being 

 13cm., or 5 J inches. These results agree closely with my own. On 

 September 9th, 84 measured between 16cm. and 30cm. (6|-11| inches), 

 the average being 21*5cm. (8| inches), which is also near what will be 

 found in the Tables appended. 



It will be noticed that the young cod in December are rather larger 

 than in either March or April, while from November to December they 

 appear to have grown 3cm., which Dr. Strodtmann considers to be 

 improbable at that season. In the course of the summer they increased 

 by 8-5cm., or 3| inches. He compares the growth at the place indicated 

 with the growth of young cod at Biisum, on the North Sea, and shows 

 that the latter at the beginning of October had a greater range of size and 

 a larger average size than in the Baltic at the middle of the month. The 

 Baltic fish ranged from 5cm. to 15cm., according to the diagram, the 

 average being 10cm., while the North Sea cod ranged from 5cm. to 16cm. 

 or 17cm., and the average was 12cm. or 13cm. (4|-5§ inches. At 

 Aberdeen in the same month the average was 12cm. also. 



In the Tables appended to this paper will be found the measurements 

 of the cod I have dealt with, grouped into centimetres, and the following 



*Laichen und Wandern der Ostseefische, p. 209. 



