38 



NOTES ON THE AGE AND GROWTH OF FISH. 



By B. STORROW. 



LEMON DAB, Pleuwnectes microceplialus. 



On 1st April, 1916, eight lemon dabs, or rather what was 

 left after the flesh had been removed by filleting, were examined 

 to ascertain if it was ^Dossible to tell the age from the otohths. 

 The otoliths were found to be small, and whilst the growth areas 

 were marked they were far from being as clear and as easilj^ read 

 as in the j)laice and common dab. As there was a small portion 

 of skin left above the j)ectoral fin some scales were examined, 

 and as will be seen from the photographs on Plate I., the growth 

 areas are most distinct. Fig. 1 is a scale from a fish 23-8 cm. 

 long, caught 17th April, and shows three summer areas of growth, 

 and the beginning of the fourth. Fig. 2 from a fish 41-5 cm. 

 long shows nine summer areas ; the demarcation between the eighth 

 and ninth summer is somewhat indistinct in the photograph, but 

 was easily seen under the microscope. 



It mil be seen from the photographs that the growth of the 

 scale is rapid at the beginning of the summer, and then gradually 

 slows down until the concentric ridges come very close together. 

 When the scale is examined under a high power there are seen at 

 the sides of the radiating grooves faint lines which connect the 

 concentric ridges here broken by the radiating grooves. These 

 faint fines are interrupted at the end of each year's growth, and 

 are of great help when determining the age of old fish. 



Before proceeding with further work in this direction it was 

 essential to see if scales from other parts of the body gave the 

 same result as those from the region above the pectoral fin. For 

 this purpose two lemon dabs were obtained, and 140 scales were 

 examined from each fish. Scales were taken from seven areas 

 on the right side of the body. The areas selected were situated 

 above and below the lateral fine, and were one-third of the length, 



