61 



The difference in size between the drift and trawled herrings 

 will be found expressed graphically on Chart 2. 



Age. — The age has been determined by examination of the 

 scales. Such difficulties as the presence of so-called secondary 

 rings and very faint, in some cases almost invisible, first winter 

 rings have been encountered, but it is hoped that by an examination 

 of a large number of scales when these difficulties occurred that a 

 correct reading of the scales has been obtained. As a general rule 

 nine scales from each herring were examined under a projection 

 microscope ; if these proved unsatisfactory further scales were 

 examined until either the sample of scales was exhausted or the 

 number of winter rings could be made out. It is for a small number 

 only that the age could not be determined with certainty. Table 

 III. gives the number and percentage of herrings having different 

 numbers of winter rings in each sample. 



The greater part of the drift net herrings were fairly young 

 fish, very few having more than five winter rings, and the highest 

 percentages were found having three and four winter rmgs, the 

 former class predominating. 



The North Sunderland samples contained no herrings with 

 more than five winter rings, and those from North Shields only 

 from 4 to 5 per cent. The age composition of the samples from these 

 two ports was practically the same if the small number of older 

 herrings in the North Shields samples be neglected. 



No herring having one winter ring only was found in the drift 

 net samples. This may be due to such fish not being present in 

 the shoals, or to the drift net, on account of the size of the mesh, 

 being selective. The latter is probably the reason, as in two of the 

 trawled sainples herrings with one whiter ring were obtained. 



The trawled herrings were older fish, the predominant year 

 class being that with four winter rings, and the number having 

 more than five whiter rings was considerably greater than in the 

 case of the drift net herrings. 



When the two classes of trawled herrings are separated and 

 the average percentages obtained from the tables, the Yorkshire 

 coast samples are found to contain older herrings than those from 

 the Dogger Bank region or the N and samples. 



