290 BULLETIN OF THE BUREAU OF FISHERIES 



migratory check formed in the estuary may occur anytime after the 1st of June in 

 the f'-y, while the first annuhis may form as early as August. The new growth (not 

 the "intermediate" growth of the estuary), outside the first winter rings, may begin 

 any time between August and the May following. 



Schneider (1910) presented some evidence to show (7) that the fall marine 

 hening may possibly form two annuli each year, as Damas (1909) had found to be 

 true in the cod (Gadus virens). Lee (1920) asserted that normally in the haddock 

 the approximated circuli of the annidus formed some time during the period July- 

 September, to which were added one or two wide sclerites in September or October 

 and additional narrow sclerites in the winter months. H. Thompson (1923) foimd 

 that the Skagcrag haddock usually formed a false ring in the first year at a body length 

 of approxim.ately 11 centimeters, when the fish descended to the bottom and encoun- 

 tered new environmental conditions. Nail (1925) reports that marking experiments 

 have shown that a considerable number of sea trout in the estuary of the Beauly 

 and Ness Rivers feed freely on sprats in nudwinter, with the result that these trout 

 put on a rapid growth, represented by a series of widely spaced rings on the scales. 

 To such fish the ordinaiy ndes for age determination can not be applied. Jacot 

 (1920) behoved that in the nmllets an annulus is the result of a long northward migra- 

 tion in the spring, which may be completed in two stages, and therefore concluded 

 that some fish may fonn two annuli in a year at times. 



Several authors contend (8) that at times one or more anmsli fail to form on the 

 scales, for individuals have been found that apparently were far too large for their 

 age, as determined from the scales. Examples of this were found among the Pacific 

 herring by W. Thompson (1917), among the shad by Roule (1920) and'Leim (1924), 

 among the haddock by H. Thompson (1923, 1924) and Saemundsson (1925), and 

 among the sea trout by Nail (1926). 



(9) In certain waters some species form no annuli at all on their scales, while 

 other species do. Schneider (1910) found definite growth zones in the scales of all 

 the African species of fish examined by him, except in a small form of Gobius(?) 

 from Madagascar. Paget informed Lee (1920) that no annuli are evident in the 

 scales of Egyptian species. Godby (1925) reports that the offspring of certain 

 Salmo solar introduced into New Zealand waters showed no winter band on their 

 scales, whereas the young of introduced Quinnat salmon did form an annulus. 



As has been pointed out by many authors, much of the confusion in the reading 

 of scales is due (10) to the formation of accessory or secondary rings (see fig. 6), which 

 are difficult to distinguish from the annuli (see W. Thompson, 1928, p. 54), (11) to 

 the indistinctness of certain annuli (Leim, 1924, p. 76), and (12) to the crowded con- 

 dition of annuli in scales of old fish or of small size. (13) Regenerated scales may 

 introduce errors in age determinations, as these scales sometunes may simulate 

 closely the normal scales, as in the marine herring (Schneider, 1910); or th» regen- 

 erated area representing the first year's growth may be so small that it is easily over- 

 looked, as, for example, in the scales of the Atlantic salmon (Milne, 1915). 



Prof. D'Arcy Thompson (1914; Sherriff, 1922) does not believe that the annuli 

 in the scales of the marine herring are invariably year rings. He can not understand 

 Hjort's and Lea's conclusions, based on scale studies, that (14) one year class 

 dominated the fisheries for five years in succession, because there must be 



