PROGRESS IN BIOLOGICAL INQUIRIES, 193 3 331 



comparing the avera<»'e spacinji; of circiili in the first j^rowth zone 

 of the scales of northern aihilts with the spacini^ in the c-orre- 

 spondincr zone of nortliern and southern juveniles and yearlings. 

 It was found that the northern juveniles and yearlings agree in 

 having a significantly wider average spacing than the southern 

 juveniles and that the frequency distribution of the spacing values 

 of northern adults indicates a mixture in almost equal proportions 

 of fish that have first growth zones characteristic of northern and 

 southern juveniles. The scales of yearling fish show similar dilfer- 

 ences between the second summer zone circuli when northern and 

 southern yearlings are compared. The great majority of northern 

 adults, however, show second zone spacing of the southern type 

 even though the first zone of about one-half of them is of the 

 northern type. 



In order to determine whether squeteague eggs are capable of 

 hatching at the temperatures prevailing in the North during the 

 spawning season, an experiment was carried out jointly by Prof. 

 A. E. Parr and R. A. Nesbit. Squeteague eggs were found to hatch 

 freely at all temperatures from 13° to 25° C. Since this exceeds the 

 range of temperature observed in the northern as well as southern 

 localities where eggs occur, it is certain that low temperatures do not, 

 as suggested previously, prevent successful reproduction in the North. 

 No explanation has yet been found for the uniform absence of sque- 

 teague larvae from the northern plankton collections. 



Thus far the evidence for the view that the great majority of 

 northern adults, including many that originated in the North, spend 

 their second summer south of Delaware Bay consists of the obser- 

 vation that in the North yearlings are never sufficiently numerous to 

 account for the numbers of older fish in subsequent yeai-s; of the 

 observation that the calculated second summer growth increments of 

 northern adults agree much better with the observed growth of 

 southern than of northern yearlings ; and of the fact that the spacing 

 between circuli of the second growth zone of the scales of northern 

 adults agrees with that of the corresponding zone of the scales of 

 southern yearlings, and differs sharply from that of the scales of 

 northern yearlings. 



Direct evidence from tagging experiments is still lacking. The 

 results of the October 1932 tagging in Pamlico Sound, N.C., indicate 

 that in 1933 very few of these fish migrated to waters north of Vir- 

 ginia. In this experiment 1,900 squeteague were tagged, of which 

 about 1,G00 were yearlings or older. In the summer of 1933, 115 

 tags from yearlings or older fish were returned, 68 from North Caro- 

 lina, 8 from Virginia and Maryland, including Chesapeake Bay, and 

 1 from New Jersey. Thirty-eight tags were returned without data 

 as to the location of recapture. Since most of the latter were 

 returned from, southern markets, it is probable that the majority 

 were recaptured in North Carolina or Virginia. The interpreta- 

 tion of this lack of northern returns is impossible because of the 

 necessity for abandoning observations of the age composition of the 

 northern catch. Previous observations have proven that increments 

 to northern stock are irregular from year to year. In 1933 very few 

 southern squeteague may have migrated North, in which case none of 



