to represent fish from the last school 

 caught 6/^ 



The fork lengths of fish comprising 

 the sample were measured to the next lower 

 one-half centimeter (i.e. lengths between 

 240,0 and 244.9 mm. would be read 24.0 cm., 

 etc.), except for every fifth fish which 

 was laid aside. The 20 fish thus selected 

 from each sample of 100 were examined to 

 determine whether scales were present. If 

 scales were missing from both sides of the 

 body, cinother fish of the same half-centi- 

 meter size class was substituted. These 

 individuals were measured to the nearest 

 millimeter £ind weighed to the nearest gram; 

 in addition, a scale sample was taken, eind 

 the sex and stage of sexual maturity were 

 noted. The date and location of the catch 

 also were recorded. 



Scales were removed from the middle of 

 the left side, below the insertion of the 

 dorsal fin; or, if missing, from the right 

 side. Individual scale seimples were placed 

 in 2-dram vials containing water to which 

 a few drops of 2-percent phenol were added 

 to prevent mold formation. The vials were 

 inserted in wooden blocks for temporary 

 storage, each block holding 20 vials. The 

 blocks were identified by a corresponding 

 number placed on the accompanying data sheet. 



Usually six scales which were symmetri- 

 cal and free from defects were selected from 

 each fish and mounted dry between two glass 

 slides. Ages were determined at the labora- 

 tory with the aid of an Eberbach projector 

 at a magnification of 40 diameters. Ages 

 were estimated from the number of rings 

 present on the scales. Fish having scjiles 

 without a ring were designed as age 0, those 

 with one ring as age 1, etc. Since ring 

 formation does not actually take place until 

 spring or early summer, a virtual ring was 

 credited at the edge of the sczile commencing 

 with January 1 until the new ring was visi- 

 ble (usually by May). Year classes were 

 designated by the year of spring hatching. 

 For example, a fish caught in July 1955 with 

 one ring on the scales would be assigned to 



(A) MIDDLE ATLANTIC AREA 

 I9S2 



1953 



I9S4 



(B) NORTH ATLANTIC AREA 

 1954 



1234 56789 



AGE 



Figure 9. --Age composition of samples from menhaden 

 puise-seine catches (A) Middle Atlantic Area, 1952- 

 54 and (B) North Atlantic Area, 1954. The 1951 year 

 class is indicated by the shaded column. 



the 1954 yeao: class. Validity of the scale 

 rings as age indicators in the Atljintic 

 menhaden has been established by McHugh, 

 Oglesby, and Pacheco (1959) and June and 

 Roithmayr (unpub. ms.) — . 



AGE C0MPC6ITION 



The average percentage age composition 

 of Seimples from the Middle Atljuitic purse- 

 seine catches from 1952 through 1954 and 



_6/ Samples from the pound-net catches 

 probably represented more than one 

 school, since a landing normsilly in- 

 cludes the accumulated catch of one 

 or more day's fishing. 



7/ Age determination of Atlantic menhaden 

 ~ from scales. U. S. Fish and Wildlife 

 Service, Bureau of Commercial Fisheries, 

 Biological Laboratory, Beaufort, N. C. 



14 



