44 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 4. — Lengths of bluefin tuna less than 20 inches long, 

 with dates and localities of capture and sources — Continued 



Date 



Length 



in 

 inches 



Num- 

 ber of 

 flsh 



Locality 



Brielle, N.J 



do 



Ocean City, Md. 

 0£E Martha's 



Vineyard, 



Mass. 

 Ocean City, Md. 



do 



Off Long Island, 



N.Y. 

 Brielle, N.J. 



do 



....do 



Ocean City, Md. 

 Brielle, N.J 



Off Martha's 



Vineyard, 



Mass. 



...do.... 



Ocean City, Md.. 

 Off the Carolinas, 



(33°10' N, 



77°25' W). 

 Ocean City, Md. . 



....do 



....do 



....do.. 



Off Martha's 



Vineyard, 



Mass. 

 Ocean Citv, Md.. 



...-do 



....do 



Brielle, N.J 



Cape Hatteras, 



N.C. 

 Brielle, N.J 



Miami area, 



....do 



....do. 



....do 



....do.... 



Off Cape Hat- 

 teras, N.C. 



ria. 



Source 



Mrs. K. R. 

 Mayer.3 



Do.a 

 F.J. Mather. 



Do. 



M. L. Dennis. 



Do. 

 Rivas (1964). 



Mrs. K. R. 



Mayer.3 



Do.3 



Do.s 



M. L. Dennis. 



Mrs. K. R. 



Mayer.3 

 R/V Carpn. F. J. 

 Mather. 



Do. 

 M. L. Dennis. 

 U.S. Fish and 

 Wildlife, Bruns- 

 wick, Ga. 

 M. L. Dermis. 

 Do. 

 Do. 

 Do. 

 MIVAlbalwss III, 

 J. Taylor.' 



M. L. Dennis. 

 Do. 

 Do. 



Mrs. K. R. 



Mayer.3 

 F. J. Mather. 



Mrs. K. R. 



Mayer. 3 

 Rivas (1964), 

 Do. 

 Do. 

 Do. 

 Do. 

 UIV Albatross 1 11. 

 R. Brigham and 

 L. Lawday.2 



' Measurements were checked with ruler on photographic prints. 



' Specimens were made availaljle to us by kindness of the individuals listed. 



3 Measurements taken by charter boat captains who tagged the tuna, 

 an d collected for us by Mrs. Mayer. 



* Measurements were made by Isaac Ginsburg and transmitted to us by 

 Dr. L. P. Schultz. 



The length frequencies for all localities combined 

 between late June and mid-October are shown 

 graphically for each half monthly period by years 

 in figures 4-10, and for all years combined, by half 

 monthly periods in figure 11. The number of fish 

 in any given size group and period varies consider- 

 ably from year to year, due to nonuniform sam- 

 pling and availability, and to variations in the 

 numerical strength of year classes. The general 

 pattern of size groupings is consistent, however, 

 with maximum and minimum numbers occurring 

 around the same lengths year after year. It 

 seems obvious that these groupings represent dif- 



50 100 150 200 250 



FORK LENGTH-CENTIMETERS 



300 



Figure 3. — Frequency distribution by 5-centimeter groups 

 of lengths of bluefin tuna for counts of annuli. 



ferent ages. We have arbitrarily designated with 

 vertical lines the points which we believe best 

 separate the various age groups. Usually there 

 seems to be little question as to where these lines 

 should be drawn. If doubtful we based our judg- 

 ment on a comparative study of data for the en- 

 tire series of years. In a few such cases, we as- 

 signed some of the fish at a low point to one age 

 and the rest to the other. Corresponding broken 

 lines separate the data in table 3. 



AGE DETERMINATION 



The question arises as to whether or not the 

 fish forming the first modal group appearing in 

 our length frequency study are young of the year. 

 In figure 12, we have compared the lengths of fish 

 in each age group as determined by counts of an- 

 nuli with the lengths of those in corresponding 

 age groups as determined by length frequencies. 

 On examining this figure, we find the assumption 

 that fish in the first modal group are young of the 



