Length-Frequency Distributions 

 of Hawaii Samples 



Use of length-frequency distributions to deter- 

 mine age and population structure of skipjack is 

 made difficult by the lack of ancillary aging meth- 

 ods. The problem is further complicated by the 

 skipjack tuna's presumably extensive migrations 

 and by fluctuations in availability which suggest 

 that the length-frequency distributions may not 

 be representative of the populations that are 

 sampled. 



Length-frequency samples were obtained by 

 systematic sampling from Hawaiian skipjack 

 landings during various months from 1948 to 

 1954 and again from 1959 to 1963. For economy 

 of space, data for 1952-63 only are presented in 



figure 4 as percent frequency. These percent 

 frequencies are based on many samples and 

 measurements for most months, so chance fluc- 

 tuations are likely to be small. These frequen- 

 cies are intended to show the size distribution 

 of skipjack for each month and should not be 

 construed as representing the relative magni- 

 tudes of the catches among the various months. 



An examination of the length-frequency distri- 

 butions shows that during the winter three domi- 

 nant modal groups may be evident. Although dur- 

 ing the summer there are typically two modal 

 groups, on occasions such as in August 1959 and 

 June 1961, three were noted. Typical modal 

 lengths for the winter are 35, 50, and 70 cm. (the 

 modal lengths given here and elsewhere in the 

 text, unless specified, give the approximate mod- 

 al values for these typical groups) . while those for 



40 60 80 100 40 60 80 100 

 FORK LENGTH (CM I 



40 60 80 100 



Figure 4. --Percent frequency distributions of skipjack samples 

 caught by the Hawaiian fishery during various months. 



