JOHNSON ET AL.: ACE. OROWTH. AND MORTALITY OF KINO MACKEREL 



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Table 10. — Mean back-calculated fork length (mm) at ages, 

 from Beaumariage (1973) and this study. Beaumariage'sdata 

 were transformed from standard length by his formula FL = 

 1.096 SL- 17.143. 



fork lengths at age were smaller in our study 

 than in his in all eases but one (7-yr old males). 

 Several explanations for the differences seem 

 reasonable. First, our back-calculations em- 

 ployed a power curve, whereas his employed a 

 linear equation. Secondly, our fish were sampled 

 from a wide geographical range, which yielded 

 fish with wide variation in age composition, 

 whereas Beaumariage sampled from a more re- 

 stricted area. Lastly, our sampling occurred 

 almost 10 yr after his, and various changes may 

 have occurred in the population owing to exploi- 

 tation or other influences. 



Compensatory Growth 



Compensatory growth (Ricker 1975) appeared 

 to occur in both male and female king mackerel. 

 Length-frequency distributions of otolith mea- 

 surements from the focus to the proximal edge of 

 the first opaque mark in both sexes showed a nor- 

 mal distribution of values. After examination of 

 the distributions, we defined slow-growing fish 

 (both sexes) as those with an incremented 50 om^u 

 or less, fast-growing males as those with an in- 

 crement of 81 om/u or more, and fast-growing fe- 

 males as those with an increment of 86 om/i or 

 more. 



Back-calculated lengths for these fish are 

 shown in Table 11. While fast-growing males 

 grew 525 mm in year 1, they grew only 135 mm 

 in year 2. The slow-growing males grew 303 mm 

 in their first year, but made up some of their size 

 difference by growing 285 mm in their second 

 year. Females showed a similar trend, with fast- 

 growing fish having a first-year increment of 

 559 mm and a second-year increment of 184 mm. 

 The slow-growing females grew 282 mm in year 

 1 and 334 mm in year 2. Beyond age 2, yearly 

 growth increments were similar within each sex. 



Growth compensation in king mackerel is 



103 



