FISHERY BULLETIN: VOL. 71, NO. 2 



Dark muscle size was determined from dis- 

 sections of fresh material — the difference in 

 the coloration of the dark muscle and the 

 rest of the muscle block was sufficiently visible 

 that the entire dark muscle could be removed 

 and weighed. Its size was expressed as a per- 

 centage of fish mass. Body shape was deter- 

 mined from dorsal and lateral photographs of 

 fresh dead fish. The maximum body height (//) 

 and maximum body width (W) as a percent 

 of fork length were averaged to represent the 



H + W 

 maximum thickness ( — - — ) of the body. The 



position of maximum thickness along the 

 length of the fish was expressed as percent 

 of fork length. It was determined by averaging 

 the measurements from both dorsal and lateral 

 views. Usually the position of maximum height 

 for a species was 1 to 3% (of fork length) more 

 posterior than the position of maximum width. 

 Data on dark muscle, blood hemoglobin, 

 maximum body thickness, and the longitudinal 

 position of maximum body thickness are pre- 

 sented for seven scombroid species in order 

 of decreasing typical swimming speeds in 

 Table 7. The size of the dark muscle (Table 7) 

 ranged from 1.8% of the body mass for Ac. 

 solandri, 125 cm long, to 10.3% of body mass 

 for Ai(. rochei, 31 cm long. Within single 

 species, the relative size of the dark muscle 

 is smaller for larger animals. For example, 

 T. obesiis approximately 55 cm long have a 

 dark muscle 7.7% of the body mass, whereas 

 those 125 cm long have a red muscle of 4% of 

 the body mass. I observed the same trend but 

 with different magnitudes for other species for 

 which a wide range of lengths were examined. 

 Blood hemoglobin ranged from 10.4 g/100 ml 

 of blood for Ac. .'<ola)tdri to 19.2 g/100 ml for 

 Alt. rochei (Table 7). This range includes values 

 comparable to mammals — man for example has 

 ca. 15 g/100 ml. 



Typical speeds were positively correlated 

 (Figure 9) with dark muscle size (r = -1-0.86, 

 II - 9, P < 0.005) and with blood hemoglobin 

 (r = +0.83, /; = 9, P < 0.005). Approximately 

 70% of the variation in both dark muscle size 

 and hemoglobin concentration are associated 

 with variation in typical speeds. The size of 

 the dark muscle and the concentration of hemo- 



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