dicated that they fed most intensively during the 

 evening hours. Again, judged on the degree of stomach 

 fullness, he found that they fed most intensively at 

 the beginning of February, in the second half of April, 

 and in May. He observed that this sporadic intensity 

 of feeding was correlated inversely with periods of in- 

 tensified spawning. 



Evans and Wares (1972) found mostly squid and 

 fishes in stomachs from sailfish captured in the 

 eastern Pacific. Voss (1953) stated, however, that 

 sailfish often feed on typical bottom dwellers such as 

 sea robins (Triglidae) and gastropod mollusks (Table 

 6). He also added that one of the cephalopods, Grim- 

 poteuthis sp., found in the stomach contents, is a bot- 

 tom dweller from rather great depths. Baughman 

 (1941a, b) stated that sailfish examined from the 

 western Gulf of Mexico contained a large proportion 

 of shrimp in their stomachs. 



3.43 Growth rate 



Sailfish apparently have a very rapid growth rate. 

 De Sylva (1957) studied the growth of sailfish in the 

 Florida region based on length frequencies of almost 

 9,000 young and adult sailfish. He stated that sailfish 

 average a total length of 17.8 cm at the end of their 

 first month, 50.8 cm by the end of the second month, 

 89 cm by the end of the third month, and 111.7 cm at 

 the end of 4 mo. He added that there was considerable 

 variation in these lengths due to variation in time of 

 spawning and subsequent variation in availability 

 and abundance of planktonic food. By the end of their 

 first year of life sailfish average 183 cm in total length, 

 216 cm the second year, and 233.7 cm by the end of 

 the third year. De Sylva noted that determination of 

 age after 2 yr was difficult. Variation in weight is 

 large; a 3-yr-old fish with a modal length of 233.7 cm 

 may vary in weight from 19 to 49.4 kg. Jolley (1974) 

 suggested the possibility of differential growth 

 between male and female Atlantic sailfish. This 

 hypothesis partially explains the wide variation in 

 weight and length at a given age described by de 

 Sylva. Jolley showed significant differences between 

 the length-weight relationship of males and females. 



Koto and Kodama (1962) estimated growth of 

 sailfish from the East China Sea. Their growth rates 

 for categories "n, n+1, n+2" were similar to those es- 

 timates by de Sylva for 1-, 2-, and 3-yr-old fish. Koto 

 and Kodama also noted marked seasonal changes in 

 growth rate with a maximum from June to December. 



Williams (1970) discussed growth of sailfish off the 

 coast of East Africa, and altbough his data were too 

 few for a detailed analysis of growth, he noted that 

 based on de Sylva's work the majority of the sailfish 

 caught off East Africa were 3 yr old or older. He stated 

 that sailfish in the Indian and Pacific oceans un- 

 doubtedly grow larger than Atlantic sailfish and this 

 could be due to a longer life span or some other feature 

 of growth. 



Table 6. — Stomach contents of 241 adult specimens of the sail- 

 fish, Istiophorus americanus (from Voss, 1953). 



109 



