Olson and Galvan Magana Food habits and consLimption rates of Coiyphaena hippurus 



293 



10 



10 



-Females (n=323) 



 - Males (n=175) 



417-650 651-800 801-950 951-1100 1101-1250 1251-1770 



B 



-Wesl(n=38) — »— East (n=116) - ■- Southwest (n=271) -^<- Southeast (n=1 15) 



417-650 651-800 801-950 951-1100 1101-1250 1251-1770 



Fork length (mm) 



Figure 7 



Mean (±1 SE) daily rations for six size strata of common dolphinfish. for all 

 samples pooled by sex (A) and by area (B). Sample sizes are given in Table 1. 

 Rations for some strata were not plotted if sample sizes were small (i.e. n<5). 



The ratios of prey length to predator length ranged from 

 0.014 to 0.720, and averaged 0.177 (Fig. 6B). The length 

 ratios, smoothed with a smoothing spline, showed a slight 

 decreasing trend with dolphinfish size. 



Consumption rates 



The values of A, ( Eq. 1 ) chosen for the various prey taxa are 

 listed in Table 2. We estimated a daily ration of 5.6 ±0.56'X 

 (mean ±1SE) of body weight per day for all common dol- 

 phinfish samples pooled. Mean ration estimates stratified 

 by sex ranged from 0.4% of body weight per day for males 

 of the smallest size group to 9.6% for males of the largest 

 size group (Fig. 7A). Except for the 801-950 mm stratum, 

 mean rations increased with dolphinfish size. Ration esti- 



mates were comparable for females and males, except for 

 those in the smallest size stratum. The estimate for females 

 in the 1251-1700 mm class was excluded from Figure 7A 

 owing to a low sample size (n=2). 



We present mean (±1 SE) daily ration estimates strati- 

 fied by area in Figure 7B, if sample sizes were five fish 

 or more. The calculations revealed that the 25 fish of the 

 651-800 mm group from the east area had ingested large 

 amounts of food. These dolphinfish accounted for the high 

 rations overall for both males and females of that size 

 class (Fig. 7A). Except for that group and perhaps the 

 651-800 mm group in the west area, the ration estimates 

 were comparable for all size classes in all areas (Fig. 7B). 

 The number of empty stomachs did not unduly influence 

 the consumption estimates by area. The percent of empty 



