FISHERY BULLETIN: VOL. 84, NO. 3 



RESULTS 



Figures 1 through 5 give finite rates of increase 

 (displayed as (A - 1) • 100) for the above ranges of 

 age at first birth, calving interval, and calf and non- 

 calf survival. The lower left corner of each panel is 

 blank because we did not consider cases where calf 

 survival exceeded the square of noncalf survival, for 

 the reason discussed in Methods. 



The maximum finite rates of increase which would 

 result from the parameter ranges included here are 

 1.08 to 1.09. Rates as low as 0.89, i.e., decreaseof 

 11%/yr. also resulted from the parameter ranges 

 used. 



Within the ranges of parameters examined here, 

 rate of increase is most sensitive to calving inter- 



val and noncalf survival rate, followed by age at first 

 birth, and is relatively insensitive to changes in calf 

 survival rate. This is an expected result following 

 the reports by Eberhardt and Siniff (1977) and Good- 

 man (1981). An increase in calving interval of 1 yr 

 results in a decrease in ROI of about 0.02, holding 

 other parameters constant. For example, the max- 

 imum ROI for a 9 yr age at first birth is about 1.07 

 with a 2 yr calving interval. This ROI drops to 1.05 

 with a 3 yr calving interval. A decrease of 0.01 in 

 noncalf survival rate results in a 0.01 decrease in 

 ROI, while a 0.10 decrease in calf survival rate 

 decreases ROI by <0.01. Age at first birth appears 

 to be nonlinearly related to ROI over the ranges ex- 

 amined here. An increase in this age from 7 to 9 yr 

 results in a 0.02 decrease in ROI, while an increase 



c 

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Figures 1-5.— Contours of percent rate of increase in dolphin population size ((A - 1) • 100), as a function 



0.50 

 0.60 



0.96 

 0.85 



0.90 



0.95 0.97 



0.95 0.97 



0.96 



0.85 0.90 0.95 0.97 



Noncalf Survival Rate (proportion) 



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O 



"+- 



i_ 



o 

 a 



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i_ 



Q. 



(D 



-t-> 



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 DC 



"co 

 > 



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i_ 



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M— 



CO 



O 



0.95 0.97 



0.96 

 0.85 



0.90 



0.95 0.97 



0.85 0.90 0.95 0.97 



Noncalf Survival Rate (proportion) 



Figure 1.— First reproduction of dolphin age class 7 yr: a) 2-yr 

 calving interval (upper panel); b) 3-yr calving interval (middle 

 panel); c) 4-yr calving interval (lower panel). 



Figure 2.— First reproduction of dolphin age class 9 yr: a) 2-yr 

 calving interval (upper panel); b) 3-yr calving interval (middle 

 panel); c) 4-yr calving interval (lower panel). 



530 



