FISHERY BULLETIN: VOL. 83, NO. 4 



Table 2.— Percentage of sexually mature females tfiat were 

 pregnant (1971-83) grouped by 1) the area in which the 

 specimens were collected; 2) the quarter of the calendar 

 year; 3) the length of time between sighting the school 

 and release of the net; 4) the observer's estimate of the 

 total school size; 5) the number of dolphins known to be 

 killed in the set; and 6) the tons of tuna caught in the 

 set. Note that total sample size varies with the availabil- 

 ity of data on the stratifying variable. Probabilities are based 

 on chi-square contingency tests. Only samples from the 

 northern offshore stock of spotted dolphins are included. 

 CYRA = Commission Yellowfin Regulatory Area. 



tested separately for these two time periods. When 

 the years 1971-73 were excluded (Tkble 4), the inter- 

 actions between percent pregnant and season, 

 dolphin kill, and tuna catch are no longer significant. 

 When tests are performed on data from 1971 to 1973 

 alone (Ikble 4), season and tuna catch are still 

 significantly related to pregnancy rate 



Percent Lactating 



Annual trends in percent lactating for the north- 

 ern stock of spotted dolphins are illustrated in 

 Figure 3. Two cases are considered: 1) the percen- 

 tage of all mature females that are lactating and 2) 

 the percentage of pregnant females that are lac- 

 tating. For both cases, a weighted regression shows 

 a significant increase in the fraction of lactating 

 females through time (P < 0.05). In the former case, 

 the regression again appears to be driven by 

 anomalous values in 1971-73. Percentages and sam- 

 ple sizes for the latter case are presented in Ikble 



Table 3. — Multiway tests of factors affecting per- 

 cent pregnant. Log-likelihood chi-square was 

 used to calculate the probability that percent 

 pregnant is independent of the stated factor(s) 

 using the log-linear model. Pregnancy state 

 (pregnant/not pregnant) is implicit as the first 

 factor in each comparison. 



Table 4. — Percentage of sexually mature females that were 

 pregnant, grouped by season, dolphin kill, and tuna catch. 

 The years 1971-73 and 1974-83 are grouped separately. 

 Probabilities are based on chi-square contingency tests. 

 Only samples from the northern offshore stock of spotted 

 dolphins are included. 



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