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Fishery Bulletin 102(2) 



ertson, in press) estimated the probability that a calf of a 

 given age class was still suckling. Given that body length 

 has a near linear relationship with age in these young 

 age classes (Perrin, 1976), this meant that for any chosen 

 length of independence, each individual smaller than that 

 cutoff value would only be counted fractionally, in effect 

 correcting for the probability that an animal of a given 

 age is not suckling. This procedure caused the method in 

 this paper to tally fewer "calves" in each set than in the 

 previous study. A secondary result of this effect was that 

 the mean deficit per set estimated in the present study 

 tended to be slightly higher than that presented by Archer 

 etal. in 2001. 



We estimated the total number of missing calves as a 

 function of the number of dolphins killed in each stock 

 (Table 3). Prior to 1995, only a fraction of the purse-seine 

 trips carried scientific observers. To estimate the number 

 killed in each stock, kill rates from the observed trips were 

 applied to unobserved trips, stratified by area and stock 

 (IATTC, 2002; Joseph, 1994 2 ). Since 1995 it has been re- 

 ported that all dolphin sets have been observed, and that 

 the number of dolphins killed is therefore known without 

 error (IATTC, 2002). 



The total calf deficit could also be estimated as a function 

 of the number of sets by multiplying the total number of 

 sets made on each stock by D s (Fig. 4). In the only study to 

 estimate the number of sets made on each stock annually. 



Archer et al. 5 used a relatively simple proration scheme of 

 unobserved sets derived from ratios of the number of sets 

 made on each stock in observed sets. However, because 

 Archer et al. 5 did not stratify unobserved sets by area, bas- 

 ing the total calf deficit on these estimates would produce 

 a different result from that presented in Table 3. Because 

 the estimates of the kill by stock included stratification 

 by area, estimates of the total calf deficit calculated by 

 multiplying the kill estimates by D,. are likely to be more 

 accurate. It is important to realize that the deficit that we 

 present is directly related to the kill observed in the sets 

 that we used. In other words, if proration schemes for un- 

 observed sets were the same for the number of sets made 

 and the number of dolphins killed, estimates of the total 

 calf deficit with either D^ or D k would be equivalent. 



Wade et al. 1 explored the effects of 50% and 100' < ad- 

 ditional fisheries-related mortality on the assessment of 

 the northeastern spotted dolphin stock. The assumption of 

 additional mortality led to higher estimates of maximum 



Archer. F.. T. Gerrodette. and A. Jackson. 2002. Prelim- 

 inary estimates of the annual number of sets, number of 

 dolphins chased, and number of dolphins captured by stock 

 in the tuna purse-seine fishery in the eastern tropical Pacific. 

 1971-2000. National Oceanographic and Atmospheric Admin- 

 istration Administrative Report LJ-02-10. 26 p. Southwest 

 Fisheries Science Center, 8604 La Jolla Shores Dr., La Jolla, 

 CA 92037. 



