FISHERY BULLETIN: VOL. 86, NO. 4 



120'W 115 110'^ lOS'^ 120°W 115" 110>^ 105° 12a'W 115" 110" 105" 



30P 



25° 



20^ 



35°N 



30° 



25° 



Figure L— Locations of release (X's) and areas of recapture selected for tagging cruise 1079 (areas delineated by 



heavy lines). 



age weights were estimated by 



w^ = 



5! w, 



ii = l 



ijPS 



X w 



'JPS 



+ 



J.W, 



1 = 1 



jBB >< '^jBB 



1=1 i=l 



1, 2) because only the sets after the dates of release 

 are considered, and the portions of the total catches 

 which are from purse seines and baitboats differ in 

 accordance with the dates considered. 



The data were analyzed by 1) Chi-square con- 

 tingency tests and 2) the binomial homogeneity test 

 described by Kendall and Stuart (1961:578-579). 



where Wj = average weight of skipjack 



tuna in stratum j, 

 Wijps and W^jp^ = weights of skipjack tuna 

 caught in purse seine set i 

 and baitboat set i, respec- 

 tively, made in stratum j, 

 n = number of purse seine or 

 baitboat sets in stratum j, 

 and 

 Wjps and Wj^b = average weights of skipjack 

 tuna caught in stratum j by 

 purse seiners and baitboats, 

 respectively. 



These are listed in Tables 1 and 2. 



The average weights usually differ within strata 

 which correspond to the months of release (Tables 



Chi-Square Contingency Tests 



A computer program, SCHOOL, was written to 

 analyze the data. For a given release date and month 

 of recapture, this program estimates the number of 

 fish caught in each set from the weight of fish caught 

 and the average weight of the fish. It then sums the 

 estimates of the numbers of fish caught and num- 

 bers of tagged fish returned for all sets and calcu- 

 lates the tagged to total ratio. This ratio is then used 

 with the equation for the binomial distribution to 

 estimate the probabilities of 0, 1, 2, 3, . . .tagged fish 

 appearing in each set if the fish are randomly mixed. 

 The sums of the probabilities for all the sets for 0, 

 1, 2, 3, . . . tagged fish are then calculated so that 

 these can be compared with the observed data, as 

 described in the next paragraph. A sample output 



634 



