, ^,,.„4<MSSS.„ „„„„„„ „„ 



Figure 1. --Western equatorial Pacific. The dotted-«tlppled border shows 

 the authorized area for tuna mothership expeditions. The solid 

 black line around the Marianas, Marshall, and Caroline Islamds 

 shows the U. S. Trust Territory of the Pacific islands. After 

 Shlmada (1951a). 



EFFECT OF TYPE OF BAIT ON THE CATCH 



The capture of a fish on a longline requires that the fish voluntarily strike at a 

 relatively motionless baited hook. Consequently, the possibility is considered that the rate of 

 capture was in part dependent on the type of bait used by the catcher vessels of the mothership 

 expeditions. Three different baits --sardines, Sardinia melanostica (Tennminck and Schlegel); 

 sauries, Cololabis saira (Brevoort); and squid--were used on the expeditions, but because squid 

 were used only incidentally, the comparisons are confined to sauries and sai dines. 



Quantitative data on the relative effectiveness of sardines and sauries are available 

 from the daily log sheets of each catcher vessel, which list the number of pieces of each type of 

 bait used each day. (Typically, a daily set of gear consisted of around 2, 000 hooks and was 

 baited with sardines or sauries or a mixture of the two.) Prior to analysis of these records, 

 each day's fishing was coded on a linear scale of to 10, with 10 representing all sauries, and 

 representing all sardines. The coded catches were then grouped by the relative annount of 

 sauries used as bait as shown in table 1. This summary of all the data indicates that the two 

 baits were about equally effective, although the higher catch rate of yellowfln on 100-percent 



