vertically, from the maximum depth reading 

 (600 feet) of the sounding tube scale (fig. 4). The 

 graph paper backed by plywood was placed ver- 

 tically against a wall. A unit of mainline was 

 modeled from a silver chain (approximately 14 

 links to an inch and 1/8 inch in diameter) and 

 the position of each hook marked; the droppers 

 were omitted. With the omission of the droppers 

 in the model, it was necessary to bring the tube 

 readings up to the mainline depth. Therefore, 

 all observed depths were adjusted by subtract- 

 ing 9 feet, because sounding tubes were usually 

 attached near the center of the 18-foot dropper. 

 A pin, inserted through the link representing 

 hook 7, was driven into the center of the graph 

 at the observed depth for hook 7. The ends of 

 the chain were brought up to and pinned at a 

 depth representing the bottom of the floatline 

 with hooks 4 and 10 of the chain passing through 

 the observed depths obtained for those hooks. 

 3y removing the pin holding hook 7 and allowing 

 the chain to swing freely to fornn a catenary, 



.-:-JGTH OF a BASKET OF MAINLINE IN FEET 

 O .'. aOO 500 600 TOO 800 900 1000 UOO 12001260 



Figure 4. --The scale model, of silver chain, 

 representing the mainline of a basket of long- 

 line gear. The method of using the model is 

 explained in the text. 



theoretical values for the 13 hooks could be 

 determined. In this way the model permitted a 

 comparison of the actual configuration of the 

 mainline in the water, as shown by the tubes 

 under fishing conditions, with that of a catenary 

 having the same distance between its supports or 

 buoys. Two very important considerations were 

 thus taken into account by the method: one, that 

 environmental forces nn a y not act unifornnly 

 throughout the depth of the basket, and two, the 

 distance between supports governs the 

 configuration of the catenary. 



To ascertain whether the baskets of longline 

 gear hung in a catenary, the observed (sounding 

 tube) and theoretical values for hooks 4, 7, and 

 10 were paired and subjected to the "t" test. 

 Depths , which were obtained from baskets skewed 

 to the extent that either the chain would not reach, 

 or it overshot the buoy line on one side or the 

 other, were omitted from the statistical analysis 

 since theoretical values could not be obtained. 

 (These represented roughly 8 percent of the 

 total nunnber of baskets, which had sounding tube 

 readings at all three hook positions.) A signifi- 

 cant difference between any of the paired values 

 would indicate that the baskets did not generally 

 hang in the form of a catenary and the sign of 

 the meanfor each hookwould suggest the direc- 

 tion that the basket deviated or skewed from the 

 catenary. Table 1 sunnmarizes the results of 

 the "t" test and suggests that generally the 

 baskets did not hang in a catenary. Hooks 7 and 

 10 show significant differences at the 1-percent 

 level. The significance detected in hook 10 and 

 the negative aspect of its nnean difference are a 

 reflection of the positive deviations observed in 

 hook 4. This is illustrated in figure 4 where 

 plots of a 5-fathom floatline basket show that a 

 positive difference (observed > theoretical) i n 

 hook 4 is reflected by a negative difference 



Table 1. --Summary of statistics for comparison of the mean differences (observed minus 

 theoretical depth values). Lower comparison was carried out with values adjusted to 

 the theoretical slope (fig. 2). Those "t" values attaining the 5-percent level and the 

 1-percent level of significance are noted by 1 and 2 asterisks respectively. 



— Two additional baskets, which previously did not reach or else overshot the float- 

 line, were added to the analysis when adjustments to the theoretical depth were made. 



