FISHERY BULLETIN: VOL. 80, NO. 2 



6a. RL/WL >0.604 (CI 05 = 0.632+0.033) 7 



6b. RL/WL <0.604 (CIos = 0.577±0.033); **RC/RL >2.890 (CI 05 = 2.97+0.122) 



Ommastrephes bartramii 



Jaw angle recessed; no hood notch at crest (Fig. 2); pigment changes with growth shown 

 in Figure 8. 



7a. RL/JW >1.137 (CI 05 = 1.197+0.059); **RC/JW >3.175 (CIos = 3.360+0.189) ....... 



Dosidicus gigas 



Jaw angle recessed; the hood is deeply notched at the crest (Fig. 2); pigment changes 

 with growth shown in Figure 9. 



7b. RL/JW <1.137 (CI05 = 1.077+0.059); **RC/JW <3.175 (CI 05 = 2.990+0.189) 



Symplectoteuthis oualaniensis 



Jaw angle recessed; the hood is moderately notched at the crest (Fig. 2); pigment 

 changes with growth shown in Figure 10. 



The wet body weight and mantle length values 

 for each species were used in linear regression 

 equations to establish a relationship with a beak 

 dimension. The regression equation has the 

 form: y — a + bx, where ij = weight or mantle 

 length, a = # intercept, b = slope of the regression 

 line, and x — beak dimension. Initially a stepwise 

 procedure, based on r 2 values, was used to deter- 

 mine if combinations of beak dimensions would 

 improve the estimate. Adding more than one in- 

 dependent variable to the regression equations 

 did not substantially increase the r 2 values of the 

 body weight and mantle length equations. 



The upper and lower beak of each species is 

 represented by a pair of equations for mantle 

 length and a pair of equations for body weight 

 (Tables 4, 5). The firstsetof equations represents 

 the best single independent variable equation 

 derived from the stepwise regression procedure. 

 The second set of equations retains the durable 

 RL dimension of the upper and lower beak as the 

 independent variable for all eight species. For 

 the body weight equations all values were trans- 



formed to natural logarithms before regression. 



DISCUSSION 



The research on cephalopod beak ratios was 

 initiated to determine whether species could be 

 separated and identified by comparing different 

 beak dimensions. Once this had been established, 

 the primary use of such a technique was consid- 

 ered to be stomach content analysis. The condi- 

 tion of beaks removed from preserved, identified 

 specimens is ordinarily much better than that of 

 specimens removed from a predator's stomach. 

 Therefore, other beak characteristics, in addi- 

 tion to maximum separation between species' 

 means, were considered when the beak ratios for 

 the key were selected. The selection was based on 

 a dimension's durability under mechanical and 

 chemical action, the effect such action would 

 have on the accuracy of the beak dimension's 

 measurement, and the ability to separate the 

 ratio means at a given confidence level (a =0.05). 

 Consequently, small dimensions with easily 



Table 4.— Regression equations and r 2 values for mantle length and body weight, 

 upper beak regression equations in centimeters, asterisk indicates best regres- 

 sion based on r 2 . 



368 



