436 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



female sardines required to produce the estimated 

 number of ova present on the spawning grounds 

 for any one season (assuming that each sardine 

 spawns only the most advanced mode of ovarian 

 ova). If the weight-fecundity relation of sample 

 SP-11 is taken as representative of that of the 

 stock of spawning sardines, the weight of spawning 

 females can be easily estimated on the basis of 

 262.8 ova per gram or 238.4 million ova per ton of 

 spawning female sardines. 



COMPARISON OF FECUNDITY-LENGTH 

 AND FECUNDITY-WEIGHT REGRES- 

 SIONS 



It has been shown that for the size-range of 

 sardines in these samples, there is very little differ- 

 ence among the regression lines of fecundity on 

 length, on length squared, or on length cubed. 

 For purposes of comparison, the fecundity-length 

 regression line was computed for the same 40 fish 

 used for the fecundity-weight regression line. The 



partial regression coefficients and the multiple 

 regression of fecundity on length and on weight * 

 were also computed (table 6). It would appear 

 from this comparison that the fecundity of these 

 sardines is not only better correlated witli their 

 weights, but that the correlation with length is 

 merely a reflection of the very good correlation 

 between length and weight. 



This comparison may be tested further by the 

 use of condition factors (Clark 1928). In the 

 present case the condition factor, K,^ equals the 

 weight of the fish in grams divided by the cube of 

 the length in millimeters and multiplied* by 10^ 

 (to give a three-digit whole number). Condition 



' Over this length-weight range the cubic relation of length to weight is 

 obscured, and the length-weight regression will approximate a straight line. 



5 The use of condition factors "corrected" by subtracting the ovary weight 

 from the fish weight before computing ii gives results that are almost identical 

 to those obtained from K computed from round weight. Theoretically it 

 might also be argued that the fish which contained more ovarian ova or larger 

 ova, or both, had produced them at the expense of other tissues and there- 

 fore the inclusion of ovary weight in fish weight should have a corrective 

 value rather than the opposite. 



120 130 140 150 



FISH WEIGHT IN GRAMS 



160 



Figure 7. — Relation between fecundity and fish weight for 40 sardines (San Pedro, Feb. 9, 1946). (Dashed line, 



K=.2628X; solid line, y=2.94-f .2402X). 



