290 



DISCOVERY REPORTS 



Table ii. Decrease in relative abundance o/ Merluccius hubbsi with increasing latitude 



* Obviously fractional hake could not long exist in nature, and it is mathematically indefensible to treat fish as indiscrete 

 objects— but I feel that the fractional expression is less misleading than giving results as hake per 100 hr. trawling in order 

 to get whole numbers, because these results are based on less than 100 hr. of comparable hauls-nn each region. 



It will be seen that these figures provide evidence of the second feature of the influence of latitude 

 already mentioned, namely, the increase in size (and weight) of the individual fish as one proceeds 

 southwards. This can better be demonstrated by considering the mean lengths and length frequencies 

 of the fish caught in the three regions, including data from the earlier surveys (Table 12). 



Table 12. Variation in size 0/ Merluccius hubbsi, as shown by the differences in mean lengths for all 

 comparable hauls in the three regions here surveyed, regardless of season. The sexes considered 

 separately 



Note. The numbers of individuals do not indicate the relative abundance in the respective regions because of the very 

 difl^erent number of hauls made m each of them. They show merely the number of individual measurements upon which 

 these mean lengths are based. The sex ratios shown at the head of the table are based on a different array of the data in- 

 cludmg some specimens sexed but not measured. ' 



Table 12 shows the mean lengths of males and females of M. hubbsi, based on all the comparable 

 data, for the three latitudinal regions, the difl^erences in mean lengths between adjacent regions and 

 their statistical significance. It can be seen that there is a clear increase in mean length with increase 

 in latitude m both sexes, and that this is strongly significant except as between the males of the inter- 

 mediate and southern regions. It can also be seen from the sex ratios given at the head of the table 



