'9 



index to Bltinr: Q'j.alities of Schools » 



Hie following is an attea.pt. to show nui-nerically the biting 

 qualities of skipjack schools o If the bitirg qualities of a 

 school recorded, as goodj fairly goodj average, poor^, and very 

 .poor, are indicated respectively by y2j y^, Jq, y«^, and y-2, 

 and the number of times of occurrence for each category is 

 expressed as p?., Pis Po? ?-i and p-2j ^'^^ index of cverage 

 biting qualities for one type of school can be shoTm by the 

 formula q = ^Ji'- o Now when 73 = 3<, Ji = 2, y^ 1^ 1, T-j = Cc5, 



and y_2 = Oel, if v/e try calculating q (table 3)s we -^et 2.1 fcr 

 schools accompanying vs'hales, lo3 for unaccompanisd schooiSj 1<,0 

 for schools accompanied by birds j and O08 for schools acco-apanying 

 sharks o An unejcpected relationship can be seen betvreen tlie biting 

 qualities of schools aad the stomach contsnts of the fish (table 

 l;)o Fish which have eaten their fill and fish with empty stomach':- 

 may either bite well or poorly j but fn.sh between these two 

 extremes tend to bite more poor.Iy the less they have in their 

 stoma,chSe It is thought that once the fish has filled its stoinechj 

 its appetite declines -,vith the progress of digestion, tiie appetite 

 becoming strong again once all the food has t>een digested and 

 continuing •ontil the absorption of nourishment again commences o 

 If this idea is correct, the apoearc-nce of the above-noted 

 correlation ivould be natural 



Index of the Value of Schools ,, 



As an approximation, assuming that the fishing efficiency 

 of all fisherra.en is equal, it can be considered that the total 

 n'omber of fish taken N' will be proportional to the number of 

 poles 1 and the dura.;ion of fishing t /this assumption does not 

 strictly conform to the facts (table Sj^o rr.arsfors, the catch 

 per pole per hom-- il^ is taken as an index of the value of a 

 school, and is called the school value indexo Vife can consider 

 that the catch per pole per hour is generslljr proportional to 

 the index of average deiisity of the school k and to the index 

 of biting qualities q» Thus 



-, ^ " 00 ^'q "r , . " akq Here is a constant » 



The fact that the products of k and q given in tables 2 and 



3 are oropcrtional to the values 01 ,,.^— calculated from 



ji t 

 observed values for K* , 1^ amd t (table 6) shoirs that this 

 idea is in general correcco As the above .formula will not 

 stand if x ^ Oo5 in calculating the value of k, x is considered 

 to be about Col» 



75 



