4.6.2 Analysis

 

 

Assume we have an equilibrium population Pe

 

This means that once the population reaches Pe

fish are being caught at the rate without a change in the size of the population.

 

can therefore be defined as the theoretical sustainable yield Y.

 

.

 

Equating the two expressions for Pe

 

we get

 

 

If we plot against f we should get straight line and we could estimate some of the parameters.

BUT we don’t know how to calculate Y?

 

Let us average the fishing effort over n years.

We then think of the population at a particular time as having resulted after n years of exploitation at this constant fishing effort.

In the early part of this century, the fishing stocks were constant and we have records of how many fish were caught. ( Let us denote this by S )

We can make an assumption that S was approximately equal to Y. So ley us replace Y by S

 

 

But this is the fishing effort. Thus we can estimate the fishing effort from the charactoristics of the graph without ever knowing the population P or the maximum population M