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