Yield per recruit

Let us now follow the fate of a single cohort through time. Why would we want to do this? Part of the answer is that we are much less certain about stock and recruitment relationships than we are about survival from one age class to the next. So, wouldn't it be nice if we could learn a lot about sustaining fisheries by simply looking at cohort dynamics and not stressing about the stock-recruitment relationship? That, at least, is the hope.

When we follow a single cohort, age a and time t are identical, if we start the time clock at age 0, for which we fix N(0) = N0, assumed to be a known constant. The dynamics of the cohort are exceedingly simple, since N(a + 1)= N(a)e—M—F(a and if individuals are recruited to the fishery at age ar and fishing mortality is knife-edge at level F the yield from this cohort is

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