Fishing for aphids: the exploitation of a natural population.
A field experiment on lucerne in British Columbia in which populations of Acyrthosiphon pisum (Harris) were harvested at various rates is described and discussed in relation to exploitation theory (which has been furthest developed for fisheries but is applicable to animal populations in general). No steady states were established, and in consequence the results do not agree well with the theory. For a rising population, curves of catch in relation to effort differed from those for a falling population. Natural mortality rates declined in compensation for losses due to harvesting. The effect of this compensation on exploitation theory is discussed.