Some populations maintain a generally low population size, but occasionally undergo abrupt bursts in number. Such behavior is frequently observed with pest species, which in some years may be almost undetectable yet a few years later are present in huge numbers. Figure 3 shows the between year abundance of the gurnard, Eutrigla gurnardus, a small bottom feeding fish. In 1992 there was a sudden peak in abundance, the reasons for which are obscure but possibly relating to optimal conditions during the spring for larval survival and the arrival of large numbers of migrants. Again there are indications of stability in the system as the population explosion is contained and consumed so that the population equally quickly subsides to the basal level. Within a few years there is frequently no trace of the previous population explosion.
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