Why fishing magnifies fluctuations in fish abundance
Resource
Nature 452: 835-854
Journal
Nature
Journal Volume
452
Journal Issue
7189
Pages
835-839
Date Issued
2008
Author(s)
erson, Christian N. K.
S
in, Stuart A.
Hewitt, Roger
Hollowed, Anne
Beddington, John
May, Robert M.
Sugihara, George
Abstract
It is now clear that fished populations can fluctuate more than unharvested stocks. However, it is not clear why. Here we distinguish among three major competing mechanisms for this phenomenon, by using the 50-year California Cooperative Oceanic Fisheries Investigations (CalCOFI) larval fish record. First, variable fishing pressure directly increases variability in exploited populations. Second, commercial fishing can decrease the average body size and age of a stock, causing the truncated population to track environmental fluctuations directly. Third, age-truncated or juvenescent populations have increasingly unstable population dynamics because of changing demographic parameters such as intrinsic growth rates. We find no evidence for the first hypothesis, limited evidence for the second and strong evidence for the third. Therefore, in California Current fisheries, increased temporal variability in the population does not arise from variable exploitation, nor does it reflect direct environmental tracking. More fundamentally, it arises from increased instability in dynamics. This finding has implications for resource management as an empirical example of how selective harvesting can alter the basic dynamics of exploited populations, and lead to unstable booms and busts that can precede systematic declines in stock levels. ©2008 Nature Publishing Group.
SDGs
Other Subjects
abundance; age structure; body size; growth rate; harvesting; hypothesis testing; population decline; population dynamics; stock assessment; temporal variation; article; body size; environmental impact; fish stock; fishing; harvesting; larva; nonhuman; population abundance; population density dependence; population growth; priority journal; United States; California Current; Pacific Ocean
Type
journal article
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