Ray Hilborn: Analysis Shows California Sardine Decline Not Caused by Too High Harvest Rate
SEAFOODNEWS.COM [SeafoodNews] (Commentary) by Ray Hilborn April 22, 2015
Two items in the last weeks fisheries news have again caused a lot of media and NGO interest forage fish. First was publication in the Proceedings of the National Academy of Sciences of a paper entitled “Fishing amplifies forage fish population collapses” and the second was the closure of the fishery for California sardine. Oceana in particular argued that overfishing is part of the cause of the sardine decline and the take home message from the PNAS paper seems to support this because it showed that in the years preceding a “collapse” fishing pressure was unusually high.
However what the PNAS paper failed to highlight was the real cause of forage fish declines. Forage fish abundance is driven primarily by the birth and survival of juvenile fish producing what is called “recruitment”. Forage fish declines are almost always caused by declines in recruitment, declines that often happen when stocks are large and fishing pressure low. The typical scenario for a stock collapse is (1) recruitment declines at a time of high abundance, ....
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