A new method for measuring biomass reveals that fish stock are more stable than widely believed, according to a University of Washington researcher.
In a study published in the journal Conservation Biology, Dr. Trevor Branch of the University of Washington said biomass data from stock assessments is a much more accurate measurement of stocks. He added that the inappropriate use of time trends in catch data “greatly” overestimates the percentage of stocks collapsed and overexploited.
If biomass data is used to gauge stocks, only 2 percent of fisheries are collapsed and 26 percent overexploited or collapsed, according to Branch. But, if catch data is used, around 30 percent of stocks are collapsed and around 70 percent are overexploited or collapsed.
Branch’s analysis suggests that fisheries management has led to stabilization, and even recovery, of many fisheries worldwide.
“Instead of focusing on what we take out of the oceans (catches), we should be examining the actual state of the ecosystem (biomass data),” said Branch. “Catch data produce seriously biased estimates of what is going on in ocean ecosystems, and we need more effort expended on scientific surveys and stock assessments, especially in areas that are currently poorly assessed.”
