Ray Hilborn Says Recent Science Paper Makes Inflated Claim about Human Impacts on Marine Species
SEAFOODNEWS.COM [SeafoodNews] August 27, 2015
Ray Hilborn sent a note regarding his comment on a paper in the August 21st issue of Science Magazine that makes the claim that humans take up to 14 times the amount of marine fish as other predators do. The extrapolation is that humans are a super predator of marine life, and take an unsustainable proportion of the adult population of various species.
Ray says the authors made a mistake in only looking at individual predators and in not considering all predation on a given species. He says that when all predation is considered, the results reverse themselves, and that natural predators take a larger proportion of adult marine fish than humans do.
His comment is below:
Comment by Ray Hilborn, University of Washington
This paper claims that humans have a up to 14 times higher exploitation rate than natural predators. There is a basic flaw in the analysis which diminishes the validity of the conclusions the authors come to. First the calculated predation rate of natural predators will depend on how many predators you look at. Dozens or even hundreds of species may prey upon a given species, most of them taking a trivial fraction of the prey. If you find data only for the most important predators (the ones that take the most of the prey species) you will estimate a high predation rate, but if you find data for all the species that prey upon a species the median will be much much lower.
In fact there are hundreds of potential predators for any species...
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