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Sharks and Cownose Rays: Background in Population Stories Different From 2007 Study?

Feb 18, 2016 02:47 PM EST

Maybe cownose rays have nothing to do with shark declines or the oyster and shellfish fishing collapse on the East Coast, says a new study. A finding like this might preserve cownose rays from bow-fishing tournaments and mottos such as "Save the Bay, Eat a Ray," as some in the Chesapeake Bay area advocated after a 2007 study implemented rays in all those things. 

The new research from Florida State University was published in Scientific Reports, which is also a Nature journal.

"Our research presents clear evidence that directly refutes the 2007 Science study," Dean Grubbs at the FSU Coastal and Marine Laboratory (FSUCML) and lead author of the study said in a release. "For instance, the declines in predatory sharks presented in the 2007 study are not nearly as severe as was reported, and the increases in cownose ray populations are biologically unrealistic."

That's in contrast to the earlier study, which was based on the idea that sharks of the apex predator type have experienced strong reductions over the last several decades. The idea was that cownose ray populations then grew unchecked for lack of serious predators, overtaking shellfish populations.

Grubbs and accompanying researchers say that successful management means that most of the species involved in the 2007 study are recovering or have recovered. The new study argues that cownose rays cannot increase their populations at the rates in the 2007 study -- this is physiologically impossible, according to the new findings. That's because rays mature slowly and only reproduce once they are six or seven years old; females produce a single offspring each year.

"One of our primary concerns that led to this study was the effect of a fishery with no harvest limits on a species with low reproductive rates, particularly as this was being incorrectly touted as an 'environmentally responsible' seafood choice," study co-author Charles Cotton, a FSUCML faculty member, said in a statement. "Evidence-based management decisions are critical in preventing overfishing, as we've seen many times in the past with unregulated fisheries for other species of sharks and rays."

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