Tuesday, March 7, 2017

Area Sharks Recovering from Over Fishing

VIMS coastal shark study shows species recovering from overfishing
 . . . a new analysis of seven coastal shark populations led by the Virginia Institute of Marine Science in Gloucester Point indicates that federal protections enacted in the 1990s have brought most of those species back from the brink.

"We've shown that, after two decades of management measures, coastal shark populations are finally starting to recover and reclaim their position as top predators, or regulators of their ecosystem," said Cassidy Peterson, a VIMS graduate student and lead scientist in the study.

VIMS is already known for conducting a long line shark survey, begun in 1973, that today is the longest-running fishery-independent monitoring program in the world for sharks, skates and rays.

A long line is a fishing line strung with a series of hooks. When a fish is caught, researchers note its measurements and its sex, then tag and release it.

The seven species sampled in the study are the large-bodied sandbar, blacktip, spinner and tiger sharks, and the smaller Atlantic sharpnose, blacknose and bonnethead sharks.

"The Chesapeake Bay is actually a nursery for the sandbar shark," Peterson said. "So we do see a lot of big, pregnant mothers coming in at the beginning of the summer season to pup and give birth, and then the young remain in the area throughout the rest of the summer."

Earlier indications from shark bycatch rates and smaller-scale surveys were that overfishing of sharks had dropped some populations by 60 percent to 80 percent by the 1990s. One species of hammerhead, said Peterson, had declined by as much as 99.9 percent.

Coastal shark surveys are typically conducted rather piecemeal — state by state — with a broader survey conducted every third year by the National Marine Fisheries Service.

But VIMS fisheries scientist Rob Latour said such approaches don't provide updated information or could be missing the bigger picture of animals that are distributed over a wide area and move seasonally up and down the coast.

"So our approach involved trying to come up with a clever way to combine the information from all the smaller-scale data sets to get a broader assessment of what the population ... might actually be doing through time," Latour said.

VIMS conducts its research survey using the same gear and methods every year, and samples in a random grid, rather than in known shark hot spots, to avoid biases in methodology
. . .
Then computer models estimated population trends over time.

The result is what Latour calls "the most comprehensive analysis of patterns in abundance ever conducted for shark species" common to this region.

"All the large-bodied sharks showed similar population trends, with decreasing abundance from the mid-1970s to the early 1990s," Peterson said. "Then a multiyear period of low abundance, and recent indications of recovery from past exploitation."

Only the blacknose shark showed a decrease, and that was in the Gulf of Mexico, where it's susceptible to bycatch in the shrimp trawl fishery.

Sharks have an especially hard time recovering from exploitation, Peterson said. They grow very slowly, the females don't mature until late in life and they bear a small number of pups.
It's rare to get an actual positive story about fish abundance. Celebrate it when it happens.

Wombat-socho has "Rule 5 Sunday: Whitewashing The Cyborg" ready for your viewing pleasure.

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