Scientists Explain Low Blue Crab Harvest - WBOC-TV 16, Delmarvas News Leader, FOX 21 -

Scientists Explain Low Blue Crab Harvest

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WILMINGTON, Del. (AP) - When you look at $200 plus for a bushel of blue crabs, shake your head and say "no way," there's just one thing to do: Blame it on the weather.

And we're not talking about the chilly winter of 2014, either, at least not here in the Delaware Bay. 

Think back to September and October. That's the weather that really matters for blue crabs in estuaries like the Delaware and Chesapeake bays. 

No big northeast winds from tropical storms or hurricanes. 

But in late summer of 2011 - the last banner year for blue crabs in the region - there were two back-to-back storms, Hurricane Irene in late August and Tropical Storm Lee a few weeks later. 

Both brought big winds from the northeast and coastal flooding, ideal conditions for getting baby blue crabs from the deep blue waters of the Continental Shelf back into big estuaries like the Chesapeake and Delaware bays. 

The life cycle of the blue crab is that females migrate to the saltier water in lower Delaware Bay to spawn, outbound tides form a current that transports them away from the coast and then, several weeks later strong, northeast winds push them back toward shore and into the estuaries.

Scientists who figured out this blue crab transport model can't really predict blue crab stock size based on this complex connection between tides, winds and currents in the estuary and ocean because of the many variables in the weather, tides and timing of the crab hatch, along with crab mortality, said Charles Epifanio, Harrington Professor Marine Science at the University of Delaware College of Earth, Ocean and the Environment. 

But, said Epifanio, "our model explains the variations from year to year." 

That said, some crab larvae will always make it back into Delaware or Chesapeake Bay. 

"We're talking huge numbers of larvae here," he said. 

A single female blue crab may produce a million eggs two to three times in her short life, he said. 

"There's always going to be some recruitment" of young crabs back into the system and because crabs are short-lived - typically no more than three years in the wild - rebounds in the population can occur quickly even after a bad year or two. 

State fisheries managers in Delaware anticipated this year's harvest would be off, just as they did the previous summer, because of data they collected during fall surveys. 

Rich Wong, a state fisheries biologist, said that in a normal year, scientists hope to see five or six juvenile crabs, the crabs that grow up to be keepers by the following summer, each time they check the device they use in sampling. 

Last fall, the numbers were less than half of a normal year, just two juvenile crabs on average, he said. And it was the second year in a row where juvenile numbers were off, he said. 

Those September and October surveys "did predict pretty poor fishing," Wong said, adding that it makes him less concerned when the catch was off this spring and summer. 

In Maryland, officials sample wintering crabs in the Chesapeake Bay by dredging them up from the mud. 

Those results, released in May, showed a decline in the number of spawning females. State officials estimated the spawning stock of females at 69 million, just below their target minimum safe number of 70 million established in 2008 as a benchmark of population sustainability. 

Maryland officials estimated that as many as 28 percent of the total wintering crab population died as a result of the cold winter and low water temperatures. 

While Delaware scientists don't conduct winter dredge surveys, a few commercial fishermen in the state do dredge for crabs during the winter. Wong said state officials received no reports from fishermen of excessive winter cold kill. 

Instead, Wong said, the lower density of crabs in Delaware Bay may have more to do with two years of poor recruitment of young crabs and this year, perhaps, a slower pace of maturity because water temperatures stayed a little cooler in the early part of the season. 

"We have been keeping an eye on the fishery," he said. "It's definitely wait and see." 

Wong said that despite the low harvest, state officials anticipate that overall harvests from Delaware Bay will be slightly higher than in 2012.

Typically, he said, the peak of the season is in September and October. By that time, many folks in Delaware are way less interested in buying and eating crabs than they are in the summer. 

Philip DeFebo, at Feby's Fishery in Wilmington, said that crabs were so scarce for the July Fourth weekend that all he could get from his Chesapeake Bay supplier was 10 bushels going into the holiday weekend. 

"There were no crabs to be had," he said. "It was a mess."

The tight supply is beginning to loosen, he said. "It's about a month behind" where it normally is.

 

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