Bay Journal

Chesapeake’s blue crab population at highest level in 4 years

Scientists point out that number is below target levels; fishery managers call for loosening of harvest limits

  • By Karl Blankenship on April 12, 2016
  • Comments are closed for this article.
Winter dredge survey finds 35 percent increase in blue crab population over last year's tally. A researcher tallies the count from a dredge during the winter crab survey.  (Dave Harp)

The Bay’s blue crab population increased to its highest level in four years, and the number of spawning-age females — a key ingredient for future abundance — nearly doubled from last year, according to survey results released Tuesday.

Results from the annual winter dredge survey conducted by Maryland and Virginia put the Bay’s crab population at 553 million, a 35 percent increase from last year’s tally, and the greatest number seen in the Chesapeake since 2012.

Fishery managers in both states said the good news may warrant some loosening of harvest restrictions imposed during recent low years, but cautioned against expecting large changes.

“The higher abundance level means that we have a little more wiggle room,” said John M.R. Bull, commissioner of the Virginia Marine Resources Commission.

But fishery managers and scientists cautioned that while the spawning age female estimate of 194 million is the highest number of spawners since 2010, it remains below the recommended target of 215 million — number that scientists say would help maintain a healthy, more stable population.

As a result, Bull said, any regulation changes would likely be modest.

“I think we can go a little bit. I don’t think we can open up the flood gates,” he said. “I would hate to see the gains and improvements that we’ve made be lost in one year due to over-exuberance.”

Likewise, Dave Blazer, fisheries director with the Maryland Department of Natural Resources, also said the uptick in crab numbers could allow for a “modest adjustment” to current regulations.

Blue crabs are the Bay’s most valuable commercial species, but persistent low numbers of crabs spurred Maryland and Virginia to enact strict harvest limits in 2008 aimed at improving the survival rate for female crabs, thereby allowing more of them to spawn in summer and fall. Those regulations have since been further tightened as poor survey results in recent years led to record low harvests in 2013 and 2014.

Preliminary Baywide harvest estimates for last year ticked up to about 50 million pounds, including 21 million in Virginia, 26.7 million in Maryland and 2.2 million in the Potomac River, officials said. That was a 40 percent increase from the 35 million Baywide harvest in 2014, the lowest catch on record.

Robert T. Brown Sr., president of the Maryland Watermen's Association, welcomed the survey results. “This just goes to show that crabs are on the rebound, and it all works in cycles,” he said. Brown noted that underwater grasses also appear to be rebounding, and suggested that water quality may have played a more important factor in crab abundance than recent catch restrictions.

Management is indeed only one factor that affects blue crab abundance. Adult crabs spawn near the mouth of the Bay, and their larvae float in Atlantic coastal waters for weeks before drifting back in as small crabs. Offshore weather conditions during that time greatly influence the number of young that return to the Bay.

Moreover, increased crab abundance does not ensure robust future populations. The 2012 survey found 765 million crabs, a huge increase from the previous year, but harvests fell for three consecutive years after that as crab numbers decreased. Scientists and fishery managers have suggested increased predation and harsh winters caused the decline.

Bull said the population needs to be rebuilt to a level that it can sustain fluctuations caused by weather and predators. “I would like this stock to no longer be on a rollercoaster,” he said.

Regulations enacted in recent years, such as daily bushel limits on crab harvests in Virginia, are helping, Bull said. As crab numbers have increased, those limits force watermen to throw more back into the water, allowing them to survive to reproduce.

“A good number are still going to be caught,” Bull said. “But we are going to be conserving more of them than ever before to reach spawning age.”

Anson “Tuck” Hines, director of the Smithsonian Environmental Research Center and a longtime Chesapeake blue crab researcher, said the survey results show that recent catch restrictions “seem to be working, but it’s not time to let up on good management.”

“While these are good news indicators in the short term,” he said, “in the longer term they are still well below where the population could be, and arguably should be.”

Ultimately, Hines said, fishery managers should consider moving toward establishing a quota each year that would set an actual limit on the number of blue crabs that can be harvested annually, based on results from the winter dredge survey.

“Fisheries that are well managed are increasingly those fisheries that have a quota paired with a good fishery independent tracking system,” Hines said.

Such a system is especially important to allow managers to better respond to population fluctuations in short-lived species such as blue crabs, he said.

The Chesapeake Bay Watershed Agreement, signed in 2014, calls for states to evaluate the potential for establishing a Baywide allocation system by 2018, which would set annual harvest levels.

The Chesapeake Bay Stock Assessment Committee, a panel of scientists and fishery managers supported by the National Oceanic and Atmospheric Administration’s Chesapeake Bay Office, is reviewing the results of the survey and will make recommendations later this summer about future management and research needs.

The winter dredge survey has been conducted annually since 1990 by scientists in Maryland and Virginia, who tally crabs dredged from the bottom at 1,500 sites across the Bay from December through March -- when they are buried in mud and stationary. Historically, the survey has provided an accurate snapshot of crab abundance, and is the primary tool for assessing the health of the crab stock.

Bay Journal staffer Timothy B. Wheeler contributed to this article.

This article has been revised to correct state harvest figures.

About Karl Blankenship

Karl Blankenship is editor of the Bay Journal and executive director of Chesapeake Media Service. He has served as editor of the Bay Journal since its inception in 1991. .(JavaScript must be enabled to view this email address).

Read more articles by Karl Blankenship

Comments

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Jake Lakota on April 13, 2016:

When and if the crab harvest reaches the totals of even 60 years ago I will rejoice. It is clear the Bay is still heavily polluted and/or we are taking more than it can sustain. Install a moratorium on catching crabs, either restrict it to just commercial, stop the harvest of females altogether, or stop it completely. And I am sure the rockfish rebound is hurting the crab population. Why have a moratorium on a predator and not the prey?


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