Monday, November 7, 2016

Blue Crab Travels: Studying Tags Offers Insights into Crab Habitats and Dispersal

From the Maryland Sea Grant Fellowship Experiences: A Student's Blog

Robert Semmler
September 15, 2016
If you caught a blue crab on the Chesapeake Bay during the past year or so, you might have seen one with a pink plastic tag attached to its shell. I’m part of a scientific research team who asked fishers and watermen to report those tags, and I am glad to report that those calls and e-mails are contributing to a better understanding of the Bay’s blue-crab population and how to sustain it.

The tags were part of a scientific study I was involved in to improve knowledge about where adult male crabs travel in the Bay. In summer 2015 I wrote on this blog about the efforts that my lab and I went through to organize and undertake this large-scale crab tagging experiment. Since then, I and the other members of the Fish and Invertebrate Ecology Lab (a.k.a. “The Crab Lab”), at the Smithsonian Environmental Research Center, have completed our work to release the tagged crabs tagging efforts across Maryland, with 8,741 adult blue crabs tagged in total. As expected, it meant a lot of early mornings with a few pinched fingers along the way.

Read the rest of the story at Maryland Sea Grant Fellowship Experiences: A Student's Blog

Tuesday, October 18, 2016

Should female sponge crabs be harvested?

Here's a recent look at the question by Pamela D'Angelo at  the newly established Chesapeake: A Journalism Collaborative.

The Atlantic blue crab, Chesapeake Bay’s signature crustacean, has been through tough times in the last 20 years. Some recent improvement has been credited to restrictions on harvesting females. Yet Virginia still allows the harvest of egg-bearing females, something Maryland banned back in 1917. The reasons why seem to be wrapped up in economics.
In late June, Ida Hall, a commercial waterman was pulling crab pots from creek just inside Virginia’s western shore of the Chesapeake Bay. As she sorted large from small male crabs she also tossed egg-bearing females, called sponge crabs, into a separate basket... Read the rest of the article here.

Wednesday, April 13, 2016

Chesapeake Blue Crab Population Increases in 2016

The blue crab population in Chesapeake Bay has increased to some of the highest levels in recent decades. It's likely to be a strong crab harvest, but it's too early to claim victory in efforts to rebuild the blue crab stock. The mature female spawning stock remains below the target of 215 million crabs and juvenile abundance was about average. While these numbers are encouraging, maintaining the current management strategy of protecting the female spawning stock is important to sustain the rebuilding effort.

Read more about the results at the Bay Journal.

Saturday, March 5, 2016

Baby Blue Crabs Blown into Chesapeake Bay

Maryland Sea Grant highlighted new research from colleagues at University of Maryland's Horn Point Lab on how important weather is for helping baby blue crabs migrate from the ocean into bays and estuaries.

New Clues to How Crab Babies Make It Back to the Bay

crab megalopa on a transparent ruler

Daniel Pendick • February 29, 2016
Every spring, female crabs near the mouth of the Chesapeake Bay spawn their young. Nearly all of the hatched larvae are swept into the open ocean by outflowing surface water. Adrift in the sea, they feed on even tinier marine creatures and speed through seven growth spurts over a month or so. Finally, as the little swimmers are just starting to look like crabs, some of them manage to make it back into the Bay and get a chance to grow into adults. 
Chesapeake Bay scientists have spent decades trying to figure out how these boomerang babies — larval crabs called megalopae — get back to the estuary. Are they carried in by nighttime tides? By underwater currents? Or by massive wind-driven inflows of ocean water? In search of answers, scientists mounted two research cruises in 2005 and 2006 to gather new data on the crab homecoming in the Chesapeake and Delaware Bays. Understanding these details might someday help regulators to fine-tune management of crab harvests...

Tuesday, October 13, 2015

Blue Crab Blog Reaches 100,000 Page Views

I want to take a moment to thank you, the readers for your continued interest in this blog. The site crossed the 100,000 page view benchmark over the weekend!

Photo Essay on the Chesapeake Blue Crab Industry

Blue crabs and the watermen who fish for them are icons of the Chesapeake Bay. Check out the great photos and story about the challenges faced by the fishery in the photo essay posted today by Reuters. It highlights some of the work my lab is doing to understand the movements and migrations of crabs.

Friday, September 4, 2015

New Study Shows Female Blue Crabs Spawn in the Ocean in Southeast US

Long thought to spawn at the mouths of bays and rivers, we're now finding out that blue crabs spawn in the ocean in some places. My latest research, highlighted in Coastal and Estuarine Science News,  shows that many or even most female blue crabs spawn in oceans waters in the Southeast US. Off the coasts of Georgia and South Carolina, female sponge crabs like the ones in the photo are found at least as far as 8 nautical miles from shore. Other researchers in Louisiana have found female blue crabs even further from shore (read more here).

Why are they going to the ocean to spawn? It's most likely that they are just looking for the salty water (salinity >25) that their larvae need to survive and grow during the first month or two of life. In places like Chesapeake Bay and Delaware Bay, these salty conditions occur within the bay mouth. In much of the Southeast US and Gulf Coast, the same conditions occur mainly in the coastal ocean.

We've known for some time that blue crab larvae spend part of their first months in the ocean where temperature and salinity are relatively constant. Now that we know there are important spawning grounds in the ocean, we need to take a closer look at how many females are there and what they are doing.

The new study also notes a substantial decline in abundance of females in offshore areas since at least 1986. Understanding what this means will be important for ensuring sustainable crab fisheries throughout the Southeast US.

Here's a link to the scientific paper in Estuaries and Coasts.