Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Research shows denser seagrass beds hold more baby blue crabs

Study is first to link habitat quality and juvenile-crab density over large areas

When it comes to nursery habitat, scientists have long known that blue crabs prefer seagrass beds compared to open areas in the same neighborhood.

The researchers used a powerful vacuum called a suction sampler to collect blue crabs from seagrass beds during their study. Plover is the name of a VIMS vessel.

A new study by researchers at the Virginia Institute of Marine Science refines that knowledge, showing that it’s not just the presence of a seagrass bed that matters to young crabs, but also its quality—with denser beds holding exponentially more crabs per square meter than more open beds where plants are separated by small patches of mud or sand (compare images).

The study, led by VIMS graduate student Gina Ralph, appeared in the August issue of Marine Ecology Progress Series. It is co-authored by VIMS Marine Scientist Kathleen Knick along with faculty members Rochelle Seitz, Robert “JJ” Orth, and Rom Lipcius.

“Vegetated habitats, particularly marsh and seagrass, have long been known as nurseries for blue crabs,” says Ralph, “with many previous field and lab studies showing higher density, survival, or growth of juveniles in seagrass habitats compared to un-vegetated areas nearby.”

“Our study,” she adds, “is one of the few to address the role of habitat complexity within seagrass beds, and the first to show on a broad scale that—all else held equal—denser, higher-quality grass beds hold more juvenile crabs.”

Ralph says that on average, “there were 30% more crabs for every 10% increase in the percentage of seagrass cover within a bed during 2007, and 14% more crabs for each 10% increase in seagrass coverage in 2008.”

Ralph says the team’s findings are important because they “suggest that the quality of seagrass habitat can influence the population dynamics of blue crabs on a baywide basis.” That raises concern given the historical decline in eelgrass—the Bay’s main seagrass species—and projections of the continued decline of this cool-water species as water temperatures rise during the coming decades due to climate change.

“The potential for a future disappearance of eelgrass from the Bay is quite disconcerting given that the blue crab fishery was declared a federal disaster in 2008 and only recently recovered due to management actions by the Virginia Marine Resources Commission and other agencies in the Bay,” says Lipcius. Tempering the team’s concern are studies suggesting that blue crabs may also be able to use other, more heat-tolerant species like widgeon grass for nursery habitat as the Bay warms.

The team conducted the fieldwork for their study between 2007 and 2008, recording blue crab numbers and the percentage of seagrass coverage at 104 randomly selected sites along the eastern and western shores of the lower Bay.

Team members caution that their study was conducted at a time when historically low numbers of juvenile blue crabs were entering the population each year, likely due to overfishing and environmental factors. That might help explain one of the study’s more unexpected results: contrary to basic ecological theory, the observed increase in the number of crabs did not level off as seagrass coverage approached the highest levels.

“The crab’s lack of a threshold response to vegetation cover could have been caused by low densities of juveniles overall,” says co-author Lipcius. “We’d like to repeat our study during a period of high recruitment to test the generality of the findings.”

The good news is that they may be able to do that fairly soon, given the growing number of adult females in the Bay since 2008 in response to the fisheries management framework established that year. Each adult female spawns an average of three million new crabs each brood, and releases about three broods per year.

David Malmquist | EurekAlert!
Further information:

Further reports about: Lipcius Marine science VIMS blue crabs water temperature

More articles from Ecology, The Environment and Conservation:

nachricht Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel

nachricht Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>