USGS Red Knot - Horseshoe Crab Research

According to a U.S. Geological Survey study, ecological links exist between
red knots and horseshoe crab populations

Population health of the red knot, a shorebird species whose population has plummeted over the last 15 years, has been directly tied to the number of egg-laying horseshoe crabs in Delaware Bay during the red knot’s northward migration each spring.

The research appears to support the hypothesis that managing horseshoe crab populations and their harvest may help conserve red knots. Horseshoe crabs are harvested for bait. They are also used in the pharmaceutical industry, which collects their blood for its clotting properties.

The study, which looked at data from more than 16,000 birds over a 12-year period, revealed that the chance of a red knot gaining significant weight after arriving at Delaware Bay is directly related to the estimated number of female horseshoe crabs that spawned during the shorebird stopover period each spring.

Birds that do not gain enough weight tend to have a lower chance of surviving the rest of the year, and in some years the difference between heavy and light bird survival can be large.

The research also found evidence that the annual survival of these birds is not only partly dependent on their body mass when they leave Delaware Bay but is also strongly related to snow conditions when the birds reach their arctic breeding grounds.

The research, Demographic consequences of migratory stopover: linking red knot survival to horseshoe crab spawning abundance, was authored by Conor McGowan (USGS), James Hines (USGS), James Nichols (USGS), James Lyons (U.S. Fish and Wildlife Service) and others.

It was published in this month’s edition of Ecosphere, a new open-access journal of the Ecological Society of America. The article is available online.

source: USGS

Chesapeake Bay Ghost Pot Removal Program

In the Chesapeake Bay, commercial watermen have hauled up more than 10,000 derelict so-called “ghost pots,” lost fishing nets, and assorted metal junk from the Chesapeake Bay and its tributaries in the third year of Virginia’s one-of-a-kind Marine Debris Removal Program.

The program, funded by NOAA through the Virginia Marine Resources Commission and administered by the Virginia Institute of Marine Science, paid the watermen to use side-imaging sonar units to detect and retrieve lost or abandoned crab pots and other marine debris that litter the Bay floor.

Many of the recovered pots had been derelict for several years, and continue to inadvertently trap and kill crabs and a variety of fish and wildlife.

The recovered crab pots were found to have captured over the winter more than 11,000 animals, including thousands of crabs, as well as turtles, fish, eels, and whelks. Scientists have determined that each functional lost crab pot can capture about 50 crabs a year.
 
The program costs roughly $1 million a year. It is funded by NOAA through blue crab disaster funds made available to the Virginia Marine Resources Commission. Recovered marine debris are disposed of or recycled.

Since the Marine Debris Removal Program began in December 2008, more than 28,000 lost or abandoned crab pots have been removed from the water, as well as 150 lost fishing nets and 1,300 pieces of assorted metal junk. More than 27,000 animals, many already dead, were found in crab pots retrieved since 2008.

More information on the program’s results can be found on the program’s website http://ccrm.vims.edu/marine_debris_removal/index.html

source: VMRC