Horseshoe crab decline threatens shorebird species

February 21, 2006

Each year, the red knot, a medium-sized shorebird, makes a 20,000-mile round-trip from the southern tip of Argentina to the Artic Circle - one of the longest migrations of any bird. And each year from April to June, the red knot stops over in the Delaware Bay to feed on horseshoe crab eggs resulting from the largest spawning of horseshoe crabs found on the East Coast of the United States.

Researchers from Virginia Tech and the New Jersey Division of Fish and Wildlife have documented a reduction in the number of red knot birds throughout the Delaware Bay tied to a decline in horseshoe crabs.

The research will be reported in The Journal of Wildlife Management, in the article, "Horseshoe Crab Eggs Determine Red Knot Distribution in Delaware Bay Habitats," by Virginia Tech fisheries and wildlife research scientist Sarah Karpanty, professor Jim Fraser, and associate professor Jim Berkson, New Jersey Division of Fish and Wildlife biologists Lawrence Niles and Amanda Dey, and Virginia Tech statistics professor Eric Smith. The article provides scientifically defensible information for wildlife management officials as well as for other members of the scientific community.

During their Delaware Bay stopover, the red knot nearly doubles its body mass as it gorges itself almost exclusively on horseshoe crab eggs. The purpose of this feeding frenzy is to ensure that the shorebirds have enough energy to complete the trip north to their breeding ground in the Artic.

However, due to horseshoe crab's popularity as bait used by fishermen, the crabs appear to be in serious decline. At the same time, there has been a great reduction in the total population of red knots, the report notes. "The number of horseshoe crab eggs was the most important factor determining the use of the beaches by red knots. The availability of horseshoe crab eggs was even more influential than the presence of human disturbance, predator occupation, and availability of other types of food," says Karpanty, a post-doc in the College of Natural Resources.

The red knot's dependence on the horseshoe crab for survival has attracted the interest of local, state, and international wildlife management officials and researchers. Due to the red knot's unusual migratory and eating behaviors, scientists from as far away as Australia frequently travel to the Delaware Bay to study this rare species.

"Biologists with the Delaware and New Jersey divisions of fish and wildlife have been very helpful during this project, and they welcome researchers from all over the world," says Fraser. "We hope to see collaborative efforts like this continue so that we can learn how to better manage wildlife resources like the red knot and horseshoe crab."
-end-


Virginia Tech

Related Fish Articles from Brightsurf:

Fish banks
Society will require more food in the coming years to feed a growing population, and seafood will likely make up a significant portion of it.

More than 'just a fish' story
For recreational fishing enthusiasts, the thrill of snagging their next catch comes with discovering what's hooked on the end of the line.

Fish evolution in action: Land fish forced to adapt after leap out of water
Many blennies - a remarkable family of fishes - evolved from an aquatic 'jack of all trades' to a 'master of one' upon the invasion of land, a new study led by UNSW scientists has shown.

How fish got onto land, and stayed there
Research on blennies, a family of fish that have repeatedly left the sea for land, suggests that being a 'jack of all trades' allows species to make the dramatic transition onto land but adapting into a 'master of one' allows them to stay there.

Fish feed foresight
As the world increasingly turns to aqua farming to feed its growing population, there's no better time than now to design an aquaculture system that is sustainable and efficient.

Robo-turtles in fish farms reduce fish stress
Robotic turtles used for salmon farm surveillance could help prevent fish escapes.

Heatwaves risky for fish
A world-first study using sophisticated genetic analysis techniques have found that some fish are better than others at coping with heatwaves.

A new use for museum fish specimens
This paper suggests using museum specimens to estimate the length-weight relationships of fish that are hard to find alive in their natural environment.

Reef fish caring for their young are taken advantage of by other fish
Among birds, the practice of laying eggs in other birds' nests is surprisingly common.

Anemones are friends to fish
Any port in a storm, any anemone for a small fish trying to avoid being a predator's dinner.

Read More: Fish News and Fish Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.