LAUREL, Md. Speculation that the welfare of a small, at-risk shorebird is directly tied to horseshoe crab populations is in part supported by new scientific research, according to a U.S. Geological Survey- led study published this week in Ecosphere, a journal of the Ecological Society of America.
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 -- between Delaware and New Jersey -- during the red knot's northward migration each spring.
"This is one of the first studies to scientifically support the ecological links between these two species," said Conor McGowan, a USGS scientist and the lead author of the study.
The research bolsters the hypothesis that managing horseshoe crab populations and their harvest may help conserve red knots. Most horseshoe crab harvest today comes from the fishing industry, which uses the crab as bait, and 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.
"Our research strongly suggests that the timing of horseshoe crab spawning, not simply crab abundance, is important to red knot refueling during their stops in Delaware Bay," McGowan added.
Horseshoe crab spawning is driven not only by tides and lunar cycles, but also by water temperatures and wave-generating storms. This means that if water temperature
|Contact: Conor McGowan|
United States Geological Survey