The Fate Of The Knot and the Horseshoe Crab.

Knots are robin-sized sandpipers that spend their summers nesting and breeding in the Arctic. Come fall, these birds then head down to different winter spots around the world, including Tierra del Fuego in Argentina. That's an 18,000 mile trip. "So demanding is the journey," writes Wilcove, "that the knots actually shrink the size of their intestines and other internal organs during the migratory period in order to reduce their flying weight."


The crucial mis-step in the tale is a bad layover in Delaware and the taking of Horseshoe Crabs when:

"Their ability to go on a sustained eating binge while at the bay is due entirely to another creature: the horseshoe crab. These bizarre animals are among the oldest on Earth."

But because:
"During the 1990s, commercial fishing for horseshoe crabs increased dramatically. People were capturing the crabs and selling them as bait for the more profitable eel and whelk fisheries. For some reason, the odor of egg-laden female horseshoe crabs (or pieces thereof) is deeply alluring to eels; either male or female horseshoe crabs works well for the less picky whelks. The annual harvest of horseshoe crabs rose from approximately 800,000 pounds in 1993 to nearly 6.4 million pounds in 1998. Over the same time period, however, the density of crabs (measured in terms of the number captured per net tow) fell sharply. The inescapable conclusion is that fishers were depleting Delaware Bay's horseshoe crab population, causing a reduction in the number of horseshoe crab eggs upon which the shorebirds feed.

"[After a 'Let's do some more studies' interval] state and federal authorities began to take action. They reduced the allowable harvest of horseshoe crabs, and they prohibited any harvest at all during the period when the shorebirds are visiting. As a consequence, the overall harvest of horseshoe crabs dropped by 62 percent between 1998 and 2003. The states of New Jersey and Delaware went even further: in 2006, they declared a two year moratorium on the harvest of all horseshoe crabs."

And then:

I wrote Wilcove to find out what happened. The horseshoe crab population has stopped crashing. It's even bounced back a little. As for the birds, he writes, "The tally of knots in Delaware Bay was 15,000 in the spring of 2008, jumping to 24,000 in 2009." That's huge. Too huge, Wilcove thinks. The 2010 tally isn't in, "but preliminary reports placed it at around 15,000 knots." So whatever is going on, the knots aren't disappearing as fast as they used to.

So what do we make of all this? Wilcove seems to think the red knot population has stabilized. "As to whether they are increasing, that won't be known until we have a few more years of data."

The lesson here is that all over the world, habitat destruction, human predation, over-exploitation and climate change are threatening migrant animals, but every so often, however improbably, what's broken can be repaired … at least a little.

Last Edited by Goodbye2You on 04/28/2011 02:27 PM