Conserve Wildlife Blog

Posts Tagged ‘horseshoe crabs’

Early days on Delaware Bay – Horseshoe Crabs Just Beginning To Breed as Shorebirds Arrive

Saturday, May 19th, 2018

by Larry Niles

Horseshoe Crabs Just Beginning To Breed as Shorebirds Arrive

 

Delaware Bay horseshoe crab eggs reach sufficient levels to give red knots and other shorebirds a good start on the fat they need to fuel the last leg of their yearly journey in the first week of the stopover ( May 12-19).  Knots need at least 180 grams to fly to the Arctic and breed successfully.  This week we caught birds that weighed 93 grams which is 30 grams below fat-free weight.  These birds had just arrived from a long flight, probably from Tierra del Fuego, Chile or Maranhão, Brazil.  In the same catch, we weighed red knots as high as 176 grams or only 5 grams from the 180-gram threshold.  These birds are probably from Florida or the Caribbean wintering areas and so arrive earlier,  resulting in them having more time to gain weight.  All together it looks like a normal early migration and a modest horseshoe crab spawn, just barely enough for the birds in the bay.

shorebirds in a net

Our team prepares a catch of knots turnstones and semipalmated sandpipers for extraction to keeping cages. The birds will be covered to prevent feather abrasion before extraction (Photo by Stephanie Feigin)

However, we are still short of about half the population.  Our bay wide count won’t take place until next week on May 22 and 26. At this point it looks like we have about 14,000 knots in the bay, of which 8,000 are in New Jersey. In the last 5 years we have had a bay wide population of about 24,000 red knots.  The situation is similar for ruddy turnstones and sanderlings.  The southernly winds of the next few days will almost certainly bring in the rest of the flock by mid-week.

The Stopover Habitat is Growing

 

The condition of the stopover is mixed.

The work of Niles & Smith Conservation Services, Conserve Wildlife Foundation of NJ, and American Littoral Society continues to supply high-quality habitat for horseshoe crabs. We have developed an efficient system for maintaining the essential requirements of a good spawning beach, deep and large grain sand with berm heights that prevent over washing in a way that keeps cost down. First, by creating low oyster reefs to break waves in lower tides, thus protecting beaches from wind waves at low and mid tides.  Second, by placing sand on beaches that typically erode fast losing sands to adjacent creek inlets and the next beach south.  This way we can use one restoration to restore three different places.  For example, Cooks Beach loses sand to South Reeds.

 

restored beach in Delaware Bay

Thompsons beach before and after restoration by American Littoral Society and partners. (Photo by Larry Niles)

Oddly these successes may be contributing to the next big problem for the birds. The state of Delaware has been carrying out much larger scale beach replenishment projects that have added significant new sandy beach for crabs spawning.  At the same time the Atlantic States Marine Fish Commission has failed to deliver on its promise to increase the number of crabs.  The population is still 1/3 below carrying capacity or the number that existed 20 years ago.  The same number of crab divided by more beach equals decreasing crab densities.  Decreasing densities means fewer eggs reaching the surface because crabs are not digging up existing eggs to lay their own.

In other words, we need more crabs.

The Industry Finds New Ways around the ARM Quota

 

But the resource agencies seem perfectly happy to keep killing adult crabs for both bait and bleeding at near historically high numbers. Bait harvests recorded as coming from the bay have stayed the same, however other states such as NY are still taking and landing large numbers of crabs despite having no known crab historic population of their own. Additionally, Virginia states that a crab population still exists in the state, even though most field biologists consider them lost.  The truth is they are very likely taking Delaware Bay crabs and landing them as their own.

The Conservation groups are no longer satisfied with this loose regulation and are calling for regulations similar to those used for Striped Bass.  The Delaware Bay harvest should be restricted to just the quota agreed upon by everyone through the Adaptive Resource Management system.  All other landed crabs should be genetically linked to a source population, and if they do in fact come from Delaware Bay they should be taken out of the ARM quota. No one should be allowed to get away with killing our crabs outside the quota.

Or just stop the senseless killing of these valuable animals as bait for the dying couch fishery.

 

crab eggs graph on Delaware Bay

This graph compares the finding of Botton et al 1994 from horsesoe crab egg surveys done in 1990 and recent counts done in 2017

 

The same goes for the killing of crabs by the companies bleeding crabs.  The industry makes untold millions (the numbers are hidden from the public) but does virtually nothing to conserve the crabs while killing thousands. Their own estimate is well over 65,000 a year, but independent estimates double that.  This killing could also stop because a new synthetic lysate is available and can be used now, potentially cutting the need for natural lysate by 90%.

An Ecosystem Collapse and the Need for More Crabs

 

Why kill such a valuable animal?  It all started because the fishing industries saw little value and figured why not destroy the population until they are no longer economically viable.  Its called economic extinction and sadly it’s a tradition amongst Delaware Bay fishers still carried out this to this day on eels, conch, and other species.  But they didn’t know back in the early 90’s they would wrecking the entire ecosystem.

In 1991, we counted an average of 80,000 horseshoe crabs/meter squared.  Now we count 8,000.  Then the eggs stayed at that level for all of May and June then hatched young at similar densities. In other words, the horseshoe crab was a keystone producer of an abundant resource that maintained the bay ecosystem.  It was not just chance that at the same time the bay has one of the most productive weakfish and blue claw crab fisheries in the Atlantic coast.  Fish populations blossomed with the flush of horseshoe crab eggs and hatched young each year.

Now we must bring it back.  For the birds, for the fish, and for the people who love to bird and fish.

 

storm delaware bay horseshoe crabs

A storm looms over Delaware Bay. The last 4 days have been rain, some intense and cold. The water temperature needs to be 59 degrees or so for Crabs to spawn. On Saturday the 19th the water temperature fell below and the spawn virtually stopped in many places. It should resume with the warmer temperatures of Saturday and Sunday.

We are grateful to the National Fish and Wildlife Foundation and other donors who make this project possible.

Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.

Red knot numbers down in wintering grounds

Monday, February 26th, 2018

The Press of Atlantic City covered the troubling findings of Conserve Wildlife Foundation’s recent expedition to Tierra del Fuego in Chile to survey wintering red knots.

The numbers of red knots – an endangered migratory shorebird that spends every May along New Jersey’s Delaware Bay coast feasting on horseshoe crab eggs – declined by more than 20 percent between the team’s counts last year and this year.

Click here for the full story.

Horseshoe Crab Rescue

Tuesday, May 30th, 2017

What do CWF biologists do in their spare time?

Higher than usual tides last week caused an extraordinary stranding event of Horseshoe crabs all along the Delaware Bay. From Fortesque Cumberland County to beaches in Cape May County horseshoe crabs were washed up into the marshes, tidal flats, roads and other areas where they were unable to get back out to the water.  ReTurn the Favor coordinators jumped into action and after an initial survey of the strandings organized rescues at the various beaches. On Saturday a team met at Pierce’s Point at sunset so as not to disturb feeding shorebirds. The group was made up of ReTurn the Favor coordinators from the Wetlands Institute and volunteers including CWF staff. The group was able to move ~3,000 crabs back to the water in a few hours. Over the next few days, rescue efforts continued at Pierce’s Point and other beaches. Allison Anholt from the Wetlands Institute reports that 7,900 crabs total were rescued at Pierce’s Point.  Thousands of more crabs were rescued at other beaches over the weekend, due to the dedication and help from the various groups and wonderful volunteers involved.

Efforts like this show that caring, dedicated people can make a difference. Thanks to all involved!

Horseshoe Crabs stranded in marsh behind Pierce’s Point beach 5/27/17

 

To Learn More and get involved:

Photo From The Field

Thursday, May 25th, 2017

Shorebirds, eagles, horseshoe crabs and more….

May is a great time to visit the Delaware Bay beaches. The horseshoe crabs are spawning and shorebirds are feeding on the eggs. Please respect the beach closures, so that the shorebirds can feed undisturbed.

Fortescue beach 5/16/17@Bob Bocci

The Importance of water temperatures, windstorms and shoals on the Delaware Bay

Friday, May 19th, 2017

By Dr. Larry Niles, LJ Niles Associates LLC

As we begin our field work on Delaware Bay shorebirds, our 21st season, oddly enough we are once again faced with extraordinary circumstances. As usual, the birds, after various flight of up to 6 days of nonstop flying, arrive in emaciated conditions. For example, in one catch this week we caught several red knots at around 86 grams far lower than normal weight of 130 grams. Putting that into perspective, a woman of 145 pounds would tip the scale at 93 pounds while a male of 175 pounds at 113 pounds! In other words, these birds are desperate to feed on the only prey on which they can build weight fast, the eggs of Delaware Bay horseshoe crabs.

But the various impacts of climate change and destructive forces of sea level rise, storm surge and out of normal weather patterns can wreak havoc on the timing of the horseshoe crab spawn. It messes with the heating and cooling of the bay and when combined with the normal variation one expects in an estuarine system, it creates almost unpredictable consequences.

Adding more uncertainty to this mix is the ongoing harvest of crabs for bait and the irresponsible bleeding by international medical companies. Both kill hundreds of thousands of crabs every year while doing nothing to create new crabs. Their combined impact has put the brakes on any recovery of the population after they both nearly mortally wounded the Bay population in the 1990’s and early 2000’s. Higher numbers of crabs would overcome a lot of early season uncertainty; lower numbers exacerbate them.

And thus, the story of this early part of the shorebird stopover. It starts with the odd weather this April and May. Can everyone remember how warm the weather of this winter? The map below is a reminder that it was one of the warmest on record. The figure below that shows how the Bay’s water warmed early reaching the threshold temperature for horseshoe crab breeding by early May. We trapped sanderling in the first week and were surprised to see a truly great crab spawn on May 4. Thank God for that.

The bays water temperature as measured at the Lewis DE buoy, increased earlier than normal until the first week of May. By that time it reached the threshold for horseshoe crab spawning. But by the second week it plunged as a consequence of the cooler than normal weather.

By the second week of May and yesterday (May 16) temperatures plunged in horseshoe crab world. We generally consider water temperature of near 59 degrees necessary for crabs to spawn in great numbers. We reached 62 degrees on May 4, then it went down to 58 degrees, lingering there for five crucial days.

At the same time, we suffered brutal westerly winds. Wind from this direction gins up waves on Delaware Bay that crash against many of the important crab spawning beaches. Crabs don’t spawn in waves.

Westerly winds turn the Delaware Bay into a tumult of breaking waves because of its relative shallow depth. Horseshoe crabs won’t breed in breaking waves

And just as the first flush of shorebirds came to the Bay, over 5,000 red knots on the New Jersey side, all the spawning shut down. All tried desperately to find enough horseshoe crab eggs to regain lost weight and begin the process of doubling their body weight.

Fortunately, breaking waves and cold water will prevent crabs from spawning on the beaches but not in the intertidal creeks. One of the key features of the New Jersey bayshore are its abundant tidal creeks. Most drain only tidal watersheds, draining and filling marshes twice every day. Naturally they build sand shoals because sand moves around the Bay generally in a south to north direction along the Cape May peninsula. When sand encounters the currents of the creeks, it settles forming shoals.

A small creek just north of Dennis Creek on Delaware Bay. The tidal creek mostly drain tidal marsh, the daily ebb and flow warming the waters making crab spawning possible when the bay waters are too cold

These shoals support most shorebirds during these early days. This is so because the intertidal flow of water into the marsh and out again warms the water that flows over the shoals. The shoals themselves are practically paradise for breeding crabs because of the loosely consolidated and large grain sand. They breed with abandon laying eggs in the shifting sands that brings many of the eggs to the surface where shorebirds can prey upon them. And they do.

This diagram by Joe Smith shows how the creeks of Delaware Bay create superior spawning and shorebird foraging habitat. Sand movement on the Cape May section of the bay moves northward because of tidal currents. This moves sand from south to north. When the American Littoral Society and CWF placed sand on Pierces, Kimbles and Cooks beaches, some part moved northward to the adjacent beaches. Ultimately it ended up on south Reeds making it a great spawning site. But on the way the sand falls out of the current and settles on the creek shoals. These shoals are large grain sand, loosely consolidated, making them perfect for crab spawning. At the same time the shoals shift exposing eggs to the sea, thus making them available to the birds. This is why the shoals are among the most important habitat on the bay.

This is what happens in the early days of this season. It was nip and tuck for most of the scientists, not knowing if the shoal resources would hold up to an ever-growing number of shorebirds arriving in desperate condition.

But today (May 19) we enjoyed warmth with the promise of the season back on track.

In the last 5 days, we were able capture enough knots, turnstones and sanderlings to track conditions and add new flags to the population for a later determination of population size. Despite adversity, so far so good. The data for each species is below.

Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.


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