The red knot, a migratory shorebird, has long fascinated scientists and bird enthusiasts with its epic biannual flights between the southern tip of South America and the Arctic.
It’s a feat requiring great stamina. And the Delaware Bay plays a key role. It is “the single most important spring stopover habitat, supporting an estimated 50% to 80% of all migrating red knots” annually, according to the U.S. Fish and Wildlife Service.
That’s because the bay has an abundance of horseshoe crab eggs, a crucial food source for red knots (subspecies rufa). The eggs allow the birds, sometimes emaciated upon arrival, to essentially double their body weight before continuing their trip.
Red knots are listed as threatened under the Endangered Species Act. According to conservation groups, last year’s spring count of red knots along the Delaware Bay was at its lowest since 1982.
The same groups are warning that proposed changes to Delaware Bay horseshoe crab harvesting rules could place the red knot population in further peril.
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On Wednesday, the Atlantic States Marine Fisheries Commission will consider changes to how it determines the number of horseshoe crabs that can be harvested annually from the Delaware Bay.
New Jersey Audubon, Earthjustice and Defenders of Wildlife penned a letter to the commission claiming the revisions will likely lead to a violation of the Endangered Species Act related to red knots. Delaware Audubon is “in full support” of their stance.
Potential violation of the Endangered Species Act
Each year, Delaware Bay horseshoe crab harvest numbers are determined by the commission’s Adaptive Resource Management framework, which links the harvest number to the bay’s red knot stopover population.
Figures from the Virginia Tech Horseshoe Crab Trawl Survey, endorsed by the U.S. Fish and Wildlife Service, have been used to determine population levels since the framework was implemented, according to a letter from the conservation groups to the commission. The revision proposes to add numbers from New Jersey and Delaware state surveys to the formula used to determine the population level.
Using the state surveys as part of the ARM framework “will generate significantly higher horseshoe crab population estimates based predominantly on surveys that are not purpose-designed to count horseshoe crabs,” according to the letter.
Presently, the framework prohibits the harvest of female horseshoe crabs until the region hosts at least 81,900 red knots or 11.2 million female horseshoe crabs. Another problem with the proposed revisions, the groups say, is the elimination of those constraints.
“The model was designed not to select for female harvest until either the female horseshoe crab or the red knot population recovered to a specified threshold, which neither species has done,” the letter states.
“Applying the revised framework would likely yield an immediate authorization for female horseshoe crab harvest in the range of 175,000 to 190,000.”
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The commission hasn’t allowed the harvest of females for the past decade, something the Delaware Center for the Inland Bays also expressed concern over. Executive Director Chris Bason said their research has shown the same horseshoe crabs that breed in the Delaware Bay breed in the inland bays.
“The center does not support approval of a harvest package that allows harvest of female crabs,” Bason said.
According to the conservation groups, the changes could significantly impair red knot breeding and feeding activities, potentially amounting to a violation of the Endangered Species Act.
Why adjust the model?
The ARM framework revisions come at the recommendation of two commission bodies, the Horseshoe Crab Management Board and Technical Committee.
The framework is due for a routine upgrade, according to Atlantic States Marine Fisheries Commission spokesperson Tina Berger.
“It is now 10 years in, and the software and platform that supports the model is obsolete. Since then, there have been advances in modeling approaches and more robust region-specific data,” she said.
“This revision of the ARM Framework represents several advancements in not only the knowledge of the population dynamics of horseshoe crabs and red knots but also how to efficiently model them.”
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The U.S. Fish and Wildlife Service issued a statement in support of the revisions, as well.
“To effectively conserve red knots, we need to consider new information and methods that build on what we have learned from previous management outcomes,” wrote spokesman David Eisenhauer. “That’s why—with a decade of new data on both red knot and horseshoe crabs, and advances in modeling techniques—the Atlantic States Marine Fisheries Commission decided to update the framework.”
The commission will hold its winter meeting virtually Jan. 25-27. They’ll consider the framework revisions, as well as a peer review of those revisions, Jan. 26.
If they choose to go forward with the revisions, a draft document would be created and released for public comment before any action is taken, Berger said.
