Effects of Horseshoe Crab Harvest in Delaware Bay on Red Knots: Are Harvest Restrictions Working?

[ "Lawrence J. Niles (e-mail: ) is chief biologist with the Conserve Wildlife Foundation of New Jersey in Bordentown."]; [ "Jonathan Bart is a research wildlife biologist with the US Geological Survey, Forest and Rangeland Ecosystem Science Center, Snake River Field Station, in Boise, Idaho."]; [ "Humphrey P. Sitters is an editor with the International Wader Study Group Bulletin in Exeter, United Kingdom."]; [ "Amanda D. Dey is principal zoologist, and Kathleen E. Clark is supervising zoologist, at the New Jersey Division of Fish and Wildlife, Endangered and Nongame Species Program, in Trenton."]; [ "Phillip W. Atkinson is research manager, Nigel A. Clark is head of projects, Jacquie Clark is head of ringing, and Simon Gillings is a research ecologist, all with the British Trust for Ornithology in Norfolk, United Kingdom."]; [ "Allan J. Baker is head of the Department of Natural History of the Royal Ontario Museum in Canada."]; [ "Karen A. Bennett is program manager, and Kevin S. Kalasz is a wildlife biologist, with the Delaware Division of Fish and Wildlife, Natural Heritage and Endangered Species Program, in Dover."]; [ "Albert S. Gates is from Princeton, New Jersey."]; [ "Patricia M. González is coordinator, Fundacion Inalafquen in Rio Negro, Argentina."]; [ "Daniel E. Hernandez is an assistant professor of biology at the Richard Stockton College of New Jersey."]; [ "Clive D. T. Minton is with the Victoria Wader Studies Group in Melbourne, Australia. R. I. Guy Morrison is a research scientist (National Wildlife Research Centre, Carleton University), and R. Ken Ross is head of the population management unit (Ontario Region, Ottawa), with the Canadian Wildlife Service."]; [ "Ronald R. Porter is from Plymouth Meeting, Pennsylvania. C. Richard Veitch is from Papakura, New Zealand."]
BioScience (Impact Factor: 5.44). 02/2009; DOI: 10.1525/bio.2009.59.2.8

ABSTRACT Each May, red knots (Calidris canutus rufa) congregate in Delaware Bay during their northward migration to feed on horseshoe crab eggs (Limulus polyphemus) and refuel for breeding in the Arctic. During the 1990s, the Delaware Bay harvest of horseshoe crabs for bait increased 10-fold, leading to a more than 90% decline in the availability of their eggs for knots. The proportion of knots achieving weights of more than 180 grams by 26–28 May, their main departure period, dropped from 0.6–0.8 to 0.14–0.4 over 1997–2007. During the same period, the red knot population stopping in Delaware Bay declined by more than 75%, in part because the annual survival rate of adult knots wintering in Tierra del Fuego declined. Despite restrictions, the 2007 horseshoe crab harvest was still greater than the 1990 harvest, and no recovery of knots was detectable. We propose an adaptive management strategy with recovery goals and annual monitoring that, if adopted, will both allow red knot and horseshoe crab populations to recover and permit a sustainable harvest of horseshoe crabs.

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