Monitoring Threatened Species and Ecological Communities

16 – Why, what, how much, and is it worth it?^213

Box 16.1. Monitoring to regulate harvesting of horseshoe crabs
to conserve the endangered red knot Calidrius canutus rufa

In the Delaware Bay, USA, the harvest of horseshoe crabs for fisheries’ bait and the
biomedical industry is thought to be impacting red knot Calidrius canutus rufa
populations. The migratory red knots stop over in the bay to feed on horseshoe crab
eggs each spawning season and unregulated harvesting of the crabs was thought to
be a contributing factor in dramatic declines in the red knot population in the

(a)

(b)

Fig. 16.1. (a) Conceptual model of the effect of horseshoe harvest management on red
knot populations. Figure reproduced with permission from McGowan et al. (2015).
(b) Red knots feeding on their migratory stopover in the Mispillion Harbor. Photo:
USFWS, Wikimedia commons.