This paper presents trends in abundance of adults of Cicindela dorsalis dorsalis Say at all known sites along the Chesapeake Bay shoreline from the 1980s and 1990s through 2014 and provides evidence for causes of these trends. This subspecies was listed as Threatened by the U. S. Fish and Wildlife Service in 1990 because of its extirpation from nearly all of its range north of Maryland and the lack of protection of Chesapeake Bay sites. Adult numbers were estimated during the period of peak abundance using the visual index count method at all known sites. Overall, we found large declines at the western shoreline sites in Virginia and one of two in Maryland and an increase in numbers at Virginia eastern shore sites. Numbers at five Calvert County sites peaked at 6,000 to over 11,000 from 1988 to 1992, but declined to less than 800 adults at one remaining site since 2004. Numbers at the two Maryland Eastern Shore sites, Janes and Cedar Islands, peaked in 2002 at 6,094 at Janes Island and over 2,464 at Cedar Island. From 2009 to 2014, numbers increased progressively to 1,893 at Cedar Island while decreasing at Janes Island to 723. The first two comprehensive surveys of Virginia's western Chesapeake Bay shoreline found over 26,000 adult C. dorsalis dorsalis in 1998 and over 33,000 in 2001 at over 60 sites. These numbers declined to less than 10,000 adults at 34 sites in 2014. By contrast, numbers along Virginia's eastern shoreline increased from a total of 32,143 adults at 35 sites in 1999 to 46,082 at 30 sites in 2009. Observations at these sites over the years provid evidence that the primary causes of declines are shoreline recession from storms, other erosional events and sea level rise, and the addition of shoreline erosion control structures. Human activity and natural enemies were also considered to be important limiting factors at some sites.Much additional study is needed to more conclusively demonstrate the causative factors.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 70 • No. 2