Application of Local Area Estimation Using Kriging to Provide Abundance Estimates of Blue Crab in Chesapeake Bay in Support of Management of Dredged Material

Abstract Competition among US ports to support larger container vessels is increasing needs for dredging in coastal ecosystems, which may conflict with provision of other ecosystem services. For example, the need to place materials dredged from approach channels in the Chesapeake Bay to the Port of Baltimore may compromise habitat quality for mature blue crab ( Callinectes sapidus ) during winter months. To assess the impacts of these important competing uses, we applied a common geostatistical approach, kriging, to estimate the abundance of blue crab in the Wolf Trap Approved Placement Site (WTAPS) and its northern extension (WTAPSNE). Data on crab abundance from an annual winter dredge survey for 1990–2020 was used to estimate both total adult and mature female abundances Baywide and for WTAPS and WTAPSNE to develop worst-case scenarios for the impact of dredged material placement. Total crab abundance in the placement sites was proportional to site area. However, mature female crabs were proportionally more abundant, indicating these placement sites are favored habitats. Analyses indicated that when Baywide female abundance was less than 150 million, the proportion of females in WTAPS was highly variable, and can be 2–3 times higher than would be predicted from area alone. When possible, dredged material placement activities in WTAPS and WTAPSNE should be limited to years when female age-1 abundance is above 150 million.