Papers by Donna Marie Bilkovic
Elsevier eBooks, 2019
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Ecological Engineering, 2022
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Understanding the relative level of stress from human disturbance on a wetland's capacity to ... more Understanding the relative level of stress from human disturbance on a wetland's capacity to perform valued ecosystem services is often part of a cumulative impact analysis associated with wetlands conservation. The ability to rapidly census wetland condition at multiple scales is attractive to resource managers, planners, and other stakeholders. Some methods assess wetland condition by levels or tiers that become subsequently finer and more data intensive down to the individual wetland scale. The Virginia Wetland Condition Assessment Tool (WetCAT) is a method that uses different levels of onsite data collection intensity to calibrate and validate remotely sensed data to develop a model that assesses wetland capacity to perform ecosystem services. To develop a repeatable, landscape-level census of wetland condition, we analyzed the surrounding landscape characteristics of all the National Wetlands Inventory (NWI) mapped nontidal wetlands in Virginia (n = 167,004), field assessed...
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Marine Policy, 2021
Abstract Local, national, and international efforts to address the issue of derelict fishing gear... more Abstract Local, national, and international efforts to address the issue of derelict fishing gear are often limited by resources and costs. Managers and policymakers have implemented various preventative, impact reducing, and curative measures to decrease derelict fishing gear abundance and impacts, but stakeholder support is essential for success. To identify stakeholder preferences and the most efficient measures to address the issue of derelict blue crab pots in Chesapeake Bay, we distributed a stated preference survey with a discrete choice experiment to 1,032 licensed commercial fishers in Virginia and received a 42% response rate. The choice experiment consisted of hypothetical scenarios with two alternatives that included a combination of derelict pot mitigation activities potentially paired with incentives, and a third alternative for maintaining the status quo. The probability that the average respondent would participate in derelict pot mitigation activities ranged from 0.46 (SE=0.07) for “Recycle at facility on land,” to 0.03 (SE=0.02) for “Pot modification.” Willingness to accept estimates were similarly variable, ranging from US $61 (SE=129) to participate in “Recycle at facility on land,” to US $1,449 (SE=359) for “Pot modification.” Non-monetary management incentives (e.g., bushel limit increase, pot limit increase, or season extension) generally did not induce participation in mitigation activities; however, heterogeneity observed in preferences of fishers could be used to target different segments of the population to participate in specific actions. Addressing the complex problems caused by marine debris, especially derelict fishing gear, is costly, and understanding stakeholder preferences and decision-making can help identify the most cost-effective solution.
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Ocean & Coastal Management, 2021
Abstract Derelict fishing gear is a growing concern in many fisheries and coastal communities. Po... more Abstract Derelict fishing gear is a growing concern in many fisheries and coastal communities. Pots and traps are prevalent forms of derelict fishing gear with numerous documented harmful effects. In the Chesapeake Bay, US, a large blue crab (Callinectes sapidus) pot fishery produces high levels of derelict gear. From 2008 to 2014, 34,408 derelict pots were removed from blue crab fishing areas in Virginia. This research first evaluates whether observed increases in catch rates occurring contemporaneously with the removal program were the result of derelict gear removals. An econometric production model is then used to estimate marginal removal benefits and assess optimal removal levels. Fishing locations with removals during the removal program were estimated to have experienced increases in harvest per pot and harvest per trip of 22.35% and 34.68%, respectively. Optimal removal levels were found to depend on location-specific fishing effort, with high-effort areas yielding greater marginal removal benefits. Fishery productivity gains, though large, were found to last only one year following removals. Assuming a removal cost of $100/pot, the optimal level of removals was estimated to be over 7000 pots/year and would generate productivity gains of ~17–18%, yielding over US $3M in annual net benefits to the commercial fishery. Optimizing mitigation and management strategies for derelict fishing gear and marine debris requires quantitative assessment of the benefits and costs of alternative policy measures.
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Estuaries and Coasts, 2017
Experiments were completed in SE Virginia during June–July 2014 and 2015 to examine the responses... more Experiments were completed in SE Virginia during June–July 2014 and 2015 to examine the responses of blue crabs (Callinectes sapidus) and diamondback terrapins (Malaclemys terrapin) to commercial-style crab pots modified in visual and other ways that might attract and retain crabs while excluding terrapins as by-catch. In a seawater tank, far fewer crabs entered crab pots fitted with red plastic by-catch reduction devices (BRDs), relative to pots without BRDs. Crab retention times, however, were significantly longer in pots fitted with red BRDs. In a second experiment, fewer terrapins entered crab pots with funnels painted red relative to black. From a field pilot study, the legal crab catch from pots with red BRDs was similar to pots without BRDs, and terrapin by-catch was reduced. Relative to those treatments, fewer crabs and more terrapins were captured in pots with orange BRDs and blue BRDs, and in pots with a magnetic field directed into the funnel openings. Based on these results, a final field trial yielded comparable crab catch from 15 pots without BRDs and 15 pots fitted with red plastic BRDs. Of a by-catch of 68 terrapins, 58 were from pots without BRDs. The structure and color of BRDs can exclude most terrapins; because crab retention rates are high, the net effect of BRDs on crab catch is relatively minor, even though fewer crabs may enter pots fitted with BRDs.
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Estuaries and Coasts, 2016
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Connectivity at the terrestrial-aquatic ecotone is critical for the health and function of estuar... more Connectivity at the terrestrial-aquatic ecotone is critical for the health and function of estuarine ecosystems. To assess the effects of human alterations along the terrestrial-aquatic ecotone, we studied the distribution of the diamondback terrapin (Malaclemys terrapin) in the Chesapeake Bay, Virginia, USA. We conducted repeated occurrence surveys at 165 sites from late spring to mid-summer in 2012 and 2013, and used occupancy models to evaluate relationships between terrapin occurrence and factors related to human modifications of the terrestrial-aquatic ecotone. All relationships were evaluated in concentric-circular neighborhoods between 0.2 km and 2 km overlapping with daily and annual diamondback terrapin space use. In order of decreasing importance, diamondback terrapin occupancy related positively to proportion of tidal salt marsh, and negatively to proportion of agriculture, relative abundance of active crab pots, proportion of armored shoreline, and proportion of low-dens...
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Ocean & Coastal Management, 2021
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World Seas: an Environmental Evaluation, 2019
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PeerJ, 2021
Nature-based shoreline protection provides a welcome class of adaptations to promote ecological r... more Nature-based shoreline protection provides a welcome class of adaptations to promote ecological resilience in the face of climate change. Along coastlines, living shorelines are among the preferred adaptation strategies to both reduce erosion and provide ecological functions. As an alternative to shoreline armoring, living shorelines are viewed favorably among coastal managers and some private property owners, but they have yet to undergo a thorough examination of how their levels of ecosystem functions compare to their closest natural counterpart: fringing marshes. Here, we provide a synthesis of results from a multi-year, large-spatial-scale study in which we compared numerous ecological metrics (including habitat provision for fish, invertebrates, diamondback terrapin, and birds, nutrient and carbon storage, and plant productivity) measured in thirteen pairs of living shorelines and natural fringing marshes throughout coastal Virginia, USA. Living shorelines were composed of mars...
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Final Report, Executive Summary, Habitat Loss Summary For each Chesapeake Bay Segment, individual... more Final Report, Executive Summary, Habitat Loss Summary For each Chesapeake Bay Segment, individual maps were created depicting potential shifts in key coastal habitats - these are presented in the appendices.
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Living Shorelines, 2017
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Papers by Donna Marie Bilkovic