Donna Marie Bilkovic

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...

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.

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.

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.

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...

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...

ABSTRACTClimate change and coastal development pressures have intensified the need for shoreline protection. Nature-first approaches that use natural habitats, particularly marshes, are being promoted globally as ecologically-beneficial alternatives to grey infrastructure. The ability of these novel shorelines to provide nursery habitat to blue crab, an ecologically and economically important species along the Atlantic and Gulf coasts of the United States, has not been quantified.We quantified the abundance and size distribution of juvenile blue crabs from a chronosequence of living shorelines (created fringing marshes) spanning 2 to 16 years in age (since construction) and compared with paired natural fringing marshes in the southern Chesapeake Bay.Both created and natural fringing marshes are being used by blue crabs as primary nursery habitats. While there were interannual differences in abundance, young blue crabs (≤ 2.5 cm carapace width) were observed in similar densities and ...

Introduction: Marshes contribute to habitat and water quality in estuaries and coastal bays. Their importance to continued ecosystem functioning has led to concerns about their persistence. Outcomes: Concurrent with sea-level rise, marshes are eroding and appear to be disappearing through ponding in their interior; in addition, in many places, they are being replaced with shoreline stabilization structures. We examined the changes in marsh extent over the past 40 years within a subestuary of Chesapeake Bay, the largest estuary in the United States, to better understand the effects of sea-level rise and human pressure on marsh coverage. Discussion: Approximately 30 years ago, an inventory of York River estuary marshes documented the historic extent of marshes. Marshes were resurveyed in 2010 to examine shifts in tidal marsh extent and distribution. Marsh change varied spatially along the estuary, with watershed changes between a 32% loss and an 11% gain in marsh area. Loss of marsh w...

Coastal shoreline hardening is intensifying due to human population growth and sea level rise. Prior studies have emphasized shoreline-hardening effects on faunal abundance and diversity; few have examined effects on faunal biomass and size structure or described effects specific to different functional groups. We evaluated the biomass and size structure of mobile fish and crustacean assemblages within two nearshore zones (waters extending 3 and 16 m from shore) adjacent to natural (native wetland; beach) and hardened (bulkhead; riprap) shorelines. Within 3 m from shore, the total fish/crustacean biomass was greatest at hardened shorelines, driven by greater water depth that facilitated access to planktivore (e.g., bay anchovy) and benthivore-piscivore (e.g., white perch) species. Small-bodied littoral-demersal species (e.g., Fundulus spp.) had greatest biomass at wetlands. By contrast, total biomass was comparable among shoreline types within 16 m from shore, suggesting the effect ...

Every year, millions of pots and traps are lost in crustacean fisheries around the world. Derelict fishing gear has been found to produce several harmful environmental and ecological effects, however socioeconomic consequences have been investigated less frequently. We analyze the economic effects of a substantial derelict pot removal program in the largest estuary of the United States, the Chesapeake Bay. By combining spatially resolved data on derelict pot removals with commercial blue crab (Callinectes sapidus) harvests and effort, we show that removing 34,408 derelict pots led to significant gains in gear efficiency and an additional 13,504 MT in harvest valued at US $21.3 million—a 27% increase above that which would have occurred without removals. Model results are extended to a global analysis where it is seen that US $831 million in landings could be recovered annually by removing less than 10% of the derelict pots and traps from major crustacean fisheries. An unfortunate co...

ABSTRACT Background/Question/Methods Watershed land cover is often associated with landscape-scale patterns in freshwater biological communities, but examples from coastal marine systems are limited. As human populations expand, there is also growing interest in the ecological consequences of replacing natural shoreline habitat with hardened structures. We examined both watershed land cover and shoreline alteration as predictors of community composition and abundance of nearshore aquatic macrofauna (fish and crabs) in Chesapeake Bay, the largest estuary in the United States. Data on 22 commonly occurring nearshore species were compiled from 648 sites spanning the entire estuary. To allow for comparison across land cover gradients, data were collected from 45 different subestuaries. Land cover around each subestuary was assessed at the whole watershed scale and within a 100m buffer from shore. Generalized linear mixed models were used to assess patterns in species specific abundance across subestuaries and habitats while accounting for the multilevel structure of the data (subestuary and site scales). In addition, we focused on the effects of shoreline alteration within a subset of 16 subestuaries that were deliberately sampled at natural (beach, marsh) and altered (riprap, bulkhead) shorelines. Redundancy analysis was used to evaluate how shoreline habitat affected community structure. Salinity, an important covariate, was accounted for in all models. Results/Conclusions There were multiple significant correlations between species-specific abundance and land cover, even when including shoreline habitat and salinity in statistical models. Patterns with land cover often emerged independent of salinity, but sometimes patterns were only observed over a specific salinity range (either 0-10 PSU or >10 PSU). Generally, species abundance patterns followed established negative relationships between human land cover and water quality. For example, there were significant negative relationships between cropland and the abundance of blue crabs and Atlantic silversides, and between developed land and the abundance of several species. Conversely, there were significant positive relationships between wetland within 100m of shore and abundance of multiple species including blue crab. At local scales, shoreline habitat explained 24.4% of the variation in macrofauna community structure within 3m from shore and 16.7% of the variation within 16m from shore. Small littoral fishes were strongly associated with marshes, while pelagic/planktivorous fishes were strongly associated with beaches. Larger bodied species were often encountered near the land/water interface at ripraps and bulkheads, which lacked crucial shallow water refuge habitat. By identifying patterns in mobile, marine species, these findings advance our understanding regarding the ecological effects of human-related activities.

Coastal shoreline hardening is intensifying due to human population growth and sea level rise. Prior studies have emphasized shoreline-hardening effects on faunal abundance and diversity; few have examined effects on faunal biomass and size structure or described effects specific to different functional groups. We evaluated the biomass and size structure of mobile fish and crustacean assemblages within two nearshore zones (waters extending 3 and 16 m from shore) adjacent to natural (native wetland; beach) and hardened (bulkhead; riprap) shorelines. Within 3 m from shore, the total fish/crustacean biomass was greatest at hardened shorelines, driven by greater water depth that facilitated access to planktivore (e.g., bay anchovy) and benthivore-piscivore (e.g., white perch) species. Small-bodied littoral-demersal species (e.g., Fundulus spp.) had greatest biomass at wetlands. By contrast, total biomass was comparable among shoreline types within 16 m from shore, suggesting the effect of shoreline hardening on fish bio-mass is largely within extreme nearshore areas immediately at the land/water interface. Shoreline type utilization was mediated by body size across all functional groups: small individuals (≤60 mm) were most abundant at wetlands and beaches, while large individuals (>100 mm) were most abundant at hardened shorelines. Taxonomic diversity analysis indicated natural shoreline types had more diverse assemblages, especially within 3 m from shore, although relationships with shoreline type were weak and sensitive to the inclusion/exclusion of crustaceans. Our study illustrates how shoreline hardening effects on fish/crustacean assemblages are mediated by functional group, body size, and distance from shore, with important applications for management.

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.