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1. Assessment of treatment-specific tethering survival bias for the juvenile blue crab Callinectes sapidus in a simulated salt marsh

   https://doi.org/10.1371/journal.pone.0289398  

   Miller, Cole R; Hyman, A Challen; Shi, Daniel H; Lipcius, Romuald N (October 2023, PLOS ONE)

   Laruelle, Goulven G (Ed.)

   The blue crab (Callinectes sapidus) is ecologically and economically important in Chesapeake Bay. Nursery habitats, such as seagrass beds, disproportionately contribute individuals to the adult segment of populations. Salt marshes dominated by smooth cordgrassSpartina alternifloraare intertidal nursery habitats which may serve as a refuge from predation for juvenile blue crabs. However, the effects of various characteristics of salt marshes on nursery metrics, such as survival, have not been quantified. Comparisons of juvenile survival between salt marshes and other habitats often employ tethering to assess survival. Although experimental bias when tethering juvenile prey is well recognized, the potential for habitat-specific bias in salt marshes has not been experimentally tested. Using short-term mesocosm predation experiments, we tested if tethering in simulated salt marsh habitats produces a habitat-specific bias. Juvenile crabs were tethered or un-tethered and randomly allocated to mesocosms at varying simulated shoot densities and unstructured sand. Tethering reduced survival, and its effect was not habitat specific, irrespective of shoot density, as evidenced by a non-significant interaction effect between tethering treatment and habitat. Thus, tethering juvenile blue crabs in salt marsh habitat did not produce treatment-specific bias relative to unvegetated habitat across a range of shoot densities; survival of tethered and un-tethered crabs was positively related to shoot density. These findings indicate that tethering is a useful method for assessing survival in salt marshes, as with other nursery habitats including seagrass beds, algae and unstructured sand. 

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2. JUVENILE BLUE CRAB (CALLINECTES SAPIDUS) SURVIVAL IN SIMULATED SEAGRASS HABITATS (ZOSTERA MARINA AND RUPPIA MARITIMA)

   Smith, Kylie (March 2017, Honor's Thesis: Ecology and Evolutionary Biology, University of Colorado at Boulder)

   Anthropogenic increases in global temperatures and nutrient loads are expected to reduce juvenile blue crab (Callinectes sapidus) survival in the Chesapeake Bay. These factors change habitat composition which can affect juvenile invertebrates and fishes that are dependent on these habitats. Eelgrass (Zostera marina) is declining due to rising water temperatures and increased nutrient loading, while widgeon grass (Ruppia maritima) can tolerate higher temperatures. An indoor mesocosm experiment was designed to test the suitability of Zostera and Ruppia as protective nursery habitats compared to sand. Artificial seagrass plots were placed in flow-through tanks. Juvenile blue crabs were tethered, and adult blue crabs and striped burrfish were introduced as predators in order to estimate juvenile crab survival in different substrates. Survival analysis revealed that Zostera provides more protection for juvenile crabs than sand. There was no significant difference between Ruppia and sand, and between Zostera and Ruppia in providing juvenile protection. This suggests juvenile survival may decrease in the future with Zostera loss and that stricter restrictions on the blue crab fishery in the Chesapeake Bay and mid-Atlantic region would be required to maintain healthy crab populations. 

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3. Prevalence, intensity of infestation, and biomarker potential of the nemertean worm, Carcinonemertes carcinophila (Kölliker, 1845), on ovigerous blue crabs, Callinectes sapidus Rathbun, 1896 (Decapoda: Brachyura: Portunidae), in Chesapeake Bay, USA

   https://doi.org/10.1093/jcbiol/ruad074  

   Schneider, Alexandra K; Pomroy, Alexandria K; Shields, Jeffrey D (December 2023, Journal of Crustacean Biology)

   Abstract The effect of individual and population-level egg mortality is important to quantify to maintain sustainable crustacean fisheries. The nemertean worm Carcinonemertes carcinophila (Kölliker, 1845) is an egg predator of the Atlantic blue crab, Callinectes sapidusRathbun, 1896; however, little is known about the impact this nemertean has on the reproduction of the blue crab. We assessed the prevalence and intensity of the infestation of nemerteans in ovigerous blue crabs using a fishery-independent trawl survey. During the primary spawning period of the crab, May–September 2022, 126 ovigerous females were collected and analyzed for worms. Prevalence over this time was 66.6% and mean brood infestation was 53.9 worms per infested crab host. Nemertean egg consumption was quantified with a six-day microcosm experiment. Of the 48 worms in the experiment, 71% actively fed on crab eggs and their consumption ranged 0.16–4.5 eggs day–1. Consumption rates were used to estimate population-level impact of nemertean feeding on crab brood mortality. Modeled proportions of brood loss per crab ranged 0–0.0044%. At the current prevalence and intensity of infestation, egg consumption by nemerteans has a negligible effect on blue crab reproductive output and batch fecundity in Chesapeake Bay. We also investigated the use of mature nemertean worms as a biomarker for establishing the spawning history of ovigerous female blue crabs and determined that the presence of worms in the clutch and in the gills can be used to indicate parity in ovigerous female crabs. 

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4. Salt marsh shoreline geomorphology influences the success of restored oyster reefs and use by associated fauna

   https://doi.org/10.1111/rec.12992  

   Keller, Danielle A.; Gittman, Rachel K.; Brodeur, Michelle C.; Kenworthy, Matthew D.; Ridge, Justin T.; Yeager, Lauren A.; Rodriguez, Antonio B.; Fodrie, F. Joel (July 2019, Restoration Ecology)

   Restoration is increasingly implemented as a strategy to mitigate global declines in biogenic habitats, such as salt marshes and oyster reefs. Restoration efforts could be improved if we knew how site characteristics at landscape scales affect the ecological success of these foundation species. In this study, we determined how salt marsh shoreline geomorphologies (e.g. with variable hydrodynamic energy, fetch, erosion rates, and slopes) affect the success of restored intertidal oyster reefs, as well as how fauna utilize restored reefs and forage along marsh habitats. We constructed oyster reefs along three marsh shoreline geomorphologies in May 2012: 1) “creek” (small‐fetch, gradual‐sloped shoreline), “ramp” (large‐fetch, gradual‐sloped shoreline), and “scarp” (large‐fetch, steep‐sloped shoreline). Following recruitment, oyster spat density was greatest on ramp reefs; however, 2 years later, the highest adult oyster densities were found on creek reefs. Total nekton and blue crab catch rates in trawl nets were highest in the creek, while piscivore catch rates in gill nets were highest along the scarp shoreline. We found no difference in predation on snails in the salt marsh behind constructed reef and nonconstructed reference sites, but there were more snails consumed in the creek shoreline, which corresponded with the distribution of their major predator—blue crabs. We conclude that oyster reef construction was most successful for oysters in small‐fetch, gradual‐sloped, creek environments. However, nekton abundance did not always follow the same trends as oyster density, which could suggest constructed reefs may offer similar habitat‐related functions (prey availability and refuge) already present along existing salt marsh borders. 

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5. Biotic and abiotic factors affecting Atlantic ghost crab (Ocypode quadrata) spatiotemporal activity at an important shorebird nesting site in Virginia

   https://doi.org/10.1371/journal.pone.0307821  

   Call, Mikayla N; Pongnon, Rasheed S; Wails, Christy N; Karpanty, Sarah M; Lapenta, Kristy C; Wilke, Alexandra L; Boettcher, Ruth; Alvino, Camille R; Fraser, James D (August 2024, PLOS ONE)

   Romanach, Stephanie S (Ed.)

   Atlantic ghost crabs (Ocypode quadrata) are predators of beach-nesting shorebird nests and chicks on the United States’ Atlantic and Gulf coasts. Ghost crabs may also disturb birds, altering foraging, habitat use, or nest and brood attendance patterns. Shorebird conservation strategies often involve predator and disturbance management to improve reproductive success, but efforts rarely target ghost crabs. Despite the threat to shorebird reproductive success, ghost crabs are a poorly understood part of the beach ecosystem and additional knowledge about ghost crab habitat selection is needed to inform shorebird conservation. We monitored ghost crab activity, defined as burrow abundance, throughout the shorebird breeding season on Metompkin Island, Virginia, an important breeding site for piping plovers (Charadrius melodus) and American oystercatchers (Haematopus palliatus). We counted burrows at shorebird nests and random locations throughout the breeding season and investigated whether ghost crab activity was greater at nest sites relative to random locations without shorebird nests. While we observed burrows at all nest sites (n= 63 nests), we found that burrow counts were lower at piping plover nests with shell cover, relative to random locations with no shell cover. Ghost crabs may avoid piping plover nest sites due to anti-predator behaviors from incubating adults or differences in microhabitat characteristics selected by piping plovers. We also investigated the effects of habitat type, date, and air temperature on the abundance of ghost crab burrows. We found that while crab burrows were present across the barrier island landscape, there were more burrows in sandy, undisturbed habitats behind the dunes, relative to wave-disturbed beach. Additionally, ghost crab activity increased later in the shorebird breeding season. Understanding when and where ghost crabs are most likely to be active in the landscape can aid decision-making to benefit imperiled shorebird populations. 

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