Dara H. Wilber

Habitat-related phenotypic variation in adult Western Atlantic stone crabs ( Menippe mercenaria Say, 1818) (Decapoda: Brachyura)

Habitat partitioning by different life stages or phenotypes in a heterogeneous marine environment could confer fitness advantages. Two distinct phenotypes of the Western Atlantic stone crab ( Menippe mercenaria Say, 1818), spotted and brown, are easily distinguishable and occupy different habitats in allopatry. Intermediate phenotypes occur in two geographic zones, the northeastern Gulf of Mexico and the southern Atlantic coast of the USA from South Carolina to northern Florida. We examined stone crab phenotypic variation and demography in two adjacent rivers near Charleston, SC, USA, the Kiawah and Stono rivers. The intertidal oyster habitat (quantified as reef per meter shoreline) in the Kiawah River is more than twice as dense as the oyster habitat in the Stono River. Significantly more brown than spotted crabs, a higher proportion of males, and larger individuals were collected in the Kiawah River in a year-long trapping study. Brown coloration for stone crabs on oyster reefs could confer a fitness advantage if these crabs are more cryptic than spotted crabs. The timing of ovigery and egg development did not differ between crabs in the Kiawah and Stono rivers or between brown and spotted stone crabs regardless of capture location. Males exhibited greater cheliped wear than females, but wear was unrelated to proximity to an oyster-reef habitat. Demographic patterns related to habitat use presented here are consistent with habitat use in the northeastern Gulf of Mexico zone of phenotypic variation. The differences in stone crab demographics in these two coastal rivers in South Carolina indicate that further studies are needed to determine whether this habitat-related phenotypic variation is representative of stone crab distributions throughout the South Atlantic Bight.

Resident Crab Associations with Sedimentation on Restored Intertidal Oyster Reefs in South Carolina and the Implications for Secondary Consumers

Abstract Benthic–pelagic coupling is an important habitat function provided by oyster reefs that is potentially affected by sedimentation impacts. In this study, the distributions of three resident crab species, the flat mud crab (also known as the flatback mud crab) Eurypanopeus depressus, the common mud crab (also known as the Atlantic mud crab) Panopeus herbstii, and the invasive green porcelain crab Petrolisthes armatus, were examined with respect to sedimentation on six restored intertidal eastern oyster Crassostrea virginica sites in South Carolina. Sedimentation among sites ranged from 4% to 60% cover and was composed of silty clay and sand. Crab associations with sedimentation differed among species. Common mud crabs and green porcelain crab densities were negatively correlated with percent sediment cover, whereas flat mud crab densities were not related to sediment cover. Flat mud crabs occupy the interstices of the reef, and their densities were positively correlated with scorched mussel Brachid...

Spatial and Temporal Associations Between Native Crabs and the Invading Green Porcelain Crab, Petrolisthes armatus, Throughout Its Northernmost Invaded Range

Increasing ocean temperatures have led to poleward range expansions of many marine organisms. The green porcelain crab, Petrolisthes armatus, was first reported on intertidal oyster reefs near Charleston, South Carolina in the mid-1990s, an expansion from its tropical to sub-tropical native range. In order to investigate the relative abundances of this introduced crab and a portion of the native crab community, resident crab assemblages were sampled on intertidal oyster reefs across four seasons from 2015 to 2016. Sampling occurred at five locations extending from Savannah, Georgia where P. armatus is now well-established, to Wilmington, North Carolina, where its inter-annual presence is intermittent. Petrolisthes armatus was the numerically dominant crab species at all locations except Wilmington, where the species was not collected in the winter. Differences between northern and southern sample locations in the taxonomic composition of crab assemblages were most pronounced in the summer (June–September) and fall (October–January), with dissimilarities largely attributed to high abundances of P. armatus at southern locations. Crab abundances of all species peaked in the summer and were lowest in the winter (February–March). Petrolisthes armatus was less abundant toward the northern range edge, whereas native crabs did not differ in abundance throughout the sampling range. Throughout the study area, adult P. armatus sex ratios shifted from unbiased or female-biased in the summer to male-biased in the fall. Adults were collected in the spring (April–June), indicating they had overwintered. While native crab densities (Panopeus herbstii, Eurypanopeus depressus) stayed relatively constant across locations, P. armatus densities varied greatly, suggesting that resources, such as shelter and food, are not limiting factors for the coexistence of these native and invading crabs.

Spacing and movement in the green porcelain crab Petrolisthes armatus: evidence for male competition and mate guarding

Abstract The green porcelain crab, Petrolisthes armatus, is a common invasive species on inter-tidal oyster reefs in the South Atlantic Bight whose behavior is largely unknown. We assessed the effects of the presence of opposite-sex conspecifics on adult crab spacing at a low density to infer potential mate acquisition behaviors. Adult crabs held in all-male, all-female, and mixed-sex treatments were observed twice daily over five days to determine nearest-neighbor (NN) distances and relative activity. Males in the mixed-sex treatment with the shortest NN distances (NN1) were most commonly (1) closest to females, and, when compared to NN1 males in the all-male treatment, were (2) closer to their NN and (3) had lower activity levels. Female movement did not differ between treatments. Percent ovigerous females at the end of trials were higher in the mixed-sex treatment, reflecting mating activity, which when observed, involved inter-molt females. Mate guarding, rather than pure-searching behavior, was the mating behavior most consistent with observed spacing and movement patterns.

Biological Monitoring of Beach Nourishment Operations in Northern New Jersey, USA: Linkages between Benthic Impacts and Higher Trophic Levels

Between 1993 and 1999 over 19 million m 3 of sand were placed on exposed, high-energy beaches along the northern coast of New Jersey (USA) as an erosion control measure. As part of a multi-faceted biological monitoring program, potential impacts of this large-scale beach nourishment project on benthic infauna and fishes in the intertidal surf zone, nearshore habitat, and offshore borrow areas were examined. Food habits analysis was conducted on northern kingfish ( Menticirrhus saxatilis ), Atlantic silversides ( Menidia menidia ) and rough silversides ( Membras martinica ) collected in the surf zone, and winter flounder ( Pleuronectes americanus ) and summer flounder ( Paralichthys dentatus ) collected at the borrow areas to assess impacts to trophic linkages in the two project areas. Monitoring of benthos and fishery resources was conducted for three years before nourishment, during placement, and up to two years afterwards. The basic sampling design included multiple reference sites and several monitoring components integrated into a cohesive program. In general, impacts on the benthos were found to be short-term (2–6 months) and spatially limited. Stomach contents analyses revealed that the fishes examined have a diverse diet that includes non-benthic prey resources. Prey biomass in kingfish and silversides was usually greater in fishes caught at beach nourishment stations rather than at reference stations when significant differences were detected. Food habits of winter flounder, a benthic omnivore, and summer flounder, an epibenthic feeder, did not change relative to the dredging activities. Winter flounder fed primarily on anemones, which were not common at any of the borrow areas. Results of the present study call into question the need for extensive monitoring of projects where a close match exists between fill and receiving beach sediments. Further studies are definitely needed, however, where fill and receiving beach sediments aredissimilar.