The majority of recent studies investigating the habitat value of intertidal oyster reefs have compared the nektonic assemblages on natural oyster reefs, salt marshes, mud bottom, and subtidal oyster shell habitats using methods that involve some degree of habitat disturbance. The current study used a novel, non-destructive sampling approach involving the deployment of a drop net around study plots to compare the nektonic assemblages associated with intertidal oyster reefs (natural and enhanced) with those of neighboring soft sediment habitats at 3 sites in South Carolina. At each site, the nektonic organisms collected on a reef plot were compared with those collected on an adjacent control plot lacking a structurally complex habitat. Nekton abundance was significantly higher on the reef plot compared with the control plot at all 3 sites. Nekton abundance also varied among seasons, with the greatest numbers occurring during summer compared with spring and fall. Notably, grass shrimp (Palaemonetes spp.) were especially dominant on reef plots. A total of 60 taxa were identified, 57 of which were identified to species level. Reef plots exhibited significantly greater taxon richness than control plots. The number of taxa present also accumulated over time at a higher rate on the reef plots than on the control plots at 2 of the 3 sites. Among the 60 taxa collected, 36 were found on both the reef and control plots, whereas 14 taxa were unique to the reef plots. For data pooled across all sites and seasons, 33 taxa were more numerous on reef plots than control plots, 3 taxa occurred in equal numbers, and 24 taxa were more numerous on control plots. For taxa collected on more than 1 occasion, paired t-tests performed with Bonferroni-adjusted significance thresholds revealed that Alpheus heterochaelis and Palaemonetes spp. were significantly more abundant on the reef plots than on the control plots, whereas unadjusted analyses revealed the same pattern for Gobiosoma bosc, Menidia menidia, and Fundulus heteroclitus. In contrast, no taxa were significantly more abundant on the control plots at either significance threshold. Although nekton abundance was generally higher on the reef plots, measures of diversity were significantly higher on the control plots, regardless of season, site, or date. Greater abundance of a limited number of species on the reef plots accounted for lower evenness and therefore lower diversity measures for this treatment. Overall, community structure was driven more by site than by treatment, whereas the seasonal occurrences of certain species on the reef plots highlighted the importance of oyster reefs as essential fish habitat for the critical life stages of finfish species with complex life histories.
Total mercury concentrations were measured in diamondback terrapin blood and scutes collected from four sites in South Carolina, USA, and at a superfund site in Brunswick, Georgia, USA. There was a strong correlation between mercury concentrations in the two terrapin body compartments (Kendall's tau = 0.79, p < 0.001). Mercury concentrations in terrapin scute and blood and in salt marsh periwinkles, Littoraria irrorata, were significantly higher in Brunswick (scute x = 3810.2 ng/g, blood x = 746.2 ng/g) than from all other sites (scute x = 309.5 ng/g, blood x = 43.2 ng/g, p < 0.001). Seasonal fluctuations of total mercury in the blood and scutes of terrapins collected in the Ashley River, South Carolina, were significantly lower in August than in April, June, or October in blood (p < 0.001); however, scute concentrations did not vary seasonally. Overall, we found higher concentrations of mercury in the scutes of females than males (n = 32, p < 0.05). Larger females may preferentially prey on larger food items, like large periwinkles, which had significantly higher mercury levels in their body tissues than smaller periwinkles (p < 0.001). Methylmercury levels in terrapin scutes were measured, revealing that 90% of the total mercury stored in this compartment was in the organic form. A methylmercury biomagnification factor of 173.5 was calculated from snails to terrapin scutes, and we found that mercury levels in scutes were representative of the mercury levels in other compartments of the ecosystem. These findings show that terrapin scutes are good predictors of mercury pollution and that this species could be used as a bioindicator for assessing mercury contamination of estuarine systems.
Abstract Little is known about the infection status of glass eel and elver stages of the American eel Anguilla rostrata by the invasive swimbladder parasite Anguillicoloides crassus. This study examined infection by adult and larval A. crassus in glass eels (n = 274) and elvers (n = 199) collected during March–December 2013 from an eel ladder at a dammed creek near Charleston, SC, USA. Among all the eels examined [total lengths (TLs), 34–156 mm], the prevalence (±SE), mean abundance, and mean intensity of A. crassus worms was 29.4 ± 2.1%, 0.88 ± 0.12, and 2.98 ± 0.34, respectively. Infection by A. crassus was not detected in the earliest glass eel development stages (pigment stages 1–3), but it was detected in more advanced stages (pigment stages 4–7) and fully pigmented elvers. From March to July, parasite prevalence increased significantly with eel TL, and all eels 125 mm or longer (n = 13) were infected. From August–December, when fewer eels were caught, parasite prevalence was generally lower and less dependent on the eel TL. Our study demonstrates the potential risk of spreading A. crassus to new areas by transporting live glass eels and elvers. This is of particular relevance because our study site was located in the Cooper River drainage, one of the few locations in the USA that permits a glass eel harvest.
The gag, Myceteroperca microlepis, is a demersal serranid found along the southeastern coast of the States and in the Gulf of Mexico. Throughout its range the gag is of both commercial and recreational importance. Because of its relatively slow growth rate and desirability, overfishing is of wide concern. The gag is a protogynous hermaphrodite, and suggested that sexual transformation occurs during the 10th or 11th year. Spawning occurs from January to March off the west coast of Florida , and the maximum reported age is 13 years in both the Gulf of Mexico and the South Atlantic Bight 1978 J. Microscopic examination of the gonads is necessary for definite sexual identification, but gonad morphology has not been specifically described.
The purpose of this study is to provide new information on the age, growth. and reproductive biology of this important species, including a description of the morphology of gag ovaries and testes.
Two new nematode species of Philometra Costa, 1845, P. carolinensis sp.n. and P. cynoscionis sp.n., are described from the spotted seatrout, Cynoscion nebulosus (Cuvier) (Sciaenidae, Perciformes) in estuaries on the Atlantic coast of South Carolina, USA.Philometra carolinensis (males and gravid and subgravid females) parasitic in the host's ovary is most similar to P. lateolabracis (Yamaguti, 1935) in female morphology, but distinctly differs from it in possessing conspicuously short spicules (81-87 µm long) with heavily sclerotized distal parts, the gubernaculum bearing a reflected dorsal barb, and in the length ratio of the gubernaculum and spicules (1:1.23-1.42) in the male.Philometra cynoscionis (only gravid females) found subcutaneously in the host's tissue (lateral to the ascending process of the premaxilla and also posteromedial to the length of each maxilla) is characterized mainly by the presence of cephalic papillae arranged in two circles (8 large papillae in outer circle and 6 small papillae in inner circle), the absence of caudal projections, the body size (length of gravid female 20-33 mm) and the location in the host.
The myxozoan Kudoa inornata is a common parasite of the skeletal muscles of spotted seatrout, Cynoscion nebulosus. This study was conducted to determine the distribution of plasmodia of K. inornata within individual C. nebulosus in order to identify muscle areas of least variation where future sampling would result in easily obtainable, repeatable, and dependable measurement of infection status. Fish were captured in the wild during June 2011. Muscle samples from 9 body areas were collected, in replicate, from each of 15 specimens of C. nebulosus of various ages and lengths infected by K. inornata. Body areas sampled included 6 locations from the fish epaxial and hypaxial muscles and 1 from each of the adductor mandibulae (cheek muscle), the cranial epaxial muscle, and the muscle of the caudal peduncle. Replicate samples were weighed and the number of plasmodia in each was recorded to determine the average density of plasmodia per gram of muscle in each area. The average density of plasmodia among fish was highly variable and was not correlated with fish size, age, or the homogeneity of distribution. Although the anterior hypaxial muscle (belly flap) was significantly more infected and the caudal peduncle less infected, when compared to all other areas examined in all fish combined, 10 out of 15 fish displayed an otherwise homogeneous distribution when data were analyzed fish by fish. Among the 5 fish with a nonuniform plasmodia distribution, 3 had a significantly higher burden in the belly flap, 1 in the area just posterior to the belly flap, and 1 in the cheek muscle. Based on these results, it was determined that hypaxial, caudal peduncle, and cheek muscles contributed greatly to the overall variation in plasmodia distribution observed whereas any portion of the epaxial muscle, as well as the cranial muscle, would be the least-variable areas to sample to determine the status of infection in any given fish.
A new myxosporean species, Henneguya cynoscioni sp.n., is described from the spotted seatrout, Cynoscion nebulosus (Cuvier) (Sciaenidae) as a causative agent of cardiac henneguyosis.This new myxosporean species is characterized by the morphology of spores and the sequence of SSU rDNA.Examination of 227 spotted seatrout from four South Carolina estuaries in 2008-2010 revealed a 33.5% total prevalence of H. cynoscioni.Henneguya cynoscioni produces lesions in the bulbus arteriosus, its specific site of infection.the severity of lesions and their impact on the bulbus arteriosus is proportional to the number of plasmodial stages developing in this segment of the heart, being most pronounced in host reaction directed against spores liberated from plasmodia.
