Lethal Parasites in Oysters from Coastal Georgia with Discussion of Disease and Management Implications

Extensive mortalities of oysters, Crassostrea virginica, occurred from 1985 through 1987 in coastal waters of Georgia. Fluid thioglycolate cultures of oysters collected from 16 of 17 locations revealed infections by the apicomplexan parasite Perkinsus marinus. An ascetosporan parasite, Haplosporidium nelsoni, was also observed in histopathological examination of oysters from 4 of the locations. While the range of H. nelsoni currently is recognized as the east coast of the United States from Maine to Florida, this is the first report of the parasite in Georgia waters. This paper documents the occurrence of these two lethal parasites in oysters from coastal waters of Georgia, along with potential disease and management implications. Results of an earlier independent and previously unpublished survey are also discussed which document the presence of P. marinus in Georgia as early as 1966.

Diet of Bottlenose Dolphins Tursiops truncatus in the Northwest Panhandle and Foraging Behavior Near Savannah, Georgia

The foraging ecology of bottlenose dolphins Tursiops truncatus in the Northwest Florida Panhandle and estuaries in northern Georgia was determined using diet analysis and behavioral surveys. Stomach content analysis was completed on bottlenose dolphins(N = 25) that stranded in the Northwest Florida Panhandle from November 2006 to March 2009. The most abundant prey species were spot Leiostomus xanthurus (20.4%), squid (10.9%), pinfish Lagodon rhombiodes (10.3%), and Atlantic croaker Micropogonias undulatus (8.5%). Dolphins that stranded during months with a red tide Karenia brevis bloom consumed more pinfish, and spot; whereas dolphins that stranded in non-bloom months consumed more squid, Atlantic croaker, and silver perch Bairdiella chrysoura. Differences in diet were also identified for dolphins that stranded inside bays/sound and dolphin that stranded outside of bays along the coast, and male and female dolphins. Surveys were conducted from south of the Savannah River to north of Ossabaw Sound in Georgia where foraging behaviors were classified. Multivariate Generalized Additive Models were used to test correlations of behaviors to dolphin group size, depth, salinity, temperature, creek width, and tide. Sightings with headstands (p = 0.009), hard stops (p = 0.019), chasing (p = 0.004), mudbank whacking (p < 0.001), herding/circling (p = 0.024), and strand feeding (p = 0.006) were correlated with shallow water or small creeks. Sightings with kerplunking (p = 0.031), mudbank whacking (p = 0.001), strand feeding (p = 0.003), and herding/circling (p = 0.026) were significantly correlated with low tide. The results of the Savannah, Georgia study were the first to characterize foraging behaviors in this area and demonstrate how bottlenose dolphins utilize the salt marsh estuary in terms of foraging. Studies like these are important to determine how dolphins forage efficiently and to provide background information on diet and foraging behavior for use in monitoring future impacts to dolphins in the Northwest Florida Panhandle and near Savannah, Georgia.

Majuro Atoll, Republic of the Marshall Islands coral reef ecosystems mapping report

Digital maps of the coral reef ecosystem (<~30m deep) of Majuro Atoll, Republic of the Marshall Islands, were created through visual interpretation of remote sensing imagery. Digital Globe’s Quickbird II satellite images were acquired between 2004 and 2006 and georeferenced to within 1.6 m of their true positions. Reef ecosystem features were digitized directly into a GIS at a display scale of 1:4000 using a minimum feature size of 1000 square meters. Benthic features were categorized according to a classification scheme with attributes including zone (location, such as lagoon or forereef, etc.), structure (bottom type, such as sand or patch reef, etc.) and percent hard bottom. Ground validation of habitat features was conducted at 311 sites in 2009. Resulting maps consisted of 1829 features covering 366 square kilometers. Results demonstrate that reef zones occurred in a typical progression of narrow bands from offshore, though forereef, reef flat, shoreline, land, backreef, and lagoon habitats. Lagoon was the largest zone mapped and covered nearly 80% of the atoll, although much of it was too deep to have structures identified from the satellite imagery. Dominant habitat structures by area were pavement and aggregate reef, which covered 29% and 18% of the mapped structures, respectively. Based on the number of features, individual and aggregated patch reefs comprised over 40% of the features mapped. Products include GIS based maps, field videos and pictures, satellite imagery, PDF atlas, and this summary report. Maps and associated data can be used to support science and management activities on Majuro reef ecosystems including inventory, monitoring, conservation, and sustainable development applications.

Influence of hard bottom morphology on fish assemblages of the continental shelf off Georgia, southeastern USA

Various reef types worldwide have inconsistent relationships among fish assemblage parameters and benthic characteristics, thus there is a need to identify factors driving assemblage structure specific to each reef type and locale. Limestone ledges are known to be key habitats for bottom fish on the continental shelf of the southeastern USA, however, the specific factors that link them to fish assemblages have not been quantified. Bottom fishes and habitat characteristics on ledges were surveyed at a study site located centrally in the southeastern USA continental shelf. Species richness, diversity, abundance, and biomass of fish were higher at ledges than on flat bottom. Species richness, abundance, and biomass of fish were well explained by ledge variables including percent cover of sessile invertebrates, total height, and height of undercut recesses. Multivariate analyses based on biomass of individual species at ledges revealed two fish assemblages associated with four ledge types. One assemblage was associated with ledges that were tall, heavily colonized with sessile invertebrates, large in area, and did or did not have undercuts. The other assemblage was associated with ledges that were short, not undercut, smaller in area, and were or were not heavily colonized by invertebrates. Seafloor classification schemes presently used in the region do not adequately capture hard bottom diversity to identify the location and extent of essential fish habitats for ecological and fisheries purposes. Given that ledges cover only ∼1% to 5% of the southeastern USA continental shelf, they merit the highest levels of consideration in regional research, conservation, and management plans.

Atlas of the shallow-water benthic habitats of Majuro Atoll, Republic of the Marshall Islands

Digital maps of the shallow (<~30m deep) coral reef ecosystems of Majuro Atoll, Republic of the Marshall Islands, were created through visual interpretation of remote sensing imagery acquired between 2004 and 2006. Reef ecosystem features were digitized directly into a Geographic Information System. Benthic features were categorized according to a classification scheme with attributes including zone (location such as lagoon or forereef, etc.), structure (bottom type such as sand or patch reef, etc.) and percent hard bottom. This atlas consists of 27 detailed maps displaying reef zone and structure of coral ecosystems around Majuro. Adjacent maps in the atlas overlap slightly to ensure complete coverage. Maps and associated products can be used to support science and management activities on Majuro reef ecosystems including inventory, monitoring, conservation, and sustainable development applications. Maps are not to be used for navigation.

Tag-reporting levels for red drum (Sciaenops ocellatus) caught by anglers in South Carolina and Georgia estuaries

A total of 1784 legal-size (≥356 mm TL) hatchery-produced red drum (Sciaenops ocellatus) were tagged and released to estimate tag-reporting levels of recreational anglers in South Carolina (SC) and Georgia (GA). Twelve groups of legal-size fish (~150 fish/group) were released. Half of the fish of each group were tagged with an external tag with the message “reward” and the other half of the fish were implanted with tags with the message “$100 reward.” These fish were released into two estuaries in each state (n=4); three replicate groups were released at different sites within each estuary (n=12). From results obtained in previous tag return experiments conducted by wildlife and fisheries biologists, it was hypothesized that reporting would be maximized at a reward level of $100/tag. Reporting level for the “reward” tags was estimated by dividing the number of “reward” tags returned by the number of “$100 reward” tags returned. The cumulative return level for both tag messages was 22.7 (±1.9)% in SC and 25.8 (±4.1)% in GA. These return levels were typical of those recorded by other red drum tagging programs in the region. Return data were partitioned according to verbal survey information obtained from anglers who reported tagged fish. Based on this partitioned data set, 14.3 (±2.1)% of “reward” tags were returned in SC, and 25.5 (±2.3)% of “$100 reward” tags were returned. This finding indicates that only 56.7% of the fish captured with “reward” tags were reported in SC. The pattern was similar for GA where 19.1 (±10.6)% of “reward” message tags were returned as compared with 30.1 (±15.6)% for “$100 reward” message tags. This difference yielded a reporting level of 63% for “reward” tags in GA. Currently, 50% is used as the estimate for the angler reporting level in population models for red drum and a number of other coastal finfish species in the South Atlantic region of the United States. Based on results of our study, the commonly used reporting estimate may result in an overestimate of angler exploitation for red drum.