The Exposed Surface Area To Volume Ratio: Is Shell More Efficient Than Limestone In Promoting Oyster Recruitment?

Planting oyster cultch is a common management approach used to enhance recruitment. The two most popular cultch materials are shell and limestone. Both are sold by volume or weight; however, once deposited on oyster grounds, only a small portion of the total surface area of each particle is available for recruitment. Shell and limestone have different surface area to volume properties, and thus provide differential settlement opportunities. Exposed surface area to volume (expSA/V) ratios of oyster shell and limestone fragments were compared, as an indicator of their recruitment potential and cost-effectiveness for cultch planting. Samples were collected from the Primary Public Oyster Seed Grounds in Louisiana by vibracore, and from the Pass Christian Tonging Grounds in Mississippi by dredge. Shell (including whole shell and fragments) and limestone particles greater than or equal to 8 mm by geometric shape were classified and their expSA/V was calculated. Mean expSA/V ratios of shell were approximately three to nine times higher than limestone. For limestone of similar particle size to provide an equivalent recruitment benefit for the same cost would require that the cost of purchase, transport, and planting be three to nine times lower than shell. Thus, shell is likely to be a more efficient material than limestone for recruitment enhancement. Nevertheless, the higher variability in expSA/V of shell and other factors such as the expected lifetime and the relative performance of small and large particles of materials should also be considered. Analysis of a Louisiana limestone plant and associated oyster cultch showed that the proportion of small and large limestone particles and the relative proportion of whole shells and fragments can greatly alter expSA/V. In this case, the a priori expectation that oyster shell would outperform limestone did not materialize because of the quantity of small limestone particles of favorable shapes in the deployed material. Even so, as yet unknown is the possible reduction in performance in situ of smaller particles that might occur if they increase the one-dimensionality of the plant

Estimating Sustainable Harvests Of Eastern Oysters, Crassostrea Virginica

Sustainability of a fishery is traditionally and typically considered achieved if the exploited population does not decline in numbers or biomass over time as a result of fishing relative to biological reference point goals. Oysters, however, exhibit atypical population dynamics compared with many other commercial species. The population dynamics often display extreme natural interannual variation in numbers and biomass, and oysters create their own habitat-the reef itself. With the worldwide decline of oyster reef habitat and the oyster fisheries dependent thereon, the maintenance of shell has received renewed attention as essential to population sustainability. We apply a shell budget model to estimate the sustainable catch of oysters on public oyster grounds in Louisiana using no net shell loss as a sustainability reference point. Oyster density and size are obtained from an annual stock assessment. The model simulates oyster growth and mortality, and natural shell loss. Shell mass is increased when oysters die in place, and is diminished when oysters are removed by fishing. The shell budget model has practical applications, such as identifying areas for closure, determining total allowable catch, managing shell planting and reef restoration, and achieving product certification for sustainability. The determination of sustainable yield by shell budget modeling should be broadly applicable to the eastern oyster across its entire range

Mortality and Condition of the American Oyster in Galveston Bay, Texas

77-94Mortality and condition of the American oyster, Crassostrea virginica , were studied on sixteen 0.1-hectare sites on reefs in the bay. Oyster mortality was evaluated by 3 methods--the box-count method (number of articulated empty shells/number of articulated empty shells plus live oysters), the catch-curve method (log frequency versus size), and by tray experiments in which open tray, closed tray, and predator-inclusion trays (in which an oyster drill, Thais haemostoma was enclosed in each) were used. A weight/volume condition index was positively correlated with a gonadal index. Glycogen concentration was negatively correlated with salinity whereas intensity of infection by Perkinsus marinus was positively correlated with salinity. High mortalities were apparently the result of frequent flooding at low salinity sites, but appeared to be caused by the oyster drill and disease (due to the protozoan P. marinus ) at high-salinity sites.http://gbic.tamug.edu/request.ht

A Restoration Suitability Index Model for the Eastern Oyster (Crassostrea virginica) in the Mission-Aransas Estuary, TX, USA

Oyster reefs are one of the most threatened marine habitats on earth, with habitat loss resulting from water quality degradation, coastal development, destructive fishing practices, overfishing, and storm impacts. For successful and sustainable oyster reef restoration efforts, it is necessary to choose sites that support long-term growth and survival of oysters. Selection of suitable sites is critically important as it can greatly influence mortality factors and may largely determine the ultimate success of the restoration project. The application of Geographic Information Systems (GIS) provides an effective methodology for identifying suitable sites for oyster reef restoration and removes much of the uncertainty involved in the sometimes trial and error selection process. This approach also provides an objective and quantitative tool for planning future oyster reef restoration efforts. The aim of this study was to develop a restoration suitability index model and reef quality index model to characterize locations based on their potential for successful reef restoration within the Mission-Aransas Estuary, Texas, USA. The restoration suitability index model focuses on salinity, temperature, turbidity, dissolved oxygen, and depth, while the reef quality index model focuses on abundance of live oysters, dead shell, and spat. Size-specific Perkinsus marinus infection levels were mapped to illustrate general disease trends. This application was effective in identifying suitable sites for oyster reef restoration, is flexible in its use, and provides a mechanism for considering alternative approaches. The end product is a practical decision-support tool that can be used by coastal resource managers to improve oyster restoration efforts. As oyster reef restoration activities continue at small and large-scales, site selection criteria are critical for assisting stakeholders and managers and for maximizing long-term sustainability of oyster resources

The Elder Orphan in Healthcare Settings: an Integrative Review

The issues of older adults outliving family members and living alone with no family support or existing social networks raise concerns on the health and wellbeing needs of this particular population group. This article explores the concept of orphaned older adults within the healthcare context through an integrative review of literature. The review utilized online health databases and online publishing platforms for grey literature. Eight articles focusing on elder orphans within the healthcare literature were included in this review. Four emerging themes were identified: characteristics of the older adult orphan; healthcare and clinical oversight; older adult orphans’ support services; and ‘older adult orphan’ as an advocacy healthcare terminology. Elder orphans are vulnerable older adults who may have current stable health status, yet are at risk of health-related issues which could hinder their decision making ability in the future. The conceptualization of becoming orphaned in advanced age opens an important dialogue in the healthcare sector and encourages attention from health professionals to consider and to be more aware of this vulnerable population group among older people. It is important that the use of this otherwise non-clinical term defining orphancy in older age or even those at risk be more visible and accepted, for the purpose of clinical assessment and coordination of care for both acute and longterm/community settings. Health professionals and clinicians act as advocates when screening and assessment for older adult orphans are undertaken at all levels and across healthcare settings