Physiological response of scup, stenotomus chrysops, to a simulated trawl capture and escape event

Scup (Stenotomus chrysops) were severely exercised by manual chasing for 6 min, and the clearance of lactate over a 12 hr period was evaluated. Lactate peaked from 0.5 to 1.0 hr following exercise with concentrations ranging from 61.0 to 126.0 mg/dL and returned to rested concentrations within 4 hr post-exercise. Concentrations of lactate in rested fish ranged from 5.2 to approximately 23.0 mg/dL. Fish were observed for 10 days following exercise for delayed mortality. A 100% survival of scup was observed with no significant difference between control and experimental populations. Swimming performance was evaluated for 14.0 to 15.0 cm fork length scup, with a towed stimulus through a still-water circular swimming channel, at prolonged and burst speeds. A maximum sustainable swimming speed of 2.2 BL/sec was observed. Between the speeds of 3.0 and 3.3 BL/sec and 4.4 BL/sec, endurance time significantly decreased with the increase in swimming speed. Blood lactate concentrations were measured at 0.5 and 4.0 hr post exercise, and were used as an indicator of white muscle recruitment. A significant difference was not found between rested and experimental mean lactate concentrations at the maximum sustainable swimming speed of 2.2 BL/sec. White muscle recruitment indicated by increases in lactic acid, was recorded at speeds above the maximum sustained swimming speed, and mean blood lactate concentrations were significantly different within blood sampling times and between swimming speeds. Based on the results of our investigations of lactate recovery in scup following a simulated trawl capture and escape event, we believe that scup interacting with a bottom trawl and subsequently escaping, are physiologically stressed by the event, but recover in less than 6 hr. All experimentally treated fish survived both exhaustive exercise and prolonged swimming, suggesting encounter mortality is minimal. The results of this study do not address the effects of possible physical damage on escape or the effect of multiple encounters

Comparative attachment, growth and mortalities of oyster (Crassostrea virginica) spat on slate and oyster shell in the James River, Virginia

Slate was investigated as a substitute for oyster shells which are used as a substrate for oyster spat (Crassostrea virginica) settlement in James River, Virginia oyster repletion programs. Oyster shells and slate fragments were planted on adjacent plots in two submerged locations about 825 m apart in July 1984. Quantitative .093 m2 (one ft2) samples were collected by a diver on seven occasions through July 1985, with additional samples collected from teh natural oyster bottoms adjacent to the two areas. Percent mortality, growth and numbers of live spat and spat scars (dead spat) per unit area of bottom were determined. As the end of the study, the number of spat on shell was 4-5 times higher than on slate; however, slate had 5-6 times more spat per unit area of bottom than the shell on the natural bottom. During the July to October setting season mortalities were much higher on slate than on shell; during the remaining period they were high but about equal on both substances

Recent history and response characteristics of Wachapreague Inlet, Virginia : Final report

Wachapreague Inlet, a large downdrift offset inlet in the barrier island complex of the mid-Atlantic coast (Delmarva peninsula), was studied during the period 1971-1974. The inlet channel width is bout 500 m and the throat cross-sectional is about 4,500 m2 • The inlet channel is about 3 km in length, approximately one-half of which is within the well-developed horseshoe shaped ebb delta complex. The maximum channel depth is 20 rn which occurs at the throat. Elements of the study included: (1) the inlet morphornetric history (120 years), (2) assessment of surficial and sub-bottom sediments within the inlet complex, (3) determination of the distribution of tidal flows within the inlet channel, (4) determination of the zone of influence of inlet hydraulic currents along the face of the updrift barrier island and (5) the determination of the response of the channel cross-sectional area to short-term variations in wave activity and tidal prisms. (more...

Bacterial Community Profiling of the Eastern Oyster (\u3cem\u3eCrassostrea virginica\u3c/em\u3e): Comparison of Culture-Dependent and Culture-Independent Outcomes

Tissue-associated bacterial community profiles generated using a nested polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) approach and culture-dependent and culture-independent isolation techniques were compared. Oyster samples were collected from 2 harvest areas along the coast of Maine, in the United States. Profiles from both isolation strategies were evaluated using Sorensen’s index of similarity and cluster analysis of gel banding patterns. Culture independent profiles were further evaluated using the Shannon diversity index. In general, the culture-dependent strategy resulted in a greater number of bands within a profile. Bacterial DGGE profiles were found to be highly similar within an isolation strategy, with a higher degree of unrelatedness between culture-dependent and -independent techniques. Cluster analysis identified bands present in the culture-dependent strategy and not the total DNA technique, and vice versa. Significant differences in community profiles between oyster-associated and seawater were observed, indicating a diverse group of specialist bacterial species inhabit and are able to proliferate within the oyster

Geologic controls on the recent evolution of oyster reefs in Apalachicola Bay and St. George Sound, Florida

This paper is not subject to U.S. copyright. The definitive version was published in Estuarine, Coastal and Shelf Science 88 (2010): 385-394, doi:10.1016/j.ecss.2010.04.019.Apalachicola Bay and St. George Sound contain the largest oyster fishery in Florida, and the growth and distribution of the numerous oyster reefs here are the combined product of modern estuarine conditions in the bay and its late Holocene evolution. Sidescan-sonar imagery, bathymetry, high-resolution seismic profiles, and sediment cores show that oyster beds occupy the crests of a series of shoals that range from 1 to 7 km in length, trend roughly north-south perpendicular to the long axes of the bay and sound, and are asymmetrical with steeper sides facing to the west. Surface sediment samples show that the oyster beds consist of shelly sand, while much of the remainder of the bay floor is covered by mud delivered by the Apalachicola River. The present oyster reefs rest on sandy delta systems that advanced southward across the region between 6400 and 4400 yr BP when sea level was 4–6 m lower than present. Oysters started to colonize the region around 5100 yr BP and became extensive by 1200 and 2400 yr BP. Since 1200 yr BP, their aerial extent has decreased due to burial of the edges of the reefs by the prodelta mud that continues to be supplied by the Apalachicola River. Oyster reefs that are still active are narrower than the original beds, have grown vertically, and become asymmetrical in cross-section. Their internal bedding indicates they have migrated westward, suggesting a net westerly transport of sediment in the bay.Funding for this research was provided by the NOAA Coastal Services Center

The role of bottom current and estuarine geomorphology on the sedimentation processes and productivity of Wreck Shoal, an oyster reef of the James River, Virginia

Indicates considerable spatial variation in the strength of the bottom current regime. The magnitude of the bottom current is inversely correlated to mean water depth. Temporal variations in the bottom current are accounted for by a net downstream current and a strong periodic tidal component. The hard-rock\u27 oyster reefs experience relatively strong bottom currents over a hydraulically rougher bottom, while the mud-shell\u27 oyster reefs experience relatively weak bottom currents over a hydraulically smoother bottom. -from Autho

Long-Term Changes in Beach Fauna at Duck, North Carolina

Source: https://erdc-library.erdc.dren.mil/jspui/Long-term changes in the beach fauna at Duck, North Carolina, were investigated. Twenty-one stations located on three transects on the oceanside and twenty-four stations located on three transects on the sound side were sampled seasonally from November 1980 to July 1981. The data collected in this study were compared to a previous study conducted in 1976 (Matta, 1977) to investigate the potential effects of the construction of the CERC Field Research Facility pier on the adjacent beaches. No effects on the benthic fauna were found. Changes observed in the benthic macrofauna on the ocean beaches were well within the range attributable to the natural variation of an open coast system. The ocean beach macrofauna was observed to form a single community, migrating on and off the beach with the seasons. On the sound beaches, changes were detected in the benthic macrofauna; however, these were attributed to a salinity increase during the 1981 sampling year

Factors affecting hydrodynamic performance of the Nordmøre Grate System: a bycatch reduction device used in the Gulf of Maine shrimp fishery

Trawl nets used in traditional shrimp fisheries are highly non-selective. While capturing shrimp, trawl nets also retain most other animals, including juveniles of commercially important species, thus depleting stocks. To maximize the efficiency of separation of shrimp from other species in trawl net catches, hydrodynamic experiments were conducted on the Nordmøre Grate System, a shrimp bycatch reduction device. The system consisted of two elements, a funnel and a grate; and experimental variables included towing speed, webbing solidity and exit to entrance area ratios for the funnel, and angle of attack, bar diameter, and shape of the grate. Filtration efficiency was inferred from flow disturbance induced by each element, as it was towed in a still water basin. Flow measurements were taken with an electromagnetic current meter at the entrance and at the exit of each funnel and each frame supporting the grates. Water was rejected in the entrance of all funnels with non-porous webbing. Water was ejected from the exit of funnels of intermediate webbing solidity and intermediate exit to entrance area ratio. Water was entrained behind all grates except the 0.32 cm bar diameter grate. Ejection of water at the funnel exit with no rejection at the funnel mouth was attained with 0.08 entrance to exit area ratio covered with 0.4 solidity ratio webbing. Optimum filtration efficiency was observed in the grate with 0.32 cm diameter, round bars placed at a 30 ° angle of attack. © 1995

Quantification of water flow and net drag in midwater trawls

The flow velocity and hydrodynamic drag of 18 quarter-scale midwater box trawl nets were quantified in a circulating water channel using electromagnetic current meters and strain gauges, with the mouth of each net attached to a rigid pipe frame to maintain geometric similarity. The experimental matrix involved three mesh sizes (25, 50, and 100 mm), three twine diameters (0.5, 1, and 2 mm), two webbing tapers (all bar and three points to one bar), and three test speeds (30, 60, and 90 cm s-1. Under this design, the significant factors affecting the velocity gradient within or ahead of the nets were found to be the solidity ratio of the webbing and the towing speed. The significant factors affecting the drag coefficient of the nets were the solidity ratio and the average webbing angle of incidence. The towing speed was not found to significantly affect the drag coefficient under the experimental conditions. © 1993