|
| FISHERIES |
Abundance and Viability of Striped Bass Eggs Spawned in the Roanoke River in 1988, 1989, 1990, 1991
Pollock's Ferry Hunting Club, on the Roanoke River near Scotland Neck served as the sampling station. Paired tow nets with flow meters (one net six inches below the surface and one net towed at an oblique angle from bottom to surface) collected samples every four hours for the duration of the spawning period. The mean number of striped bass eggs per net, percentage of viable eggs, and stage of development were determined. In this way, egg density and total numbers of eggs were estimated. River stage, surface water velocity, water temperature, DO, pH, and total dissolved solids were also recorded for each sample, so that water quality correlations could be drawn. To estimate the production and viability of striped bass eggs spawned in 1988, samples were taken at Pollock's Ferry on the Roanoke River, NC, from 10 April to 7 June 1988 using paired nets towed along the surface for 5 minutes every 4 hours for 60 days. The steady water discharge from Roanoke Rapids Dam likely caused the steady water quality conditions observed. 20,144 eggs were collected, beginning on 12 April and continuing sporadically until 2 June. Estimated total production in the Roanoke River in 1988 was 2,082,130,728 eggs. The major portion of the eggs was collected between 11 and 12 May. Three minor peaks were observed (15-16 May, 20 May, and 24-25 May). With the exception of 1986, production was the highest since 1975. Viability was estimated at 89%, the highest since 1972. Age distributions were calculated for the eggs collected. Water temperature and flow characteristics were also recorded. 79% of the eggs were collected in water of 18- 21.9 degrees Celsius; 99.5% of the eggs were collected at water velocities between 60 and 99.9 cm/sec; 85% of the eggs were collected in water with DO between 6.0 and 7.9 mg/l; 92% of the eggs were collected in pH above 7.0. In 1989, eggs were collected at Pollock's Ferry on the Roanoke River, NC, from 16 April to 9 May. A big and prolonged release from the reservoir forestalled the peak spawning until late May and may have been the cause of sporadic egg production. Three peaks of spawning occurred 23-24 May, 26-27 May, and 31 May - 1 June. A total of 4,722 eggs were collected. Estimated total production in the Roanoke River in 1989 was 637,919,162 eggs. Viability was estimated at 41.8%, the seventh lowest on record. Age distributions were calculated for the eggs collected. Water temperature and flow characteristics were also recorded. Over 50% of the eggs were collected in water flowing at velocities between 100 and 119.9 cm/sec, 22% were collected at velocities from 60 to 79.9 cm/sec. Studies for 1990 and 1991 contain identical information for each respective year.
An Evaluation of the Blue Crab Fishery
Weekly sampling by gear type was conducted throughout the fishing seasons. Harvest rates and bycatch in the crab pot and trawl industries in Pamlico Sound were assessed. Types of physical injury; incidence of immediate mortality; and incidence of delayed mortality of healthy, damaged, and severely damaged blue crabs in these industries were determined. Fishery-dependent data were analyzed in an effort to develop management strategies for the crab pot and trawl fisheries. Specific management recommendations appear in the final report. An Examination of Alternative Fishing Devices for the Estuarine Shrimp and Crab Trawl Fisheries The destruction of nontarget organisms by the shrimp and crab trawl fisheries is a major concern of managers, fishermen, and the public. The ecological consequences of this problem are poorly understood. However, there is general agreement among all concerned parties that methods need to be examined that reduce bycatch through manipulation of existing gears or by developing new gears that are species specific. The reduction of bycatch in the crab trawl fishery through the use of finfish excluder devices would reduce the loss of finfish in crab trawling. The development of species-specific gears for the harvest of shrimp would reduce finfish bycatch and should be more cost- effective.
An Examination of Alternative Fishing Devices for the Estuarine Shrimp and Crab Trawl Fisheries
The destruction of nontarget organisms by the shrimp and crab trawl fisheries is a major concern of managers, fishermen, and the public. The ecological consequences of this problem are poorly understood. However, there is general agreement among all concerned parties that methods need to be examined that reduce bycatch through manipulation of existing gears or by developing new gears that are species specific. The reduction of bycatch in the crab trawl fishery through the use of finfish excluder devices would reduce the loss of finfish in crab trawling. The development of species-specific gears for the harvest of shrimp would reduce finfish bycatch and should be more cost- effective.
Anemic Blue Crabs
In this research project, concentrations of hemocyanin (functionally equivalent to hemoglobin) were measured in blue crabs (Callinectes sapidus) throughout coastal NC in an effort to (1) determine whether the low hemocyanin levels observed in Pamlico River crabs in September 1988 were associated with a particular season; (2) delineate the areas in which abnormalities occur; and (3) obtain background information on seasonal variability in "unstressed" populations of blue crabs. Spatial and temporal differences in concentrations of hemocyanin may be due to environmental conditions (salinity, hypoxia, and disease organisms or agents such as parasites, bacteria, and viruses). Anthropogenic contaminants, particularly organics, may also be causal factors in lowering levels of hemocyanin. Lower concentrations of hemocyanin were not correlated with age, sex, salinity, or oxygen tension. These preliminary studies suggest that hemocyanin levels are most likely related to water quality.
APES Fish Tissue Baseline Study 1989
The report is a compilation of fish tissue data from 41 locations in the Albemarle-Pamlico Estuarine Study area. It includes the results of 743 samples analyzed for metals and 98 samples analyzed for synthetic organic chemicals. Some general findings include: Only 6 of 420 fish fillet samples analyzed for mercury contained concentrations at or above the FDA action level of 1.0 mg/kg. However, four of the six came from the same site of the Chowan River. High percentages (70%) of detectable lead concentrations were found in whole fish samples from 5 tributaries. Concentrations of metals, particularly mercury, in the fish fillet portions of edible fish are lower in the estuarine portions than in freshwater portions of the study area. No pesticides were detected at or above FDA levels. DDT metabolite levels appeared to have decreased by approximately 70% between 1980 and 1989.
Blue Crabs: Hemocyanin Concentrations as a Measure of Environmental Quality in the Albemarle-Pamlico Estuary
This research project explored the basis for the earlier observations of abnormally low concentrations of hemocyanin in the hemolymph (blood) of blue crabs in the A/P estuarine system. This study determined that the blue crab populations in the Pamlico and Neuse Rivers continued to have low hemocyanin concentrations in their hemolymph, similar to the low concentrations found in 1988 and 1989. In selected North Carolina estuaries, hemocyanin concentrations in crab hemolymph appears to be correlated with location of collection and time of year. In the Pamlico and Neuse Rivers, it appears that there is no direct correlation between contaminant accumulation and either depressed hemocyanin or shell disease. Of the "natural stressors" examined, depressed dissolved oxygen and elevated temperature correlated well with lowered concentrations of hemocyanin in the hemolymph of blue crabs. This observation suggests that long-term exposure to reduced dissolved oxygen may indirectly cause reduction in hemocyanin concentration among blue crabs in the Neuse and Pamlico Rivers. Crabs with reduced hemocyanin may be at a physiological disadvantage which could result in susceptibility to parasitic infection, an inability to molt successfully, and an inability to repair shell trauma, which in turn could serve as a focus for shell disease.
Determining the Relationship between Water Quality and Ulcerative Mycosis in Atlantic Menhaden
This project is designed to determine the relationship between the development of ulcerative mycosis (UM) in fishery populations and selected water-quality conditions. The project will try to identify which of several factors (temperature, dissolved oxygen, salinity, pH, nitrate, and ammonia) have the greatest potential effect on fish health and so warrant further study. In the first year of the study tanks were set-up on location on the Pamlico River, and UM was observed to develop in low salinity areas. In the second year of the study, more tanks were placed at sites on the Pamlico River and stocked with "low risk" (high salinity) menhaden prior to the two customary seasons of UM outbreak (late fall and late spring). Fish observations and water quality analyses were conducted.
Evaluation of Turtle Excluder Devices in the Pamlico Sound Shrimp Fishery
Four different devices were tested in the Pamlico shrimp trawl fishery during October-November 1987 to determine their ability to reduce finfish bycatch while retaining shrimp. The devices were the Scottish Separator Trawl (SST), the Florida Fish Excluder (FFE), the Georgia TED (GT), and the Parrish TED (PT). Testing was conducted on board a local shrimp vessel using a randomized incomplete block design, including a control net. The SST appeared to separate flounder from non-demersal fish but lost shrimp. The PT caught less fish and shrimp than the control net. The GT and FFE both had reduced bycatches of finfish and no significant differences in shrimp catch relative to the control net. Both of these gears deserve further testing in North Carolina. Because of its smaller size and ease of installation, the FFE is recommended over the GT at this time as a device for reducing finfish bycatch in the Pamlico Sound shrimp trawl fishery.
Fishing Practices Mapping and Literature Review of Environmental Impacts
Research Triangle Institute summarizes current fishing practices and provides maps of the areas where these practices are used. The completed locational database, along with other A/P study data (e.g., location of toxic "hot spots," land use, location of critical nursery area), will reside in the North Carolina Center for Geographic Information and Analysis (NC CGIA) computer facility and is useful for developing management strategies for fisheries resources.
Food and Feeding in Larval Fishes
Starvation has been hypothesized as being one of the principle causes of mortality of larval Roanoke River striped bass, especially during unusually high or low flow years. Samples were taken and all fish larvae were identified and enumerated. Up to 53 fish from each sample were studied to determine type and number of ingested prey organisms. Using a computer analysis, relationships were found between (1) fish abundance/distribution and zooplankton abundance/distribution; (2) ingested prey and zooplankton species abundance; and (3) the feeding success of each species of fish relative to striped bass. Samples from 1985, 1986, and 1988 were analyzed. (Flood conditions in 1987 swept all striped bass larvae through the system before they developed to the feeding stage).
Mitigation for the Losses of North Carolina Bay Scallops in the 1987-88 Red Tide Outbreak
Draft. Sampling of adult and new recruit scallops was conducted at 9 sites in 1988 and 1989 in Bogue, Back, Core, and Pamlico Sounds. At the same sites, spat collectors were deployed in the early autumn of 1988 and 1989 to measure settlement. Settlement results suggest that surface area of the substrate is an important determinant of recruitment and that recruitment is a reliable index of relative settlement intensity. Bay scallops appear to be recruitment-limited by meso-scale or sound-wide abundance of spawning adults. In Bogue and Back Sounds, recruitment-scallop year-classes have been extremely poor since the severe red tide mortalities of adults and new recruits in 1987-88. Recruitment limitation may imply a need for management intervention to enhance the spawning stock in these depleted areas.
Proceedings: Fish Disease Workshop
This document presents the papers given at the workshop held by Water Resources Research Institute (WRRI) in Raleigh, NC, on September 22, 1987. The main concerns about fish disease relate to the economy associated with the fisheries, human health, and the overall health of the environment. Widespread fish disease (ulcerative mycosis) was first discovered in southern flounder in the Pungo and Pamlico Rivers in 1982 and in menhaden in 1984. Direct relationships between pollution sources, the quality of ambient waters, and fish kills have almost never been established in the A/P area. The pathogen (the fungi Aphanomyces and Saprlegnia) causing ulcerative mycosis in menhaden has been isolated, but little is known about the process of infection; there is indication of localized reduced immunocompetence playing a role in infection. Evidence does exist that environmental factors play a role in the development of fish disease and general biological stress. The disease primarily affects young fish in areas of lower salinity in May and June. Fortunately, no signs of ulcerative mycosis (UM) have occurred incommercial catches of menhaden, but effects of the disease on the population as a whole are still unknown. The workshop produced a series of recommendations regarding needed specific research and public education.
Recruitment and Growth of the Eastern Oyster in North Carolina
Oyster recruitment varies spatially and temporally but has declined in recent years along the western edge of Pamlico Sound. Oyster recruitment was generally greater along the Outer Banks in high salinity sites than it was in low salinity sites along the western side of Pamlico Sound. Recruitment was also less at shallow depths, where mats were located immediately adjacent to the shore, than was recruitment at greater depths further from shore. Recruitment was greatest on the bottom surfaces of shoals. Spat density in the fall reflected patterns in the intensity of recruitment, thus, greater numbers of spat were found at sites where recruitment was the highest, in deeper locations, and on the underside of shoals. In many instances, however, fall spat densities were reduced in the presence of other organisms and by the degree of sedimentation.
Shell Disease in Blue Crabs
Shell disease is now a common problem in certain areas of the A/P region. Shell lesions were found to have great numbers of bacteria associated with them, but no greater than the shells of clinically normal crabs. Crab hemolymph (blood) has a powerful bacteriocidal activity, but is inhibited at high temperatures and high concentrations of sodium chloride. A bioassay was developed to test this activity. Lower antibacterial activity was observed in crabs with shell disease and lower antibacterial activity (as little as one-fifth the activity) was observed in crabs from riverine areas.
Striped Bass and Precious Waters
Two exhibits have been developed for the NC Aquarium at Pine Knoll Shores. In one, the life history of the striped bass and the environmental stresses affectingstages of the life history are described through the use of graphics, interactive computers, and a large aquarium. Movements of the spawning adults and the juveniles returning to the sea are followed in the display and the importance of salt marsh nursery areas are emphasized. In the other exhibit, aquaria, graphics, an interactive map, and videos promote awareness and appreciation of the region's fragile coastal environment.
The Value of Recreational Fishing on the Albemarle and Pamlico Estuaries
The investigators (1) conducted a literature survey to review all economic models currently available to describe the demand for comparable types of marine recreational fishing and the values of improvements in its quality; (2) developed a database that included a complete description of a samples users' recreational fishing opportunities and decisions, and a measure of the environmental quality; (3) developed a model of recreational decisions; and (4) estimated and evaluated the models (including estimates of average catch rates for specific entry points) based on an enhanced database. The primary users are residents of coastal and near-by counties. A 25% increase in the catch rate would increase the value of a typical trip for an average fisherman by $10-71 (1981 dollars). Such estimates are, however, very sensitive to the original assumptions employed. Subsequent research has altered the assumptions employed by this study. These preliminary results, however, allow initial determinations to be made of the value of improving certain locations and the changes in patterns of use that could be expected to result.
|
|
|
