Browsing by Author "Joseph E. Hightower, Committee Chair"

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    Abundance and migratory patterns of anadromous fish spawning runs in the Roanoke River, North Carolina
    (2003-07-17) Hewitt, David Allen; Joseph E. Hightower, Committee Chair; Peter S. Rand, Committee Member; Kenneth. H. Pollock, Committee Member
    Anadromous fishes often support significant commercial and recreational fisheries. Obtaining the information needed for their effective management can be problematic, however, because of the difficulties associated with sampling coastal rivers. Objectives of this research were to: (1) evaluate two novel methods for characterizing the spawning runs of anadromous fishes in southeastern coastal rivers, and (2) develop a method for estimating the total size of a spawning run. We operated a fishwheel on the Roanoke River, North Carolina during the spring seasons of 2000, 2001, and 2002, and conducted stationary, split-beam, side-looking hydroacoustic monitoring at the same site in 2001. The fishwheel captured 39 species over the three seasons, but fishwheel effectiveness appeared to vary among species and with changes in river conditions. The turning speed of the baskets was nearly always lower than what is considered optimal, suggesting that water velocities were too low for most effective operation. Daily fishwheel catches provided good information about the timing of migration for anadromous species that were captured in sufficient number, primarily striped bass and blueback herring. Catches of anadromous species varied substantially through each season, both due to the timing of migration and to changes in the fishwheel's effectiveness. Daily fishwheel catches provided information about the spawning runs at finer temporal scales than is typically possible, and the size distributions and annual catch rates of striped bass obtained by fishwheel sampling were similar to results from electrofishing. We developed a model for estimating run size using data from split-beam sidelooking hydroacoustic monitoring. The model is based on counts of upstream migrants and makes adjustments for: (1) the proportion of the day that was sampled (temporal sampling fraction), (2) the proportion of the river that was sampled (spatial sampling fraction), (3) the proportion of fish detected that were included in the counts (detectability), and (4) the proportion of the counts comprised by the species of interest (species proportion). Future refinements of the model should include: (1) methods to account for variation in detection probability as it relates to a target's location in the beam, and (2) stratification procedures to use in calculating the spatial sampling fraction(s). Stationary, split-beam, side-looking hydroacoustic monitoring was effective for assessing the abundance and temporal and spatial patterns in the 2001 spawning run of striped bass. The striped bass run was characterized by a number of distinct peaks, which were not related to river discharge. The pattern of the run was generally consistent with that obtained from daily fishwheel catches. We found that the number of striped bass migrating upstream was significantly greater during nighttime hours than during the day. Most striped bass migrated within 1.5 m of the river bottom and were evenly distributed across the channel, as would be expected based on river morphology and flow conditions. By combining acoustic counts of upstream migrants with supplemental sampling data from the fishwheel, we estimated that 262,789 striped bass participated in the spawning migration in 2001. Our estimate is in good agreement with run size estimates for 1956-1980, but is considerably lower than more recent estimates based on virtual population analysis modeling. Fishwheels and split-beam, side-looking hydroacoustics both hold promise as sampling methods for anadromous fishes in southeastern coastal rivers. Each gear provides valuable information about spawning runs that is difficult to obtain by more traditional means. Reliable run size estimates and detailed information about the temporal and spatial patterns in spawning runs should provide managers with a stronger foundation for building sustainable fisheries.
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    Migration and spawning of anadromous shads in the Roanoke River, North Carolina
    (2010-01-21) Harris, Julianne Elaine; Joseph E. Hightower, Committee Chair
    Anadromous alosines are ecologically, commercially, and recreationally valuable fishes. Some populations of alosines are at historically low levels, as a result of overfishing, pollution and habitat change, including the presence of dams, which block access to historic spawning sites upstream and alter spawning habitat downstream. To aid in the restoration of alosine stocks, I evaluated several methods for spawning habitat identification and characterization and evaluated trap and transport as a method to give American shad Alosa sapidissima access to additional spawning habitat above dams in the Roanoke River, North Carolina and Virginia. The Roanoke River has four anadromous shads: American shad, hickory shad A. mediocris, blueback herring A. aestivalis, and alewife A. pseudoharengus. For all four alosines, spawning sites river-wide were most efficiently identified using plankton tows. Spawning habitat selection for hickory shad and river herring (blueback herring and alewife) could be evaluated using spawning pads, whereas American shad eggs were unsuccessfully sampled by spawning pads and spawning habitats were best examined by visual observations of spawning splashes. Unlike the other alosines in this study, very little is known about spawning habitat for hickory shad. Hickory shad eggs were collected at water temperatures from 10 to 23 ºC, and peaked from 11 to 14 ºC. Spawning generally occurred in water velocities ≥0.1 m/sec, over substrates free from silt. Standard USFWS and Bayesian belief network formats were used to develop preliminary habitat suitability models for hickory shad. Bayesian belief networks are a relatively new method for modeling habitat suitability for fishes, but could prove very useful in the future, especially for species such as American shad which have been the focus of more study and are in need of restoration. We evaluated movement patterns and spawning of sonic-tagged adult American shad transported to habitats above dams on the Roanoke River. Most transported fish spent relatively little time in the riverine habitat considered suitable for spawning and no eggs were collected by plankton sampling. American shad appeared to move more effectively through a smaller as compared to a larger reservoir, but migration was best when fish were released directly into riverine habitat. Low mortality resulted from downstream migration through each dam turbine, but many individuals were observed just upstream from a dam late in the season, suggesting that structures to increase downstream passage may be beneficial. We used data on behavior and outmigration of American shad adults and fry released above and below dams on the Roanoke River to develop a deterministic, density-dependent, stage-based matrix model to predict possible population-level effects of transporting American shad to upper basin habitats. The American shad population in the Roanoke River appears small compared to assumed values of carrying capacity in the lower river and would appear to benefit from transport only under optimal conditions of young survival and effective fecundity. The matrix model predicts that under present conditions, improvements to survival rates of young or adults would likely lead to greater improvements in the stock size of American shad in the Roanoke River.
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    Movement, habitat selection and growth of early-juvenile Atlantic sturgeon in Albemarle Sound, North Carolina
    (2003-11-20) Armstrong, James Leland; Richard L. Noble, Committee Member; Leonard A. Stefanski, Committee Member; Mary L. Moser, Committee Member; Joseph E. Hightower, Committee Chair
    We characterized habitat use, growth, and movement of early juvenile Atlantic sturgeon in Albemarle Sound, North Carolina through field work conducted in 1997 and 1998. Most of the Atlantic sturgeon encountered in the study were estimated to be age-1 fish. The presence of numerous age-1 Atlantic sturgeon near a historic spawning river (Roanoke River) suggests that these fish are likely native to the system. Recaptures of tagged Atlantic sturgeon allowed us to describe the growth of early juveniles using simultaneous analysis of length increment and length composition data. Growth of Atlantic sturgeon in Albemarle Sound was similar to growth rates observed in other systems, and suggests that Albemarle Sound serves as an adequate nursery habitat. Among telemetered individuals, we observed a preferred depth interval of 3.6 to 5.4 m. Additionally, the organic rich mud substrate type was used significantly more than expected under the null hypothesis of random movement. Site-constrained movement was demonstrated by some fish. Occasional large catches of Atlantic sturgeon in our survey gear suggested that these fish may aggregate in the sound. Bycatch of Atlantic sturgeon by a commercial flounder gillnetter in eastern Albemarle Sound was dominated by fish within the expected age-2 size range. The impact of local gillnet fisheries on the Atlantic sturgeon population in the Roanoke River/Albemarle Sound system remains an important and unanswered question.
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    Use of Split-Beam Sonar to Estimate Anadromous Fish Runs in the Roanoke River, North Carolina.
    (2008-11-24) Magowan, Kevin James; Joseph E. Hightower, Committee Chair; Kenneth H Pollock, Committee Member; Jeffrey A Buckel, Committee Member
    ABSTRACT MAGOWAN, KEVIN JAMES. Use of Split-beam Sonar to Estimate Anadromous Fish Runs in the Roanoke River, North Carolina. (Under the direction of Joseph E. Hightower.) Annual in-river population estimates of anadromous fishes in the Roanoke River would be useful for managing this resource. The goal for some species (American shad Alosa sapidissima, alewife Alosa pseudoharengus, and blueback herring Alosa aestivalis) is to monitor current restoration efforts. For other species (striped bass Morone saxatilis, hickory shad Alosa mediocris and white perch Morone americana), the goal is to manage sustainable commercial and recreational fisheries. Hydroacoustic methods are useful for estimating the abundance of anadromous fishes, because these methods are non-intrusive, have been proven to work in other river systems, and are capable of generating real-time population estimates. The goal of this project was to estimate the numbers of anadromous fishes returning to the Roanoke River in 2006 and 2007. We used fixed-location split-beam sonar in conjunction with drift gill netting and boat electrofishing to estimate run size of alewife, American shad, blueback herring, hickory shad, striped bass and white perch migrating upstream past a study site at river kilometer 64 near Williamston, North Carolina. The default estimates (and SEs) for 2006, assuming a uniform cross-channel distribution of upstream migrants and a fixed river depth cut-off point to separate fish migrating near the river bank (i.e., in water < 3 m deep) from fish migrating in the river channel (i.e., in water > 3 m deep), were: total run size 819,063 (± 31,234), alewife 60,622 (± 7,871), American shad 35,483 (± 4,936), blueback herring 88,281 (± 8,689), hickory shad 40,465 (± 6,155), striped bass 217,439 (± 14,236), white perch 83,035 (± 8,054), and other fish species 293,737 (± 13,356). In 2006, the estimates were generated for fish that migrated past the monitoring site from March 18 to May 29. In 2007, under the same assumptions, an estimated total of 1,137,921 (± 32,310) fish migrated upstream past the study site from March 5 to May 26. Species-specific run size estimates were: alewife 270,478 (± 16,138), American shad 5,175 (± 1,401), blueback herring 173,796 (± 16,660), hickory shad 102,645 (± 12,720), striped bass 139,517 (± 14,890), white perch 45,522 (± 2,057), and other fish species 400,787 (± 22,224). The profile of the river channel at the monitoring site allowed for the acoustic beam to sample about 59% of the cross-sectional area of the river channel. This was an increase in the percentage of area covered by the acoustic beam, relative to an upriver site used in 2004-2005. Increasing the area sampled should lead to a more accurate estimate of the total number of upstream migrants. However, the reliability of species-specific run size estimates is hard to assess because high species diversity and low catches made estimating species composition difficult. There were strong diurnal patterns in migration. Mean fish passage was significantly higher during daylight hours (06:00 to 20:59). Based on hydroacoustic results, upstream migrants at night were larger, swam slower and were located closer to the river bank. Upstream migrating fish also responded to changes in flow, with fish being evenly distributed across the river channel during flows < 4,000 ft3s-1 (113 m3s-1), but closer to shore during periods of higher flows. Most projects using sonar in rivers to count fish are done in rivers with low species diversity, so obtaining accurate species-specific run-size estimates in a species-rich environment like the Roanoke River, North Carolina is challenging. The greatest improvements in the reliability of hydroacoustic estimates will likely come from increasing the area of the sampled river cross-section, eliminating bottom interference, and refining the methods used to estimate species composition.