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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.

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.

Current spatiotemporal modeling techniques used to understand and predict ecosystem processes can often be categorized into one of two distinct modeling frameworks. Eulerian frameworks are often used to balance changes and fluxes of mass and energy and usually used in the simulation of physicochemical regimes. Lagrangian frameworks are often used to simulate the movement and/ or behavior of individuals, groups of individuals, or populations. The use of different frameworks has created a disconnect between the modeling capabilities of physiochemical modelers (usually engineers) and biological population modelers (usually biologists). I describe a modeling framework, the Coupled Eulerian-Lagrangian Hybrid (CEL Hybrid) Ecological Modeling System, which couples the two frameworks into a comprehensive, unified framework for simulation of ecological processes. The CEL Hybrid modeling framework provides the means to simulate the spatiotemporal population processes, particularly movement dynamics, of higher trophic level species in aquatic environments.