Development in the southeastern US coastal plain generates the need for a better understanding of how survival and abundance of estuarine nekton respond to urbanization. Apparent survival and density of the dominant Atlantic coast salt marsh fish, the mummichog Fundulus heteroclitus , were estimated in four North Carolina tidal creeks using a model simultaneously fitted to mark-resight and mark-recapture data. Rates of weekly loss (mortality plus emigration) were high (~ 10%). Sampling for tagged fish within and outside of study creeks showed high site fidelity to each creek, indicating that loss largely resulted from mortality rather than emigration. Estimated rates of apparent survival were lowest in the creek with the least instream- and watershed-level impacts. This creek has direct (non-culvert) access downstream to a larger waterbody, suggesting that enhanced access by predators and/or greater rates of permanent emigration may have contributed to lower apparent survival in this creek. There was a positive relation between minnow trap catch-per-unit-effort (CPUE) and density allowing the relationship between CPUE and habitat and urbanization to be examined in a total of six creeks. The largest CPUE estimates occurred early in each growing season and were associated with creeks possessing characteristics most representative of undisturbed salt marsh mosaics: high percentage of marsh coverage instream and downstream and high percentage of marsh edge. Given generally limited movement outside of creeks, differences in abundance among creeks likely result from different levels of recruitment that are related to salt marsh availability. Priority preservation of salt marsh habitats may be warranted by natural resource planners to maintain abundance levels of this trophically important species.

Mark-recapture (M/R) surveys are a standard approach for monitoring White Sturgeon (WS) Acipenser transmontanus populations; however, they can be resource-intensive, may affect fish health, and often lack enough precision to detect population change reliably. Hydroacoustics surveys provide a non-intrusive method that is well-established in fisheries research, but have been applied relatively seldom to sturgeon populations. During 2016, an alternative method was tested for estimating WS abundance by using side-scan sonar within a 58-km reach in the middle Snake River, Idaho, USA, and comparing the results to a standard M/R estimate. Using replicate count data within a N-Mixture model, the sonar method estimated a lower abundance with higher precision (153, 101–213 95% Bayesian credible interval) than that of M/R (219, 138–398 95% confidence interval). Relative to M/R, side-scan sonar took 75% fewer sample-days, exhibited overlapping abundance estimates, and provided similar sturgeon length distributions. These results suggest that side-scan sonar can provide a rapid and precise alternative to M/R for estimating sturgeon abundance.

We used fish body depth to predict trap center-to-center mesh sizes that would optimize size selection of black sea bass Centropristis striata for both current and proposed minimum size limits for this species. We fished trap types of five different square mesh sizes/configurations: (1) 38.1mm mesh, (2) 38.1mm mesh on five sides and 50.8mm mesh on one side (back panel trap), (3) 50.8mm mesh, (4) 57.2mm mesh, and (5) 63.5mm mesh. The 38.1mm mesh trap was the control trap type. Back panel traps are the minimally legal mesh configuration in this region while 50.8mm mesh traps are commonly used in this fishery to further reduce culling of sub-legal black sea bass by fishers. Two previously untested mesh sizes, 57.2 and 63.5mm, were evaluated because a previously published morphometric relationship between black sea bass body depth and total length (TL) predicted that the diagonal openings of these two respective mesh sizes would retain black sea bass close to the current (279mm) and proposed minimum TL limits (305mm). We estimated size selection of each experimental trap type by comparing catches of control and experimental traps. All but the back panel trap displayed relatively steep selection around the fish length at which 50% of individuals were selected (l50). Initial size at retention (l10) by the 57.2 and 63.5mm trap types were nearly identical to current and proposed minimum fish sizes, respectively. Predictions from the body depth: TL relationship were very similar to estimates of l10 and l50, based on uncompressed body depth and compression to 93%. The 57.2mm mesh and 63.5mm mesh trap types maintained catches of legal fish but reduced catches of sub-legal fish compared to the back panel and 50.8mm mesh trap types. Relative to back panel and 50.8mm mesh traps, use of 57.2mm mesh traps would reduce rates of discard and discard mortality given current size limits in this fishery.

We evaluated the performance of small (12.5 mm long) passive integrated transponder (PIT) tags and custom detection antennas for obtaining fine-scale movement and demographic data of mummichog Fundulus heteroclitus in a salt marsh creek. Apparent survival and detection probability were estimated using a Cormack Jolly Seber (CJS) model fitted to detection data collected by an array of 3 vertical antennas from November 2010 to March 2011 and by a single horizontal antenna from April to August 2011. Movement of mummichogs was monitored during the period when the array of vertical antennas was used. Antenna performance was examined in situ using tags placed in wooden dowels (drones) and in live mummichogs. Of the 44 tagged fish, 42 were resighted over the 9 mo monitoring period. The in situ detection probabilities of the drone and live mummichogs were high (similar to 80-100%) when the ambient water depth was less than similar to 0.8 m. Upstream and downstream movement of mummichogs was related to hourly water depth and direction of tidal current in a way that maximized time periods over which mummichogs utilized the intertidal vegetated marsh. Apparent survival was lower during periods of colder water temperatures in December 2010 and early January 2011 (median estimate of daily apparent survival = 0.979) than during other periods of the study (median estimate of daily apparent survival = 0.992). During late fall and winter, temperature had a positive effect on the CJS detection probability of a tagged mummichog, likely due to greater fish activity over warmer periods. During the spring and summer, this pattern reversed possibly due to mummichogs having reduced activity during the hottest periods. This study demonstrates the utility of PIT tags and continuously operating autonomous detection systems for tracking fish at fine temporal scales, and improving estimates of demographic parameters in salt marsh creeks that are difficult or impractical to sample with active fishing gear.

We estimated survival rates of discarded black sea bass (Centropristis striata) in various release conditions using tag–recapture data. Fish were captured with traps and hook and line from waters 29–34 m deep off coastal North Carolina, USA, marked with internal anchor tags, and observed for release condition. Fish tagged on the bottom using SCUBA served as a control group. Relative return rates for trap-caught fish released at the surface versus bottom provided an estimated survival rate of 0.87 (95% credible interval 0.67–1.18) for surface-released fish. Adjusted for results from the underwater tagging experiment, fish with evidence of external barotrauma had a median survival rate of 0.91 (0.69–1.26) compared with 0.36 (0.17–0.67) for fish with hook trauma and 0.16 (0.08–0.30) for floating or presumably dead fish. Applying these condition-specific estimates of survival to non-tagging fishery data, we estimated a discard survival rate of 0.81 (0.62–1.11) for 11 hook and line data sets from waters 20–35 m deep and 0.86 (0.67–1.17) for 10 trap data sets from waters 11–29 m deep. The tag-return approach using a control group with no fishery-associated trauma represents a method to accurately estimate absolute discard survival of physoclistous reef species.

The aim of this study was to document and model the population dynamics of zebra mussels Dreissena polymorpha (Pallas, 1771) in Pool 8 of the Upper Mississippi River (UMR), USA, for five consecutive years (1992-1996) following their initial discovery in September 1991. Artificial substrates (concrete blocks, 0.49 m(2) surface area) were deployed on or around the first of May at two sites within each of two habitat types (main channel border and contiguous backwater). Blocks were removed monthly (30 +/- 10 d) from the end of May to the end of October to obtain density and growth information. Some blocks deployed in May 1995 were retrieved in April 1996 to obtain information about over-winter growth and survival. The annual density of zebra mussels in Pool 8 of the UMR increased from 3.5/m(2) in 1992 to 14,956/m(2) in 1996. The average May-October growth rate of newly recruited individuals, based on a von Bertalanffy growth model fitted to monthly shell-length composition data, was 0.11 mm/d. Model estimates of the average survival rate varied from 21 to 100% per month. Estimated recruitment varied substantially among months, with highest levels occurring in September-October of 1994 and 1996, and in July of 1995. Recruitment and density in both habitat types increased by two orders of magnitude in 1996. Follow-up studies will be necessary to assess the long-term stability of zebra mussel populations in the UMR; this study provides the critical baseline information needed for those future comparisons.

We collected 1,399 striped bass Morone saxatilis from western Albemarle Sound, North Carolina, during May through October of 2002 and 2003 to characterize diet, prey type selectivity, and prey size selectivity. Herrings Alosa spp., Atlantic menhaden Brevoortia tyrannus, bay anchovy Anchoa mitchilli, silversides Menidia spp., and yellow perch Perca flavescens dominated the diets of age-1 striped bass, while Atlantic menhaden dominated the diets of older striped bass. Selectivity was calculated for three categories of striped bass (ages 1, 2, and 3+ [3-7]) based on fish prey collections from a 61-m beach seine and a 76-m purse seine. Striped bass of all ages primarily consumed fish prey regardless of the month or year. Each age category of striped bass selected for one or more species of prey from the suborder Clupeoidei. Age-1 striped bass selectivity of Alosa spp. generally increased with the progression of each sampling season, whereas selectivity for Atlantic menhaden, Menidia spp., and yellow perch decreased over time within each season. Striped bass of all ages displayed strong selection for Atlantic menhaden and strong selection against spiny-rayed fish prey. Striped bass displayed selection for specific prey, although the mechanisms responsible for selection appear to vary through time and may differ for different prey types. Striped bass either displayed neutral size selectivity or selected for relatively small prey. The mean and maximum sizes of fish prey increased with increases in striped bass size, but the minimum prey size changed little. Our results of seasonal and age-specific changes in selectivity will be valuable for modeling the impact of striped bass predation on resource prey species.

Largemouth bass Micropterus salmoides, an intensively studied sport fish of temperate North America, has been introduced into tropical regions, but with little evaluation of fishing or natural mortality rates. Previous research in Puerto Rico suggested that annual mortality rates are high, but whether the extended spawning season (nearly 6 months annually), high angler harvest, or a combination was the cause of the elevated mortality was unresolved. Using ultrasonic telemetry, we tracked 44 adult largemouth bass over an 18-month period to quantify patterns of natural, fishing, and total mortality. Using a general capture-recapture model, we estimated the annual instantaneous rates of fishing (0.584, SE = 0.164) and natural mortality (0.310, SE = 0.122). Natural mortality varied seasonally and generally increased during periods of spawning activity; however, fishing mortality was fairly consistent throughout the study. Given the relatively high fishing mortality rate, restrictions on harvest could probably be used to alter the age and size distribution of this population.

Despite the large number of low-head dams on North Carolina streams and rivers, fishways have rarely been used to restore access to habitat upstream of dams. The goal of this study was to determine the use of a prefabricated Alaska steeppass fishway installed at a low-head dam on Black Creek, a blackwater tributary of the Neuse River near Smithfield, North Carolina. Between 21 February and 2 June 2003 study period, the ladder was used by 949 gizzard shad (Dorosoma cepedianum), 2 American shad (Alosa sapidissima), and 1 golden shiner (Notemigonus crysoleucas). Upstream passage of gizzard shad was marginally correlated (P = 0.06) with stage height of a nearby stream. These results illustrate that fish passage should be considered not only for anadromous fishes but also riverine species that undertake a spring spawning migration or that make upstream movements for feeding or other life cycle requirements. Prefabricated fishways are simple to install and could restore access to the considerable habitat upstream of low-head dams.

The traditional multiple-year tag return method is a fundamental approach to estimating fishing and natural mortality rates in fisheries. It can provide reliable and precise estimation of the parameters when the tag reporting rate, lambda, is known. However, it is often difficult to estimate lambda accurately. An additional disadvantage is that this method has to estimate natural mortality indirectly because natural deaths are not observable. Recently, fisheries biologists have begun to implement telemetry methods to estimate fishing and natural mortality. The advantage of a telemetry method is that it contains direct information about natural mortality and survival. A shortcoming is that there is no direct information on fishing deaths. In this paper, we combine the two methods, using direct information about both fishing and natural mortality to obtain more precise and effectively unbiased parameter estimates, including reporting rate estimates for the regular tags. Using simulation when the telemetry tag relocation probability equals 1, we found that the relative standard error (RSE) of natural mortality estimates in the combination method is much improved relative to those of the tag return and telemetry methods. Annual fishing mortality estimates can also be estimated precisely. As expected, as the relocation probability of telemetry tags decreases the RSE of natural mortality and the other parameter estimates increases, but only slightly. Studies clearly should have relocation probabilities that are as high as possible. The tag reporting rate estimates are typically precisely estimated in the combined model. This is very important, as the tag reporting rate is not easy to estimate with other methods.

We examined long-term data sets from large rivers in the northern, central, and southern parts of the ranges of anadromous river herring (alewife Alosa pseudoharengus and blueback herring A. aestivalis) to assess the current status of these species and for evidence of fishery-induced effects on their demographic characteristics. Both species show signs of overexploitation in all rivers examined, such as reductions in mean age, decreases in percentage of returning spawners, and decreases in abundance. These two species should be managed separately since exploitation within a given river is often biased toward one or the other and there are enough differences in their biology so that a single management option will affect them differently These species are not distinguished in commercial catches, which hinders understanding of their exploitation.

Although most species of anadromous sturgeons worldwide are threatened with extinction, information on the estuarine and marine components of their life history is gen- erally lacking. During March 1997 to July 1999, we used ultrasonic telemetry to examine estuarine and marine habitat use of adult Gulf sturgeon Acipenser oxyrinchus desotoi from the Choctawhatchee Bay/River System, Florida. During winter and spring, telemetered Gulf sturgeon were distributed nonrandomly within Choctawhatchee Bay, with most relocations in nearshore areas 2-4 m deep. Within the bay, Gulf sturgeon occasionally moved long dis- tances but usually remained in localized areas (<1 km 2 ) for several weeks. Areas where Gulf sturgeon remained for prolonged periods were characterized by sandy substrate harboring a benthic community dominated by crustaceans and annelids. Most male Gulf sturgeon re- mained exclusively in Choctawhatchee Bay during the winter and spring. In contrast, most females during this time were either relocated in the Gulf of Mexico or were absent at sam- pling locations, having last been detected at bay entrances. Declines in habitat quality in Choctawhatchee Bay and the Gulf of Mexico may hinder recovery of this species, since adult Gulf sturgeon rely on these areas for nourishment during periods of gonadal growth.

The Gulf sturgeon ( Acipenser oxyrinchus desotoi) was listed as a threatened species in 1991 because of declines in abundance throughout the Gulf of Mexico. One recommendation of the recovery plan for Gulf sturgeon was to characterize critical habitats. In this study, radio telemetry was used to determine summer ( June August) distribution and habitat use of Gulf sturgeon in the Choctawhatchee River, Florida Alabama. Ranging from 74 to 222 cm total length, 63 radio-tagged fish were located 398 times during weekly or biweekly searches in June August of 1994-1997. A 10-km section of the lower Choctawhatchee River (river km 40-49.9) accounted for 38% of the summer locations of immature fish ( less than 1.3 m fork length) and 73% for mature fish. Fish were typically located at sites that were 2 5 m in depth, with water temperatures of 25-28 degreesC and a sand substrate. Spring discharges account for up to one-third of the mainstem river flow in this reach, but water temperatures at fish locations were similar to temperatures at fish locations in all other sections of the river. Efforts to monitor and improve habitat quality should be focussed on this river reach, given that a high percentage of the total Choctawhatchee River population occurs there during summer.

Green sturgeon ( Acipenser medirostris) movement patterns and habitat use within the Rogue River, Oregon were evaluated using radio telemetry. Nineteen specimens ranging from 154 to 225 cm total length were caught by gill netting and tagged with radio transmitters during May July 2000. One tagged green sturgeon was verified as a female near spawning condition. Individual green sturgeons spent more than 6 months in fresh water and traveled as far as river kilometer (rkm) 39.5. Green sturgeon preferred specific holding sites within the Rogue River during summer and autumn months. These sites were typically deep ( > 5 m) low-gradient reaches or off-channel coves. Home ranges within holding sites were restricted. All tagged individuals emigrated from the system to the sea during the autumn and winter, when water temperatures dropped below 10 degreesC and flows increased. This species is extremely vulnerable to habitat alterations and overfishing because it spawns in only a few North American rivers and individuals reside within extremely small areas for extended periods of time.

The Atlantic sturgeon ( Acipenser oxyrinchus oxyrinchus) was historically abundant within Albemarle Sound and the Roanoke River in North Carolina, but declined dramatically in the late 1800s in response to intensive fishing. Recent evidence suggests that the population may be recovering, following a statewide prohibition on harvest in 1991. A recruitment index generally increased from 1992 through 2001. Estuarine habitat for juveniles appears to be suitable, resulting in mean growth rates for age 1 fish ranging from 0.59 to 0.81 mm day(-1). A restoration goal of 7000 - 21 000 subadult and adult Atlantic sturgeon was developed for the Roanoke River, based on historical landings records. Bycatch mortality because of commercial gill-netting in Albemarle Sound could affect recovery. Telemetry and netting data indicate that juvenile Atlantic sturgeon in the sound are most abundant in shallow nearshore areas where commercial gill-netting is concentrated. However, immediate mortality rates from survey and commercial gill-netting in Albemarle Sound were only 0-2%. Additional field studies are needed to re ne estimates of immediate- and longer-term mortality associated with gill-net bycatch.

Natural mortality can substantially affect fish population dynamics, but the rate is difficult to estimate because natural deaths are rarely observed and it is difficult to separate the effects of natural and fishing mortality on abundance. We developed a new telemetry approach for estimating natural and fishing mortality rates and applied it to the population of striped bass Morone saxatilis in Lake Gaston, North Carolina and Virginia. Our analyses were based on a sample size of 51 telemetered striped bass that were known to be alive and in Lake Gaston at least 1 month after capture and surgery. Relocations of live fish and fish that died of natural causes were used to estimate natural and fishing mortality rates and the probability of relocating telemetered fish. Fishing mortality rates varied seasonally, but few natural deaths were observed, so the best model incorporated a constant annual instantaneous natural mortality rate (M; +/- SE) of 0.14 +/- 0.02. With the uncertainty in model selection accounted for, the average annual M was 0.16 +/- 0.04 For 1997 and 0.12 +/- 0.04 for 1998. Estimated annual fishing mortality rates (F) were 0.74 +/- 0.13 for 1997 and 0.34 +/- 0.18 for 1998. This telemetry approach for estimating mortality rates does not rely on angler reporting of tagged fish. The relative standard errors for;M (24-33%) were comparable to those obtained from traditional ragging methods with large sample sizes. This approach is most applicable in closed systems, where fishing mortality estimates are not biased by emigration. A high relocation probability is critical to reliably establishing seasonal changes in mortality.

Adult striped bass Morone saxatilis perform best when water temperatures are below 26degreesC and dissolved oxygen levels are above 2 mg/L and will begin to exhibit stress responses at higher temperatures or lower oxygen levels. In southern U.S. reservoirs, summer conditions may result in a reduction of suitable habitat for adult striped bass and therefore influence population dynamics and distribution. We tracked 51 adult striped bass that had been implanted with individually coded sonic transmitters for 2 years in Lake Gaston, Virginia-North Carolina, to determine the impact of habitat availability on seasonal trends in movement and distribution. Monthly movement rates of individual fish averaged 7,340 m (SE = 544 m) over the course of the study, and no significant differences in movement rates were detected among seasons or between sexes. Striped bass were relocated throughout the reservoir in all seasons despite evidence of spatial variability in the availability of suitable habitat during the summer months. Individual striped bass tended to occupy specific reservoir areas in all seasons and years of the study, with the exception of spring spawning runs. Home ranges of individual fish were not clearly related to the availability of summer habitat refuges but tended to be located in large, downlake basins or near the tailrace of an upstream dam. Fidelity of striped bass to limited areas within the reservoir suggests that spatially explicit management strategies are appropriate for reservoir populations of striped bass.

Striped bass Morone saxatilis and American shad Alosa sapidissima in the Neuse River, North Carolina, historically migrated up to 435 km upriver to spawn. However, migration was impeded in 1952 by the construction of Quaker Neck Dam at river kilometer 225 (measured from the point where the Neuse River enters Pamlico Sound). To determine the fraction of tagged fish that migrated upstream of this low-head dam and the characteristics of selected spawning habitat, we implanted sonic transmitters in 25 striped bass and 25 American shad during 1996 and 1997. We determined preferred depth, water velocity, and substrate composition by measuring those characteristics at both randomly selected sites and sites where spawning was observed. Of 13 striped bass and 8 American shad with transmitters that migrated to the base of Quaker Neck Dam, only 3 striped bass passed the structure, indicating that the dam was an impediment to migration. Striped bass spawning was observed only in the area directly below (within 1.5 km of) Quaker Neck Dam. Although none of the telemetered American shad passed Quaker Neck Dam, American shad spawning was observed from the base of the dam to 1.5 km downstream as well as 3 km above the dam. Striped bass spawned at sites with significantly higher water velocity and significantly larger substrate than on average was found at randomly sampled locations. American shad spawned at sites that were significantly shallower and had significantly larger substrate than was found in random samples. The type of spawning habitat selected by both species is more abundant above than below Quaker Neck Dam, indicating that improved access to upstream reaches would benefit both species.

Information about spawning migration and spawning habitat is essential to maintain and ultimately restore populations of endangered and threatened species of anadromous fish. We used ultrasonic and radiotelemetry to monitor the movements of 35 adult Gulf sturgeon Acipenser oxyrinchus desotoi (a subspecies of the Atlantic sturgeon A. oxyrinchus) as they moved between Choctawhatchee Bay and the Choctawhatchee River system during the spring of 1996 and 1997. Histological analysis of gonadal biopsies was used to determine the sex and reproductive status of individuals. Telemetry results and egg sampling were used to identify Gulf sturgeon spawning sites and to examine the roles that sex and reproductive status play in migratory behavior Fertilized Gulf sturgeon eggs were collected in six locations in both the upper Choctawhatchee and Pea rivers. Hard bottom substrate, steep banks, and relatively high flows characterized collection sites. Ripe Gulf sturgeon occupied these spawning areas from late March through early May, which included the interval when Gulf sturgeon eggs were collected. For both sexes, ripe fish entered the Choctawhatchee River significantly earlier and at a lower water temperature and migrated further upstream than did nonripe fish. Males entered the Choctawhatchee River at a lower water temperature than females. Results from histology and telemetry support the hypothesis that male Gulf sturgeon may spawn annually, whereas females require more than 1 year between spawning events. Upper river hard bottom areas appear important for the successful spawning of Gulf sturgeon, and care should be taken to protect against habitat: loss or degradation of known spawning habitat.

Gulf sturgeon Acipenser oxyrinchus desotoi, a subspecies of Atlantic sturgeon A. oxyrinchus, were once abundant in coastal rivers of the eastern Gulf of Mexico but have declined substantially due to habitat loss and overexploitation. Because relatively little is known about their population status in the Apalachicola River, Florida, we used capture-recapture data collected during 1982-1991 to assess the population of Gulf sturgeon at the Jim Woodruff Lock and Dam, which limits upstream migration. Wt, estimated that about 100 fish greater than 45 cm total length were present below the dam, although the estimates were biased to an unknown degree because of violations of capture-recapture model assumptions. To obtain a less biased estimate, we conducted an intensive 10-week capture-recapture experiment in 1993 that accounted for most of the assumption violations. We also used radiotelemetry to test the assumption that the population remained closed to immigration and emigration during sampling. The 1993 results also indicated a population of about 100 Gulf sturgeon below the dam; however, movement in and out of the sampling area occurred, so the population at the dam was not closed. Using simulation, we found that Jolly-Seber and Schnabel capture-recapture models were generally unbiased when fish had a high probability of returning to the study area after temporary emigration. However when fish had a low probability of returning to the study area after temporary emigration, substantial bias occurred in both models. Length composition data from 1982 to 1991 and for 1993 suggested that low recruitment may account for the failure of the population to rebuild. We recommend identifying all areas of concentration of Gulf sturgeon in the Apalachicola River and developing a standardized sampling program for monitoring this threatened species.