Striped Bass Population Research Articles

Diet of Striped Bass in the Southern Gulf of St. Lawrence (Canada) with Emphasis on the Spring Spawning Aggregation

The southern Gulf of St. Lawrence (sGSL) population of Morone saxatilis (Striped Bass) increased over 50 fold between the mid-1990s and 2013–2015, which led to interest in how their feeding might affect populations of commercially and recreation-ally important species. Information on the feeding habits of Striped Bass in all Canadian waters is scarce; therefore, a large number (n = 2220) of sGSL Striped Bass (19–86 cm fork length [FL]) stomachs were collected seasonally (2013–2015) in the Miramichi Estuary (where almost the entire population of individuals >30 cm FL aggregates during spring) and smaller estuaries that empty into the sGSL (summer only), by means of trap nets and by angling. Striped Bass collected during May–early June fed almost exclusively upon Osmerus mordax (Rainbow Smelt) but also consumed a few juvenile Salmo salar (Atlantic Salmon). Striped Bass collected in trap nets during 5–30 June mainly ate a mix of Alosa pseudoharengus (Alewife) and A. aestivalis (Blueback Herring); those collected by angling consumed aquatic insects and Crangon septemspinosa (Sevenspine Bay Shrimp). Striped Bass collected during July–September (30–45 cm FL) ate C. septemspinosa, Palaemon vulgaris (Common Grass Shrimp), and small estuarine fishes. The autumn sample was too small to be considered representative of the population; nevertheless, these fish (32–73 cm FL) ate juveniles of Microgadus tomcod (Atlantic Tomcod), Urophycis tenuis (White Hake), and Gadus ogac (Greenland Cod). The data collected herein would permit reasonable estimates of prey consumed by the sGSL Striped Bass population during spring and, for fish <45 cm total length, during summer, but estimation of annual prey consumption by the sGSL Striped Bass population requires additional data.

Looking for Striped Bass in Atlantic Canada: The Reconciliation of Local, Scientific, and Historical Knowledge

Morone saxatilis (Striped Bass) occurs throughout the provinces of Atlantic Canada, but its full distribution in the region is undescribed. Canadian Striped Bass populations are grouped by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) into 3 geographically distinct Designatable Units: Saint Lawrence River, Southern Gulf of St. Lawrence, and Bay of Fundy. Striped Bass also occurs in many other unclassified Canadian regions, and growing evidence suggests that some of these locations may support distinct, uncharacterized populations. The recreational fisheries for Striped Bass are rapidly increasing in popularity in Canada, and thus, it has become of great importance to both recognize the species' full distribution and manage the fisheries therein. We compiled recent research, certified angling catches, historic accounts, grey literature, and anecdotal reports to identify coastal sites and rivers where Striped Bass have been reported. Our findings will help managers and researchers target rivers and coastal areas for assessment and study to encompass the entirety of the species' range in Canadian waters. Our report suggests that a fourth Designatable Unit for Eastern Cape Breton Island and Northeastern Nova Scotia is needed to both monitor and manage assemblages of Canadian Striped Bass.

SNP panel development for genetic management of wild and domesticated white bass (Morone chrysops).

White bass (Morone chrysops), striped bass and their interspecific hybrid are important game fishes, whereas the hybrid striped bass is an important aquaculture species in the US. Numerous state, federal and private hatcheries, therefore, rear these species for stocking purposes as well as for food fish. Although striped bass populations (both wild and domesticated) have been extensively evaluated, relatively little effort has been directed toward the study and improvement of white bass. In this study, we developed SNP resources to examine the genetic relationships among a long-term domesticated white bass line and five potential founder stocks for selective breeding collected from drainages in Arkansas, Texas and Alabama. Using genotyping-by-sequencing, we generated 13872 genome-wide SNP loci across the six populations. Stringent filtering of SNP-calling parameters identified 426 informative SNP loci. Population genetic and structure analyses using these loci revealed only moderate genetic differentiation between populations (global Fst =0.083) and indicated two major genetic clusters. A final 57-SNP assay was successfully designed and validated using the MassARRAY system. The developed SNP panel assigned 96 additional genotyped individuals to their population of origin with 100% accuracy. The SNP resources developed in this study should facilitate ongoing efforts in selective breeding and conservation of white bass.

Exploring Causal Factors of Spawning Stock Mortality in a Riverine Striped Bass Population

AbstractThe recovery of the Atlantic Striped Bass Morone saxatilis stock in the 1990s is an important example of effective natural resources management. Implementation of Atlantic States Marine Fisheries Commission (ASMFC) harvest regulations reduced mortality, protected older and more fecund females, and contributed to the formation of dominant year‐classes in the 1980s and 1990s. However, Striped Bass stocks south of Albemarle Sound, North Carolina, are not subject to ASMFC management plans, and many populations have failed to attain recovery goals. Catch‐curve analyses indicate that the Neuse River Striped Bass population continues to experience spawning stock exploitation rates similar to those implicated in the decline of the Atlantic Migratory and Albemarle Sound/Roanoke River stocks in the 1970s. From 1994 to 2015, Striped Bass instantaneous fishing mortality (F) in the Neuse River ranged from 0.12 to 0.84 and exceeded the overfishing threshold (FThreshold = 0.41) in 12 of 22 years. A global linear model using environmental and exploitation factors accounted for 55% of the variability in spawning stock discrete annual mortality. An information‐theoretic approach was used to elucidate the best linear model for predicting discrete annual mortality. The best model included previous‐year gill‐net effort and same‐year commercial harvest (Akaike weight = 0.64, R2 = 0.50). Model‐averaged coefficients for gill‐net effort and commercial harvest suggested total exploitation impacts that were congruent with other studies of Neuse River Striped Bass. Results indicate that reducing exploitation to target levels will require substantial reductions in gill‐net effort in areas of the Neuse River where Striped Bass occur. Reducing exploitation may increase spawning stock biomass and advance the age structure of spawning females, conferring an increased likelihood of successful recruitment and production of dominant year‐classes during periods of favorable environmental conditions.

Modeling the Effects of Vital Rate Manipulation and Management Scenarios to Predict the Population Impact of Restoration Programs on an Unrecovered Coastal Population of Striped Bass

AbstractStriped Bass Morone saxatilis have supported important fisheries along the Atlantic coast of North America. However, the species experienced major declines due to overharvest, water quality degradation, and dam construction. Restoration efforts have been successful for specific stocks but unsuccessful for the Striped Bass population in the Neuse River of North Carolina. Ongoing research programs have estimated stage‐ and source‐specific mortality rates to identify mechanisms associated with the lack of recovery of the population. These demographic data are useful; however, they give little insight into the effectiveness of potential restoration programs. To develop effective management strategies, we used estimated mortality rates from the literature to build an age‐structured population model. We estimated that if vital rates remained constant, the Neuse River adult Striped Bass population would consist of 18,457 individuals (95% credible interval = 8,176–34,314). We then conducted a life stage simulation analysis to determine the adult population abundance and age structure that would result from a 50% decrease of the following: juvenile and adult natural mortality, recreational discard and harvest, and commercial discard and harvest. Finally, we simulated the potential impacts of six possible management scenarios on population abundance and age structure. We determined that the abundances of adults (age 3+) and older adults (age 6+) were most sensitive to natural mortality of juveniles and adults and next most sensitive to commercial harvest and discard. We further estimated that eliminating all fishing mortality would have the greatest impact on the population and would result in a 26‐fold increase in abundance of age‐6+ adults. Our results suggest that high mortality rates are preventing the development of a sufficient abundance of adult spawning stock. We recommend that managers use this model to identify the most effective management scenario—given specific goals and constraints—to help increase Striped Bass abundance in the Neuse River.

Juvenile and Adult Striped Bass Mortality and Distribution in an Unrecovered Coastal Population

AbstractStriped Bass Morone saxatilis fisheries have been important in the eastern United States since the 1700s, but many populations have declined from historic levels. Enhancement programs, harvest reduction, water quality improvements, and habitat restoration have led to successful recoveries for specific stocks. However, these efforts have not been successful for the Striped Bass population in the Neuse River of North Carolina. Possible mechanisms inhibiting recovery of this population include overharvest, high discard mortality, poor water quality, and altered flow regimes. These mechanisms and their impacts on the Neuse River population are unclear; therefore, to gain insight, we estimated mortality and distribution of the population. Specifically, we tagged 100 hatchery‐reared phase II juveniles (202–227 mm TL) and 111 resident adults (349–923 mm TL) with acoustic transmitters (a subset of 50 adults was also tagged with external high‐reward tags). We used telemetry to monitor movement and seasonal distribution from December 2013 until September 2015. Telemetry and tag reporting data informed mortality models, and we estimated that annual discrete total mortality of phase II stocked juveniles was 66.3% (95% credible interval [CI] = 47.4–82.4%). Annual discrete total mortality of adults was 54.0% (95% CI = 41.5–65.4%). Adult discrete natural mortality was 20.1% (95% CI = 8.7–39.1%), and neither juvenile nor adult natural mortality was correlated with seasonal variation in dissolved oxygen, temperature, or salinity. These results show that poststocking mortality is significant and that juvenile mortality should be considered when establishing stocking goals. Additionally, adult natural mortality is within the range predicted by maximum age and by previous studies; however, adult total mortality is higher than targeted rates. These results can help to inform management decisions and develop measures to rebuild depressed Striped Bass populations like that in the Neuse River.

Philometra rubra (Nematoda: Philometridae) — first description of the male from striped bass (Morone saxatilis) and implications for re-introduction of an extirpated population

Philometra rubra (Leidy, 1856) is a pathogenic parasitic nematode infecting striped bass (Morone saxatilis (Walbaum, 1792)) in eastern North America. Identification of philometrids is difficult, male P. rubra have never been found, and transmission is poorly understood. To re-establish the “Extirpated” striped bass population in the St. Lawrence Estuary (SLE), Quebec, young-of-the-year (YOY) striped bass from the Miramichi River, New Brunswick, were collected and released into the SLE. The present study was undertaken to find Philometra in striped bass from the Miramichi River, for identification, description, and examine transmission and lesions. Philometra rubra was identified in 100% of 32 YOY (intensity = 26–125) and 100% of nine 1-year-old (intensity = 4–25 in five striped bass) striped bass collected in summer 2011. The swim bladder and body cavity were sites of infection in YOY with no tissue response observed histopathologically. Gravid P. rubra females occurred in the body cavity and swim bladder, with males predominately in the latter site. Males were short-lived, being absent in 1-year-old bass. Adult male and adult female P. rubra are described. Males of P. rubra can be distinguished from other described species based on spicule, gubernaculum, and body-length measurements. This parasite may have implications for the re-introduction program and conservation of striped bass in the SLE and in other populations.

The Misunderstood Striped Bass of the Saint John River, New Brunswick: Past, Present, and Future

AbstractThe Striped Bass Morone saxatilis of the Saint John River, New Brunswick, is an enigma, having now existed in a state of uncertain species status for more than four decades. Despite a well‐established historical record of adult occurrence in large numbers, the available literature, historical accounts, and status reports contain no evidence for the persistence of a native, reproducing Striped Bass population. In 2012, the Committee on the Status of Endangered Wildlife in Canada listed the Saint John River Striped Bass as endangered as part of the Bay of Fundy designatable unit. This listing lacked current peer‐reviewed literature and based its conclusions predominately on restatements of findings and opinions from the 1970s and 1980s. After the apparent failure of Striped Bass spawning in the 1975, the decline of native Saint John River Striped Bass was accredited to many factors ranging from chemical pollutants to overfishing to the installation of a sizeable hydropower facility. Modest attempts to locate eggs and juveniles of the native species have been taken; however, the results have been inconclusive due to ineffective, infrequent, and poorly timed sampling. Here we reviewed all available information, literature, reports, and data to effectively describe the Saint John River Striped Bass population in an effort to help manage and recover (if required) this apparently missing population.Received March 8, 2016; accepted September 14, 2016Published online January 24, 2017

Predation on Fishes in the Sacramento-San Joaquin Delta: Current Knowledge and Future Directions

doi: http://dx.doi.org/10.15447/sfews.2016v14iss2art8 The Sacramento–San Joaquin Delta (Delta) is a heterogeneous, highly modified aquatic system.I reviewed relevant predator–prey theory, and described extant data on predator–prey relationships of Delta fishes. I ranked predator consumption rates as occasional, moderate, and common, based on frequency-of-occurrence data, and evaluated the frequency, and hypothesized the effects of predation on native and invasive species. I identified 32different predator categories and 41 different prey categories. Most predators were occasional consumers of individual prey species, although I also observed moderate and common consumption of some prey types. My analysis yielded few generalizations regarding predator–prey interactions for Delta fishes; most predators consumed a variety of both native and invasive fishes. The only evidence for predator specialization on either native or invasive fishes occurred in Prickly Sculpin which, when it consumed fishes, ate mostly native species. BothStriped and Largemouth Bass exhibited wide dietary breadth, preying upon 32 and 28 categories of fish prey respectively. Sacramento Pikeminnow, a native predator, also displayed wide dietary breadth of piscine prey, with 14 different prey categories consumed. Data for reptilian, avian, and mammalian predators were sparse; however, these predators may be significant fish predators in altered habitats or when hatchery salmonids are released. The database for predators and their fish prey was not strong, and I recommend long-term dietary studies combined with prey availability and behavioral and experimental studies to establish predator preferences and antipredator behaviors, rather than just consumption.The behavioral effects of contaminants on prey species also warrant further examination. Although it has been suggested that a reduction in the StripedBass population be implemented to reduce predation mortality of Chinook Salmon, the large number of salmon predators in the Delta make it unlikely that this effort will significantly affect salmon mortality.

Fully Equipped to Succeed: Migratory Contingents Seen as an Intrinsic Potential for Striped Bass to Exploit a Heterogeneous Environment Early in Life

Migratory contingents, groups of individuals belonging to the same population that adopt different migratory patterns, have been identified in numerous Striped Bass (Morone saxatilis) populations along North American East Coast. We tested the hypothesis that migratory contingents may develop early in life to maximize the exploitation of the variety of habitats faced by a recently introduced fish population. Using the discriminatory power provided by otolith chemistry, we studied early-life history stages of Striped Bass in a recently reintroduced population in the St. Lawrence Estuary. Migratory patterns were inferred using multivariate analysis of four otolith trace elements (Sr, Ba, Mn, and Mg) on juveniles (0+ and 1+). Three migratory contingents were identified during early-life history stages: freshwater residents, oligohaline migrants, and mesohaline migrants. This study demonstrates the rapid establishment, in less than 10 years since initial stocking, of three migratory contingents initiated early in life among the St. Lawrence Striped Bass population. We postulate that diversification provided by the establishment of distinct migratory contingents among early-life history stages promotes the rapid colonization of new environments through the exploration and exploitation of an increased number of nursery habitats.

Movement Patterns and Stock Composition of Adult Striped Bass Tagged in Massachusetts Coastal Waters

AbstractThe coastal migratory stock of Striped Bass Morone saxatilis has supported fisheries off the Massachusetts (MA) coast for centuries. However, despite this historical importance, limited information is available regarding Striped Bass seasonal movement patterns or migratory pathways within MA coastal waters and beyond. Using passive acoustic telemetry, we evaluated the seasonal residency, coastal migration, and stock composition of 159 adult Striped Bass (65–110 cm TL) by using a network of fixed acoustic receivers deployed from 2008 to 2012 in MA coastal waters and along the U.S. East Coast as part of the Atlantic Cooperative Telemetry (ACT) Network. Seasonal monitoring of tagged individuals indicated that adult Striped Bass were present in MA coastal waters north of Cape Cod annually during May–November, moving into and out of the region via the Cape Cod Canal and along the east side of Cape Cod. Of the 159 tagged individuals, 125 (79%) were detected outside of MA coastal waters by the ACT Network and were observed to make seasonal migrations along the coast to overwintering areas of the mid‐Atlantic and major spawning areas (Chesapeake Bay, Delaware River, and Hudson River). Numerous tagged individuals exhibited interannual fidelity to summer foraging habitat in MA coastal waters, returning to the region for up to 2 years after tagging. Detection of tagged individuals in known spawning areas revealed that Striped Bass from each major stock were present within MA coastal waters during the summer months, with the Chesapeake Bay stock appearing to be the largest contributor to the population from 2008 to 2010. Collectively, these observations suggest that the seasonal population of adult Striped Bass in MA coastal waters has a diversity of origins, demonstrating the importance of the health of each spawning component to the MA seasonal fishery.Received October 11, 2013; accepted January 23, 2014

Genetic Structure of Striped Bass in the Southeastern United States and Effects from Stock Enhancement

AbstractUnderstanding the genetic relationships of Striped Bass Morone saxatilis populations within and between watersheds is necessary to identify appropriate management units. Determining temporal changes in genetic relationships as well as the genetic diversity of the populations is important in understanding how stock enhancement influences population units. A suite of 12 microsatellites was used to evaluate patterns of Striped Bass gene flow both spatially and temporally across watersheds in the southeastern United States. Populations from the study watersheds were genetically diverse with the exception of the Savannah River, South Carolina–Georgia, which is recovering from a major population decline. Striped Bass in the Roanoke and Cape Fear rivers, North Carolina, represented a single population, most likely due to historical transfer stocking across the state from Roanoke River stock. Watersheds in South Carolina contained genetically distinct Striped Bass populations, although the difference between Striped Bass populations in the Ashepoo–Combahee–Edisto (ACE) and Santee–Cooper watersheds has decreased over the past 15 years, likely due to the stocking of Santee–Cooper system fish into the ACE Basin. Conversely, supportive breeding of fish from the Santee–Cooper system has helped to maintain genetic diversity of the population. Striped Bass populations in the southeastern United States are good examples of the positive and negative effects of stock enhancement that must be considered and monitored when implementing or assessing a stock enhancement program.Received May 14, 2013; accepted March 5, 2014

The precautionary approach to non-native fisheries—The case of striped bass in Texas

Fisheries managers have long relied on non-native fish to improve, sustain, or create recreational fishing opportunities, often without adequate consideration of potentially negative ecological consequences. There is growing advocacy for using the precautionary approach to avoid potentially serious or irreversible harm to the environment in the face of scientific uncertainty. This paper uses striped bass (Morone saxitilis) in Texas to examine possible effects that might have resulted had the precautionary approach been applied before stocking began in the 1960s when the species was considered non-native to Texas. The current range of reproducing striped bass populations extends from the North Atlantic Ocean to the U.S.–Mexico border. However, the western extent of the species current range beyond Louisiana is probably the result of stocking begun in 1965 that continues today. The historic range is yet unresolved. The best available information suggests that striped bass are not native to Texas, fish stocking has resulted in beneficial economic impacts, and any negative effects (i.e., harm) are currently unknown. It seems unlikely that application of the precautionary approach would have led to different outcomes in Texas than currently exist. However, the complete striped bass story has yet to be written.

Infections with Philometra sp. associated with mortalities in wild-hatched captive-raised striped bass, Morone saxatilis (Walbaum)

The striped bass, Morone saxatilis (Walbaum), once represented an important resource for fisheries in the St Lawrence River (Quebec, Canada). A restoration programme, involving captive propagation, was implemented with the objective of restocking the population, which had disappeared in the late 1960s. An unusually high rate of mortality was observed during the winter of 2006 in captive-raised fingerlings that were originally collected from the Miramichi River (New Brunswick, Canada) the previous summer. Post-mortem examinations revealed extensive granulomatous and hyperplastic peritonitis associated with numerous nematodes of the genus Philometra. Given the severity of the lesions, high intensity of infection by Philometra sp. was presumed to be the primary factor in the unusual mortalities reported that winter. Observations suggest that this nematode, which was acquired in the wild, cannot establish itself in a captive environment, most likely because of the absence of the obligate intermediate host. Examination of archived specimens of striped bass showed that this parasite was probably present in the St Lawrence River population prior to its extirpation. Consequently, the introduction of infected fish into this ecosystem should not be a concern. Nevertheless, infection-related mortalities of fingerlings might affect dynamics of wild striped bass populations.

MYCOBACTERIOSIS‐ASSOCIATED MORTALITY IN WILD STRIPED BASS (MORONE SAXATILIS) FROM CHESAPEAKE BAY, USA

The striped bass (Morone saxatilis) is an economically and ecologically important finfish species along the Atlantic seaboard of the United States. Recent stock assessments in Chesapeake Bay (U.S.A.) indicate that non-fishing mortality in striped bass has increased since 1999, concomitant with very high (>50%) prevalence of visceral and dermal disease caused by Mycobacterium spp. Current fishery assessment models do not differentiate between disease and other components of non-fishing mortality (e.g., senescence, predation); therefore, disease impact on the striped bass population has not been established. Specific measurement of mortality associated with mycobacteriosis in wild striped bass is complicated because the disease is chronic and mortality is cryptic. Epidemiological models have been developed to estimate disease-associated mortality from cross-sectional prevalence data and have recently been generalized to represent disease processes more realistically. Here, we used this generalized approach to demonstrate disease-associated mortality in striped bass from Chesapeake Bay. To our knowledge this is the first demonstration of cryptic mortality associated with a chronic infectious disease in a wild finfish. This finding has direct implications for management and stock assessment of striped bass, as it demonstrates population-level negative impacts of a chronic disease. Additionally, this research provides a framework by which disease-associated mortality may be specifically addressed within fisheries models for resource management.

Modeling the Effects of Potential Salinity Shifts on the Recovery of Striped Bass in the Savannah River Estuary, Georgia–South Carolina, United States

Increased salinity in spawning and nursery grounds in the Savannah River estuary was cited as the primary cause of a 97% decrease in adult striped bass (Morone saxatilis) and a concomitant 96% decrease in striped bass egg production. Restoration efforts focused on environmental remediation and stock enhancement have resulted in restored salinity patterns and increased egg and adult abundances. However, future water needs or harbor development may preclude further recovery by reducing freshwater inflow or increasing salinity intrusion. To assess the effect of potential changes in the salinity regime, we developed models relating discharge, tidal phase, and salinity to striped bass egg and early larval survival and re-cast these in a quantitative Bayesian belief network. The model indicated that a small upstream shift (< or =1.67 km) in the salinity regime would have the least impact on striped bass early life history survival, whereas shifts >1.67 km would have progressively larger impacts, with a 8.33-km shift potentially reducing our estimated survival probability by >28%. Such an impact could have cumulative and long-term detrimental effects on the recovery of the Savannah River striped bass population. The available salinity data were collected during average and low flows, so our model represents some typical and some extreme conditions during a striped bass spawning season. Our model is a relatively simplistic, "first-order" attempt at evaluating potential effects of changes in the Savannah River estuarine salinity regime and points to areas of concern and potential future research.

Genetic Variation and Management of Striped Bass Populations in the Coastal Rivers of South Carolina

Abstract The coastal rivers of South Carolina possess reproducing populations of striped bass Morone saxatilis. Historically, all of these populations have been augmented with hatchery stocks from the Santee–Cooper drainage. Concern has been expressed that locally adapted, reproductively isolated populations may exist in these coastal rivers. Thus, the objective of this effort was to assess the distinctiveness of reproducing striped bass populations in these coastal rivers. Tagging studies indicated that the interriver movement of striped bass was minimal. A population estimate of 406 striped bass longer than 30 cm was obtained for the Combahee River, suggesting a relatively small breeding population. Genetic assays at three nuclear restriction fragment length polymorphism sites showed highly significant allele frequency differences among seven coastal rivers, suggesting reproductive isolation. Partially or fully isolated populations can develop beneficial adaptations to local environmental conditions. Th...

Effects of historic PCB exposures on the reproductive success of the Hudson River striped bass population.

Scientists and regulatory agencies have expressed concern that exposures to polychlorinated biphenyls (PCBs) might be contributing to reductions in the abundance of fish populations exposed to these chemicals. The specific effects of concern involve impairment of fish reproduction, including both reduced egg production and decreased viability of eggs and larvae. We tested hypotheses concerning the effects of PCBs on fish populations using long-term data sets available for the striped bass population of the Hudson River, NY, a population that has long been a subject of regulatory concern because of potential effects of PCB exposures. The data sets examined include both measurements of PCB concentrations in adult female striped bass over the period from 1976 through 1997 and estimates of the numbers of striped bass eggs, larvae, and juveniles produced annually during this same period. We found strong correlations between estimates of the abundance of spawners and the number of eggs and larvae produced by those spawners and also between independent estimates of year-class strength derived from different sampling programs. However, we found no relationships between PCB exposure and any measure of striped bass abundance or reproduction. Although inconsistent with the expected effects of PCB exposures, trends in all measures of striped bass abundance and reproductive success were consistent with the expected effects of striped bass harvest restrictions that were imposed during the 1980s. Our results demonstrate a need for caution in inferring risks to populations in nature from effects observed in laboratory studies.

Maturation and fecundity of a stock‐enhanced population of striped bass in the Savannah River Estuary, U.S.A

The striped bass Morone saxatilis population in the Savannah River (south‐eastern U.S.A.) collapsed in the 1980s, and recent eorts to restore the population have resulted in increased catch‐per‐unit‐eort (CPUE) of striped bass in the Savannah River Estuary (SRE). The abundance of eggs and larvae, however, remain well below historic levels. The primary cause of the population decline was remedied, and environmental conditions seem suitable for striped bass spawning. Regression analysis of data derived from ultrasonic imaging of 31 striped bass resulted in a statistical model that predicted ovary volume well (r2=0.95). The enumeration of oocytes from ovarian tissue samples and the prediction of ovary volume allowed fecundity to be estimated without sacrificing the fish. Oocyte maturation in Savannah River striped bass seemed to progress normally, with oocytes developing to final stages of maturity in larger fish (&gt;750 mm LT). Additionally, fecundity estimates were comparable to a neighbouring striped bass population. The environmental cues needed to trigger development and release of striped bass oocytes into the SRE appeared to be present. If most of the striped bass females in the SRE are still young (&lt;7 years), the ability to produce large numbers of eggs will be limited. As these young fish mature, egg production probably will increase and the density of striped bass eggs eventually will approach historic levels, provided suitable habitat and water quality are maintained.

Potential Competition between Hybrid Striped Bass (Morone saxatilis X M. americana) and Striped Bass (M. saxatilis) in the Cape Fear River Estuary, North Carolina

Gillnet surveys from 1990 to 1992 and from 1996 to 1999 indicated a two-fold decrease in native striped bass (Morone saxatilis) populations and a concomitant two-fold increase in hybrid striped bass (Morone saxatilis × M. americana) in the Cape Fear River estuary, North Carolina. Gut content analysis indicated high diet overlap, and tagrecapture data suggested that hybrid striped bass participate in spawning migrations. These data provide circumstantial evidence that hybrid striped bass compete with striped bass for food and that they may compete for mates or habitat on the spawning grounds. Increasing abundance of adult hybrid striped bass in this system elevates the likelihood of hybrid introgression. We recommend that stocking of hybrid striped bass be terminated to preserve native striped bass populations.