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Native to the central USA, the Blue Catfish Ictalurus furcatus and the Flathead Catfish Pylodictis olivaris have been widely introduced into many Atlantic slope rivers and are now found in several drainages of the Chesapeake Bay. Fisheries managers are concerned that these large, long-lived catfish species may be contributing to observed declines in anadromous species, such as the American Shad Alosa sapidissima, Blueback Herring A. aestivalis, and Alewife A. pseudoharengus, all of which once comprised major U.S. fisheries. We assessed spatiotemporal variability and selectivity in the diets of Blue Catfish and Flathead Catfish during the spawning migration of these alosines. Catfish stomachs were collected during March–May in nontidal freshwater, tidal freshwater, oligohaline, and mesohaline portions of the James River. Diet contents were extracted from 2,495 catfish, 69.86% of which had prey items present in their foreguts (N = 1,743). We used DNA barcoding to identify degraded fish prey; nearly ...

The anadromous Hickory Shad Alosa mediocris (Mitchill, 1814) (Clupeiformes: Clupeidae) is reviewed, specifically regarding morphometric and meristic variation. Despite its long history as recognized species, few descriptions of Hickory Shad morphometric and meristic characters exist in the literature. Most authors of the historic literature have failed to provide capture location for specimens, analyze large numbers of Hickory Shad, or document how morphometric and meristic characters of the species vary spatially. To address this information gap, a total of 717 mature Hickory Shad were collected from 23 different locations in Maryland, Delaware, Virginia, North Carolina, South Carolina, Georgia, and Florida using electroshocking, gill net, or rod and reel. All specimens were frozen, thawed, and 17 morphometric characters and four meristic characters were examined; a random subset (n = 463) were analyzed for an additional four meristic counts of gill rakers. Overall specimens ranged from 206-389 mm SL with a mean + SD of 278.41 + 27.69 mm, 232-435 mm FL with a mean of 310.98 + 30.35 mm, and 272-508 mm TL with a mean of 365.62 + 35.52 mm. The linear relationships between FL and TL, and FL and SL, were investigated and found to be: TL = 1.169*FL + 1.660 (n=705, r2=0.995) and SL = 0.909*FL - 4.274 (n=717, r2=0.992). Substantial differences in character means for many morphometric measurements were found between male and female specimens, suggesting strong sexual dimorphisms relating to shape. However, meristic characters did not show differences in character means by sex. No one morphometric measurement could distinguish Hickory Shad from other morphologically similar clupeids, but the meristic count of gill rakers on the lower limb of the first arch were important to separate Hickory Shad (19-22) from American Shad A. sapidissima (Wilson, 1811), Alewife A. pseudoharengus (Wilson, 1811), and Blueback Herring A. aestivalis (Mitchill, 1814).

Recent declines in anadromous river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis) have been documented in much of their range using fishery-independent spawning run counts. A lack of rigorous long-term run counts and demographic data for Chesapeake Bay spawning stocks resulted in the declaration of unknown stock status in a 2012 stock assessment and made it difficult to evaluate responses to conservation and restoration efforts. The objectives of the present study were to (1) conduct the first spawning run counts of river herring in the Choptank River, Maryland, since the run counts performed over a 2-year period in 1972 and 1973, (2) evaluate population structure and dynamics, and (3) identify environmental variables associated with run timing. Spawning runs of Alewives and Blueback Herring were recorded from March 10 to June 4, 2014, using imaging sonar and processed manually to produce hourly run counts of fish with TLs ranging from 200 to 350 mm. A total of 1,659,09...

In the nearshore Gulf of Maine, a combination of factors (overfishing, ecosystem change, and ocean warming) is thought to govern groundfish recovery. We analyzed feeding habits of demersal predatory fish from Midcoast Maine (abundant river herring) and Passamaquoddy Bay (low river herring) in eastern Maine, using stomach content and stable isotope analyses, to determine the prevalence of river herring (alewife, Alosa pseudoharengus, and blueback herring, A. aestivalis) in nearshore (

Bycatch of mid-trophic-level anadromous fishes that connect marine and freshwater ecosystems is a growing conservation concern. Anadromous alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) are important components of coastal freshwater and marine food webs, but have experienced dramatic declines in the abundances of spawning adults. Freshwater-focused restoration efforts have yielded few consistent signs of recovery, raising concerns that bycatch in Northwest Atlantic commercial fisheries may be negating these conservation actions. Using data from 15 microsatellites genotyped for baseline populations and bycatch, we conducted genetic stock identification to understand how bycatch was partitioned among previously identified regional genetic stocks. We then combined this information with fishery observer data to estimate genetic stock-specific bycatch mortality for the southern New England Atlantic herring fishery (2012–2013). Bycatch overall, but especially in the Atlantic herring fishery, was disproportionately assigned to the most severely depleted genetic stocks (alewife southern New England stock — 70% of assignments; blueback herring mid-Atlantic stock — 78% of assignments). These genetic stocks overlap in the region surrounding Long Island Sound, suggesting that bycatch taken from this area in recent years may be negatively impacting recovery efforts in this region. Our study suggests that mitigating bycatch on the southern New England fishing grounds may benefit recovery efforts for alewife and blueback herring genetic stocks that have experienced the greatest declines in spawning adult abundances.

River herring (Alewives; Alosa pseudoharengus and Blueback Herring; Alosa aestivalis) populations have undergone dramatic declines in recent years. Although the exact causes for these population declines are unclear, evidence suggests that factors such as habitat loss and dam construction may prevent upstream migration to spawning grounds, resulting in river herring spawning below the head of tide. As below the head of tide spawning may prematurely expose river herring embryos and larvae to saline environments, a series of experiments were conducted to determine the effect of elevated salinity on embryonic and larval survival. Embryos of both species were acutely exposed to salinities of 2, 5, 10, 15, 20, 25, and 30 g/L as well as to simulated tidal salinity fluctuations, and survival was assessed. Larvae (1–8 days post hatch; DPH) were acutely transferred to 2.5–30 g/L water, and survival was assessed after 24 h. Larvae (0–12 DPH) were also gradually acclimated to salinities ranging from 2.5–30 g/L, and survival assessed 24 h post exposure. Embryonic alewife survival was high (>97%) at salinities ≤10 g/L while blueback herring embryos displayed a wide salinity tolerance throughout the range. Embryos of both species exhibited high survival in tidal salinity exposures. Survival of acutely-transferred alewife and blueback herring larvae decreased with increasing salinity (>20 g/L). Both species were tolerant of high salinity conditions by 15 DPH. These experiments demonstrate that survival of river herring embryos and larvae may be possible in tidally-influenced areas, depending on the developmental stage and rate of salinity exposure.

Anadromous fishes are commonly thought to use inland waters for spawning and for rearing in the first growing season. Thereafter, they emigrate seaward to feed, grow, and mature. However, yearling (age 1+) alosine herrings have been observed in the Hudson River estuary during the spawning season. We quantified the frequency of this behavior for Blueback Herring (Alosa aestivalis) in two contrasting time periods: the 1980s–1990s, a period of relatively high abundance, and 2012–2013, a period of low abundance. Using otolith chemistry, we (1) assayed whether yearlings captured during the spawning run had egressed to sea and then returned to fresh water, and (2) examined adult spawners and retrospectively estimated the frequency of yearling returns to fresh water in these recruited fish. At least 36 % and up to 90 % of yearlings showed evidence of overwintering at sea or very far down the estuary prior to returning to fresh water with the spawning adults. Of the adults, 67–75 % showed evidence of returns up to fresh water as yearlings, despite large changes in population size and demographic characteristics. We conclude that this cryptic, “non-textbook” migratory behavior is common, and suggest that the importance of estuarine and freshwater nurseries may extend beyond the young-of-year period.

Due to an oversight during typesetting, the original version of this article unfortunately contained a mistake.

Environmental DNA (eDNA) sampling has emerged as a powerful tool to detect and quantify species abundance in aquatic environments. However, relatively few studies have compared the performance of eDNA-based abundance estimates to traditional catch or survey approaches in the field. Here, we have developed and field-tested a qPCR assay to detect eDNA from alewife and blueback herring (collectively known as 'river herring'), comparing eDNA-based presence and abundance data to traditional methods of quantification (ichthyoplankton sampling and adult observations). Overall, the qPCR assay showed very high target specificity in lab trials, and was successful in detecting river herring for 11/12 Chesapeake Bay tributaries in spring 2015 and 2016, with 106 out of 445 samples exhibiting positive eDNA hits. We found a strong correlation between eDNA abundance and ichthyoplankton count data (Spearman's Rho = 0.52), and Phi-tests (correlation of presence/absence data) showed higher correlation between eDNA and ichthyoplankton data (Phi = 0.45) than adult data (Phi = 0.35). Detection probability was significantly lower on western vs. eastern shore tributaries of Chesapeake Bay, and blueback herring and alewife were more likely detected on the western and eastern shores, respectively. Temporal patterns of eDNA abundance over the spring spawning season revealed that alewife were present in high abundances weeks ahead of blueback herring, which aligns with known differences in spawning behavior of the species. In summary, the eDNA abundance data corresponded well to other field methods and has great potential to assist future monitoring efforts of river herring abundance and habitat use.

The purpose of this study was to document timing and habitat of alosines (Hickory Shad Alosa mediocris, American Shad A. sapidissima, Alewife A. pseudoharengus, and Blueback Herring A. aestivalis) and Striped Bass Morone saxatilis in the lower Tar River, a North Carolina coastal watershed partially restricted by an unused industrial dam. Alosines and Striped Bass are usually separated in time or space during spawning activity but occasionally overlap in some systems. Results show that both eggs and larvae of Hickory Shad and Striped Bass predominated catches, followed by American Shad. Alewife and Blueback Herring had negligible catches of eggs and larvae, but a separate study conducted 48 river kilometers downstream of the study area collected larvae of both species. Eggs and larvae of target species overlapped spatially and were most abundant in downstream tributaries, which seasonally reached hypoxic to anoxic conditions. The origins of spawning are unknown, but the collection of eggs suggests ...

Concern over the impacts of incidental catches of Alewife, Alosa pseudoharengus and Blueback Herring, A. aestivalis (collectively managed as ‘river herring’) in the commercial Atlantic Herring (Clupea harengus) and Atlantic Mackerel (Scomber scombrus) fisheries has resulted in the recent implementation of river herring incidental catch limits. These incidental catches are highly variable in frequency and magnitude, and the environmental conditions associated with these catches are poorly understood. We used generalized additive models (GAMs) to describe habitat associations of Alewife, Blueback Herring, Atlantic Herring, and Atlantic Mackerel. Bottom temperature, bottom depth, bottom salinity, solar azimuth and elevation, and region of the Northeast U.S. continental shelf were all significant in the habitat models; GAMs explained 25.2, 16.9, 18.9, and 20.6% of the deviance observed for the presence/absence of Alewife, Blueback Herring, Atlantic Herring, and Atlantic Mackerel. A subset of the data was omitted from the model and the probability of presence was compared with observations; 66–77% of observations were correctly predicted. The individual probabilities of presence were used to quantify and evaluate the accuracy of modelled overlap of Alewife and Blueback Herring with Atlantic Herring (68–72% correct predictions) and Alewife and Blueback Herring with Atlantic Mackerel (57–69% correct predictions). Our findings indicate that environmental gradients influence the distributions and overlap of Alewife, Blueback Herring, Atlantic Herring, and Atlantic Mackerel, and with further testing and refinement these models could be developed into a tool to aid industry in reducing incidental catches of river herring.

Manganese is a commonly found constituent in fish otoliths, yet a direct correlation with ambient water concentrations as observed for other elements has proven elusive. There is compelling evidence that Mn uptake is related to the availability of reduced Mn (Mn2+) resulting from hypoxia (Limburg et al. 2015) but that fish growth rate also plays a role. We tested the latter possibility by examining otoliths from anadromous river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis) in New York waters. A significant correlation was found between the ages at which shifts in otolith daily growth increments (assumed proportional to somatic growth) and shifts in otolith Mn:Ca ratios were detected. Furthermore, significant positive Spearman's rank correlations were observed between mean otolith daily growth and otolith Mn:Ca. Species- and site-specific differences were evident, but significant positive correlations were found for these relationships within each species and at most sa...

Understanding the location and duration of habitat use by young fish is important for management and restoration efforts, but is largely unknown in anadromous species. We used otolith microchemistry and ambient water concentrations of Ca, Ba, Mn, and Sr to identify habitat use in the first year of growth for 131 returning adult blueback herring (Alosa aestivalis) collected in seven spawning runs along the coast of Maine, USA. Ambient Sr:Ca ratios were correlated with salinity and were used as primary indicators of habitat use. Results revealed variable individual migration histories with several discrete migratory patterns; some fish migrated into seawater well before the end of the first year, while the majority exhibited longer residency in freshwater or low salinity habitat. Total area of available habitats ranged from approximately 213 to 6053 ha fresh water and 204 to 3395 ha estuary. Residency in freshwater or low salinity habitats was positively correlated with extent of freshwater habitat (r = 0.37, P < 0.001). Results emphasize the importance of conserving a variety of habitat types to maintain variation in life histories and ensure plasticity in migratory behavior of diadromous species.

The abundance of alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) has declined throughout their range, and there are increasing concerns about their conservation status. Because of their diadromous life history, variability in rates of survival in fresh water can affect overall recruitment. The objective of our study was to assess how river temperature and flow influence young of the year (YOY) river herring recruitment in the Northeast US. Observations of adult and juvenile fish in five rivers were used to construct spawner–YOY recruits models; these rivers were chosen because of the length of the time series (>15 years) and the paired observations of spawners and juveniles. An environmentally explicit stock–recruitment model explained a substantial fraction (41% to 80%) of the variance in YOY abundance, depending on river system. Our approach allowed for a preliminary discussion of potential mechanisms, which need to be further substantiated by focused field and laboratory studies. Early summer river flow and river temperature had the greatest influence, indicating the importance of conditions in nursery habitats. In certain systems, spring or fall conditions were also important determinants of survival, suggesting additional effects of the environment on spawning of adults and juvenile egress from freshwater nursery habitats.

River herring (Alewives Alosa pseudoharengus and Blueback Herring A. aestivalis [bluebacks]) are congeneric, anadromous clupeid fishes that hybridize in areas of sympatry. Peritoneal pigmentation is the most diagnostic characteristic used to distinguish the species, but pigmentation has not been examined in hybrids. We developed a molecular-based assay to distinguish purebred river herring species from F1 hybrids and compared the peritoneal pigmentation among captive-raised purebred and hybrid individuals. Both wild-caught Alewife and blueback females tank-spawned with conspecific and congeneric males, but Alewives required exogenous hormone administration. Larvae of both species and hybrids were raised for ∼290 d posthatch, and peritoneal pigmentation was quantified. A nuclear gene (rag2) restriction fragment length polymorphism assay was used for species and hybrid identification. The peritoneal pigmentation was significantly darker in hatchery-spawned bluebacks than in Alewives, and hybrids exh...

Precipitous declines in wild populations of river herring species (Alewives Alosa pseudoharengus and Blueback Herring A. aestivalis) have led to increased interest in stock enhancement efforts. Additionally, their popularity as a baitfish among recreational anglers has generated interest in commercial production of these species for marine baitfish markets. The objective of this investigation was to elucidate practical culture protocols for captive propagation of these species for commercial and restoration purposes. Wild Blueback Herring, captured during their annual spawning migration, spawned in tanks volitionally, while Alewives required exogenous hormone administration. Larvae of both species were successfully raised through metamorphosis using a feeding regime comprised of enriched rotifers followed by Artemia nauplii and a commercially available diet. Survival of early larvae acclimated to salinities ranging from 5‰ to 15‰ was high for both species (>94.0%) while that for older larvae accli...

We compared the accuracy of different combinations of natural markers, specifically otolith elemental (Sr:Ca and Ba:Ca) and isotopic ratios (87:86Sr) with and without genetic stock constraints to evaluate their ability to distinguish among anadromous river herring (i.e., alewife, Alosa pseudoharengus, and blueback herring, Alosa aestivalis) populations from their US ranges. Model accuracy increased when constrained to a regional level by genetic stocks. Both species were misclassified to sites up to 1000 km from their collection location when only otolith chemistry was used. The inclusion of genetic constraints improved reclassification rates, and the longer time scale of genetic variation makes this method less sensitive to interannual variation. We recommend the combined approach of otolith chemistry and genetics as a means to trace river herring in marine bycatch back to river of origin.

The objectives of this work were to quantify the spatial and temporal distribution of the occurrence of anadromous fishes (alewife Alosa pseudoharengus, blueback herring Alosa aestivalis and American shad Alosa sapidissima) in the stomachs of demersal fishes in coastal waters of the north-west Atlantic Ocean. Results show that anadromous fishes were detectable and quantifiable in the diets of common marine piscivores for every season sampled. Even though anadromous fishes were not the most abundant prey, they accounted for c. 5-10% of the diet by mass for several marine piscivores. Statistical comparisons of these data with fish diet data from a broad-scale survey of the north-west Atlantic Ocean indicate that the frequency of this trophic interaction was significantly higher within spatially and temporally focused sampling areas of this study than in the broad-scale survey. Odds ratios of anadromous predation were as much as 460 times higher in the targeted sampling as compared with the broad-scale sampling. Analyses indicate that anadromous prey consumption was more concentrated in the near-coastal waters compared with consumption of a similar, but more widely distributed species, the Atlantic herring Clupea harengus. In the context of ecosystem-based fisheries management, the results suggest that even low-frequency feeding events may be locally important, and should be incorporated into ecosystem models.

Concern over incidental catches in commercial fisheries has been increasing, and while simple mitigation strategies have been effective, few effective mitigation strategies have been established for more complex species interactions. Incidental catches of alewife (Alosa pseudoharengus) and blueback herring (A. aestivalis) in the commercial Atlantic herring (Clupea harengus) fishery have received substantial attention on the Northeast U.S. continental shelf, despite an existing bycatch avoidance program. This study evaluates the utility of existing species distribution forecasts to predict river herring catches in the southern New England small mesh bottom trawl Atlantic herring fishery, with the ultimate goal of incorporating incidental catch forecasts into the bycatch avoidance program. Commercial Atlantic herring bottom trawl vessels assisted with field-based evaluation of alewife, blueback herring, and Atlantic herring species distribution forecast models. Vessels were equipped with conductivity, temperature, and depth probes, and sampling occurred throughout the fishery season (January – March). Locations of expected low and high forecasted incidental catches were sampled, as well as locations the captain expected to find low and high incidental catches. This allowed us to sample within the spatial area the fishery occurs, and to evaluate the forecasted conditions, and predictions, at the spatial scale of the fishery. Catch differences between high and low probability stations were small and variable, as were differences in modeled probability of species presence. No differences were observed between observations at model-predicted stations and captain-selected stations. The sampling provided a better understanding of the potential effectiveness of distribution forecasts for further reducing incidental catches. Existing models have limited use at the spatial scale of this fishery, but could be improved by developing models with fishery-dependent data. Collaborations between researchers, managers, and the Atlantic herring commercial fleet have improved relationships between the groups, and continued collaboration in the development and evaluation of incidental catch reduction tools is key for further reducing incidental catches.

Recent investigations into the nutrient cycling of coastal ecosystems have suggested that migratory or anadromous fish could be important vectors of marine nutrients. Anadromous fish have assimilated marine nutrients that would contribute to the nutrient budgets of freshwater systems by excretion, gamete release, or the decay of post-reproductive carcasses. However, the extent to which freshwater predators utilize marine material is not well understood. In systems where anadromous fish temporarily constitute a major portion of the fish community, they may contribute substantially to the diet of piscivorous fish and other predators. Here we show the contribution of anadromous blueback herring, shad, and alewife (Alosa) to diets of large, non-indigenous piscivorous catfish (Ictalurus furcatus) using δ34S and δ13C. The spawning anadromous Alosa, captured in tidal freshwater, had enriched δ34S and δ13C values compared to resident, native freshwater species. As a result of consuming the anadromous Alosa, the I. furcatus isotope signature shifted towards the marine signal. The isotope analysis revealed that anadromous fish contribute substantially to the diet of most captured I. furcatus. The percentage of anadromous Alosa carbon and sulfur that was incorporated into I. furcatus (≥38 cm total length) ranged from 0 to 84% and 10 to 69%, and had means (±SD) of 42 (±24) and 43 (±16)%, respectively. Although the δ15N signal of marine-derived biomass is enriched by approximately 3‰ relative to terrestrial or freshwater biomass, it was not as useful as δ34S and δ13C for nutrient source owing to trophic fractionation. This study demonstrates that anadromous fish may be a significant source of nutrients to tidal freshwater apex predators.

Populations of Blueback Herring Alosa aestivalis, an important anadromous forage fish in the northeastern USA, have declined from historic levels. Measures to reduce mortality from many sources, including entrainment by hydroelectric turbines, are cited by fishery managers to be important to restoring populations. At the Crescent Hydroelectric Project (Crescent) on the Mohawk River, New York, pulsed ultrasound (122–128 kHz) was used to deter adult and juvenile Blueback Herring migrating out to sea from entering the intake channel to the headrace and turbines, where mortality may occur. To increase the deterrence rate, the sound field was extended further upriver to expose juvenile Blueback Herring to an increasing sound gradient as they migrate downriver and allow them more time to avoid the intake channel. When juvenile Blueback Herring were present upstream of Crescent and exposed to an ultrasound field, mean catch per unit effort (CPUE) by pelagic trawling in the main channel downriver of the u...

We investigated the spatial and temporal accuracy of otolith chemistry for distinguishing populations (and subpopulations) of anadromous river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis) from New York watersheds. Water chemistry of selected analytes (Sr:Ca, Ba:Ca, 87:86Sr, and δ18O) differed spatially and interannually among sites within the Hudson River as well as between the Hudson River and Long Island estuaries. Otolith chemical markers for juvenile river herring differed significantly among all sampling sites, with combined elemental and isotopic ratios differing significantly between species and between years, although the effect of year did not influence assignments at broad spatial scales (i.e., 105 m). Adult river herring collected in the Hudson River were assigned to natal sites using all juvenile otolith markers except δ18O, which had methodological problems. Adult Alewives and Blueback Herring were classified to Hudson River populations at 73% and 42%, res...

In the U.S. northwest Atlantic, the incidental catch of river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis) by midwater trawl vessels targeting Atlantic Herring Clupea harengus and Atlantic Mackerel Scomber scombrus has become a concern for river herring conservation. Reduction of this incidental catch is a focus of fisheries managers, but information about river herring bycatch is limited. To improve the information available to fishery managers, we combined portside and at-sea observations to examine (1) the size of river herring, (2) the concentration of river herring with respect to the target species, and (3) the yearly contribution of different fishery areas to the total catch of river herring. We divided the fishery's spatial range into four nearshore areas and tested two null hypotheses: (1) length frequency distributions of river herring are similar between areas and between species and (2) bycatch ratios are similar among areas. We also used length frequency d...

Alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), also known collectively as either river herring or gaspereau, are anadromous clupeid fishes that display spatiotemporal overlap during riverine spawning migrations. Both species have experienced severe population declines within portions of their ranges. Evidence that they home to their natal rivers to spawn suggests the likelihood of ecologically significant population structure, yet this hypothesis has not been rigorously tested. We examined genetic diversity, differentiation and population structure in 34 alewife and four blueback herring populations spanning a 2,500 km portion of their northern range, using 14 microsatellite loci. Significant differentiation was detected among most rivers, and eight genetically defined alewife population clusters that largely corresponded to hydrographic regions were identified. Similar population structure was seen for blueback herring. Genetic isolation by distance was not significant among alewife populations in regions that have been historically influenced by dams, and/or stock transfers, but was highly significant in two regions that have not been subject to these influences. Genetic differentiation of alewife populations was strongest in the Bay of Fundy. Bottleneck tests revealed evidence of demographic bottlenecks in all of the alewife populations. Lastly, our results indicated that hybridization between alewife and blueback herring is common.

A major challenge in conservation biology is the need to broadly prioritize conservation efforts when demographic data are limited. One method to address this challenge is to use population genetic data to define groups of populations linked by migration and then use demographic information from monitored populations to draw inferences about the status of unmonitored populations within those groups. We applied this method to anadromous alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), species for which long-term demographic data are limited. Recent decades have seen dramatic declines in these species, which are an important ecological component of coastal ecosystems and once represented an important fishery resource. Results show that most populations comprise genetically distinguishable units, which are nested geographically within genetically distinct clusters or stocks. We identified three distinct stocks in alewife and four stocks in blueback herring. Analysis of available time series data for spawning adult abundance and body size indicate declines across the US ranges of both species, with the most severe declines having occurred for populations belonging to the Southern New England and the Mid-Atlantic Stocks. While all alewife and blueback herring populations deserve conservation attention, those belonging to these genetic stocks warrant the highest conservation prioritization.

River herring, which comprise two species of anadromous alosines (alewife, Alosa pseudoharengus , and blueback herring, Alosa aestivalis ), are under consideration for listing under the US Endangered Species Act. River herring populations have not rebounded despite reductions in directed fishing on these species and improvements in their freshwater and estuarine habitats. We examined recent (2005–2009) spatial and temporal patterns of fishing effort in the US fishery for Atlantic herring, Clupea harengus , and river herring bycatch patterns in this fishery. During the year, Atlantic herring fishing activity shifts spatially and temporally from the Northern Mid-Atlantic Bight and Southern New England waters in January–February, to Southern New England waters in March–April, to the Gulf of Maine in May–June, expanding to the Gulf of Maine and Georges Bank in July–August and September–October, respectively, and then contracting to the Gulf of Maine and Southern New England waters in November–December. At-sea fisheries observer data indicate that river herring bycatches in the Atlantic herring fishery occur mostly during January–April and September–December, primarily in Southern New England and the Northern Mid-Atlantic Bight waters. We discuss possible management measure to reduce these bycatches. Similar size, shape, and schooling behaviors between river herring and other pelagic species—and the high volume nature of the Atlantic herring fishery—limit the potential efficacy of gear-based bycatch mitigation measures. Hence, approaches such as regulatory management measures (e.g., time–area closures and catch caps) and improved fleet communication strategies (e.g., “move-on” rules) may be more practical and effective in minimizing river herring bycatch in the Atlantic herring fishery.

Historically, multiple species of diadromous fishes served as a coastal food source for commercially valuable nearshore predators. However, severe declines in diadromous fish populations in the nearshore Gulf of Maine (GOM) have impacted trophic dynamics and increased pressure on other estuarine-dependent forage resources. The objective of this study was to compare the trophic positions and interspecific interactions of diadromous fishes as predators and prey in relation to current GOM forage fishes. Empirical biomass data along with diet compositions and vital rates were used to construct a static model of a representative GOM coastal food web: the Saco River estuary (SRE) in Maine. A series of sensitivity analyses based on model outputs was performed to determine the trophic role of diadromous fishes in this estuarine food web. Model results suggested that juvenile marine transients played a greater role as forage species for SRE predators than did the anadromous Blueback Herring Alosa aestivalis and Alewife Alosa pseudoharengus. Due to the abundant forage fish base, Atlantic Sturgeon Acipenser oxyrinchus and Shortnose Sturgeon Acipenser brevirostrum were estimated to have a greater trophic position than reported in past literature. Lower-trophic-level fishes functioned as keystone prey species for sturgeon. The use of holistic approaches to update the ecological data on predator–prey interactions among diadromous fishes and forage resources within coastal ecosystems is necessary for the future management of these ecologically significant and threatened species. Received January 4, 2016; accepted May 20, 2016

Target strength (TS) was estimated from in situ and ex situ measurements of juvenile blueback herring Alosa aestivalis during their fall downriver migration at the Crescent Hydroelectric Project in the Mohawk River, New York. The blueback herring is an ecologically important anadromous species that must transit fish passage facilities at hydroelectric dams. Measurements of TS are necessary to distinguish juvenile blueback herring from other fishes as well as to scale echo integration results to numerical fish densities during hydroacoustic studies. This study presents the first measurements of TS for juvenile blueback herring. The TS measurements were collected from an echosounder operating at 420 kHz with two split-beam transducers (one down-looking and one side-looking). Single echo detections associated with tracked fish echoes and the echoes at the periphery of schools in the headrace of the powerhouse were used in estimating in situ TS. Mean total length (TL) of 192 individuals captured by c...

At the Crescent Hydroelectric Project (Crescent), New York, the Mohawk River is impounded by two dams separated by an island, which creates two channels; the turbine channel conveys water to the hydroelectric turbines, and the main channel conveys water around the turbines. Our objective was to determine whether ultrasound could be used to divert juvenile blueback herring Alosa aestivalis from entering the turbine channel during their fall downriver migration. Fixed-location hydroacoustics (420 kHz) was used to continuously monitor fish passage in the main channel upriver and downriver of the 122–128-kHz ultrasonic projectors. A relative index of abundance was derived from echo integration of acoustic backscatter collected from three horizontally aimed single-beam transducers sampling across each channel, while the proportion and speed of fish moving downriver were estimated from upward-facing split-beam transducers. The presence of juvenile blueback herring was verified by castnetting. Fish migr...

We estimated the variation in the instantaneous rates of growth and mortality between cohorts of larval alewife Alosa pseudoharengus and blueback herring A. aestivalis in the Tar–Pamlico River, Pamlico Sound, North Carolina. The age of larvae captured by push net was estimated by counting the daily rings on sagittal otoliths. Weight-at-age and abundance-at-age data were used to generate instantaneous daily growth (G) and mortality rates (M) for 7-d cohorts. The instantaneous daily growth rate was relatively constant between cohorts, ranging from 0.103 to 0.277 for alewives and from 0.105 to 0.200 for blueback herring. The instantaneous daily mortality rate was more variable between cohorts, ranging from 0.064 to 0.270 for alewives and from 0.100 to 0.251 for blueback herring. All but one blueback herring cohort had an M/G value exceeding 1.0, indicating that these cohorts were losing biomass during the early larval stage. For alewives, M/G values were more variable, with 50% of the cohorts having...

Zooplankton composition and abundances were quantified in the lower Roanoke River and Albemarle Sound, North Carolina. The spatial and temporal overlap between larval alosines, including American shad Alosa sapidissima, river herring (alewife A. pseudoharengus and blueback herring A. aestivalis), hickory shad A. mediocris, and zooplankton were examined to determine whether larval alosines in this system are food limited. Samples were collected weekly at 19 stations from March through June 2008–2009 in three habitats: River, Delta, and Sound. Spatial differences in zooplankton were observed, with the abundance in the Sound (16,546 ± 14,678 [number/m3 ± SD]) being significantly higher than those in the River (4,934 ± 3,806) and Delta areas (4,647 ± 2,846). Zooplankton composition was dominated by Daphniidae, Bosminidae, calanoid and cyclopoid copepods, copepod nauplii, and rotifers. The spatial patterns in alosine abundance were the opposite of those for zooplankton, being highest in the River (21....

A standard dual-frequency identification sonar (DIDSON) was deployed in the Herring River, Harwich, Massachusetts, for 3 d in late April 2011 to capture video-like images of migrating adult river herring (alewife Alosa pseudoharengus and blueback herring Alosa aestivalis). Images recorded 24 h a day were used to manually count and assign species based on DIDSON images of fish size, shape, and behavior. From these counts, the run size was estimated to be 1,976–2,059 individuals during the study. At first, river herring often hesitated to swim through the sample area where the weirs and DIDSON were deployed; however, they eventually did pass, often multiple times. This unique hesitation behavior complicated counting efforts, though it was beneficial to discerning species using DIDSON images. In addition, extremely shallow water upstream of the study site, lack of tree cover, and a high threat of avian predation likely contributed to river herring milling activity at the study site. By providing man...

Over the past two decades, declines in the populations of river herring (alewife Alosa pseudoharengus and blueback herring Alosa aestivalis) have been documented across both species’ ranges. Information concerning the natal origins of spawning adult fish could aid in their restoration but has been unattainable. We investigated the efficacy of otolith microchemistry for identifying the natal environment of alewife and blueback herring in Connecticut. In both 2008 and 2009, water and juvenile and adult fish were sampled from 10 sites across the state. The relationships between water and otolith Sr:Ca ratios differed for alewives and blueback herring, necessitating the development of separate classification models for assigning individuals to capture locations. Reclassification of age-0 alewives to their site of origin was variable (50–100%) but demonstrated that age-0 fish could be accurately reclassified to their natal environment at some sites. Discriminant function reclassification rates to site...

Anadromous blueback herring Alosa aestivalis are declining throughout much of their range, and fishery closures in some systems have failed to produce population recovery. A potential contributing factor is increased predation pressure from sympatric striped bass Morone saxatilis. We integrated data on the predator–prey interaction between striped bass and blueback herring during vernal migrations into the Connecticut River with data on the in-river striped bass fishery to assess the potential for mitigation of blueback herring mortality via increased striped bass harvest. Striped bass abundance, size structure, diets, and angler catches were assessed within a river segment during spring 2005–2008. We estimate that striped bass consumed 400,000 blueback herring (90% confidence interval = 200,000–800,000) annually in our study area during the spring migration season. The predator–prey interaction between striped bass and blueback herring was predator size dependent. Blueback herring were most comm...

The Saco River estuary is a narrow estuary in southern Maine, for which the fauna has not been described in nearly 30 years. Beach seining, otter trawling, and beam trawling were conducted between April and October of 2007 and 2008 to assess seasonal variation in fi sh assemblage structure. Twenty-four species were observed over the two sampling seasons, and nearly all species were at lengths indicative of juvenile age. Clu- pea harengus (Atlantic Herring), Pseudopleuronectes americanus (Winter Flounder), Anguilla rostrata (American Eel), Microgadus tomcod (Atlantic Tomcod), Pomatomus saltatrix (Bluefi sh), and Osmerus mordax (Rainbow Smelt) are either commercially or recreationally valuable, while Acipenser oxyrynchus oxyrynchus (Atlantic Sturgeon), Alosa aestivalis (Blueback Herring), and Rainbow Smelt are federally listed species of concern. Substantial historical assemblage changes were observed, including both the loss of commercially important species and the addition of species of concern. Regular monitoring of estuarine habitats is necessary to identify changes in assemblages and to better understand potential drivers of ecosystem change.

From 1996 to 2011, researchers observed Phoca vitulina concolor (Western Atlantic Harbor Seal) on regional overwintering grounds in the Great Bay–Mullica River estuary in southern New Jersey. Over this 15-y time series, 299 observations were completed, with maximum local abundance increasing from 100 individuals in 1996 to 160 individuals in 2011. Our study did not document the presence of Atlantic Harbor Seal pups. In addition, we analyzed 142 scat samples, resulting in 1419 sagittal fish otoliths recovered and identified. Dominant recovered otoliths were as follows: 48% Phycidae (Urophycis regia [Spotted Hake]/Urophycis chuss [Red Hake]; 25% Clupeidae (Clupea harengus [Atlantic Herring], Alosa sapidissima [American Shad], Brevoortia tyrannus [Atlantic Menhaden], A. pseudoharengus [Alewife], and A. aestivalis [Blueback Herring]); 13% Ammodytidae (Ammodytes americanus/A. dubius [sandlance]); 6% Pseudopleuronectes americanus (Winter Flounder); and 4% Scophthalmus aquosus (Windowpane Flounder). Average back-calculated prey lengths across all prey groups (min–max = 5–41 cm, average = 19.75 cm) indicated that Western Atlantic Harbor Seals might utilize both estuarine and ocean environments for foraging. This temperate estuary currently represents the southern limit of routine Western Atlantic Harbor Seal occupancy in the Northeast. As such, our results are valuable in monitoring future changes in habitat use potentially resulting from climate change.

The erection of dams alters habitat and longitudinal stream connectivity for migratory diadromous and potamodromous fish species and interrupts much of organismal exchange between freshwater and marine ecosystems. In the US, this disruption began with colonial settlement in the seventeenth century but little quantitative assessment of historical impact on accessible habitat and population size has been conducted. We used published surveys, GIS layers and historical documents to create a database of 1356 dams, which was then analyzed to determine the historical timeline of construction, use and resultant fragmentation of watersheds in Maine, US. Historical information on the anadromous river herring was used to determine natural upstream boundaries to migration and establish total potential alewife spawning habitat in nine watersheds with historic populations. Dams in Maine were constructed beginning in 1634 and by 1850 had reduced accessible lake area to less than 5% of the virgin 892 km2 habitat and 20% of virgin stream habitat. There is a near total loss of accessible habitat by 1860 that followed a west-east pattern of European migration and settlement. Understanding historic trends allows current restoration targets to be assessed and prioritized within an ecosystem-based perspective and may inform expectations for future management of oceanic and freshwater living resources.

Characterization of riverine spawning habitat is important for the management and restoration of anadromous alosines. We examined the relative effectiveness of oblique plankton tows and spawning pads for collecting the eggs of American shad Alosa sapidissima, hickory shad A. mediocris, and “river herring” (a collective term for alewife A. pseudoharengus and blueback herring A. aestivalis) in the Roanoke River, North Carolina. Relatively nonadhesive American shad eggs were only collected by plankton tows, whereas semiadhesive hickory shad and river herring eggs were collected by both methods. Compared with spawning pads, oblique plankton tows had higher probabilities of collecting eggs and led to the identification of longer spawning periods. In assumed spawning areas, twice-weekly plankton sampling for 15 min throughout the spawning season had a 95% or greater probability of collecting at least one egg for all alosines; however, the probabilities were lower in areas with more limited spawning. Co...

Blueback herring Alosa aestivalis are anadromous, iteroparous, winter spawners in the St. Johns River, Florida, but published data about this population are limited. We collected adults by electrofishing in the upper St. Johns River during the 2002–2005 spawning runs to examine the abundance, distribution, size, sex ratio, reproductive biology, and feeding habits of the population. When possible, data from the present study were compared with those for blueback herring collected with seine nets in the lower St. Johns River during the 1972 and 1973 spawning runs. Blueback herring began upstream migration by January and stayed in the river until at least April. The average fish size was significantly smaller in 2002–2005 than in 1972–1973, but sex ratios were not different from 1:1 in 5 of the 6 years studied. The more recent collections suggest that blueback herring females released multiple batches of eggs during one spawning season (spawning a batch every 3–4 d on average) and that spawning occu...

Telemetry is a potential approach for assessing how effectively ultrasound steers blueback herring Alosa aestivalis away from undesirable locations. The objectives of this study were to determine (1) whether gastric implantation of radio tags prevented adult blueback herring from reacting to ultrasound and (2) if not, whether radio tag implantation diminished the fish's escape reactions. Eight groups, each consisting of four blueback herring in good condition, were exposed in a circular tank to a single pulse of broadband ultrasound eight times; each time was considered a trial. Radio tags were gastrically implanted in blueback herring from four of the groups. The four untagged groups were used to confirm that blueback herring would react to ultrasound in the tank, while the four tagged groups were used to determine whether tagging prevented a reaction. These reactions were confirmed by measuring the swimming speed immediately before and after a pulse of sound. Blueback herring in both the tagged...

Rivers throughout the Gulf of Maine once contributed billions of juvenile fish into the marine ecosystem where they served as a critical forage base for cod and other groundfish. In the Central Gulf of Maine—Bay of Fundy watershed alone, over sixty rivers formed nine drainage basins and thirteen estuaries. For the past 12,000 years, the immense runs of migratory fish from these Gulf rivers provided important cultural, economic and ecological services throughout the Gulf watershed. However, in just a few short centuries, the heavy hand of humans has decimated native migratory populations and has broken the connections between rivers and the ocean. The resilience of these native species has allowed them to survive in low numbers throughout the Gulf, but fundamental shifts in fisheries management are needed to prevent their ultimate demise. Though much attention has been given to depleted groundfish stocks in the Gulf, there is a growing interest in restoring the historic, native assemblage of migratory fish to the rivers spanning the Gulf. Ecosystem management that has worked well on land is being adapted to the Gulf as scientists now recognize the strong linkages between the freshwater and marine environments. In the past several years, historic researchers such as Ted Ames and Deb Trefts have documented the disappearance of migratory forage stocks such as the river herrings and the subsequent disappearance of inshore cod stocks in both the 1800s and 1900s. The emergence of this practical knowledge and the awareness of the restoration potential of the rivers flowing into the Gulf is now generating Gulf-wide interest in implementing strategies that collectively contribute to the restoration of migratory fish and groundfish stocks. More than twelve species of migratory fish once returned each year to the major rivers in the Gulf of Maine. While the decline of Atlantic salmon has garnered much recent attention, it is, of course, only part of a larger decline in once-abundant migratory fish populations that historically defined rivers in the Gulf of Maine. Native populations of Atlantic and endangered shortnose sturgeon, American shad, alewives, blueback herring, and sea lamprey have also been nearly or completely extirpated from many of our larger rivers. The populations of other native sea-run species, such as American eel, rainbow smelt, striped bass, and tomcod, which have fared somewhat better, are severely limited in production potential compared to historical conditions.

Native diadromous fishes have been extirpated from much of the Susquehanna River system for nearly a century. Recent restoration efforts have focused on removal of dams, but there are hundreds of dams and presently there is no biologically based system to assist in prioritizing their removal. We present a new method that uses existing habitat suitability index models (HSI) for American shad Alosa sapidissima, alewife A. pseudoharengus, blueback herring A. aestivalis, and American eel Anguilla rostrata to prioritize the removal of non-hydropower dams within the Susquehanna River system. We ranked HSI scores for each of the four species, association between a landscape-scale factor and HSIs, length of river opened by removing a dam, and distance from the mouth at Chesapeake Bay for each dam and then calculated a mean rank prioritization for dam removal by averaging the ranks for the seven criteria. This prioritization method is resistant to outliers, is not strongly affected by somewhat arbitrary decisions on metrics included in the analysis, and provides a biologically based prioritization for dam removal that can be easily amended to include other metrics or adapted to other river systems and that complements other social and economic considerations that must be included in decisions to remove dams. Published in 2008 by John Wiley & Sons, Ltd.

This study addressed the question whether the increase in the abundance of striped bass Morone saxatilis in the Hudson River that began after 1990 and the associated increase in predatory demand could have been responsible for the observed declines in the abundance of juvenile river herring (i.e., blueback herring Alosa aestivalis and alewife A. pseudoharengus), Atlantic tomcod Microgadus tomcod, and white perch Morone americana as well as the apparent decline in the survival of juvenile striped bass in the Hudson River. The seasonal (August through October) predatory demand of Hudson River striped bass (ages 1-13) was estimated to have increased from an average of 3.4 million kg/year for the period 1982-1990 to an average of 15.0 million kg/year for the period 1991-2004. Since 1990, the average abundance of juvenile fish in the Hudson River has declined—60% for river herring, 69% for Atlantic tomcod, and 59% for white perch—and juvenile striped bass survival has declined 87%. These declines coul...

Dams within the Susquehanna River drainage, Pennsylvania, are potential barriers to migration of diadromous fishes, and many are under consideration for removal to facilitate fish passage. To provide useful input for prioritizing dam removal, we examined relations between landscape-scale factors and habitat suitability indices (HSIs) for native diadromous species of the Susquehanna River. We used two different methods (U.S. Fish and Wildlife Service method: Stier and Crance (1985), Ross et al. (1993a, 1993b, 1997), and Pardue (1983); Pennsylvania State University method: Carline et al. (1994)) to calculate HSIs for several life stages of American shad Alosa sapidissima, alewives Alosa pseudoharengus, and blueback herring Alosa aestivalis and a single HSI for American eels Anguilla rostrata based on habitat variables measured at transects spaced every 5 km on six major Susquehanna River tributaries. Using geographical information systems, we calculated land use and geologic variables upstream from...

Historically, the fisheries for adult river herring (i.e., alewife Alosa pseudoharengus and blueback herring A. aestivalis) and American shad A. sapidissima were economically important in Albemarle Sound, North Carolina. Stocks of these species are in decline, while stocks of striped bass Morone saxatilis have increased roughly 10-fold in the Albemarle Sound-Roanoke River since the early 1990s. The goal of this study was to quantify the predatory impact of age-1 striped bass on age-0 prey fishes by estimating striped bass consumption rates and comparing loss rates from predation with total prey loss rates using catch curves. Age-1 striped bass and their potential prey were collected with beach and purse seines from western Albemarle Sound from spring to fall, 2002 and 2003. Commercially and ecologically important prey in one or both years included river herring, American shad, Atlantic menhaden Brevoortia tyrannus, and yellow perch Perca flavescens. Predation by age-1 striped bass had a marked ef...

Adult blueback herring Alosa aestivalis (N = 116) were collected during the 1999, 2000, and 2002-2004 spawning runs from sites on the Hudson and Mohawk rivers, and gut contents were analyzed. Thirty-four fish (33% of those examined) were found to contain food material. Food items were present in 41% of Mohawk River samples and 11% of Hudson River samples; all Hudson River fish containing food were captured in small tributaries above the head of tide. Hudson River fish predominantly consumed zooplankton, while Mohawk River fish consumed benthic aquatic insects in large quantities, including Baetidae, Ephemeridae, and Chironomidae. Using stable isotope analysis and a mixing model, we found that fish collected later in the season had significantly decreased marine-derived C. Condition indices of later-season fish were equal to or greater than those of fish collected earlier in the season. Blueback herring in this system may face increased energy requirements as they migrate farther upstream during s...