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Anadromous river herring have declined in many parts of their range, leading to fisheries management efforts to help repopulate this species by improving connectivity of rivers and restoring populations by fish transfers. With data lacking on parasites in these species, this study sought to better understand myxozoans across various life stages and habitats in river herring populations in New Jersey, USA. We compared fish from riverine habitats during early-life growth and adults returning to spawn, marine-phase fish, and landlocked Alewife populations. Three myxozoan species were identified in young-of-the-year (YOY) anadromous river herring, including Kudoa clupeidae in the skeletal musculature, Myxobolus mauriensis in the rib cartilage, and an uncharacterized coelozoic myxozoan within the lumen of mesonephric tubules. In YOY river herring, Blueback Herring were 2 times more likely to be infected by K. clupeidae than Alewife (p = 0.019) and in the Maurice River, fish were 4 times more likely to be infected with M. mauriensis than fish from Great Egg Harbor River (p = 0.000) and 11 times more likely than the Delaware River (p = 0.001). Spawning adult river herring were infected with a previously undescribed myxozoan parasite infecting the kidney. Sequencing the 18S rDNA indicated this species is closely related to Ortholinea species. Myxobolus mauriensis and the Ortholinea-like species were absent from marine-phase river herring indicating that infections were linked to river environments occurring during early-life growth and spawning, respectively. No myxozoans were present in landlocked Alewife, showing that similar infections occurring in rivers were absent in lake environments in the region.

Anadromous alosines are widespread throughout the Northern Hemisphere. Juveniles of this clade are notoriously fragile animals that are at high risk of injury and death associated with passage at hydroelectric facilities. Although turbine mortality is a common concern, conditions encountered when bypassed around these routes may also be hazardous. Downstream bypass structures typically discharge into plunge pools, which are highly turbulent and may cause mechanical injury. We subjected live, actively migrating juvenile blueback herring to a suite of realistic plunge pool conditions (3 m drop, pool depth of 60–180 cm, and discharge of 0.28–1.70 m3/s) and monitored them for ≥ 96 h. Survival was generally higher than expected (>80% in all cases). However, both plunge pool volume and total discharge affected survival with elevated discharge and shallow conditions associated with increased mortality. Mortality was often delayed: rates remained elevated throughout the monitoring period, indicating that survival studies based on shorter periods underestimate total mortality.

Geography and nursery-specific dynamics guide environmental drivers of growth for young-of-year (YOY; larval and juvenile) Alewife (Alosa pseudoharengus) and Blueback Herring (Alosa aestivalis), two species collectively termed river herring; of these factors, temperature is considered one of the most influential. To better understand future YOY growth relative to climate change, this study was designed to determine the site-specific growth rates of YOY river herring in Potomac River tributaries, and determine if temperature was a driving factor of growth. Daily ages were ascertained from YOY otoliths and used to calculate growth rates using nine growth models. Weighted Akaike information criterion (AICw) determined the best-fit model for both species was the von Bertalanffy growth model. Von Bertalanffy growth parameters differed between species (p

We analyzed four decades of presence–absence data from a fishery-independent survey to characterize the long-term phenology of river herring (alewife, Alosa pseudoharengus; and blueback herring, Alosa aestivalis) spawning migrations in their southern distribution. We used logistic generalized additive models to characterize the average ingress, peak, and egress timing of spawning. In the 2010s, alewife arrived to spawning habitat 16 days earlier and egressed 27 days earlier (peak 12 days earlier) relative to the 1970s. Blueback herring arrived 5 days earlier and egressed 23 days earlier (peak 13 days earlier) in the 2010s relative to the 1980s. The changes in ingress and egress timing have shortened the occurrence in spawning systems by 11 days for alewife over four decades and 18 days for blueback herring over three decades. We found that the rate of vernal warming was faster during 2001–2016 relative to 1973–1988 and is the most parsimonious explanation for changes in spawning phenology. The influence of a shortened spawning season on river herring population dynamics warrants further investigation.

Microplastics in aquatic environments, and specifically their effects on the health of organisms, are of growing concern worldwide. Of particular concern are microplastics in a similar size range to zooplankton, as they have been found in the digestive tracks of organisms, such as fish, who typically seek zooplankton as a food source. It is unclear, however, to what degree, if any, fish select for or against microplastic particles when feeding. It is also unclear whether ingestion of microplastics affects fish condition. To answer these questions, the estimated physical condition and degree of selective feeding on microplastics were determined for juvenile fish collected from the Hudson River. Considering only particles 0.335–5.0 mm, microplastics made up 12% of fish diets but 21% of particles found in the surrounding water column. Relying on Jacob's Modified Electivity (JME) to quantify selectivity in feeding, our results reveal selective feeding on zooplankton and avoidance of microplastics. There was no correlation between condition and degree of selectivity toward any particular food types, including microplastics. Future work needs to consider fish with different feeding strategies and potential bioaccumulation of microplastics in the food web. Fish selectivity of ingestion in regards to microplastics should additionally be tested on wider spatial and temporal scales.

Captain John Smith and his band of English colonists arrived at the Chesapeake Bay in 1607, discovering an estuary little changed by human activity. This contrasted sharply with the European rivers of that era. The estuaries he knew from England and Europe all suffered from dam-building, overfishing, sedimentation, and pollution. The decedents of the original colonizers, and the many thousands that came subsequently reshaped the Bay by their exploitation of its food resources. Over harvesting, damming of waterways, and oyster reef destruction decimated oysters (Crassostrea virginica) and migratory species of finfish, including; shad (Alosa sapidissima), alewife (Alosa pseudoharengus) blueback herring (Alosa aestivalis) and striped bass (Morone saxatilis). In the twentieth century, application of scientific fisheries methods built around the concept of maximum sustainable yield (MSY) and habitat restoration has yielded only partial recovery of these and other species. Ecosystem based management (EBM) is discussed as a sustainable alternative to MSY that takes into account non-human consumers of the exploited resource. The chapter also reviews the various fishing techniques used on the Bay, including those invented by Native Americans and later methods that facilitated industrial scale harvesting.

Anthropogenic activities are placing increasing pressure on many species, particularly those that rely on more than one ecosystem. River herring (alewife, Alosa pseudoharengus and blueback herring, A. aestivalis collectively) are anadromous fishes that reproduce in rivers and streams of eastern North America and migrate to the western Atlantic Ocean. Here, we use data from single nucleotide polymorphisms (SNPs) to provide a comprehensive analysis of population structure for both species of river herring throughout their native ranges. We sampled river herring spawning runs in rivers from Newfoundland to Florida, examining a total of 108 locations, and genotyping over 8000 fish. We identified geographic population groupings (regional genetic groups) in each species, as well as significant genetic differentiation between most populations and rivers. Strong correlations between geographic and genetic distances (i.e., isolation by distance) were found range-wide for both species, although the patterns were less consistent at smaller spatial scales. River herring are caught as bycatch in fisheries and estimating stock proportions in mixed fishery samples is important for management. We assessed the utility of the SNP datasets as reference baselines for genetic stock identification. Results indicated high accuracy of individual assignment (76–95%) to designated regional genetic groups, and some individual populations, as well as highly accurate estimates of mixing proportions for both species. This study is the first to evaluate genetic structure across the entire geographic range of these species and provides an important foundation for conservation and management planning. The SNP reference datasets will facilitate continued multi-lateral monitoring of bycatch, as well as ecological investigation to provide information about ocean dispersal patterns of these species.

Stream corridors contain many features that act as barriers to fish during migration. We built a model to determine the likelihood that each of 776 dams, culverts and waterfalls in New Jersey act as barriers to each of thirteen fish species during migration. We assessed each fish species at each potential barrier to determine if the fish could jump high enough to clear the barrier, swim fast enough to overcome the velocity of water to reach the barrier, dive deep enough in the plunge pool to reach maximum jump height, and persist with migration given predicted water temperatures. If all four were possible, the potential barrier was deemed passable. Blockages were mostly the result of predicted weak jumping abilities and water temperatures outside the acceptable range during migration. The model successfully predicted presence and absence above potential barriers for all species except the ubiquitous white sucker (C. commersonii). All locations with possible barriers were predicted to block at least two migratory fish species; 89% were predicted to block all species. Alewife (A. pseudoharengus) and blueback herring (A. aestivalis) were predicted to be blocked the most. Results allow prediction of which potential barriers block passage for each species, the length of waterways blocked by each barrier, and the reasons each barrier is predicted to block each species. We present our fish passage model as a tool for identifying possible barriers which if restored or removed, given appropriate field assessment, might reconnect migratory fish species with additional spawning habitat.

Levels of total mercury were measured in tissue of six species of migratory fish (alewife, American shad, blueback herring, rainbow smelt, striped bass, and sea lamprey), and in roe of American shad for two consecutive years collected from the Penobscot River or its estuary. The resultant mercury levels were compared to reference doses as established in the U.S. Environmental Protection Agency (EPA) Integrated Risk Information System and wildlife values. Mercury concentrations ranged from 4 μg/kg ww in roe to 1040 μg/kg ww in sea lamprey. Sea lamprey contained the highest amounts of mercury for both seasons of sampling. Current health advisories are set at sufficient levels to protect fishers from harmful consumption of the fish for mercury alone, except for sea lamprey. Based upon published wildlife values for mink, otter, and eagle, consumption of rainbow smelt, striped bass, or sea lamprey poses a risk to mink; striped bass and sea lamprey to otter; and sea lamprey to eagle. For future consideration, the resultant data may serve as a reference point for both human health and wildlife risk assessments for the consumption of anadromous fish. U.S. EPA works with federally recognized Tribes across the nation greatly impacted by restrictions on sustenance fishing, to develop culturally sensitive risk assessments.

Alosa aestivalis and A. pseudoharengus are herring congeners that are important forage species for piscivorous fish and birds. We measured population structure metrics for these species using microsatellite markers. The Southern Gulf of Maine study area allowed the assessment of these species at an inter- and intra-watershed level. We found no detectable population structure within or among watershed for either species which agrees with other recent research. Our results support regional-scale (e.g., Gulf of Maine) plans for management for A. aestivalis and A. pseudoharengus. We found that 5.4% of our samples were hybrids. Our study adds to a growing body of evidence that hybridization and introgression should be management concerns for these species, and precautions should be taken to preserve species barriers. An error rate of morphological identification was calculated by comparing morphological identifications against genetic classifications. We found an overall identification error rate of 1...

Nontarget catch restrictions are becoming common in fisheries management. We test a potential tool for reducing nontargeted catch that combines species’ distribution models and ocean forecast models. We evaluated our approach for Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus), alewife (Alosa pseudoharengus), and blueback herring (Alosa aestivalis). Catch of the latter two species is capped in commercial fisheries of the former two species. Ocean forecasts were derived from a data-assimilative ocean forecast model that predicts conditions 0–2 days into the future. Observed oceanographic conditions were derived from CTD casts and observed fish presence–absence was derived from fishery-independent bottom trawl collections. Species distribution models were used to predict presence–absence based on observed and forecasted oceanographic conditions, and predictions for both were very similar. Thus, most of the error in predicted distributions was generated by the species distribution models, not the oceanographic forecast model. Understanding how predictions based on forecasted conditions compare with predictions from observed conditions is key to developing an incidental catch forecast tool to help industry reduce nontarget catches.

Blueback Herring Alosa aestivalis populations throughout the East Coast have declined precipitously since the late 1980s and were listed as a Species of Concern in 2006 by the National Oceanic and Atmospheric Administration. Natural resource agencies are attempting to restore this species to viable and sustainable levels with fry stockings cultured in hatcheries. To evaluate the long-term contribution of stockings to populations, agencies need an accurate method to track these stocking efforts. Genetic parentage-based tagging is recognized as a feasible means of assessing hatchery contribution of stocked fish to rivers of interest. However, Blueback Herring lack a reliable set of genetic markers to conduct parentage-based tagging. To this end, we analyzed previously described microsatellites as well as new microsatellite markers identified through NextGeneration sequencing to create a suite of 14 Blueback Herring markers useful for parentage-based tagging. The markers were successful in parentage analysis for Blueback Herring collected from the Chowan River, North Carolina. An additional challenge in the management of Blueback Herring is the ability to phenotypically distinguish Blueback Herring from the closely related Alewife Alosa pseudoharengus. Furthermore, recent studies provide evidence that these two species, collectively referred to as river herring, may be hybridizing with one another in some systems. Microsatellite marker AsaC334 can be utilized to discriminate between the two species, as well as to identify their F1 hybrids, thereby providing another genetic tool for hatchery management.

The catch of non-target species or discarding of target species (bycatch) in commercial fisheries can result in negative species level and ecosystem wide impacts as well as adverse social and economic effects. Bycatch has become one of the foremost, global issues of fishery managers and conservationists, especially when the non-target species is from a protected or threatened population. However, the impact and spatial distribution of bycatch is frequently unknown making it difficult to develop effective, justifiable mitigation regulations. This challenge is exemplified by the bycatch of river herring (alewife, Alosa pseudoharengus , and blueback herring, A. aestivalis ) and American shad ( A. sapidissima ) in the northwest Atlantic mid-water trawl fishery targeting Atlantic herring ( Clupea harengus ) and Atlantic mackerel ( Scomber scombrus) . As an alternative to immediate management action, a voluntary bycatch avoidance program was established through an industry, state government, and university partnership. Here the program is described and its impact is evaluated by comparing fleet behavior and bycatch prior to and during the program. The combined results suggest that consistent communication, facilitated by the avoidance program, positively influenced fishing habits and played a role in the approximately 60% decrease in total bycatch and 20% decrease in the bycatch ratio observed during the program. However, the success of small scale move-along strategies to reduce bycatch ratios varied greatly in different areas of the fishery and years. This suggests the program is best viewed as an intermediate or complimentary solution. Overall, this project exemplifies of how collaborative programs can help alleviate difficult management scenarios.

Migrations of springtime Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis, collectively referred to as river herring, are monitored in many rivers along the Atlantic coast to estimate population sizes. While these estimates give an indication of annual differences in the number of returning adults, links to the subsequent timing and duration of spawning and freshwater juvenile productivity remain equivocal. In this study, we captured juvenile river herring at night in 20 coastal Massachusetts lakes using a purse seine and extracted otoliths to derive daily fish ages and back-calculate spawn dates. Estimates of spawning dates were compared with fishway counts of migrating adults to assess differences in migration timing and the timing and duration of spawning. We observed a distinct delay between the beginning of the adult migration run and the start of spawning, ranging from 7 to 28 d across the 20 lakes. Spawning continued 13–48 d after adults stopped migrating into freshwater, fur...

Concern has been increasing over the impacts of incidental catches of river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis) in commercial fisheries for Atlantic Herring Clupea harengus and Atlantic Mackerel Scomber scombrus, but historical information on mixed-species catches and their driving factors is lacking. We examined data from spring and fall bottom trawl surveys (National Oceanic and Atmospheric Administration, Northeast Fisheries Science Center) for temporal trends in overlap and potential ecosystem drivers of overlap trends. Species overlap changed substantially over time, with changes varying by season and region of the northeastern U.S. continental shelf. In the fall, changes in overlap were positively related to abundance in Georges Bank and southern New England. In the spring, most changes in species overlap were positively related to increasing species abundances. Positive relationships between overlap and abundance suggested that as species distributions increased with abundance, distributional overlap with other species increased as well. During the fall, changes in species overlap were positively related to bottom temperature in the Gulf of Maine, whereas in the spring, the relationship with bottom temperature was less consistent. Temperature-related changes in overlap implied that species distributions changed at different rates in response to climatic changes, thus leading to changes in overlap. Our findings suggest that fisheries management should take an adaptive approach to managing incidental catches by using region- and season-specific policies and should incorporate the effects of species abundances and climate change on species interactions. Received September 28, 2015; accepted October 11, 2016

In a 2013 pilot study, acoustic tags were inserted into two species of river herring, Alewife Alosa pseudoharengus and Blueback Herring Alosa aestivalis. The primary objectives were to identify han...

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...