American Shad Research Articles

The Rapid Establishment, Dispersal, and Increased Abundance of Invasive American Shad in the Pacific Northwest

AbstractAmerican shad (Alosa sapidissima) were repeatedly introduced into two Pacific coastal rivers in the late 1800s. They rapidly established, dispersed, and expanded their range over 5,000 km of coastline from Mexico to Russia. American shad also increased dramatically in abundance and now comprise the largest spawning run of anadromous fish in the Columbia River (>4 million fish annually). Despite constituting a remarkable biological invasion, invasive shad have not been the subject of much scientific investigation and remain relatively obscure in the Pacific Northwest. In this first of two complementary articles, we attempt to raise the profile of invasive American shad among fisheries professionals and generate scientific interest in this biological invasion. We provide an overview of the history of their introduction and discuss the mechanisms that may have contributed to the species ‘establishment, rapid dispersal along the Pacific coast, and its increased abundance in the Columbia River. In the second accompanying article we discuss the possible ecological consequences of the invasion in Pacific coastal ecosystems but also its inherent value to studies of ecology and evolution. These articles are designed to be read in succession.

Passage of American Shad: Paradigms and Realities

AbstractDespite more than 250 years of development, the passage of American shad Alosa sapidissima at dams and other barriers frequently remains problematic. Few improvements in design based on knowledge of the swimming, schooling, and migratory behaviors of American shad have been incorporated into passage structures. Large‐scale technical fishways designed for the passage of adult salmonids on the Columbia River have been presumed to have good performance for American shad but have never been rigorously evaluated for this species. Similar but smaller fishway designs on the East Coast frequently have poor performance. Provision of effective downstream passage for both juvenile and postspawning adult American shad has been given little consideration in most passage projects. Ways to attract and guide American shad to both fishway entrances and downstream bypasses remain marginally understood. The historical development of passage structures for American shad has resulted in assumptions and paradigms about American shad behavior and passage that are frequently unsubstantiated by supporting data or appropriate experimentation. We propose that many of these assumptions and paradigms are either unfounded or invalid and that significant improvements to American shad upstream and downstream passage can be made via a sequential program of behavioral experimentation, application of experimental results to the physical and hydraulic design of new structures, and controlled tests of large‐scale prototype structures in the laboratory and field.Received March 22, 2011; accepted August 24, 2011

Introduction to a Special Section: American Shad and River Herring

The American shad Alosa sapidissima once ranked among the top two or three commercial fisheries in the United States and was rated among the choicest fish to eat (Blackford 1916). It was one of the first North American species to be artificially propagated (Clift 1872) and was introduced into numerous water bodies (see Hasselman et al. 2012 for a history of its transfer to West Coast waters). Similarly, its congeners, the alewife A. pseudoharengus and blueback herring A. aestivalis (together known as river herring), constituted important commercial and subsistence fisheries during the first several hundred years following the appearance of Europeans in North America. The early colonists marveled at the sheer abundance of these fish in American waters, especially the massive spawning migrations of anadromous herrings. Coastwide, American shad ran in the tens of millions and river herring probably numbered in the hundreds of millions or billions into the early nineteenth century. Over the next two centuries, the all too familiar threesome of overfishing, habitat loss, and pollution decimated populations (Limburg and Waldman 2009). Today, fisheries are closed in many states to allow stocks to rebuild, and river herring are listed as a species of concern under the U.S. Endangered Species Act (as of this writing, they are under consideration for listing as threatened). There is renewed interest in these long marginalized fish, as managers and researchers begin to understand their ecological, cultural, and economic importance and advocate for ways to restore their abundance. This was evidenced at a 2-d symposium held at the 140th Annual Meeting of the American Fisheries Society in Pittsburgh. Sufficient interest was generated to produce this special section of 16 articles. We thank our coeditors, namely, Kristin Miller, Anthony Overton, and John Waldman, as well as Marine and Coastal Fisheries editor-in-chief Donald Noakes and journals production coordinator Laura Hendee. We would also like to acknowledge the U.S. Fish and Wildlife Service, Northeast Region, Mid-Atlantic Fishery Resources Office, for its generous sponsorship of the publication. We dedicate this special section to the memory of two special biologists: Joseph Loesch and John Olney. Both scientists at the Virginia Institute of Marine Sciences (VIMS), Joe passed away in June 2009 and John died an untimely death in January 2010. Both headed up VIMS's Anadromous Fish Program during their careers. Joe and John made fundamental contributions to the scientific understanding of blueback herring and American shad, respectively. We know they would be proud to see this collection of articles.

Demographic Population Model for American Shad: Will Access to Additional Habitat Upstream of Dams Increase Population Sizes?

AbstractAmerican shad Alosa sapidissima are in decline in their native range, and modeling possible management scenarios could help guide their restoration. We developed a density‐dependent, deterministic, stage‐based matrix model to predict the population‐level results of transporting American shad to suitable spawning habitat upstream of dams on the Roanoke River, North Carolina and Virginia. We used data on sonic‐tagged adult American shad and oxytetracycline‐marked American shad fry both above and below dams on the Roanoke River with information from other systems to estimate a starting population size and vital rates. We modeled the adult female population over 30 years under plausible scenarios of adult transport, effective fecundity (egg production), and survival of adults (i.e., to return to spawn the next year) and juveniles (from spawned egg to age 1). We also evaluated the potential effects of increased survival for adults and juveniles. The adult female population size in the Roanoke River was estimated to be 5,224. With no transport, the model predicted a slow population increase over the next 30 years. Predicted population increases were highest when survival was improved during the first year of life. Transport was predicted to benefit the population only if high rates of effective fecundity and juvenile survival could be achieved. Currently, transported adults and young are less likely to successfully out‐migrate than individuals below the dams, and the estimated adult population size is much smaller than either of two assumed values of carrying capacity for the lower river; therefore, transport is not predicted to help restore the stock under present conditions. Research on survival rates, density‐dependent processes, and the impacts of structures to increase out‐migration success would improve evaluation of the potential benefits of access to additional spawning habitat for American shad.Received March 19, 2011; accepted August 22, 2011

Evaluating the Current Status of American Shad Stocks in Three Virginia Rivers

AbstractDirected commercial fisheries for American shad Alosa sapidissima in the primary Virginia tributaries of the Chesapeake Bay have been under moratorium since 1994. Monitoring of adult American shad within these rivers has been ongoing since 1998 through a cooperative program involving commercial fishers. The monitoring program is designed to mimic traditional commercial fishing practices so that stock status can be inferred by comparing contemporary catch‐per‐unit‐effort levels with those derived from historic logbooks. In this paper, we present analyses of the available monitoring and historic catch rate data along with updated stock status information for American shad in the James, York, and Rappahannock rivers. Two analytical methods were used to derive annual indices of relative abundance; both methods yielded very similar patterns for each river system. Comparisons of contemporary and historic indices of relative abundance suggest that American shad in the James and York rivers continue to persist at low levels of abundance. Measures of stock abundance in the Rappahannock River have been higher than the logbook reference value for much of the monitoring period. However, current moratoria and restoration strategies, which include hatchery releases of fry, the removal of obstructions blocking spawning and nursery habitat, and reductions in bycatch from other fisheries, should continue into the foreseeable future.Received March 30, 2011; accepted August 21, 2011

Estimating the Food Requirements and Prey Size Spectra of Larval American Shad

AbstractWidespread declines in American shad Alosa sapidissima along the Atlantic coast have been attributed to overfishing, a decrease in water quality, and loss of habitat. Recent surveys along the Roanoke River and Albemarle Sound, North Carolina, suggest that stocks are continuing to decline despite extensive management and stock enhancement efforts. Laboratory experiments were conducted to evaluate the effect of prey density on the growth and survival of American shad and to determine whether larvae can survive and grow in a riverine environment with a limited forage base. Larvae were reared from 11 to 20 d posthatch in one of five treatments: (1) no food; (2) low food (1 prey/L), which simulated the prey densities in the Roanoke River; (3) medium food (50 prey/L), which simulated the prey densities typical of coastal watersheds; (4) high food (500 prey/L); and (5) Artemia spp. (500/L). Larval survival was 35 ± 7% (mean ± SE) and was not significantly different among treatments. Treatments with starved fish had the lowest survival (22 ± 12%), while the highest survival was observed in treatments with high densities of wild zooplankton (46 ± 18%) and Artemia (40 ± 16%). Length‐specific growth rates were 0.017 mm/d for the starved treatments and 0.024, 0.029, 0.034, and 0.039 mm/d for the low‐prey, medium‐prey, high‐prey, and Artemia treatments, respectively. Larval growth as a function of length was not significantly different between the Artemia and high‐prey treatments; however, growth in these treatments was significantly higher than in those with lower prey densities. Weight‐specific growth rates (Gw) were significantly higher for the Artemia treatment (Gw = 0.129) than for all the other treatments (Gw = 0.081). Analysis of stomach contents indicated that American shad were selectively feeding on the smallest zooplankton (80–250 μm) and that larvae exhibited a strong preference for copepod nauplii and rotifers. These results suggest that spatial and temporal overlap between larvae and zooplankton is important for larval growth and survival.Received March 31, 2011; accepted September 12, 2011

A Bayesian Spawning Habitat Suitability Model for American Shad in Southeastern United States Rivers

Abstract Habitat suitability index models for American shad Alosa sapidissima were developed by Stier and Crance in 1985. These models, which were based on a combination of published information and expert opinion, are often used to make decisions about hydropower dam operations and fish passage. The purpose of this study was to develop updated habitat suitability index models for spawning American shad in the southeastern United States, building on the many field and laboratory studies completed since 1985. We surveyed biologists who had knowledge about American shad spawning grounds, assembled a panel of experts to discuss important habitat variables, and used raw data from published and unpublished studies to develop new habitat suitability curves. The updated curves are based on resource selection functions, which can model habitat selectivity based on use and availability of particular habitats. Using field data collected in eight rivers from Virginia to Florida (Mattaponi, Pamunkey, Roanoke, Tar, Neuse, Cape Fear, Pee Dee, St. Johns), we obtained new curves for temperature, current velocity, and depth that were generally similar to the original models. Our new suitability function for substrate was also similar to the original pattern, except that sand (optimal in the original model) has a very low estimated suitability. The Bayesian approach that we used to develop habitat suitability curves provides an objective framework for updating the model as new studies are completed and for testing the model's applicability in other parts of the species' range.

Assessment of Genetic Diversity for American Shad in the Santee–Cooper River Basin of South Carolina prior to Hatchery Augmentation

AbstractAmerican shad Alosa sapidissima once supported large commercial fisheries along the Atlantic coast, but by the early 1980s many of these fisheries had declined precipitously. In contrast to most Atlantic coastal rivers, the abundance of American shad in the Santee–Cooper River basin of South Carolina has grown substantially; still, much of their upstream spawning habitat in this watershed has been restricted or adversely affected by impoundments. In an effort to rebuild populations in upstream river reaches of the Santee–Cooper basin, state and federal agencies developed an approach relying on hatchery augmentation, the relocation of prespawning adults, and the construction of permanent fish passage structures. Genetic monitoring was adopted to ensure that the genetic integrity of the population remains intact during the rebuilding process. Our study provided an initial assessment of genetic diversity for the genetic monitoring program. There were three components to the study: an assessment of within‐basin genetic stock structure, a comparison of genetic diversity (the number of alleles and observed heterozygosity) between hatchery and wild stocks, and an evaluation of molecular tags for monitoring hatchery returns. The estimation of genetic diversity and the assessment of molecular tags were based on 10 microsatellite loci. We found no apparent stock structure in the Santee–Cooper basin and no difference in genetic diversity between broodstock and their wild counterparts. Eight microsatellite markers provided enough resolution to successfully (>95% assignment success) match returning American shad with their respective hatchery parents. Our results highlight the utility and importance of integrating genetic information in supportive breeding programs in an effort to evaluate the programs’ effectiveness (both in terms of increasing the census size and in terms of maintaining the long‐term viability of a population).Received March 18, 2011; accepted August 8, 2011

Use of a Natural Isotopic Signature in Otoliths to Evaluate Scale‐Based Age Determination for American Shad

AbstractWe used δ18O signatures in otoliths as a natural tag for hatch year to evaluate the scale‐based age determination method used for adult American shad Alosa sapidissima in the York River, Virginia. Juveniles of the 2002 year‐class exhibited high δ18O values in otolith cores that identified adult members of the cohort as they returned to spawn. Recruitment of the 2002 cohort was monitored for three consecutive years, identifying age‐4, age‐5, and age‐6 individuals of the York River stock. The scale‐based age determination method was not suitable for aging age‐4, age‐5, or age‐6 American shad in the York River. On average, 50% of the individuals from the 2002 year‐class were aged incorrectly using the scale‐based method. These results suggest that the standard age determination method used for American shad is not applicable to the York River stock. Scientists and managers should use caution when applying scale‐based age estimates to stock assessments for American shad in the York River and throughout their range, as the applicability of the scale‐based method likely varies for each stock. This study highlights a promising new direction for otolith geochemistry to provide cohort‐specific markers, and it identifies several factors that should be considered when applying the technique in the future.Received March 21, 2011; accepted August 18, 2011

Findings on American Shad and Striped Bass in the Hudson River Estuary: A Fish Community Study of the Long‐Term Effects of Local Hydrology and Regional Climate Change

AbstractIt has been hypothesized that climate change is an underlying factor in determining fish abundances in the Hudson River estuary (HRE). To study the effects of hydrology and climate on the HRE fish community, we applied multivariate statistical methods to data on 20 species–life history stages collected from 1974 to 2005. We confirm that the HRE fish community has changed over this period. These changes are correlated with local hydrology (freshwater flow and water temperature) and regional climate (the Atlantic Multidecadal Oscillation [AMO] and North Atlantic Oscillation). We found that the abundances of striped bass Morone saxatilis larval stages are positively correlated with high freshwater flows and those of juvenile American shad Alosa sapidissima negatively correlated with the AMO or warmer sea surface temperatures. Our findings suggest that climate‐related variability affects HRE juvenile shad abundances and that management strategies for this declining species should include the implications of climate change.Received March 19, 2011; accepted January 10, 2012

Relative Sensitivity of New England American Shad to Fishing, Discard Mortality, and Dam Passage Failure or Mortality

AbstractAmerican shad Alosa sapidissima in Atlantic coastal rivers of the New England states are affected by anthropogenic sources of mortality, such as discards of immature fish (bycatch) in various fisheries, directed fishing on prespawning adults, and the passage failure or mortality of mature fish at migratory barriers. We evaluated the relative importance of these factors, independently and in combination, by modeling the predicted lifetime spawning stock biomass of an age‐1 female recruit (SSBR) with an assumed constant rate of natural mortality. Discard losses had the greatest impact on the SSBR, followed by directed fishing and upstream passage mortality, upstream passage failure (the fish survived but did not pass the barrier or spawn), and downstream losses of postspawning adults. Fishery managers strive to keep mortality rates below those that reduce SSBR to less than 30% of that of a stock with no anthropogenic mortality. In our modeling, SSBR dropped below that benchmark when bycatch rates exceeded 0.21, directed fishing or upstream passage mortality exceeded 0.45, and upriver passage failure without mortality exceeded 0.70. Since the downriver passage mortality of adults occurred after spawning, SSBR did not decline below the benchmark even at 100% downriver loss. The impacts of upstream passage mortality always exceeded those from comparable downstream passage mortality. Fishing and discard losses seriously reduced any gain in SSBR from reduced fish passage mortality or failure. The results in this paper suggest that among the anthropogenic factors evaluated, American shad in New England are most sensitive to discard losses of immature shad in ocean fisheries and that fish passage improvements at dams are most effective when they are developed in combination with reductions in fishery‐related losses.Received April 25, 2011; accepted November 29, 2011

Alosine Restoration in the 21st Century: Challenging the Status Quo

AbstractDespite the expenditure of millions of dollars on restoration efforts for depleted North American stocks of alosine fishes, rangewide abundance levels for multiple species have declined to historic lows. Stocking practices aimed at rebuilding spawning runs are deemed successful when numerical abundance levels are shown to increase in response. However, these practices may only yield short‐term gains in abundance at the ultimate expense of population genetic integrity and do not ensure the long‐term persistence and evolutionary potential of a species. Although molecular methods are now widely employed in fisheries management and provide a suite of powerful management tools, these approaches have not been well integrated into alosine management strategies. We review the net effects of stocking practices on population genetic integrity and species’ long‐term persistence as it is currently understood and highlight what is known in this regard for alosines in North America, with particular focus on American shad Alosa sapidissima. We find that stocking practices carry a substantial risk to the persistence of genetically distinct alosine spawning populations and suggest that future restoration efforts proceed by providing access to historical spawning grounds, either through dam removal or through providing effective fish passage, followed by natural recolonization of reclaimed habitat. We also identify important areas of research relevant to future alosine restoration that require exploration and identify recent developments that may alter future restoration decisions in an adaptive management framework.Received March 18, 2011; accepted October 6, 2011

Foraging Potential of Larval Alosines in the Lower Roanoke River and Albemarle Sound, North Carolina

AbstractZooplankton 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 (21.0 ± 127.6) and lower in the Delta (7.5 ± 35.5) and Sound (4.6 ± 24.8). Mouth gape models for each alosine species showed that copepod nauplii and rotifers are the most suitable‐sized prey for the first feeding after yolk sac absorption. There was a high degree of spatial and temporal overlap between larval alosines and size‐appropriate prey items, suggesting that the larval alosines are not food limited in Albemarle Sound.Received March 25, 2011; accepted January 24, 2012

Identification of American Shad Spawning Sites and Habitat Use in the Pee Dee River, North Carolina and South Carolina

AbstractWe examined spawning site selection and habitat use by American shad Alosa sapidissima in the Pee Dee River, North Carolina and South Carolina, to inform future management in this flow‐regulated river. American shad eggs were collected in plankton tows, and the origin (spawning site) of each egg was estimated; relocations of radio‐tagged adults on spawning grounds illustrated habitat use and movement in relation to changes in water discharge rates. Most spawning was estimated to occur in the Piedmont physiographic region within a 25‐river‐kilometer (rkm) section just below the lowermost dam in the system; however, some spawning also occurred downstream in the Coastal Plain. The Piedmont region has a higher gradient and is predicted to have slightly higher current velocities and shallower depths, on average, than the Coastal Plain. The Piedmont region is dominated by large substrates (e.g., boulders and gravel), whereas the Coastal Plain is dominated by sand. Sampling at night (the primary spawning period) resulted in the collection of young eggs (≤1.5 h old) that more precisely identified the spawning sites. In the Piedmont region, most radio‐tagged American shad remained in discrete areas (average linear range = 3.6 rkm) during the spawning season and generally occupied water velocities between 0.20 and 0.69 m/s, depths between 1.0 and 2.9 m, and substrates dominated by boulder or bedrock and gravel. Tagged adults made only small‐scale movements with changes in water discharge rates. Our results demonstrate that the upstream extent of migration and an area of concentrated spawning occur just below the lowermost dam. If upstream areas have similar habitat, facilitating upstream access for American shad could increase the spawning habitat available and increase the population's size.Received March 22, 2011; accepted July 14, 2011

Describing juvenile American shad and striped bass habitat use in the Hudson River Estuary using species distribution models

Species distribution models (SDMs) are currently being used to identify essential fish habitat and guide fisheries management worldwide. We present SDMs based on generalized linear mixed models (GLMM) of the fall distribution or occurrence of juvenile American shad (Alosa sapidissima) and juvenile striped bass (Morone saxatilis) in the Hudson River estuary (HRE) based on data from a fishery-independent survey. The distribution of both species were modeled over a 6-year period (2000–2005) as a function of dissolved oxygen, salinity, water temperature, distance along the HRE denoted as river mile, time or Julian day, distance from submerged aquatic vegetation (SAV), and sediment characteristics. Salinity, river mile, and Julian day were the most important environmental determinants of juvenile American shad presence, and sediment type, salinity, river mile, and Julian day were the most important environmental determinants of juvenile striped bass presence. Calibration plots showed a high level of agreement between predictions generated by each model and actual observations of each species’ occurrence. Based on this result, we mapped the predicted distribution of each species. We found the highest predicted probabilities of juvenile American shad presence in the upper HRE, but the highest predicted probabilities of juvenile striped bass presence were in the lower HRE. Our results suggest that habitat partitioning between these two species is present during the fall in this system but the mechanism is unclear.

Is Cating's Method of Transverse Groove Counts to Annuli Applicable for all Stocks of American Shad?

AbstractA scale aging method was reported by Cating in 1953 for American shad Alosa sapidissima in the Hudson River and subsequently validated by recapturing fish marked and released in the Connecticut River. However, American shad spawn in all major rivers from Canada to Florida and their scales record growth events occurring in three distinct biogeographic provinces. Thus, a single scale aging method may not be applicable across the latitudinal range of this species. To address this concern, scales from American shad from one southern river (the St. Johns), three Middle Atlantic rivers (the Delaware, Hudson, and Connecticut), and one northern river (the Merrimack) were examined. Scales were cleaned, impressed in acetate, and analyzed by the same reader using a digital imaging system. The transverse grooves, the key morphological character used in Cating's method, were counted to the distal edge of the freshwater zone and the first three annuli. In most instances, these groove frequencies were statistically different from Cating's data for the Hudson River. Moreover, our data showed enough overlap in groove frequencies that they cannot be relied on as diagnostic characters for the freshwater zone and first three annuli in fish with difficult‐to‐interpret scales. Scale size explained more of the variance in groove frequencies than fish age did. Regardless of the specific process creating transverse grooves, we provide evidence that Cating's method should not be used to age American shad.

Movement Patterns of American Shad Transported Upstream of Dams on the Roanoke River, North Carolina and Virginia

AbstractAmerican shad Alosa sapidissima are in decline throughout much of their native range as a result of overfishing, pollution, and habitat alteration in coastal rivers where they spawn. One approach to restoration in regulated rivers is to provide access to historical spawning habitat above dams through a trap‐and‐transport program. We examined the initial survival, movement patterns, spawning, and downstream passage of sonic‐tagged adult American shad transported to reservoir and riverine habitats upstream of hydroelectric dams on the Roanoke River, North Carolina and Virginia, during 2007–2009. Average survival to release in 2007–2008 was 85%, but survival decreased with increasing water temperature. Some tagged fish released in reservoirs migrated upstream to rivers; however, most meandered back and forth within the reservoir. A higher percentage of fish migrated through a smaller (8,215‐ha) than a larger (20,234‐ha) reservoir, suggesting that the population‐level effects of transport may depend on upper basin characteristics. Transported American shad spent little time in upper basin rivers but were there when temperatures were appropriate for spawning. No American shad eggs were collected during weekly plankton sampling in upper basin rivers. The estimated initial survival of sonic‐tagged American shad after downstream passage through each dam was 71–100%; however, only 1% of the detected fish migrated downstream through all three dams and many were relocated just upstream of a dam late in the season. Although adult American shad were successfully transported to upstream habitats in the Roanoke River basin, under present conditions transported individuals may have reduced effective fecundity and postspawning survival compared with nontransported fish that spawn in the lower Roanoke River.Received August 8, 2010; accepted December 30, 2010

Catch Density: A New Approach to Shifting Baselines, Stock Assessment, and Ecosystem-Based Management

Since 1995, researchers have worked to incorporate historical perspectives into fisheries management. however, problems of scale and distribution, data incompatibilities, and strictures of standard stock assessment models have limited success so far. here we offer a new metric, catch density (CD = catch/area fished), as a simple way to examine fish concentration that standardizes historical and modern catch by geographical area fished. we present three case studies based on historical gulf of maine fisheries. The first compares five discrete datapoints of annual catch and CD for american shad from 1634 to 1999. Changes in fish habitat, fishing effort, and geographical area make direct comparison of catch alone misleading, but CD declined three orders of magnitude over four centuries. The second study compares discontinuous and continuous time series of yearly catch and CD for 18 species and two species groups from 1887 to 1945 and from 1989 to 2005. modern catch is aggregated over each stock's entire range; the historical area is the gulf of maine. in each case, historical context explains the results. overall catch is higher today, while CD was higher historically, likely reflecting expanded vessel range and catch per unit effort. finally, when catch, CD, and average trophic level are compared for functional groups over the same time periods, CD accurately reflects shifts in trophic level not seen in catch alone. CD standardizes catch across spatial and temporal scales, timeframes, and geographic distribution. By integrating fisheries history with fisheries science, it offers a new perspective, quickly obtained, that may aid in developing ecosystem-based management.

Breaking the Deadlock: Improving Water-Release Policies on the Delaware River Through Operations Research

The Delaware River provides half of New York City's drinking water, is a habitat for wild trout and American shad, and has suffered three major floods in the last five years. The water releases from three New York City dams on the Delaware River's headwaters impact the reliability of the city's water supply, the potential for floods, and the quality of the aquatic habitat. This project's objective was to revise the release policies to benefit river habitat and fisheries without increasing New York City's drought risk. Changes in the release policies were constrained by the dictates of two US Supreme Court Decrees and the need for unanimity among four states and New York City. We describe the analyses and the politics that led the Delaware River Basin Commission to implement our operations-research–based adaptive release framework in October 2007. In addition to meeting our habitat improvement goals and drought-risk constraint, our algorithm conservatively decreases end-of-summer reservoir levels more in wet years, thereby modestly increasing flood protection during the hurricane season, and is substantially simpler to administer.

Mitochondrial genome of the American shad Alosa sapidissima

The complete mitochondrial genome of Alosa sapidissima has been determined. The total length of the mitogenome was 16,697 bp and had a gene content (13 protein-coding, 22 tRNAs and 2 rRNAs. Except for the seven tRNA and Nd6 genes, all other mitochondrial genes are encoded on the heavy strand. The overall base composition of the heavy strand is 28.3% A, 24.8% T, 28.9% C, 17.9% G, with an AT content of 53.1%. The DNA sequence of Alosa. sapidissima shared 97.1, 93.9, 88.8 and 82.3% sequence identity with that of Alosa alosa, Alosa pseudoharengus. Molecular data here presented provide a useful toll for evolutionary as well as population genetic studied.