Atlantic Menhaden Research Articles

Seasonal Mortality of Wild Atlantic Menhaden (Brevoortia tyrannus) Is Caused by a Virulent Clone of Vibrio (Listonella) anguillarum; Implications for Biosecurity along the Atlantic Coastal United States

Atlantic menhaden are a highly migratory marine species in the Eastern United States that suffer from seasonal chronic mortality. Affected fish show neurologic signs referred to as spinning disease, including circling at the surface and erratic corkscrew swimming before death. We investigated three similar menhaden mortality events consistent with spinning disease in coastal New Jersey and New York between 2020 and 2021 to understand the cause. A unique strain of Vibrio (Listonella) anguillarum (serogroup O3) was detected regularly in high loads, particularly in the brains of moribund fish, by both metagenomics and bacterial isolation. The most common histopathological changes in moribund fish were hemorrhagic meningitis, encephalitis, pyknosis, and karyorrhexis of hematopoietic tissues in the kidney and spleen. Whole genome sequencing of isolates from moribund fish representing a wide spatial and temporal range showed that they were nearly identical clones, suggesting it to be a pathogenic strain circulating in the population. Though V. anguillarum is believed to be the main pathogen associated with spinning disease and mortality, Yersinia ruckeri (serotype O1) was isolated from smaller numbers of fish. Considering the highly migratory nature of Atlantic menhaden throughout the eastern United States and their use as bait for other fisheries, these findings identify potential biosecurity challenges that should be considered in Atlantic salmon aquaculture, fisheries, and emerging marine aquaculture in the region.

Evaluation of alternative harvest policies for striped bass and their prey, Atlantic menhaden

Ecosystem approaches to fisheries management are being explored worldwide, but few evaluations of multispecies harvest control rules (HCRs) exist. Our goal was to perform a simulation test of a suite of HCRs using an age-structured predator–prey model to represent the dynamics of a small pelagic fish, Atlantic menhaden ( Brevoortia tyrannus), and its predator, striped bass ( Morone saxatilis). We evaluated a suite of static and dynamic single and multispecies HCRs to estimate effects on stock performance metrics. No single HCR achieved ecosystem management objectives for both stocks given their current reference points, but HCRs that involved the “40–10 rule” for striped bass performed well across all predator performance metrics. The most influential factor determining performance of striped bass HCRs was striped bass fishing mortality, and relatively few HCRs achieved target SSB for Atlantic menhaden. Our study indicated that some HCRs recommended for forage fish management may not be effective in systems with generalist predators, and that ecosystem management objectives might be achievable by simultaneously adopting HCRs for both predator and prey stocks that complement one another.

The reproductive biology and fecundity of female Atlantic Menhaden

AbstractObjectiveAtlantic Menhaden Brevoortia tyrannus support fisheries that yield the largest landings by volume on the U.S. East Coast and fulfill a critical ecological role as a forage species. The spawning reference point of the stock assessment model that is routinely applied to this species requires information on total annual fecundity. The goal of this study was to generate a contemporary, histology‐based evaluation of the reproductive biology and fecundity of female Atlantic Menhaden.MethodsFemale Atlantic Menhaden (n = 559) were collected between Cape Cod, Massachusetts, and Cape Hatteras, North Carolina, from 2013 to 2019. Ovarian tissues were prepared using standard histological techniques which, when coupled with oocyte size‐frequency and count data, were used to classify reproductive mode and estimate batch fecundity, spawning frequency, and maturity. Monthly gonosomatic indices were combined with published female reproductive information and spatiotemporal patterns in larval and juvenile abundance to designate spawning seasonality.ResultHistological preparations and oocyte size‐frequency patterns of female Atlantic Menhaden ovaries were consistent with indeterminate batch spawning. Batch fecundity increased with fork length, while spawning seasonality extended from September 15 to April 15 with a spawn every 7.5 ± 2.3 days. Female maturity probabilities transitioned from 0.2 to 0.8 over fork lengths of 214.8–226.5 mm (approximately ages 2.0–2.3 years). Estimated mean per capita female annual fecundity varied from 465,757 to 3,250,135 oocytes for fish ranging from 215.8 to 284.8 mm fork length (ages 2–6 years), which represented a 614–2267% (mean = 1656%) increase in annual female reproductive output relative to previous estimates.ConclusionFemale Atlantic Menhaden exhibit indeterminant batch spawning while spawning seasonality and mean per capita female annual fecundity were appreciably greater than previously reported. This new reproductive information illuminates the robust reproductive productivity of this species and will aid routinely conducted stock assessments.

Bycatch reduction devices exclude diamondback terrapins and maintain blue crab catch in two Virginia tidal creeks

AbstractObjectiveThe diamondback terrapin Malaclemys terrapin is frequently caught as bycatch in both commercial and recreational blue crab Callinectes sapidus fisheries throughout its range along the Atlantic and Gulf coasts of North America. Bycatch reduction devices (BRDs) are plastic or wire rectangles mounted in the entrance funnels of crab traps, designed to exclude terrapins while still allowing crabs to enter. In this study conducted in two tidal creeks in Virginia, USA, we assessed the effectiveness of four BRD designs, including two novel oval designs, against control traps with no BRDs.MethodsWe tested four replicates of each of the five trap treatments (1.75‐inch oval BRD, 2‐inch oval BRD, 1.75‐inch rectangular BRD, 2‐inch rectangular BRD, and a control trap without a BRD) in each tidal creek, for a total of 20 traps per creek and 40 traps total. We fitted traps with wire chimneys that extended above the high tide water line to allow trapped terrapins to surface for air. For eight weeks during summer 2021, we baited traps with Atlantic Menhaden Brevoortia tyrannus each day, beginning on Monday. Tuesday–Friday, we emptied traps of any animals inside, and recorded terrapin sex, terrapin carapace length, terrapin carapace width, and terrapin shell height, as well as blue crab carapace length.ResultWe found that all four BRD designs were highly effective at excluding terrapins and maintaining crab catch when compared to control traps. We found a significant difference (p = 0.003) in catch per unit effort (CPUE) of diamondback terrapins among treatments, with the control group (those without BRDs) having the highest CPUE (0.97 ± 0.18). All traps fitted with BRDs decreased terrapin capture significantly compared to the control group. Oval BRDs excluded more terrapins than their rectangular counterparts with the same height dimension, although these differences were not significant. We found no significant difference in CPUE of blue crabs among treatments (p = 0.392), or in the size of legal crabs caught in each treatment (p = 0.216).ConclusionThis study provides evidence of the effectiveness of both rectangular and oval‐shaped BRDs to exclude terrapins and maintain crab catch in Virginia waters, where BRDs are not currently required.

DNA metabarcoding of cloacal swabs provides insight into diets of highly migratory sharks in the Mid-Atlantic Bight.

The abundances of migratory shark species observed throughout the Mid-Atlantic Bight (MAB) during productive summer months suggest that this region provides critical habitat and prey resources to these taxa. However, the principal prey assemblages sustaining migratory shark biomass in this region are poorly defined. We applied high-throughput DNA metabarcoding to shark feces derived from cloacal swabs across nine species of Carcharhinid and Lamnid sharks to (1) quantify the contribution of broad taxa (e.g., invertebrates, fishes) supporting shark biomass during seasonal residency in the MAB and (2) determine whether the species displayed distinct dietary preference indicative of resource partitioning. DNA metabarcoding resulted in high taxonomic (species-level) resolution of shark diets with actinopterygian and elasmobranch fishes as the dominant prey categories across the species. DNA metabarcoding identified several key prey groups consistent across shark taxa that are likely integral for sustaining their biomass in this region, including Atlantic menhaden (Brevoortia tyrannus), Atlantic mackerel (Scomber scombrus), and benthic elasmobranchs, including skates. Our results are consistent with previously published stomach content data for the shark species of similar size range in the Northwest Atlantic Ocean, supporting the efficacy of cloacal swab DNA metabarcoding as a minimally invasive diet reconstruction technique. The high reliance of several shark species on Atlantic menhaden could imply wasp-waist food-web conditions during the summer months, whereby high abundances of forage fishes sustain a diverse suite of migratory sharks within a complex, seasonal food web.

Estimating potential menhaden consumption by double-crested cormorants along the coast of North Carolina

The south Atlantic coast supports one of the highest assemblages of non-breeding double-crested cormorants (Nannopterum auritum) known and is a convergence area for Atlantic menhaden (Brevoortia tyrannus) during the winter months. We surveyed cormorants along the coast of North Carolina and used a bioenergetics approach to estimate potential menhaden consumption. We estimated cormorant numbers using a network of repeatable aerial transects along the outer coast (366 km) and within sounds (266 km) during fall migration, winter and spring migration (2019-2021). We estimated the number of bird days, metabolic demand and menhaden equivalents of demand. Cormorant numbers peaked around 122,000 to 131,000 during southward migration, reached a low of 30,000 to 39,000 in winter and then increased to 67,000 to 68,000 during northward migration. We did not capture the peak of spring migration during the study period (20 November through 24 March). We estimated the number of cormorant days within the study period to be 8.6 x 106 and 9.2 x 106 for the two field seasons respectively. We estimated that cormorants consumed approximately 5,334 and 5,660 mt of menhaden equivalents within the study area. Estimated consumption peaked between 76 and 81 mt-d during fall passage and reached a low of 19 and 24 mt-d during the winter. Annual menhaden take by humans and predatory fish is around 354,000 mt. Menhaden consumption by cormorants within the study area represents 4% of the commercial and recreational take and 7% of the estimated consumption by predatory fish or 2.5% of the known take.

Food supplementation increases reproductive performance of ospreys in the lower Chesapeake Bay

The Atlantic States Marine Fisheries Commission (ASMFC), the governing body responsible for managing fisheries on the U.S. East Coast, formally adopted the use of Ecological Reference Points (ERPs) for Atlantic menhaden, Brevoortia tyrannus. Scientists and stakeholders have long recognized the importance of menhaden and predators such as ospreys, Pandion haliaetus, that support the valuable ecotourism industry and hold cultural significance. Landings in the reduction fishery are at their lowest levels and menhaden is facing potential localized depletion. Mobjack Bay, located within the lower Chesapeake Bay, has been a focus of osprey research since 1970 and represents a barometer for the relationship between osprey breeding performance and the availability of their main prey, menhaden. Since local levels of menhaden abundance were not available, we conducted a supplemental menhaden feeding experiment on osprey pairs during the 2021 breeding season. Our main objective was to determine if the delivery rate of menhaden had an influence on nest success and productivity. Nest success (χ2 = 5.5, df = 1, P = 0.02) and productivity (β = 0.88, SE = 0.45, CI = 0.049, 1.825, P = 0.048) were significantly higher within the treatment group. Reproductive rates within the control group were low and unsustainable suggesting that current menhaden availability is too low to support a demographically stable osprey population. Menhaden populations should be maintained at levels that will sustain a stable osprey population in which they are able to produce 1.15 young/active nest to offset mortality.

Forage Fish Species Prefer Habitat within Designated Offshore Wind Energy Areas in the U.S. Northeast Shelf Ecosystem

AbstractAs the world develops sources of renewable energy, there is an intensifying interest in offshore wind energy production. The Northeast U.S. Continental Shelf (NES) ecosystem has favorable wind dynamics, with active development of wind energy. In this study, we present species distribution models that consider both occupancy and biomass responses for a broad spectrum of fish and macroinvertebrate taxa (n = 177). Building upon prior analyses, habitat was differentiated into overall and core habitats based on statistical distributions of habitat scores. Overall habitat was used to show each species' regional distribution based on fishery‐independent survey captures between 1976 and 2019, whereas core habitat represented where the focus of the species' abundance was located as a subset of overall habitat. Wind energy developments may modify the water column in ways that impact lower‐trophic‐level productivity; therefore, added attention was given to the response of forage species. Over 20% of species showed preferential use of putative and potential wind development areas, including a disproportionate number of forage taxa. Principal usage varied by season, with forage species like Atlantic Menhaden Brevoortia tyrannus and Atlantic Mackerel Scomber scombrus preferentially using the lease areas in spring and Round Herring Etrumeus teres and longfin inshore squid Doryteuthis pealeii using lease areas in autumn. For species with relatively low usage of the lease areas, there was a tendency for the usage related to overall habitat to be lower than usage for core habitat; in contrast, for species with high usage of the lease areas, that usage was higher for overall habitat than for core habitat. The area of habitat tended to have positive trends across species, with these positive trends being disproportionately higher among forage taxa. These results frame the importance of wind lease areas for species in the NES, particularly forage taxa that fulfill many important ecological functions.

Bioeconomic analysis of harvesting within a predator–prey system: A case study in the Chesapeake Bay fisheries

Sustainable use of biological resources is very important as over exploitation on the long run may lead to stock depletion, which in turn may threaten biodiversity. The Chesapeake Bay is an extremely complex ecosystem, and sustainable harvesting of its fisheries is essential both for the ecosystem’s biodiversity and economic prosperity of the area. Here, we use ecosystem based mathematical modeling to study the population dynamics with harvesting of two key fishes in the Chesapeake Bay, the Atlantic Menhaden (Brevoortia tyrannus) as a prey and the Striped Bass (Morone saxatilis) as a predator. We start by fitting the generalized Lotka–Volterra model to actual time series abundance data of the two species obtained from fisheries in the Bay. We derive conditions for the existence of the bio-economic equilibrium and investigate the stability and the resilience of the biological system. We study the maximum sustainable yield, maximum economic yield, and resilience maximizing yield policies and their effects on the fisheries long term sustainability, particularly with respect to the menhaden-bass population dynamics. This study may be used by policy-makers to balance the economic and ecological harvesting goals while managing the populations of Atlantic menhaden and striped bass in the Chesapeake Bay fisheries.

Assessing individual movement, habitat use, and behavior of non-breeding marine birds in relation to prey availability in the US Atlantic

Resource availability is a key factor driving marine bird movements and distributions, but direct information on prey availability is difficult to obtain at relevant scales. We present novel methods for describing multi-scale trophic associations, combining movement analyses of marine birds with estimates of forage fish surface aggregations from digital aerial survey data and species occupancy from bottom trawl survey data. We analyzed satellite telemetry data from northern gannets Morus bassanus, red-throated loons Gavia stellata, and long-tailed ducks Clangula hyemalis in the US Atlantic during the non-breeding period. Using discrete-time hidden Markov models to distinguish area-restricted (i.e. putative foraging) from transit movements, we examined how environmental factors influence movement, and how forage fish species distributions and surface aggregations influence habitat use by gannets and loons that have greater dietary reliance. Our results suggest that chlorophyll a concentration significantly affected movement behavior across species, highlighting the importance of higher-productivity areas around estuaries during colder months when regional productivity is low. Though variable across species and seasons, spatial cross-correlation analysis revealed that herring species (Family Clupeidae), including Atlantic menhaden Brevoortia tyrannus, may be important resources; it also showed positive spatial correlations with forage fish aggregations. This suggests that prey patch dynamics and factors driving aggregation formation may be as important as species composition. However, spatial patterns were generally low (<0.3), suggesting a mismatch in spatiotemporal resolution, exemplifying the challenges in quantifying trophic relationships in marine systems. Disentangling predator-prey relationships is critical to understanding the mechanisms driving marine bird behavior in rapidly changing marine systems.

Identification of important forage fish and implications of increased predator demand through Ecopath modeling

Fisheries on lower trophic levels act as and compete with predators in aquatic ecosystems for potentially limited prey resources. Multiple predators in a system are often managed to achieve a Bmsy that could result in a total predator consumption level the ecosystem cannot support. We developed an Ecopath model for Pamlico Sound, NC and its tributaries to address this issue. The model is comprised of 43 compartments with an emphasis on piscivores and their prey and represents the 2012–13 time period. We estimated total predator demand for fish prey and identified important species of forage fish and top piscivorous predators in Pamlico Sound. We compared local fishing fleet removals and predator consumption in forage fish, penaeid shrimp, and blue crabs. Finally, we evaluated the impact of increased predator demand on the system, by increasing biomass levels of five predators to equal their management thresholds and using mixed trophic impact analysis. Atlantic menhaden (Brevoortia tyrannus), anchovy (Anchoa hepsetus and A. mitchilli), spot (Leiostomus xanthurus), and Atlantic croaker (Micropogonias undulatus) were the most important forage fish in the system, representing over 80% of the fish consumed (by weight). Lizardfish (Synodus foetens) and bottlenose dolphins (Tursiops truncates) were top predators based on trophic level, while bluefish and longnose gar (Lepisosteus osseus) were top predators in terms of total fish consumption. The highest overlap in forage fish usage exists between fisheries and piscivores for Atlantic croaker and spot. Total forage fish removals through predation and harvest was greater than 65% of the production for each of the four-forage fish and, under the higher predator biomass model, total removals exceeded production for spot; total removals in either scenario did not exceed the production of penaeid shrimp and blue crab. Thus, the tradeoff between fisheries for forage fish and piscivores should be considered when assessing and managing fisheries in Pamlico Sound.

The feeding ecology of striped bass and the role of ontogeny

Amidst constantly changing biotic and abiotic conditions, a more thorough understanding of the ecological consequences of dynamic predator-prey interactions will likely enable increasingly sustainable fisheries management. This study assessed the diet of striped bass, a generalist marine predator in coastal Massachusetts that feed on a variety of prey species and impose top-down pressure on other important fishery species, such as the American lobster and Atlantic menhaden. We explored the role of ontogeny using both stomach content and stable isotope analyses. Empirical results from 158 striped bass collected in northern Massachusetts revealed that striped bass in this area may have shifted from feeding predominantly on Atlantic menhaden in the late 1990s and early 2000s to Atlantic mackerel in this study. Stable isotope data suggested that the diet of striped bass is significantly linked with ontogeny: larger fish feed more heavily on benthic prey, particularly in the latter half of their seasonal residency in Massachusetts. Our study suggests that large striped bass gain an energetic advantage, as indicated by a liver somatic index, by feeding on benthic prey, possibly due to decreased foraging costs. Collectively, this work illustrates the ability of predatory fish to capitalize on the variability of forage fish populations, but highlights the importance of invertebrate prey for large striped bass and proposes underlying mechanisms driving ontogenetic diet switches from piscivory to benthivory

COI amplicon sequence data of environmental DNA collected from the Bronx River Estuary, New York City

In this data paper, we describe environmental DNA (eDNA) cytochrome c oxidase (COI) amplicon sequence data from New York City’s Bronx River Estuary. As urban systems continue to expand, describing and monitoring their biodiversity is increasingly important for sustainability. Once polluted and overexploited, New York City’s Bronx River Estuary is undergoing revitalization and restoration. To investigate and characterize the area’s diversity, we collected and sequenced river sediment and surface water samples from Hunts Point Riverside and Soundview Parks (ntotal = 48; nsediment = 25; nwater = 23). COI analysis using universal primers mlCOIintF and jgHCO2198 detected 27,328 Amplicon Sequence Variants (ASVs) from 7,653,541 sequences, and rarefaction curves reached asymptotes indicating sufficient sampling depth. Of these, eukaryotes represented 9,841ASVs from 3,562,254 sequences. At the study sites over the sampling period, community composition varied by substrate (river sediment versus surface water) and with water temperature, but not pH. The three most common phyla were Bacillariophyta (diatoms), Annelida (segmented worms), and Ochrophyta (e.g. brown and golden algae). Of the eukaryotic ASVs, we identified 614 (6.2%) to species level, including several dinoflagellates linked to Harmful Algal Blooms such as Heterocapsa spp., as well as the invasive amphipod Grandidierella japonica. The analysis detected common bivalves including blue (Mytilus edulis) and ribbed (Geukensia demissa) mussels, as well as soft-shell clams (Mya arenaria), in addition to Eastern oysters (Crassostrea virginica) that are being reintroduced to the area. Fish species undergoing restoration such as river herring (Alosa pseudoharengus, A. aestivalis) failed to be identified, although relatively common fish including Atlantic silversides (Menidia menidia), menhaden (Brevoortia tyrannus), striped bass (Morone saxatilis), and mummichogs (Fundulus heteroclitus) were found. The data highlight the utility of eDNA metabarcoding for analyzing urban estuarine biodiversity and provide a baseline for future work in the area.

Catch Fish Profile at Amagarapati Fish Landing Port, East Flores Regency, East Nusa Tenggara Province

East Nusa Tenggara (NTT) Province has many business potentials in the marine and fisheries sectors, especially fish as a commodity. East Flores District is one of the fish landing centers for fishing vessels in the East Nusa Tenggara Province. The objective of this study was to determine the activities of fishing vessels and to find out the catches that have been landed at Amagarapati Fish Landing Port. The location of this study was determined by purposive sampling, while the research location was carried out at Amagarapati Fish Landing Port. This research was conducted in July-October 2021. A descriptive survey was chosen as the data collection method by conducting direct observations in the field such as giving interviews and distributing questionnaires to the fishermen and Amagarapati Fish Landing Port’s employees. The results of this study showed that fishing activities at Amagarapati Fish Landing Port were running normally as usual even though Implementation of restrictions on community activities (PPKM) was implemented in East Flores Regency, the fish caught were dominated by Skipjack, Mackerel Tuna, Tuna, Mackerel Scad, and Atlantic Menhaden. There was an obstacle in the decline in fish prices due to the decline in people's purchasing power, tuna exports to the United States experienced a decline due to the lockdown destination countries. The catch that landed at Amagarapati Fish Landing Port 2,527.5 Tons of catches were reduced due to bad weather, the availability of fish bait for pole and line vessels was limited so that it hampered fishing activities.Keywords: Amagarapati Fish Landing Port, Fish Catch, and Fishing Vessels

Modeling ecological issues in fish dynamics: Competing predators, invasiveness, and over-harvesting

A mathematical model of a three-species dynamical system is employed to analyze some ecological issues in fish dynamics, namely, competition between predators, effect of an invasive species, and over-harvesting of either the prey or one of the predators. To address the issue of competition between predators, we assume that one of the predators is a specialist predator using a Holling Type II response while the other one is a generalist predator using a Holling Type III response. The latter assumption is also used to analyze the effect of having an invasive species as a second predator. We use an analytical approach to compute the equilibria and investigate the linear stability of each point. We also compute the bionomic equilibria and find conditions for their existence. We use a numerical approach to analyze the effects of harvesting efforts on the prey and on one of the predators. The proposed dynamical system may be used to analyze special fish dynamics in the Chesapeake Bay with the Atlantic menhaden as prey as well as striped bass and catfish as competing predators. In particular, we address a recent policy on eating-the-invaders as a way to control the growth of the catfish as an invasive species in the Chesapeake Bay.

Using Environmental DNA to Detect Whales and Dolphins in the New York Bight

Determining how cetaceans and other threatened marine animals use coastal habitats is critical to the effective conservation of these species. Environmental DNA (eDNA) is an emerging tool that can potentially be used to detect cetaceans over broad spatial and temporal scales. In particular, eDNA may present a useful complementary method for monitoring their presence during visual surveys in nearshore areas, and for co-detecting prey. In conjunction with ongoing visual surveys, we tested the ability of eDNA metabarcoding to detect the presence and identity of cetaceans in the New York Bight (NYB), and to identify fish species (potential prey) present in the area. In almost all cases in which humpback whales and dolphins were visually observed, DNA from these species was also detected in water samples. To assess eDNA degradation over time, we took samples in the same location 15 and 30 min after a sighting in seven instances, and found that eDNA often, but not always, dropped to low levels after 30 min. Atlantic menhaden were detected in all samples and comprised the majority of fish sequences in most samples, in agreement with observations of large aggregations of this important prey species in the NYB. While additional data are needed to better understand how factors such as behavior and oceanographic conditions contribute to the longevity of eDNA signals, these results add to a growing body of work indicating that eDNA is a promising tool to complement visual and acoustic surveys of marine megafauna.

Distribution and Abundance of Marine Mammals in the Estuarine Waters of the Piscataqua River, Maine, USA

The estuaries and tidal rivers of the Gulf of Maine have rarely been surveyed systematically for marine mammals. We report here on three years of survey data, 2017 to 2019. This study employed a shipboard visual line-transect methodology study design, collecting data on marine mammals in the lower Piscataqua River, which is confluent with the Gulf of Maine. Marine mammal species observed most often were harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus), with a resulting in-water density estimate of 1.02 seals/km2 and an abundance estimate of seven harbor seals and one gray seal (CV = 19.3%) in the survey area. Seals were present in all months of the year. No live pups were detected. Harbor porpoises (Phocoena phocoena) and minke whales (Balaenoptera acutorostrata) were also observed, but the sightings (6 harbor porpoises; 7 minke whales) did not yield enough data to estimate density or abundance. The minke whales were present during August and September 2018, concurrent with an influx of Atlantic menhaden (Brevoortia tyrannus), a prey species. The consistent albeit relatively low marine mammal species sightings and abundances suggest that the lower Piscataqua River is used regularly by a relatively small number of harbor and gray seals, although not for pupping, and occasionally by harbor porpoises and by foraging minke whales. This is the first study of its kind in an estuarine environment in the Gulf of Maine.

Maintaining Ecosystem and Economic Structure in a Three-Species Dynamical System in Chesapeake Bay

We consider a three-species fish dynamical system in Chesapeake Bay consisting of the Atlantic menhaden as the prey and its two competing predators, the striped bass and the catfish. Building on our previous work in this system, we consider the issue of balancing economic harvesting goals (financial gain for fishermen) with ecological harvesting goals (non-extinction of species). In particular, we investigate the bionomic equilibria, maximum sustainable yield, and the maximum economic yield. Analytical computations and numerical simulations are employed to provide some mathematical guidance on fisheries management policies.

The Path to an Ecosystem Approach for Forage Fish Management: A Case Study of Atlantic Menhaden

Atlantic menhaden (Brevoortia tyrannus) support the largest fishery by volume on the United States East Coast, while also playing an important role as a forage species. Managers’ and stakeholders’ increasing concerns about the impact of Atlantic menhaden harvest on ecosystem processes led to an evolution in the assessment and management of this species from a purely single-species approach to an ecosystem approach. The first coastwide stock assessment of Atlantic menhaden for management used a single-species virtual population analysis (VPA). Subsequent assessments used a forward projecting statistical catch-at-age framework that incorporated estimates of predation mortality from a multispecies VPA while analytical efforts continued toward the development of ecosystem models and explicit ecological reference points (ERPs) for Atlantic menhaden. As an interim step while ecosystem models were being developed, a series of ad hoc measures to preserve Atlantic menhaden biomass for predators were used by managers. In August 2020, the Atlantic States Marine Fisheries Commission formally adopted an ecological modeling framework as a tool to set reference points and harvest limits for the Atlantic menhaden that considers their role as a forage fish. This is the first example of a quantitative ecosystem approach to setting reference points on the United States Atlantic Coast and it represents a significant advance for forage fish management. This case study reviews the history of Atlantic menhaden stock assessments and management, outlines the progress on the current implementation of ERPs for this species, and highlights future research and management needs to improve and expand ecosystem-based fisheries management.

Baleen whale distribution, behaviour and overlap with anthropogenic activity in coastal regions of the New York Bight

ABSTRACT The New York Bight (NYB) is one of the busiest waterways along the US East Coast, and has recently seen an apparent increase in baleen whale presence. With growing anthropogenic pressures, a better understanding of their distribution and behaviour is needed. Encounter rates (sightings km−1) and behaviour of humpback (Megaptera novaeangliae), fin (Balaenoptera physalus) and minke (Balaenoptera acutorostrata) whales were obtained from dedicated non-systematic small vessel surveys conducted from May–November 2017–2019 in previously under-surveyed coastal areas of the NYB. Humpback whales were the most frequently sighted species, and their distribution in the NYB varied significantly by region and season. Within the mid-shelf region (10–60 km from shore), sightings of all species were generally concentrated spatially and temporally in mixed-species aggregations where feeding on sand lance (Ammodytes spp.) was observed. In the nearshore region (<10 km from shore), sightings of all species were more dispersed and typically occurred in close proximity to Atlantic menhaden (Brevoortia tyrannus). Humpback whales were commonly observed lunge feeding on these prey patches. The prevalence of foraging behaviour throughout the study area supports the hypothesis that the NYB may be an important supplementary feeding area for some species. Encounter rates were generally higher in areas overlapping with anthropogenic activity, suggesting that whales may be particularly vulnerable to anthropogenic impacts in the NYB. The observed species distribution patterns and importance of the NYB as a foraging habitat for baleen whales provides valuable information for the development of new baselines and best management practices within this heavily urbanized region.