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At least 901 records · Page 50Linked to original sources
USGS2011

Abiotic & biotic responses of the Colorado River to controlled floods at Glen Canyon Dam, Arizona, USA

Closure of Glen Canyon Dam reduced sand supply to the Colorado River in Grand Canyon National Park by about 94% while its operation has also eroded the park's sandbar habitats. Three controlled floods released from the dam since 1995 suggest that sandbars might be rebuilt and maintained, but only if repeated floods are timed to follow tributary sand deliveries below the dam. Monitoring data show that sandbars are dynamic and that their erosion after bar building is positively related with mean daily discharge and negatively related with tributary sand production after controlled floods. The March 2008 flood affected non-native rainbow trout abundance in the Lees Ferry tailwater, which supports a blue ribbon fishery. Downstream trout dispersal from the tailwater results in negative competitive interactions and predation on endangered humpback chub. Early survival rates of age-0 trout increased more than fourfold following the 2008 flood, and twofold in 2009, relative to prior years (2006-2007). Hatch-date analysis indicated that early survival rates were much higher for cohorts that emerged about 2 months after the 2008 flood relative to cohorts that emerged earlier that year. The 2009 survival data suggest that tailwater habitat improvements persisted for at least a year, but apparently decreased in 2010. Increased early survival rates for trout coincided with the increased availability of higher quality drifting food items after the 2008 flood owing to an increase in midges and black flies, preferred food items of rainbow trout. Repeated floods from the dam might sustainably rebuild and maintain sandbars if released when new tributary sand is available below the tailwater. Spring flooding might also sustain increased trout abundance and benefit the tailwater fishery, but also be a potential risk to humpback chub in Grand Canyon.

Arizona;Nevada;Utah↗
USGS2014

The influence of logjams on largemouth bass ( Micropterus salmoides ) concentrations on the lower Roanoke River, a large sand-bed river

This study examines the relation between logjams and largemouth bass (Micropterus salmoides) on the alluvial sand-bed lower Roanoke River. Disparate data sets from previous bank erosion, fisheries, and large wood studies were used to compare the distribution of largemouth bass with logjam frequency. Logjams are related to the frequency of bank mass wasting increasing from near an upstream dam to the middle reach of the study segment and then decreasing as the river approaches sea level. The highest concentration of largemouth bass and logjams was in the middle reach (110 fish per hour and 21 jams per km). Another measure of largemouth bass distribution, fish biomass density (g h1 ), had a similar trend with logjams and was a better predictor of fish distribution versus logjams (R2= 0.6 and 0.8 and p = 0.08 and 0.02 for fish per hour and g h1 versus logjam, respectively). We theorize that the preference for adult bass to congregate near logjams indicates the use of the jams as feeding areas. The results of a principal component analysis indicate that fish biomass concentration is much more related to logjam frequency than channel geometry (width, depth, and bank height), bed grain size, bank erosion, or turbidity. The results of this research support recent studies on in-channel wood and fisheries: Logjams appear to be important for maintaining, or increasing, both largemouth bass numbers and total biomass of fish in large eastern North American rivers. Persistent logjams, important as habitat, exist where relatively undisturbed river reaches allow for bank erosion inputs of wood and available anchoring locations. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

North Carolina↗
USGS2026

A tool for prioritizing gravel augmentation reaches for sediment starved rivers

Gravel augmentation is a widely used restoration technique used to improve habitat below dams, including salmonids spawning habitat. However, gravel augmentation can be cost-prohibitive, and it is often unclear which stream segments have the highest potential to benefit spawning salmonids. A tool to help prioritize reaches for gravel restoration could aid managers in making good decisions. To address this need, we convened a group of fishery managers to create Intrinsic Potential (IP) habitat models. We used stream attributes related to salmonid spawning habitat: elevation, width, and gradient from the synthetic stream channel dataset NetMap. We then used the IP models to develop an easy-to-use and flexible tool for identifying high spring-run Chinook Salmon ( Oncorhynchus tshawytscha ) IP along ~100 m reaches based on a conceptual model developed by the fishery managers. The tool allows for the inclusion of winter steelhead ( O. mykiss ) IP spawning habitat and allows users to incorporate mean August stream temperature maxima under recent conditions and projected under future climate change, land ownership (public or private or both), reach access distance, distance to and type of gravel sources, and relative gravel movement potential. We explore the prioritization tool with three demonstration strategies for the Upper Rogue River basin, Oregon, USA: (1) Spring Chinook Salmon Strategy, (2) Co-occurrence with winter steelhead Strategy, and (3) Climate Change Strategy. Our analysis demonstrates that altering management priorities directly influences which stream reaches are identified for gravel augmentation. In the three strategies we compared, a small number of current conservation reaches located downstream of spring Chinook Salmon spawning were identified using the tool. In addition, we identified a small number of reaches with no conservation strategy for winter steelhead spawning that meet prioritization criteria. Furthermore, under a climate change scenario, we highlight how new gravel source permitting could expand the set of viable augmentation reaches. The tool is publicly available on GitHub.

Oregon↗
USGS2015

Assessment and Mmanagement of North American horseshoe crab populations, with emphasis on a multispecies framework for Delaware Bay, U.S.A. populations: Chapter 24

The horseshoe crab fishery on the US Atlantic coast represents a compelling fishery management story for many reasons, including ecological complexity, health and human safety ramifications, and socio-economic conflicts. Knowledge of stock status and assessment and monitoring capabilities for the species have increased greatly in the last 15 years and permitted managers to make more informed harvest recommendations. Incorporating the bioenergetics needs of migratory shorebirds, which feed on horseshoe crab eggs, into the management framework for horseshoe crabs was identified as a goal, particularly in the Delaware Bay region where the birds and horseshoe crabs exhibit an important ecological interaction. In response, significant effort was invested in studying the population dynamics, migration ecology, and the ecologic relationship of a key migratory shorebird, the Red Knot, to horseshoe crabs. A suite of models was developed that linked Red Knot populations to horseshoe crab populations through a mass gain function where female spawning crab abundance determined what proportion of the migrating Red Knot population reached a critical body mass threshold. These models were incorporated in an adaptive management framework wherein optimal harvest decisions for horseshoe crab are recommended based on several resource-based and value-based variables and thresholds. The current adaptive framework represents a true multispecies management effort where additional data over time are employed to improve the predictive models and reduce parametric uncertainty. The possibility of increasing phenologic asynchrony between the two taxa in response to climate change presents a potential challenge to their ecologic interaction in Delaware Bay.

Book chapter↗
USGS1980

Toxicity of five forest insecticides to cutthroat trout and two species of aquatic invertebrates

The Northern Rocky Mountain region has had scattered infestation of the western spruce budworm Christoneura occidentalis since the early 1900's (U.S. DEPARTMENT OF AGRICULTURE (USDA) 1976b). On the basis of aerial surveys in 1975, TUNNOCK et al. (1976), estimated that budworm defoliation occurred on 2,278,804 acres of six National Forests in Montana. Since the use of DDT was banned in 1972, there has been a need to develop alternative insecticides with the efficacy of DDT but without its environmental risk. These insecticides must be effective in controlling the budworm, but should not persist in the environment or be toxic to other organisms. The organophosphate and carbamate insecticides are relatively nonpersistent and generally present only a moderate hazard to fish when applied according to label recommendations. The USDA Forest Service has been investigating the effectiveness of these two classes of insecticides against the budworm, and the Columbia National Fisheries Research Laboratory of the U.S. Fish and Wildlife Service has been cooperating with the Forest Service conducted pilot control projects in eastern Montana in 1975 and 1976 to determine the efficacy and environmental impact of acephate, carbaryl, and trichlorfon in controlling the western budworm (USDA 1976 b). In 1975, a similar type project was carried out in Maine with aminocarb, fenitrothion, and trichlorfon (USDA 1976 a). Acephate, fenitrothion, and trichlorfon (organophosphate insecticides) and aminocarb and carbaryl (carbamate insecticides) were selected for toxicity tests against cutthroat trout ( Salmo clarki ), a stonefly ( Pteronarcella badia ), and a freshwater amphipod ( Gammarus pseudolimnaeus ) edemic in streams of the northern Rocky Mountains. Populations of cutthroat trout inhabit lakes and streams in the Rocky Mountains which include some of the most pristine habitat and fisheries in North America. Pteronarcella and Gammarus provide forage for cutthroat trout and feed on decaying vegetation in riffle areas in streams and rivers. Stonefly naiads and amphipods were selected as test organisms because of their importance as trout food and their wide distribution in mountain stream communities. We determined the effect of various water types representing different biogeographical areas in the Intermountain West on the toxicity of these five forest insecticides.

Bulletin of Environmental Contamination and Toxico↗
USGS2024

Wide-ranging migration of post-nesting hawksbill sea turtles (Eretmochelys imbricata) from the Caribbean island of Nevis

Little is known about the post-nesting migration and foraging areas of hawksbill turtles ( Eretmochelys imbricata ) nesting on St. Kitts and Nevis, an important nesting site for hawksbills in the eastern Caribbean. To elucidate internesting, migration and foraging patterns of hawksbills from Nevis, we satellite tagged 28 post-nesting turtles between 2006 and 2022. Internesting, migrating and foraging activity periods were determined using a switching state–space model to estimate the behavioral state of the turtle’s locations. Twenty-five turtles (83–2,171 tracking days) established a foraging area, migrating between 5.3 and 2,799.5 km from the nesting beach. Twenty-one turtles were tracked during internesting movements with internesting areas ranging between 1.9 and 28.2 km 2 . Nearly half of the internesting centroids were located closer to a different beach than the beach where the turtle was originally encountered nesting. Hawksbills crossed through 29 different Exclusive Economic Zones (EEZs), including zones with legal sea turtle fisheries or traditional subsistence use. Core foraging areas (KDE 50%) ranged between 3.8 and 69.0 km 2 . Nearly a third of foraging centroids were within a Marine Protected Area (MPA), while nearly a quarter were within a legal sea turtle fishery EEZ. Hawksbills nesting on Nevis disperse to local, regional, and Caribbean wide foraging grounds, emphasizing the necessity of cooperative efforts to protect turtles and their habitats to ensure support of the recovery of hawksbill turtles throughout the wider Caribbean.

Caribbean, Nevis↗
USGS2018

The influence of angler values, involvement, catch orientation, satisfaction, agency trust, and demographics on support for habitat protection and restoration versus stocking in publicly managed waters

Resource managers benefit from knowledge of angler support for fisheries management strategies. Factors including angler values (protection, utilitarian, and dominance), involvement (attraction, centrality, social, identity affirmation, and expression), catch-related motivations (catching some, many, and big fish, and keeping fish), satisfaction, agency trust, and demographics may relate to fisheries management preferences. Using results from a mail survey of Minnesota resident anglers, we explored how these factors were related to budget support for fish stocking relative to habitat protection/restoration. Results suggest that values, angler involvement, catch orientation, satisfaction, total and recent years fishing, age, and education influence relative support for stocking versus habitat protection/restoration. Utilitarian values, angling centrality, an orientation to catch many fish, satisfaction with the number of fish caught, number of recent years fishing, and age positively related to support for stocking over habitat management, while protection values, attraction to angling, total years fishing, and education level were negatively related to relative support for stocking.

Environmental Management↗
USGS2025

Economic costs of invasive carps in the United States: Case study and management implications

Biological invasions can have far-reaching impacts and incur enormous monetary costs. Economic considerations play an important role in management decision-making. We used the invasion of U.S. waterways by silver ( Hypophthalmichthys molitrix ) and bighead ( H. nobilis ) carp as a case study of the costs of aquatic invasive species. Although these carps are well-known invaders, published reports on their economic costs are lacking. Our study included market values for commercial fisheries, non-market values for recreational fisheries, and management costs. Our results showed that by 2020, U.S. federal and state agencies had spent nearly $592 million in cumulative management costs. A difference-in-difference model testing for the effect of invasive carp on commercial harvest in invaded versus uninvaded reaches of the Mississippi and Illinois Rivers showed no statistical significance. A benefit transfer analysis of invasion effects on total economic value of recreational fishing, an important ecosystem service, in a heavily invaded section of the Illinois River estimated a total loss of more than $10 million over 10 years. While there are other known impacts on ecosystem services, including alteration of aquatic food webs, plankton communities, and native fish communities, these could not be quantified in economic terms in our analysis.

conterminous United States↗
USGS2021

Stock composition of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) encountered in marine and estuarine environments on the U.S. Atlantic Coast

Atlantic sturgeon ( Acipenser oxyrinchus oxyrinchus ) is a large, anadromous fish native to the Atlantic Coast of North America. Although this species once supported important fisheries, centuries of exploitation and habitat degradation have resulted in dramatic declines, presumed extirpation in some rivers, and ultimately listing under the U.S. Endangered Species Act (ESA). Under the ESA, Atlantic sturgeon are listed as five separate Distinct Population Segments (DPSs), which form the basis for federal management. Despite state and federal protections Atlantic sturgeon still face significant threats to their recovery, including fisheries bycatch mortality, marine construction, dredging, dams, and vessel strikes. However, because subadult and adult Atlantic sturgeon migrate extensively across estuarine and marine environments and frequently form mixed-stock aggregations in non-natal habitats, it can be difficult to determine how these threats impact specific populations and DPSs. To better understand ontogenetic shifts in habitat use and stock-specific exposure to anthropogenic threats, we performed a mixed-stock analysis of 1704 Atlantic sturgeon encountered across the U.S. Atlantic Coast. Collections made north of Cape Cod, MA and south of Cape Hatteras, NC were dominated by individuals from regional stocks; however, we found extensive stock mixing in the mid-Atlantic region, particularly in coastal environments where individuals from all five DPSs were commonly observed. Subadults and adults that were encountered in offshore environments had moved, on average, 277 km from their natal source; however, 23% were sampled over 500 km from their natal river suggesting long-distance movements are relatively common in these age classes. Overall, our work highlights that Atlantic sturgeon populations are vulnerable to threats over vast areas and emphasizes the need for continued genetic monitoring to track recovery progress.

Atlantic Coast↗
USGS2012

Demographic patterns in the peacock grouper ( Cephalopholis argus ), an introduced Hawaiian reef fish

This study took advantage of a unique opportunity to collect large sample sizes of a coral reef fish species across a range of physical and biological features of the Hawaiian Archipelago to investigate variability in the demography of an invasive predatory coral reef fish, Cephalopholis argus (Family: Epinephelidae). Age-based demographic analyses were conducted at 10 locations in the main Hawaiian Islands and estimates of weight-at-length, size-at-age, and longevity were compared among locations. Each metric differed among locations, although patterns were not consistent across metrics. Length-weight relationships for C. argus differed among locations and individuals weighed less at a given length at Hilo, the southernmost location studied. Longevity differed among and within islands and was greater at locations on Maui and Hawaii compared to the more northern locations on Oahu and Kauai. Within-island growth patterns differed at Kauai, Oahu, and Hawaii. This work provides a case study of fundamental life history information from distant and/or spatially limited locations that are critical for developing robust fishery models. The differences observed both among and within islands indicate that variability may be driven by cross-scale mechanisms that need to be considered in fisheries stock assessments and ecosystem-based management.

Hawai'i↗
USGS2021

Submerged aquatic vegetation habitat use of age-0 Florida bass Micropterus floridanus

Hatchery-raised, age-0 Florida bass Micropterus floridanus are commonly used for fish enhancement efforts to support popular recreational fisheries and are ecologically important as both a food source and consumer. Despite their importance and frequent use of submerged aquatic vegetation (SAV) habitats, critical information is lacking on the specific characteristics of SAV that influence habitat occupancy. Using the SAV species Vallisneria americana and Potamogeton illinoensis , which are native to the southeast USA , and the invasive SAV Hydrilla verticillata , we conducted seven different habitat choice experiments to examine hatchery-raised, age-0 M . floridanus habitat use of different SAV populations (i.e., hydrologically isolated collection sources of varied physical characteristics), population diversity (i.e., increased richness of genotypically and phenotypically variable SAV), species, and species diversity (i.e., increased species richness). Fish spent more time in taller, larger V. americana but did not seem to favor any particular P. illinoensis population, SAV species, or species diversity tested. Additionally, fish spent more time in increased V. americana population diversity when the populations used were randomized, but fish spent more time in decreased population diversity when their favored V. americana population was used in all choices. This research adds additional nuance to our understanding of optimal vegetation for fish habitat use and is informative for future SAV plantings and invasive SAV management aimed at maximizing fish habitat and restoring recreational fisheries.

Environmental Biology of Fishes↗
USGS2024

Age, growth, and reproductive biology of Achilles tang (Acanthurus achilles) around Hawai'i Island, USA

A culturally important food fish in Hawai'i, Achilles tang ( Acanthurus achilles Shaw), recently experienced sharp declines in biomass, density, and average length in west Hawai'i Island. In December 2022, State resource managers placed a 2-year moratorium on the Achilles tang fishery in west Hawai'i Island so that the cause of the collapse could be explored. The lack of life-history information for Achilles tang from Hawai'i, or elsewhere in its range, has been noted as an impediment to decision-making. Therefore, our objectives were to characterize this population’s age, growth, and reproductive biology. In working with community fishers, we collected 363 individuals ranging 69 – 264 mm in fork length (FL) and 0 – 39 years in age based on estimates from otoliths. Achilles tang in Hawai'i exhibit a high growth rate, reaching 138 ± 11 mm FL (mean ± SE) in their first year, and exhibit relatively little growth after their second year (< 5 mm yr −1 ). The majority of males (92.0% of n = 101) and females (73.6% of n = 159) were classified as spawning capable or actively spawning, without annual or lunar periodicity. Our study highlights that the basic biology of Achilles tang poses unique challenges to fisheries managers looking to ensure its sustainable harvest. Future research will aim to characterize the susceptibility of recruits’ habitat to local environmental stressors and the relative connectivity of juvenile and adult habitats.

Hawaii↗
USGS2010

An index of reservoir habitat impairment

Fish habitat impairment resulting from natural and anthropogenic watershed and in-lake processes has in many cases reduced the ability of reservoirs to sustain native fish assemblages and fisheries quality. Rehabilitation of impaired reservoirs is hindered by the lack of a method suitable for scoring impairment status. To address this limitation, an index of reservoir habitat impairment (IRHI) was developed by merging 14 metrics descriptive of common impairment sources, with each metric scored from 0 (no impairment) to 5 (high impairment) by fisheries scientists with local knowledge. With a plausible range of 5 to 25, distribution of the IRHI scores ranged from 5 to 23 over 482 randomly selected reservoirs dispersed throughout the USA. The IRHI reflected five impairment factors including siltation, structural habitat, eutrophication, water regime, and aquatic plants. The factors were weakly related to key reservoir characteristics including reservoir area, depth, age, and usetype, suggesting that common reservoir descriptors are poor predictors of fish habitat impairment. The IRHI is rapid and inexpensive to calculate, provides an easily understood measure of the overall habitat impairment, allows comparison of reservoirs and therefore prioritization of restoration activities, and may be used to track restoration progress. The major limitation of the IRHI is its reliance on unstandardized professional judgment rather than standardized empirical measurements. ?? 2010 US Government.

Environmental Monitoring and Assessment↗
USGS2007

Use of multiple chemical tracers to define habitat use of Indo-Pacific mangrove crab, Scylla serrata (Decapoda: Portunidae)

The mangrove or mud crab, Scylla serrata, is an important component of mangrove fisheries throughout the Indo-Pacific. Understanding crab diets and habitat use should assist in managing these fisheries and could provide additional justification for conservation of the mangrove ecosystem itself. We used multiple chemical tracers to test whether crab movements were restricted to local mangrove forests, or extended to include adjacent seagrass beds and reef flats. We sampled three mangrove forests on the island of Kosrae in the Federated States of Micronesia at Lelu Harbor, Okat River, and Utwe tidal channel. Samples of S. serrata and likely food sources were analyzed for stable carbon (??13C), nitrogen (??15N), and sulfur (??34S) isotopes. Scylla serrata tissues also were analyzed for phosphorus (P), cations (K, Ca, Mg, Na), and trace elements (Mn, Fe, Cu, Zn, and B). Discriminant analysis indicated that at least 87% of the crabs remain in each site as distinct populations. Crab stable isotope values indicated potential differences in habitat use within estuaries. Values for ??13C and ??34S in crabs from Okat and Utwe were low and similar to values expected from animals feeding within mangrove forests, e.g., feeding on infauna that had average ??13C values near -26.5???. In contrast, crabs from Lelu had higher ?? 13C and ??34S values, with average values of -21.8 and 7.8???, respectively. These higher isotope values are consistent with increased crab foraging on reef flats and seagrasses. Given that S. serrata have been observed feeding on adjacent reef and seagrass environments on Kosrae, it is likely that they move in and out of the mangroves for feeding. Isotope mixing model results support these conclusions, with the greatest mangrove ecosystem contribution to S. serrata diet occurring in the largest mangrove forests. Conserving larger island mangrove forests (> 1 km deep) appears to support crab foraging activities. ?? 2007 Coastal and Estuarine Research Federation.

Estuaries and Coasts↗
USGS2022

Societal values of inland fishes

a. Aim: To demonstrate the societal values of inland fishes through nine services provided by inland fishes. Each service is defined, key stakeholders identified, and threats enumerated. Diverse case studies (geography, taxonomy, fishery-type) provide examples to highlight the societal values around the world. b. Main concepts: Nine societal services of inland fishes – 1. Livelihoods and subsistence income; 2. Commercial income; 3. Food and nutrition; 4. Recreational services; 5. Cultural services; 6. Educational and scientific opportunities within fisheries; 7. Biodiversity and ecosystem function; 8. Regulation and indicator of freshwater quality ; and 9. Regulation of freshwater quantity and natural flow regimes. c. Conclusion/outlook: Inland fishes have immense social, economic, and ecological importance. Freshwater ecosystems face a diverse array of pressures that threaten the fulfillment of societal services. Addressing key knowledge gaps can assist with sustainable management and conservation of these important resources.

Book chapter↗
USGS2024

Fish bioenergetics modeling

A bioenergetics model for a fish is defined as a quantitative description of the fish's energy budget. Bioenergetics modeling can be applied to free-ranging fish in rivers, lakes, and oceans to estimate annual food consumption by fish populations; such applications have proven useful in managing fisheries. In addition, bioenergetics models have been used to better understand fish growth and consumption in ecosystems, to guide conservation management of endangered or threatened fish populations, to determine the importance of the role of fish in cycling nutrients within ecosystems, to predict fish growth and consumption under climate change , and to identify the important factors regulating contaminant accumulation in free-ranging fish. Over the past 60 years, fish bioenergetics modeling has led to significant advancements in both aquatic ecology, especially fish ecology, and fisheries management.

Book chapter↗
USGS2008

Rivers and streams: Physical setting and adapted biota

Streams and rivers are enormously important, with their ecological, and economic value, greatly outweighing their significance on the landscape. Lotic ecology began in Europe with a focus on the distribution, abundance, and taxonomic composition of aquatic organisms and in North American with a focus on fishery biology. Since 1980, stream/river research has been highly interdisciplinary, involving fishery biologists, aquatic entomologists, algologists, hydrologists, geomorphologists, microbiologists, and terrestrial plant ecologists. Stream and river biota evolved in response to, and in concert with, the physical and chemical setting. Streams/rivers transport water and move sediments to the sea as part of the hydrologic cycle that involves evaporation, plant evapotranspiration, and precipitation. Ephemeral streams flow only in the wettest year, intermittent streams flow predictably every year during capture of surface runoff, and perennial streams flow continuously during wet and dry periods, receiving both stormflow and groundwater baseflow. The lotic biota, for example, algae, macrophytes, benthic invertebrates, and fishes, have evolved adaptations to their running-water setting. Dominant physical features of this setting are current, substrate, and temperature. Key chemical constituents are dissolved gases, dissolved inorganic ions and compounds, particulate inorganic material, particulate organic material, and dissolved organic ions (nitrogen and phosphorus) and compounds.

Book chapter↗
USGS2015

Implementation of a framework for multi-species, multi-objective adaptive management in Delaware Bay

Decision analytic approaches have been widely recommended as well suited to solving disputed and ecologically complex natural resource management problems with multiple objectives and high uncertainty. However, the difference between theory and practice is substantial, as there are very few actual resource management programs that represent formal applications of decision analysis. We applied the process of structured decision making to Atlantic horseshoe crab harvest decisions in the Delaware Bay region to develop a multispecies adaptive management (AM) plan, which is currently being implemented. Horseshoe crab harvest has been a controversial management issue since the late 1990s. A largely unregulated horseshoe crab harvest caused a decline in crab spawning abundance. That decline coincided with a major decline in migratory shorebird populations that consume horseshoe crab eggs on the sandy beaches of Delaware Bay during spring migration. Our approach incorporated multiple stakeholders, including fishery and shorebird conservation advocates, to account for diverse management objectives and varied opinions on ecosystem function. Through consensus building, we devised an objective statement and quantitative objective function to evaluate alternative crab harvest policies. We developed a set of competing ecological models accounting for the leading hypotheses on the interaction between shorebirds and horseshoe crabs. The models were initially weighted based on stakeholder confidence in these hypotheses, but weights will be adjusted based on monitoring and Bayesian model weight updating. These models were used together to predict the effects of management actions on the crab and shorebird populations. Finally, we used a dynamic optimization routine to identify the state dependent optimal harvest policy for horseshoe crabs, given the possible actions, the stated objectives and our competing hypotheses about system function. The AM plan was reviewed, accepted and implemented by the Atlantic States Marine Fisheries Commission in 2012 and 2013. While disagreements among stakeholders persist, structured decision making enabled unprecedented progress towards a transparent and consensus driven management plan for crabs and shorebirds in Delaware Bay.

Biological Conservation↗