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Results for “Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science”

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At least 19 recordsLinked to original sources
USGS2018

Efficacy of otoliths and first dorsal spines for preliminary age and growth determination in Atlantic Tripletails

The Atlantic Tripletail Lobotes surinamensis is a popular sport fish for which age and growth data are scarce in general and nonexistent for Georgia (GA), USA, waters. These data are necessary to ensure that management regulations are adequate to protect this species, especially given its popularity as a sport fish. We evaluated whether otoliths and spines were suitable for determining the estimated age (hereafter, “age”) and growth rates of Atlantic Tripletails, and we ascertained whether one method was more accurate than the other. Atlantic Tripletails were sampled by angling and trawling during March 30–August 10, 2009, and March 14–August 6, 2010, in nearshore GA waters of the Atlantic Ocean. During the study, 243 Atlantic Tripletails were captured and sampled for aging structures. Sagittal otoliths and the first dorsal spine were removed from each fish and used to estimate the age and growth rate. Mean differences in TL at age for spine and otolith data were evaluated with ANOVA. Estimated ages for males and females ranged from 1 to 5 years based on otoliths and spines. Both otolith and spine mean TLs at ages 1 and 2 were significantly different from each other as well as all other age‐classes, whereas mean TLs for ages 3–5 were not significantly different. Differences in Atlantic Tripletail TL among the otolith‐ and spine‐derived age‐classes were not significant. Each method used to age Atlantic Tripletails had advantages and disadvantages. Otoliths had higher initial reader agreement than spines, although agreement between the structures was 84.1%. However, otoliths require sacrifice of the fish, whereas a spine can be taken without sacrificing the fish. The lack of concrete life history data and population estimates suggests that when feasible, nonlethal aging methods would be preferred over lethal methods to ensure the survival of Atlantic Tripletail populations.

Georgia↗
USGS2018

Does what go up also come down? Using a recruitment model to balance alewife nutrient import and export

Migrating adult Alewives Alosa pseudoharengus are a source of marine-derived nutrients on the East Coast of North America, importing nitrogen and phosphorus into freshwater habitats. Juvenile migrants subsequently transport freshwater-derived nutrients into the ocean. We developed a deterministic model to explore the theoretical nutrient dynamics of Alewife migrations at differing spawner abundances. Net nutrient balance was calculated relative to these abundances along the spawner–recruit curve. The ecological consequences of these subsidies in a particular watershed depend on the magnitude of adult escapement relative to the habitat’s carrying capacity for juveniles. At low escapement levels and assuming complete habitat access, the number of recruits produced per spawner was high and juvenile nutrient export dominated. At high escapement levels, fewer recruits were produced per spawner because recruitment is density dependent. As a result, adult nutrient import dominated. At varying levels of freshwater productivity and fisheries mortality for upstream spawners, this trend remained the same while the magnitude of the endpoints changed. Productivity level was the major determinant of export, while fisheries mortality had the strongest effect on adult import. The dynamics of this nutrient trade-off are important for managers to consider as a recovering population will likely shift from net export to net import as escapement increases. This transition will be sensitive to both harvest rates and to fish passage efficacy at dams and other barriers.

Marine and Coastal Fisheries: Dynamics, Management↗
USGS2018

Juvenile Chinook salmon and forage fish use of eelgrass habitats in a diked and channelized Puget Sound River Delta

Eelgrass Zostera marina can form extensive meadows on Puget Sound river deltas. The extent to which these meadows provide critical rearing habitat for local estuarine fishes, especially out‐migrating juvenile salmon, is not well understood. Further, delta eelgrass has been impacted by diking and river channelization with unknown consequences for fish. We sampled fish in the Skagit River delta, Washington, during April–September with a lampara net, which is well suited to capturing fish in eelgrass. We compared abundance and body size of Chinook Salmon Oncorhynchus tshawytscha and three forage fish species between eelgrass and nearby unvegetated habitat. We also assessed combined effects of eelgrass characteristics (meadow size and morphology) and oceanographic conditions (temperature and salinity), which covaried according to proximity and orientation to channelized distributary outlets, diked shorelines, and a jetty. Chinook Salmon were more abundant in eelgrass than in unvegetated habitat in June–July and were relatively more abundant in eelgrass compared with unvegetated habitat in regions with intact eelgrass than offshore from a channelized distributary outlet. Abundances of Pacific Herring Clupea pallasii and Shiner Perch Cymatogaster aggregata were consistently severalfold higher in eelgrass than in unvegetated habitat. Surf Smelt Hypomesus pretiosus were more abundant in eelgrass than in unvegetated habitat at some locations, but never less abundant in eelgrass. Our results suggest that conservation and restoration of delta eelgrass would benefit these species and help to identify the settings in which these actions would be most beneficial.

Washington↗
USGS2019

Fish assemblage structure and fisheries resources in Puerto Rico’s riverine estuaries

Tropical estuaries are diverse and productive habitats with respect to their fish assemblages and associated fisheries, but these ecosystems and fisheries are imperiled by multiple anthropogenic threats. Despite the economic, social, and biodiversity value of tropical estuarine fish assemblages, they are poorly understood, especially those on Caribbean islands. We sampled the fish assemblages of four estuaries that were broadly representative of riverine estuaries in Puerto Rico, including the Río Grande de Arecibo, Río Espiritu Santo, Río Mameyes, and Río Sabana. We used a combination of passive (gill nets) and active (seine) gears at locations that spanned the salinity gradient of each estuary during July–October 2013–2014 (rainy season) and March 2015 (dry season). Fish species richness among the riverine estuaries varied from 18 to 29 and was highest in the Río Espiritu Santo estuary. Nonmetric multidimensional scaling differentiated fish assemblages among estuaries but not by season or consistently by location within an estuary. Spearman's rank correlation analysis also revealed dissimilarity among each estuary's fish assemblage, as most pairwise correlations between the species compositions were not significant. We identified common and widespread species among estuaries, including sport fishes, such as the Tarpon Megalops atlanticus and Common Snook Centropomus undecimalis . As the only multi‐river assessment of riverine estuary fish assemblages in Puerto Rico, our results provide the best available information about the spatial variability of assemblages and fisheries resources. This information will benefit future conservation and fisheries management efforts, which are needed due to increasing anthropogenic impacts, such as illegal harvest, invasive species, and water diversions.

Puerto Rico↗
USGS2019

Seasonal use of a nonnatal marine basin by juvenile hatchery chinook salmon

Information on the movement patterns of fishes is essential for managers that are making critical resource decisions. We examined the frequency of a keystone species, Chinook Salmon Oncorhynchus tshawytscha that migrated from different marine basins to the Nisqually River estuary, which lies within the southernmost marine basin (hereafter, “South basin”) in Puget Sound (Washington, USA). Hatchery‐reared juvenile fish were sampled by using beach seine, lampara seine, and fyke nets to determine seasonal trends in frequency, habitat use, and the influence of different capture methods. The captured fish originated from three marine basins, nine Puget Sound rivers, and fourteen hatcheries. The data revealed a consistent pattern showing that most of the tagged fish (72%) were from the nearby Nisqually River (in the South basin), but fish from more northerly marine basins (hereafter, “Outbasin”) were also common. Although the majority of the tagged fish (99%) that were captured during April and May were originally released into rivers adjacent to the South basin, 90% of the fish that were captured in August and September had originated from rivers adjacent to Outbasin locations (up to 130 km distant). A comparison of sampling methods showed that the beach seine produced 27% Outbasin fish compared with 53% that were obtained with the lampara seine. The analysis of habitat use suggested that during June and July, more Outbasin fish (>40%) were captured in delta flats and nearshore habitats than in estuarine emergent marsh habitat (26%). Release location (river basin), but not distance, appeared to be an important factor that influenced the percentage of Outbasin fish that were captured in the South basin. However, it appeared that the fish that were released at light weights and early dates were more likely to be captured. Information on the movement of juvenile salmon to a nonnatal marine basin may help to increase our understanding of features of life history and survival, and it has application elsewhere, as many marine species are artificially propagated, released in large numbers, and have the potential to use nonnatal habitats.

Washington↗
USGS2020

Trends in oyster populations in the northeastern Gulf of Mexico: An assessment of river discharge and fishing effects over time and space

Within the Big Bend region of the northeastern Gulf of Mexico, one of the least developed coastlines in the continental USA, intertidal and subtidal populations of eastern oyster Crassostrea virginica (hereafter referred to as “oyster”) are a critical ecosystem and important economic constituent. We assessed trends in intertidal oyster populations, river discharge, and commercial fishing activity in the Suwannee River estuary within the Big Bend region using fisheries‐independent data from irregular monitoring efforts and publicly available environmental data. We used generalized linear models to evaluate counts of oysters from line‐transect surveys over time and space. We assessed model performance using simulation to understand potential bias and then evaluated whether these counts were related to freshwater inputs from the Suwannee River and commercial oyster fishing effort and landings at different time lags. We found that intertidal oyster counts have declined over time and that most of these declines are found in inshore intertidal oyster bars, which are becoming degraded. We also found a significant relationship between oyster counts and a 1‐year lag on mean daily Suwannee River discharge, but including commercial fishery trips or landings did not improve model fit. It is unclear whether declines in intertidal oyster bars are offset by formation of new oyster reefs elsewhere. These results quantify rapid declines in intertidal oyster reefs in a region of coastline with high conservation value that can be used to inform ongoing and proposed restoration projects in the region.

Florida↗
USGS2021

Rapid phenotypic stock identification of Chinook Salmon in recreational fishery management

Rapid phenotypic stock identification in mixed-stock fisheries can provide a useful alternative to more time-intensive methods (e.g., coded wire tags, genetics) in assessing harvest and informing management decisions. We leveraged local ecological knowledge, existing stock identification methods, and understanding of life history differences to develop rapid stock identification tools for fall-run Chinook Salmon Oncorhynchus tshawytscha encountered in the Buoy 10 recreational fishery at the mouth of the Columbia River. Specifically, we sought to differentiate between the fishery’s two dominant genetic lineages: lower river tules and upriver brights. We sampled recreationally landed Chinook Salmon in 2017, 2018, and 2019, assigned sampled individuals to functional reporting groups using a single-nucleotide-polymorphism-based genetic baseline, and collected measurements on phenotypic traits. Using traits including pigmentation patterns (e.g., spotting), fin morphology, characteristics indicative of sexual maturity, and muscle lipid content, random forest classification models provided consistently high classification success across and within genetic groups (i.e., up to 90%). Classification success remained consistent over time within fishery seasons and between years but showed meaningful bias between sexes. Based on observed classification success, we developed and evaluated a categorical visual identification guide capable of facilitating more rapid trait observations and on-site stock identification. The resulting classification key, built using classification trees and visual guide observations from 2019, achieved slightly lower classification success across and within genetic groups and had variable success among samplers. Compared with the existing use of coded wire tags in harvest assessment, phenotypic stock identification methods can provide more rapid and more numerous assignments, albeit with a greater degree of individual assignment error. Applied as a complement to standard methods like coded wire tags, the use of rapid phenotypic stock identification methods offers the potential for increased overall precision and timeliness in harvest assessments.

Oregon, Washington↗
USGS2021

Activity patterns of anadromous fish below a tide gate: Observations from high‐resolution imaging sonar

The construction of dams and tide gates on waterways has altered the physical structure of many coastal, estuarine, and freshwater systems. These changes have come at a cost to fish populations, most notably diadromous species, which rely on connectivity between marine and freshwater systems. These anthropogenic structures can have direct effects on migrating fish, such as blocking fish passage, or have more subtle effects, such as changing movement patterns. This study used a high‐resolution Adaptive Resolution Imaging Sonar to examine the behavior of Striped Bass Morone saxatilis , a large coastal predator, and Alewife Alosa pseudoharengus and Blueback Herring Alosa aestivalis (collectively known as river herring), which are forage fish, below a tide gate structure on the Herring River in Wellfleet, Massachusetts, during the river herring spring spawning run. Striped Bass were persistently present downstream of the tide gate and exhibited strong diurnal and tidal patterns. Activity of Striped Bass was highest at night and during ebb tides. During peak outflow periods, river herring were observed milling downstream of the dam in a scour pool, indicating delayed upstream passage. River herring upstream migration was primarily associated with daytime and during incoming tides. Downstream‐migrating river herring were primarily observed during nighttime hours. While it was documented that the tide gates provided a physical impediment to migration, their effect on predator behavior could pose an additional challenge to migrating river herring, further complicating their recovery efforts. Due to the prevalence of obstructed waterways, studying the behavior of fish around anthropogenic structures is important in understanding the full range of impacts that these systems have under varying ecological conditions and on ecological relationships.

Massachusetts↗
USGS2021

Characterizing downstream migration timing of American Eels using commercial catch data in the Penobscot and Delaware rivers

Adult “silver-phase” American Eels Anguilla rostrata were a focus of commercial fisheries in the 1970s and 1980s, but stocks have been depleted due to many anthropogenic factors. One significant source of mortality occurs during the downstream migration of eels when passing through turbines at hydroelectric facilities. We sought to construct a model to predict eel migration timing to inform optimization of mitigation actions that might reduce mortality. We utilized commercial catch collected from 16 tributaries in the Penobscot River watershed, Maine (2–10 years), and the Delaware River, New York (31 years). A Bayesian hierarchical approach was used to model the relationship between the timing of silver eel capture and environmental conditions that are known to be related to their movements (i.e., river discharge, water temperature, and lunar cycle). Among river systems, daily catch was associated with higher-than-average flows, temperatures of 7–22°C, and new lunar phase cycles. A cross-validation approach to evaluate the ability of the models to make predictions for new data demonstrated a greater ability (higher R 2 values) to predict weekly eel catch (0.01–0.92) compared to daily eel catch (0.00–0.42). In addition, we examined the model’s ability to forecast migration events by applying posterior simulations to make predictions of eel catch by ordinal date. Predicted daily eel catch generally followed the trend of observed daily catch and was stronger for the Delaware River ( R 2 = 0.67) than for Souadabscook Stream, Maine ( R 2 = 0.07). Sharp pulses in observed catch were not reflected by the predicted catch. Additionally, variability observed among rivers suggests that site-specific modeling may be advantageous (and necessary) to capture local conditions, thereby improving predictive power. More broadly, our work highlights a novel use of fishery-dependent data in a Bayesian modeling framework to predict intervals of risk for migrating fish.

Maine, New York↗
USGS2021

Disentangling stationary and dynamic estuarine fish habitat to inform conservation: Species-specific responses to physical habitat and water quality in San Francisco Estuary

Estuaries represent critical aquatic habitat that connects surface water distributed between Earth’s landmasses and oceans. They are dynamic transitional ecosystems, which provide important habitat for fishes and other aquatic organisms. Effective conservation of species inhabiting estuaries requires knowledge of the habitat features that drive their abundance and distribution. We sought to elucidate how stationary (i.e., wetlands, shoals, and channels) and dynamic (i.e., salinity, temperature, turbidity, and chlorophyll concentration) habitat features interact to drive distributions of individual fish species. The Pacific coast of the conterminous United States has over 400 estuaries of various types. The largest (historical surface area) is San Francisco Estuary, California. We conducted extensive field observations of fishes in the central San Francisco Estuary among stationary habitat types (i.e., wetland, shoal, and channel) over a 19-month period encompassing substantial variability in dynamic water quality conditions. Most of the species observed, especially native species of special management interest, were associated with tidal wetland habitat. Few species exhibited associations with water quality conditions driven by seasonal (temperature) or a combination of broad- and fine-scale ecosystem processes (salinity and turbidity). Our study provides (1) an empirical demonstration of how researchers can deal with the complex and dynamic expressions of habitat in estuarine systems to address urgent natural resource problems and (2) a clear demonstration of the urgent need for habitat restoration and its likely outcome in systems such as San Francisco Estuary. Restoration of suitable tidal wetland habitat on the West Coast of the United States is likely to be an effective conservation tool to support estuarine fishes given that over 90% of historical tidal wetland habitat in San Francisco Estuary and 85% of vegetated wetland habitat along the Pacific coast of the United States has been lost due to human modification.

California↗
USGS2021

Stock composition of the historical New York Bight Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) intercept fishery revealed through microsatellite analysis of archived spines

A targeted commercial fishery for Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus once operated in the New York Bight, where it was assumed that most harvested Atlantic Sturgeon were natal to the Hudson River population. However, more recent evidence suggests that the fishery may have been targeting a mixed-stock aggregation, in which case harvested Atlantic Sturgeon could have been comprised of individuals from multiple populations throughout the species’ range. Although there is now a moratorium on Atlantic Sturgeon harvest in the New York Bight, modern molecular approaches provide an opportunity to use archived tissues to perform a retrospective mixed-stock analysis on the fishery. Genomic DNA extracted from archived fin spines from 80 Atlantic Sturgeon collected nearly 30 years ago suggests that the fishery primarily harvested individuals from the Hudson River population. However, based on individual-based assignment tests, our results indicate that the fishery also harvested individuals from at least eight other populations located throughout the species’ range. This study highlights how archival hard parts that were previously used for age and growth analyses can be employed for retrospective genetic analyses. Further, because the New York Bight harbors relatively high concentrations of Atlantic Sturgeon, the study shows how localized management decisions can influence Atlantic Sturgeon conservation at rangewide scales. When integrated with more recent knowledge of species ecology, these analyses can be used to evaluate the efficacy of previous management strategies and understand the effects of historical processes on contemporary demography.

New York↗
USGS2022

Phenological variation in spring migration timing of adult alewife (Alosa pseudoharengus) in coastal Massachusetts

The timing of biological events in plants and animals, such as migration and reproduction, is shifting due to climate change. Anadromous fishes are particularly susceptible to these shifts as they are subject to strong seasonal cycles when transitioning between marine and freshwater habitats to spawn. We used linear models to determine the extent of phenological shifts in adult Alewife Alosa pseudoharengus as they migrated from ocean to freshwater environments during spring to spawn at 12 sites along the northeastern USA. We also evaluated broadscale oceanic and atmospheric drivers that trigger their movements from offshore to inland habitats, including sea surface temperature, North Atlantic Oscillation index, and Gulf Stream index. Run timing metrics of initiation, median (an indicator of peak run timing), end, and duration were found to vary among sites. Although most sites showed negligible shifts towards earlier timing, statistically significant changes were detected in three systems. Overall, winter sea surface temperature, spring and fall transition dates, and annual run size were the strongest predictors of run initiation and median dates, while a combination of within-season and seasonal-lag effects influenced run end and duration timing. Disparate results observed across the 12 spawning runs suggest that regional environmental processes were not consistent drivers of phenology and local environmental and ecological conditions may be more important. Additional years of data to extend time series and monitoring of Alewife timing and movements in nearshore habitats may provide important information about staging behaviors just before adults transition between ocean and freshwater habitats.

Massachusetts↗
USGS2022

Multidecadal trends in body size of Puget Sound Chinook Salmon: Analysis of data from the Tengu Derby, a culturally unique fishery

In Pacific salmon Oncorhynchus spp., downward trends in size and abundance have been reported for species and stocks for over 40 years, but the patterns are inconsistent among regions and species. Interpretation of these trends is complicated by many possible contributing factors, including short time series, data comprising a mix of stocks, and varying gear types. Here, we present data on the mass of individual Chinook Salmon Oncorhynchus tshawytscha caught in the winter from 1946 to 2019 in central Puget Sound, Washington, by participants in what may be the longest running Pacific salmon derby in North America, the Tengu Derby. In this annual recreational fishing competition, established by Japanese Americans immediately after release from internment camps at the end of World War II, participants follow strict gear, area, and methods regulations and catch almost exclusively salmonids originating from and remaining in Puget Sound. Records revealed an overall decline in fish mass over the decades, with a high degree of variability throughout the time series. Specifically, resident Chinook Salmon exhibited several shifts, including a decrease in size from a high in the 1950s to a low around 1980, followed by an increase to another high around 1990 and then a decline over the most recent 30 years. These size trends of residents differed from those of Puget Sound Chinook Salmon as a whole. We infer that the resident fish experienced ecological conditions affecting their growth that were distinct from those of fish feeding along the Pacific Ocean in the same periods. These distinct trends in size of Chinook Salmon from common origins indicate that the different migration patterns of fish within stocks must be considered in the analysis and interpretation of body size trends and also in patterns of survival.

Washington↗
USGS2022

Temporal and spatial relationships of Yellowfin Tuna to deepwater petroleum platforms in the northern Gulf of Mexico

In 2006–2007, 110 Yellowfin Tuna Thunnus albacares were tagged with acoustic transmitters near deepwater oil platforms and one drillship in the northern Gulf of Mexico off the Mississippi River delta to determine the extent to which platforms act as fish aggregating devices (FADs). Vemco acoustic receivers were installed on six deepwater platforms to detect the presence of tagged individuals. Five of 12 Yellowfin Tuna captured in 2006 were detected in 2007, demonstrating multi-year presence in the region. Ninety Yellowfin Tuna were detected in 2007, resulting in 221 platform residencies and 32 single detections. Duration of residence at a platform was positively correlated with the platform's depth, and the number of transitions decreased with platform-to-platform distance. In total, 109 movements between platforms by 46 (51%) different individuals were detected, traveling distances of up to 98.2 km. Yellowfin Tuna displayed interactions with deepwater platforms in the northern Gulf of Mexico similar to their interactions with FADs and other studied geological features, by way of aggregating or using them as meeting points, landmarks, and stopovers within a movement corridor. The large number of oil and gas platforms located in the northern Gulf of Mexico may have a significant effect on distribution, retention, and migration of Yellowfin Tuna populations in this area of the gulf.

Louisiana↗
USGS2023

Fish assemblages in the Penobscot River: A decade after dam removal

The Penobscot River Restoration Project in Maine was a large river rehabilitation project that culminated in the removal of the two lowermost dams and improvements to fish passage on several remaining dams. Fish assemblages were surveyed for 3 years prior to rehabilitation, 3 years after rehabilitation, and 8 years after rehabilitation. Approximately 475 km of shoreline were sampled via boat electrofishing, yielding 133,394 individual fish of 41 species. The greatest shifts in assemblage structure occurred immediately after dam removal in formerly impounded sections, with an increased prevalence of riverine and migratory species. Long-term sampling documented changes within tributaries and tidally influenced river segments, where large schools of adult and young-of-the-year alosines increased in abundance. Upstream of the lowermost dam, the river remains dominated by lacustrine species, while adult anadromous fishes continue to be most abundant immediately downstream of the lowermost dam. Our results provide increased evidence that dam removals result in altered fish assemblages, which are now dominated by riverine and anadromous species in previously impounded habitats. Alosines in the Penobscot River have exhibited the greatest long-term response to river restoration efforts.

Maine↗
USGS2023

Forage fish species prefer habitat within designated offshore wind energy areas on the US Northeast Shelf ecosystem

As 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.

Marine and Coastal Fisheries: Dynamics, Management↗
USGS2023

Application of a catch multiple survey analysis for Atlantic horseshoe crab Limulus polyphemus in the Delaware Bay

Objective This paper applies a catch multiple survey analysis (CMSA) to Atlantic horseshoe crabs Limulus polyphemus in the Delaware Bay to generate robust population estimates for harvest management. Currently, horseshoe crabs along the U.S. Atlantic coast are harvested as bait for other fisheries and collected for their blood, which is used in a biomedical industry. The Delaware Bay is home to the largest population of horseshoe crabs and is a significant stopover for shorebirds to rebuild energy by consuming horseshoe crab eggs prior to completing their northward migration. To address this interrelationship, the Adaptive Resource Management (ARM) Framework has been used since 2013 to ensure that horseshoe crab harvest within the region takes into account the forage needs of migratory birds. Since its inception, the ARM Framework has used a single trawl survey's swept area-based population estimates of horseshoe crab relative abundance and a theoretical population model developed primarily from literature-derived values. With more data collected in the region in recent years and other sources of mortality that can now be quantified, a catch survey model can provide horseshoe crab population estimates going forward. Methods A CMSA was used to estimate male and female horseshoe crab population size for 2003–2021 using all quantifiable sources of mortality and three fishery-independent indices of abundance. Result The CMSA results indicated that adult abundance of male and female horseshoe crabs was stable from 2003 to 2013 and then began to increase through 2017, a result that is consistent with stock rebuilding following a period of harvest restrictions as recommended by the ARM Framework. Population estimates were lower in recent years but remained above the levels estimated before implementation of the ARM Framework. In 2021, the CMSA estimated that there were over 6 million mature females and nearly 16 million mature male horseshoe crabs in the region. Conclusion The CMSA provides the best and most comprehensive population estimates of horseshoe crabs in Delaware Bay and will improve modeling efforts within the ARM Framework going forward.

Delaware, Maryland, New Jersey↗
USGS2023

Data-limited fishery assessment methods shed light on the exploitation history and population dynamics of Endangered Species Act-listed Yelloweye Rockfish in Puget Sound, Washington

Objective The distinct population segment (DPS) of Yelloweye Rockfish Sebastes ruberrimus inhabiting the Puget Sound/Georgia Basin was listed under the Endangered Species Act (ESA) in 2010, and a formal recovery plan for the DPS was published by National Oceanic and Atmospheric Administration Fisheries in 2017. In this recovery plan, the biological criteria for delisting or downlisting were specified as certain levels of spawning potential ratio (SPR), a commonly used metric of equilibrium stock status for commercially exploited fishes. Although this metric can be estimated from length compositions, the combination of length data with a catch history (which was not previously available for this DPS) improves our understanding of population dynamics over time and allows us to estimate a different measure of stock status, relative (to unfished) spawning stock biomass (SSB), rather than only SPR. Methods To estimate relative SSB and reconstruct the historical dynamics of this DPS, we reconstructed the catch history from fisheries records, collated length data from historical and contemporary hook-and-line surveys, and fitted a data-limited version of a statistical catch-at-age model. Result Despite a high level of uncertainty, we estimated that Yelloweye Rockfish in Puget Sound are above 25% of unfished biomass (a reference point detailed in the recovery criteria) under the assumption of deterministic recruitment, presenting the first direct estimates of Yelloweye Rockfish population status in Puget Sound. Conclusion However, as informed by recent genetic studies, the DPS boundaries of ESA-listed Yelloweye Rockfish extend from South Puget Sound to Queen Charlotte Strait in British Columbia. The Canadian portion of this population is managed separately and is currently estimated to be at 32% of unfished biomass (95% quantiles = 15%–68%). Thus, the disjunction between the biological boundaries of the population and the jurisdictional boundaries between Canada and the United States presents an additional source of uncertainty in assessing recovery that must be addressed to achieve DPS-wide recovery goals.

Washington↗