Objective This project aimed to present a novel method for collecting data on Atlantic Sturgeon Acipenser oxyrinchus in the open waters of the Gulf of Maine using a minimally invasive technique and to highlight the potential for surveying protected species.Methods In the winter and spring of 2025, a stratified random optical trawl survey was conducted in the western Gulf of Maine. Video footage from the survey was reviewed manually to identify and record occurrences of Atlantic Sturgeon and their location, depth, and temperature.Results In total, 44 Atlantic Sturgeon were observed in the video trawl surveys during 2025, with an aggregation of 42 individuals occurring approximately 5 km west of Herring Cove in Provincetown, Massachusetts. The aggregation occurred within a 30-min span across approximately 2.75 km of mud and silt bottom at depths ranging from 46 to 52 m.Conclusions This study provides information on an Atlantic Sturgeon aggregation from an optical trawl survey, demonstrating the potential for nonextractive survey methods to collect data on endangered species without violating their protections. A video-based trawl system recorded an aggregation of Atlantic Sturgeon without capturing or handling the fish. These observations show that optical gear can collect data on endangered species, with the potential to prevent violations of their protections.
Objective Yellowfin Tuna Thunnus albacares and Bigeye Tuna T. obesus are highly migratory pelagic species and major targets of distant-water fisheries worldwide. The distribution and abundance of their populations are highly susceptible to environmental variability caused by climate change, with notable time lags in response. However, such lagging effect still remains unclear, which imposes challenges to the fishery management of those populations of ecological and commercial importance. Methods This study therefore uses a Transformer model to analyze the influence of the Oceanic Ni & ntilde;o Index (ONI) on the catch per unit effort (CPUE) of Yellowfin Tuna and Bigeye Tuna caught by longline fisheries in the western and central Pacific Ocean (WCPO) from 1978 to 2021 to explore the impact of climate change on the adult Yellowfin and Bigeye Tuna populations in the WCPO and its lagging effect further. The study simulates the response of CPUE to ONI under different lag periods (0-60 months). Results The results indicate Transformer's suitability for analyzing lag effects between characteristics of these populations and climatic index like the ONI. Also, the CPUE shows a delayed response to the ONI, with the lag period being related to their life histories, and exhibits both short-term (within 3 months) and long-term (1-3 years) lag responses to the ONI. Conclusions As the lag period increases (>40 months), the response of CPUE to the ONI weakens gradually. The findings and the methodology underpinning this work provide new insights into the mechanisms of resource fluctuations for the populations of key species in the WCPO.
Objective In this study, we provide historical records of sawfishes (family: Pristidae) captured by commercial fishers at Eighty Mile Beach, Western Australia, during the early 21st century. Using rostra donated by members of the public and unpublished catch data, we provide information on the occurrence of pristids in Western Australia and identify important habitats for these rays.Methods Species identifications were conducted for rostra based on the meristics and morphology of specimens, with specific reference to the number, spacing, and physical attributes of rostral teeth.Results Donated rostra comprised 17 specimens, which represented all four sawfish species that occur in the Indo-West Pacific: the Narrow Sawfish Anoxypristis cuspidata (n = 5), the Dwarf Sawfish Pristis clavata (n = 6), the Largetooth Sawfish P. pristis (n = 1), and the Green Sawfish P. zijsron (n = 5). Standard lengths of rostra suggested that one Largetooth Sawfish and one Green Sawfish were mature upon capture. Remaining specimens were estimated to have belonged to juveniles, including two Narrow Sawfish, two Dwarf Sawfish, and four Green Sawfish that were estimated to be less than 1 year of age. Additional individual catch records of immature sawfish were collated for 19 Narrow Sawfish, 15 Dwarf Sawfish, and 25 Green Sawfish encountered at Eighty Mile Beach and adjacent Cape Keraudren between 2003 and 2008.Conclusions The sizes of donated rostra, combined with historical catch data, suggests that the nearshore waters of Eighty Mile Beach and Cape Keraudren may have served as a nursery area for Narrow Sawfish, Dwarf Sawfish, and Green Sawfish during the early 21st century. Given the cessation in commercial fishing activities and introduction of protection measures for these sites over the past two decades, it is possible that these sites function as a nursery for sawfish in the present day. Donated rostra and historical catch records demonstrate the importance of Eighty Mile Beach and Cape Keraudren, Western Australia, in supporting juvenile sawfishes during the early 21st century and suggest that these sites also functioned as a nursery area for the Narrow Sawfish, Dwarf Sawfish, and Green Sawfish during this period.
Objective The American horseshoe crab Limulus polyphemus is harvested for use in bait and biomedical industries. The Atlantic States Marine Fisheries Commission began managing the Delaware Bay stock in 1998. We developed two-stage hurdle models for this stock to evaluate the influence of external factors on CPUE, estimate relative abundance, and compare model- and design-based estimates.Methods We conducted stratified random trawl surveys along the mid-Atlantic coast (New Jersey-Virginia) annually since 2003, with strata based on bottom topography and distance from shore. Hurdle models (delta-lognormal) were developed for all six demographic groups (immature males, newly mature males, mature males, immature females, newly mature females, and mature females) to estimate year effects. Variable selection utilized forward stepwise regression, and quantile intervals for year effects were calculated using a 1,000-iteration bootstrap analysis. Predictive power was assessed through k-fold cross validation.Results Design- and model-based approaches produced similar relative abundance estimates across demographic groups, differing significantly in only a few years. Longitude, average depth, distance from shore, time of day, and month consistently affected CPUE. September yielded the highest mean CPUE for most groups. Night trawls generally resulted in higher abundance estimates. Relative abundance fluctuated over time.Conclusions Model- and design-based estimates of relative abundance were similar, although model-based estimates were typically more precise. Relative abundance varied over time, with a downward trend for newly mature females since 2016. We recommend using model-based estimates for future management decisions. Future research should focus on improving survey stratification and ensuring balanced sampling across months and times of day to validate this study's findings. We developed and compared model-based with historical design-based estimators of relative abundance of American horseshoe crabs on the mid-Atlantic coast. Model-based estimates were, on average, more precise. We suggest that model-based estimates be used to inform management decision making going forward.
Objective To evaluate the impacts of hook size on catch and discards of reef fish using an electronic monitoring video platform in collaboration with two commercial bottom longline vessels in the eastern Gulf of Mexico.Methods Vessels deployed a standard hook size commonly used in the fishery (13/0) for comparison with a larger version (15/0) during 16 fishing trips conducted between April 2022 and January 2023.Results The study successfully documented hook-specific attributes, including hook size and location, and used hook counts to generate projected discard and retention rates. Red Grouper Epinephelus morio, the primary target in this fishery, showed a reduction in projected discards with the use of 15/0 hooks, being 38% lower on average when compared with 13/0 hooks. An average decrease in discards of 21 undersized Red Grouper per haul and an average loss of six legally retainable Red Grouper per haul was projected while using 15/0 hooks. Catch rates for Red Snapper Lutjanus campechanus were lower with 15/0 hooks, which was also evident in other important reef fish species, such as Yellowedge Grouper Hyporthodus flavolimbatus, Tilefish Lopholatilus chamaeleonticeps, Blueline Tilefish Caulolatilus microps, Gray Snapper Lutjanus griseus, Lane Snapper L. synagris, and Red Porgy Pagrus pagrus.Conclusions In multispecies fisheries with elevated discard rates and associated mortality, gear modifications that reduce bycatch can enhance sustainability and support increases in allowable harvest. However, potential trade-offs, including reduced catch of some economically valuable targeted species, must be carefully evaluated. The application of electronic monitoring in this study proved to be an effective tool for capturing detailed gear-specific data, allowing for species-specific discard rates and impacts to be evaluated in a timely and efficient manner. Two bottom longline vessels tested 13/0 and 15/0 hook sizes to evaluate their impacts on catch and discards. Larger 15/0 hooks reduced Red Grouper discards by 38% but lowered the catch of other targeted species. Video electronic monitoring provided hook-specific data.
Objective The range of American monkfish (the commercial name for Goosefish) Lophius americanus in northwest Atlantic Ocean waters extends from the Grand Banks and the northern Gulf of St. Lawrence to at least North Carolina and includes both shallow inshore and offshore waters. Its fishery in the USA has been assessed and managed as two distinct units since the inception of its fishery management plan in 1999, with the boundary between the two management units being Georges Bank. However, biological data supporting this division are largely lacking. Our objective in this study was to use a genetic approach, microsatellite DNA analysis, to determine if monkfish constitute a single or multiple genetic stocks over almost their entire coastwide distribution.Method American monkfish-specific microsatellite loci were identified and 11 loci were genotyped in 2,395 monkfish specimens from 19 different project strata collected in 2013 and 2019 from Atlantic Canada to North Carolina through the combined efforts of a network of commercial fisherman and dealers, governmental trawl surveys, and academic institutions.Results Moderate levels of allelic diversity were observed across all loci; however, we failed to find significant genetic differentiation among any of the collection areas or between combined collection areas north and south of the stock boundary line bisecting Georges Bank.Conclusions The most parsimonious interpretation of our microsatellite data is that American monkfish constitute a single genetic stock across their entire coastwide distribution. Therefore, our results do not support the current practice of managing monkfish as two distinct stocks, although it would be prudent to further investigate this question with an even more sensitive approach, single nucleotide polymorphism analysis. American monkfish in U.S. waters are managed as two distinct stocks; however, there is an absence of biological data supporting this division. Our study demonstrates that American monkfish likely constitute a single genetic stock across their entire coastwide distribution.
Objective We focused on the fish communities collected seasonally and interannually from the Minjiang estuary (MJE), China, to improve our understanding of the temporal dynamics of fish communities in estuarine ecosystems and their responses to environmental changes.Methods Fishery data were collected across four seasons in 2006 and 2016, along with nine functional traits of fishes related to their ecology, life history, and morphology. Community-weighted mean trait values were calculated to describe the functional trait composition of the fish communities. Functional richness and redundancy were calculated to describe the functional diversity of the communities.Results Our results showed that the functional trait composition of the fish communities in the MJE substantially changed at seasonal and interannual scales. The variations were directly related to community-weighted mean trait values and were indirectly related to environmental variables. The data in 2016 showed lower species richness and functional redundancy but higher functional richness compared with the 2006 data. The changes in species richness had a high influence on functional richness but no significant effect on functional redundancy.Conclusions Considering the interannual changes in species richness, functional richness, and functional redundancy, we proposed that the stability of the fish communities in the MJE has declined over time. Our findings provide insights into the seasonal and interannual dynamics of the fish communities in the MJE and evidence that a trait-based approach is necessary in making priority conservation policies for fishes. Using a trait-based approach, this study of China's Minjiang estuary analyzed community-weighted mean traits, functional richness, and redundancy to assess seasonal and interannual shifts. We showed that key environmental variables directly drove functional structure changes, and divergent trends in species richness, functional richness, and redundancy reveal eroding community stability. The findings provide a theoretical basis for fishery conservation.
Objective We used data from a long-term trawl survey to describe multi-decadal variation in the spatial distribution and relative abundance of the Hogchoker Trinectes maculatus in Chesapeake Bay and its three southernmost tributaries in relation to abiotic factors for three different life stages. Additionally, we compared relative abundance of Hogchokers in Chesapeake Bay with that of other commonly captured species. Lastly, we described trophic interactions of Hogchokers as prey within the Chesapeake Bay food web.Methods We used 35 years of bottom trawl survey data from Chesapeake Bay and three of its southern tributaries from a stratified random sampling design that included fixed and random stations to estimate relative abundance of Hogchokers in the James, York, and Rappahannock rivers and the lower Chesapeake Bay. We used generalized additive models to examine life-stage-specific distribution in relation to abiotic variables and seasons. We evaluated the role of Hogchokers in the Chesapeake Bay food web through published and unpublished diet studies.Results From 1988 to 2022, more than 2,293,000 Hogchokers were captured. Abundance in the York River ranked first (1,124,978 individuals), followed by that in the James River (825,711), the Rappahannock River (307,022), and lastly the main stem of Virginia's portion of Chesapeake Bay (36,016 individuals). Annual relative abundance varied by three orders of magnitude within Chesapeake Bay; even greater variability was observed in specific regions within the bay and tributaries. Indices of Hogchoker relative abundance showed nearly 100-fold differences among years in the James River, whereas abundance patterns in remaining sampling areas showed less dramatic variations. Bottom water temperature, depth, salinity, and dissolved oxygen explained most of the observed variation relative to abundance among the size-classes examined. Distribution patterns were related to fish size, with smaller individuals found in brackish-freshwater habitats, whereas larger Hogchokers resided in more saline habitats. The seasonal distribution of Hogchokers was life stage specific, with early juveniles occurring in the upper portions of tributaries in summer and winter and larger juveniles and mature individuals occurring in the tributaries in winter and throughout all regions in summer.Conclusions Hogchokers are widely distributed based on size, and their distribution is affected by water temperature, salinity, depth, and dissolved oxygen. Hogchokers consume benthic invertebrates, potentially forming an important link between benthic productivity and higher trophic levels, but investigations of potential fish predators revealed limited consumption of Hogchokers despite their high abundance. Thus, Hogchokers may represent a carbon and nutrient sink in Chesapeake Bay and other temperate estuaries. Hogchoker seasonal distribution in lower Chesapeake Bay is affected by their size, water temperature, salinity, depth, and dissolved oxygen. Despite ranking among the most abundant demersal species in the survey, few Hogchokers are reported in diets of predators, suggesting that Hogchokers are rarely consumed.
Objective Estuarine ecosystems are dynamic habitats where the convergence of marine water and freshwater results in constant fluxes in abiotic environmental conditions. Organisms must face these fluctuating conditions within their optimal range to minimize physiological costs, often by moving from unsuitable to more suitable areas. Anthropogenic hydrologic discharges further alter environmental conditions and may cause population-wide movement responses of mobile organisms. Organismal responses to anthropogenic and natural fluctuations can differ based on time of year, life history stage, or individual characteristics.Methods We used acoustic telemetry to track the movements of Common Snook Centropomus undecimalis, a euryhaline sport fish, before, during, and after high-discharge events in a managed waterway.Result We did not find large-scale, synchronous movement. Common Snook were more likely to move during a high-discharge event and with increased changes in salinity. Although size and sex did not influence movement on a larger scale within the estuary, small to intermediate size-classes (602-786 mm TL) occupied adjacent slower flow habitats that mimicked natural conditions during high discharge, likely due to decreased energy expenditure. Individual identity played a role in determining the probability of movement, which may reflect behavioral contingencies that exhibit differences in habitat preference and movements.Conclusions This sport fish population may be more resilient to this type of disturbance than previously hypothesized. Understanding the relationships between the movement of fish and abiotic and anthropogenic factors can guide the management of waterways and provide insight into how changes will affect their distribution in estuarine environments. We examined the response of Common Snook to periods of high discharge. No large-scale movements in response to discharges were found; instead, individuals reacted differently. Common Snook appear more adaptable and resilient to these disturbances than previously thought.
Objective: Blueline Tilefish Caulolatilus microps have a relatively brief history of exploitation in United States Atlantic waters. A stock assessment in 2017 indicated that age-structured models, although preferred over age-aggregated models, should not be used without reliable maturity estimates and age data for Blueline Tilefish. However, there have been only four immature Blueline Tilefish collected to date. Therefore, we collaborated with the charter boat sector of the recreational fishery to target small (<400 mm total length), potentially immature Blueline Tilefish to better estimate sexual maturity. In addition, we combined known data sets on age and reproduction from fish that were sampled from the southeastern U.S. Atlantic (SEUS) and U.S. mid-Atlantic (USMA) regions to determine the overall spawning season, sex ratios, and sexual maturity of Blueline Tilefish. Methods: Gonad histology was used to microscopically identify sexes and reproductive phases to determine the spawning season and sex ratios. Generalized additive models were used to analyze gonad weight-whole weight and gonad weight-month relationships. Length and age at maturity were estimated using logit, probit, and Gompertz models. Maturity was defined in four ways, based on different histological thresholds of oocyte stages, to separate fish that are expected to spawn (mature; n = 1,532) from those that will not spawn (immature; n = 9). Results: Sex ratios were female skewed in both regions and deviated significantly from 1:1 in the USMA. Gonad weight increased with whole weight in both regions. Female spawning peaks were identified as May-June and August-September for the SEUS and USMA, respectively, but USMA sample sizes remained low in most months. Despite targeted sampling, sample size remained low for immature fish (n = 9 total) as well as for fish from suspected nonspawning months. The Gompertz model for length at maturity and logit model for age at maturity in maturity scenario 4, whereby females in early development with cortical alveolar oocytes present were considered to be immature and females in vitellogenesis were scored as mature, were considered the best fit models for maturity ogives. These models estimated length and age at 50% maturity to be 337 mm total length and 3.1 years, respectively. Conclusions: Through a collaborative analysis of multiple data sets, it was possible to determine the spawning season, sex ratios, and sexual maturity of Blueline Tilefish in the SEUS and the USMA. Targeted sampling remains the only known method to acquire immature fish needed for better sexual maturity estimates, so we suggest that collaborative relationships with industry be maintained.
Objective: The Common Snook Centropomus undecimalis is a species widely distributed throughout the western Atlantic, playing a key ecological role in coastal and estuarine ecosystems. Despite its broad distribution from Florida to southeastern Brazil, little is known about the genetic patterns underlying its population connectivity. This study aimed to characterize the genetic structure of this species and to infer patterns of genetic diversity and connectivity across its range. Methods: A total of 100 individuals collected from Florida to southeastern Brazil were genotyped at 11 microsatellite loci. Genetic structure was assessed using Bayesian clustering analysis, discriminant analysis of principal components, and analysis of molecular variance. Genetic differentiation among populations was estimated by pairwise F-ST, and recent gene flow was inferred from migration proportions among the identified genetic profiles. Results: Three distinct genetic profiles were identified: one exclusive to the southern Gulf of Mexico (Gulf Profile) and two along the Atlantic coast (Northern and Southern profiles), both contributing to a central mixed zone in northern South America. Analysis of molecular variance revealed greater variation within populations (68.8%). When admixed individuals (<80% assignment) were excluded, the variation among groups increased to 27.2%, while within-group variation remained high (68.4%). The Gulf Profile showed strong differentiation from the others (F-ST = 0.33-0.39), whereas differentiation between the Northern and Southern profiles was lower but significant (F-ST = 0.038). Recent migration analysis indicated high genetic self-recruitment within each profile (68-99%) and limited gene flow among them, except for significant migration from the Southern Profile to the Northern Profile (migration rate = 0.301). Genetic diversity was high across all profiles, with greater allelic richness and heterozygosity in the Gulf Profile and lower values in the Southern Profile; 90 private alleles were identified, most of them in the Gulf Profile. Conclusions: The Common Snook exhibits an isolated stock in the southern Gulf of Mexico, likely maintained by historical processes and local oceanographic dynamics, such as the Loop Current and cyclonic vortices. Along the Atlantic coast, two distinct genetic profiles (Northern and Southern) are connected by a transitional zone in northern South America characterized by extensive genetic admixture. Atlantic connectivity appears to be facilitated by ocean currents and the species' broad ecological plasticity, including tolerance to salinity variation and diadromous migrations. These findings provide valuable insights for conservation and fisheries management strategies throughout the distributional range of this species.
Objective Red Snapper Lutjanus campechanus is an economically and ecologically important fish for the Mississippi coast. Sustainability concerns are of importance to both stakeholders and managers. The objective of this work is to understand the environmental, habitat, and fishery characteristics that influence catch per unit effort of sublegal- and legal-sized Red Snapper in the northern Gulf of America (also known as the Gulf of Mexico). Methods We used descriptive statistics to understand patterns of habitat- and depth-specific catch per unit effort (CPUE). To explore the factors that determine catch, we employed a gradient-boosting ensemble machine learning technique on CPUE. Continuous CPUE data were modeled by converting them to a binary variable, above and below mean ln(CPUE + 1). We used data from a scientific survey of sublegal- and legal-sized Red Snapper (>406.5 mm TL) in the region collected using vertical longline from 2016 to 2019. A suite of predictors (termed "features") reflecting fishing season, habitat, and environmental characteristics was used in machine learning models. Results In the descriptive analysis of CPUE, we found that positive CPUE for both sublegal- and legal-sized fish was observed at artificial reef and oil and gas platforms in both the mid and deep strata. Conversely, CPUE in undifferentiated bottom habitat was low for all depth strata, with only a single, sublegal fish recorded in the deep depth stratum. Catch-per-unit-effort ln(CPUE + 1) was evaluated, and model output was assessed using variable importance metrics and Shapley additive explanation values for visualization and to determine the direction and magnitude of feature influence. Models were created for both sublegal- and legal-sized Red Snapper. Both models achieved accuracies above 0.90. For sublegal Red Snapper, greater-than-mean ln(CPUE + 1) was associated with high surface salinity and small hook size. For legal-sized Red Snapper, below-mean ln(CPUE + 1) was associated with small hook size. Conclusions Our descriptive analysis indicated that CPUE was greatest in structured habitats. The machine learning model indicated that the variables that predicted binary CPUE for the sublegal- and legal-sized fish were different. For both size-classes examined, our findings that hook size was an important predictor of the binary natural-log-transformed CPUE variable has implications to selectivity and perhaps gear restrictions in the fishery. These analyses can inform fisheries managers of the factors that are most influential in the catch of sublegal- and legal-sized Red Snapper in the study region.
Objective Closed areas are commonly used in fisheries management to rebuild marine species. Large-scale closed areas (>10 km2) have proven effective in rebuilding offshore Atlantic sea scallop Placopecten magellanicus populations in the U.S. federal fishery; however, little is known about the effect of small-scale, inshore closed areas (<10 km2) on sea scallops. This study, which involved a multi-sector collaboration, sought to evaluate the effect of small-scale closed areas on the Atlantic sea scallop in Maine. Methods Between 2013 and 2017, annual scuba surveys were conducted to assess the density and shell height (SH) of adult scallops inside and adjacent to two closed areas. Spat abundance was also determined with the use of spat bags at one of the closed areas. Results We observed larger SHs, a pulse of juvenile scallop (SH < 70 mm) recruitment in 2014, and potential settlement to the seabed in one of the closed areas but not in the adjacent open area; however, results were not statistically significant in all years. Conclusions Atlantic sea scallops are broadcast spawners, with increasing reproductive output as size increases. With a greater number of larger scallops in closed areas, there could be higher rates of successful reproduction, meaning that closed areas may be a larval source in coastal waters. However, oceanographic models and genetic analyses would be needed to test this hypothesis and further explore inshore scallop population dynamics. Ultimately, small-scale closed areas could prove to be a useful tool in management if areas with suitable habitat are selected and if closure implementation and duration align with successful recruitment events.
Objective The objective of this study was to examine the movements of Common Snook Centropomus undecimalis, a tropical euryhaline species, out of the Shark River, Everglades National Park, Florida, USA, and gain a better understanding of their long-distance regional movements.Methods This study used 7 years (2017-2023) of acoustic telemetry data from the Shark River Florida Coastal Everglades Array and from five other collaborative telemetry arrays in southwestern Florida to assess out-of-system movements for 119 Common Snook. Generalized linear models were used to assess the relationships between out-of-system movements and biological and environmental variables.Results Most Common Snook departures took place during the spawning season, with 121 departures (80.1%). Of 67 departed individuals, 26 were detected by the collaborative arrays (both north and south of our array, 38.8%). Of the departed Common Snook, 35 returned to the Shark River (52.2%), with most returning to the lower river (62.7%), and with a trend for larger fish to have a higher probability of return. Last, Common Snook that spent less time outside were more likely to return to the upper part of the Shark River.Conclusions Our study leveraged five collaborative acoustic telemetry arrays to investigate long-distance movements of Common Snook across southwest Florida, revealing that the true scales of movement and population connectivity remain largely unknown. Despite limited receiver coverage, detections of Common Snook outside the Shark River were higher than expected, with half of the individuals exhibiting site fidelity by returning to the river. These findings underscore that a single river system may only represent a portion of an organism's home range, highlighting the need for further studies and expanded receiver coverage to elucidate broader patterns of snook movement and population connectivity. Collaborative telemetry networks near south Florida observed forays of tagged Common Snook to neighboring arrays up to 88 km away from the river of tag origin. Varying degrees of return behavior suggest that a single river system may only represent a portion of snook home range.
Objective The objective of this study was to evaluate the effects of dissolved oxygen (DO), other environmental factors, and fishing on the spatial distributions of brown shrimp Farfantepenaeus aztecus and white shrimp Litopenaeus setiferus on the Louisiana continental shelf.Methods Generalized additive models and Bayesian regression models were applied to long-term (1987-2017) trawl survey and environmental data to investigate factors that drive the spatial distributions of shrimp during summer (June-July) when hypoxia is typically most severe. Markov chain-Monte Carlo methods were used to characterize uncertainty in the fitted relationships. The best fit models were used to generate annual spatial distribution maps for the month of July for both species on the Louisiana shelf. The effective area occupied was computed from the distribution maps as an indicator of habitat compression, and its relationship to both hypoxia severity and shrimp trawling effort was evaluated.Results The DO avoidance thresholds were low for brown shrimp (1.82 mg/L) and white shrimp (1.50 mg/L), and both species were most abundant at moderately low DO (2-4.5 mg/L), where sublethal effects are common in other shrimp and decapod crustaceans. Sediment composition, water depth, distance to the coast, and spring sea surface temperature were also important predictors of shrimp spatial distributions. For both species, habitat compression increased in years when hypoxia was severe, consistent with hypoxia-induced habitat loss and increased aggregation on the shelf. However, the spatial distributions of shrimp have also expanded in recent decades in association with declines in shrimping effort and shrimp landings and increases in survey catch rates, most likely due to positive density dependence (i.e., expanded spatial distributions when abundance is high).Conclusions Our results indicate that the spatial distributions of shrimp on the Louisiana shelf are the result of multiple factors that operate from seasonal to decadal time scales, including summer hypoxia, the contemporaneous and lagged effects of other environmental factors, and fishing effort in the shrimp fishery. This study quantified the effects of low dissolved oxygen, other environmental factors such as sediment type and sea surface temperature, and fishing effort in the shrimp fishery on the spatial distribution of brown shrimp and white shrimp on the Louisiana shelf. This work highlights the need to consider hypoxia within the context of other environmental factors and fishing that also influence shrimp spatial distributions over contemporaneous to decadal time scales. The modeling approach enhances our understanding of factors that govern spatial patterns in shrimp abundance and provides a framework for forecasting spatial distributions for shrimp that can be used to support fisheries management.
Objective We examined first-feeding Striped Bass Morone saxatilis postlarvae (larvae that had absorbed their yolk sacs) in the Choptank River, Maryland, during 2023-2024 to address whether their feeding success on zooplankton could be a major factor behind a series of poor year-classes during 2019-2024.Methods We estimated Choptank River Striped Bass postlarval feeding incidences on primary zooplankton prey and their associations with daily instantaneous growth and mortality rates of postlarvae from seven 1980s surveys (low and high mortality and poor to strong year-classes) to establish criteria with which to evaluate feeding during 2023-2024. Distributions of larvae by water temperature and conductivity during 1980s surveys were used to direct 2023-2024 postlarval collections for feeding analysis.Results Feeding incidences of first-feeding Striped Bass postlarvae on copepods in the Choptank River during 2023-2024 were high; feeding incidence on cladocerans was also high in 2024. Estimates of a proxy index for postlarval daily instantaneous mortality during 2023 and 2024 were low. However, year-class success was dismal during 2023 and low in 2024.Conclusions This feeding investigation did not encompass the entire 2019-2024 drought in year-class success, but the 2023-2024 surveys did not indicate a consistent, prominent role for feeding success of postlarvae. High feeding incidence of first-feeding Striped Bass postlarvae on zooplankton and low mortality did not always translate to better year-class success during the 1980s and 2023-2024. A prominent role of poor larval feeding success on zooplankton was not suggested for continuous poor year-class success during 2019-2024.
Objective To more precisely capture the relationship between sea surface temperature (SST) and the catch per unit effort (CPUE) levels of Pacific Chub Mackerel (also known as Chub Mackerel) Scomber japonicus in the northwest Pacific Ocean, a geographically and temporally weighted regression model incorporating double temporal factors was devised.Methods For the convenience of comparative study, several models were employed, including ordinary least squares, geographically weighted regression, geographically and temporally weighted regression (GTWR) with one time factor, and GTWR with double temporal factors (DTF-GTWR). First, we employed ordinary least squares to confirm that SST exerted significant influence on the resource abundance of Pacific Chub Mackerel. Subsequently, we used the DTF-GTWR model to examine the heterogeneity of the influence of SST on resource abundance of Pacific Chub Mackerel across different years, seasons, and spatial areas.Results The results showed that the adjusted R2 of the DTF-GTWR was 0.48 and its corrected Akaike information criterion was the lowest among all the candidate models, indicating that the DTF-GTWR model revealed a higher explanatory power for the spatiotemporal heterogeneity of the effects of SST on Pacific Chub Mackerel CPUE. As the year progressed, the relationship between SST and CPUE changed substantially for most fishing zones, transitioning from positive correlations to negative ones from 2014 to 2020. A seasonal analysis revealed that SST exhibited a positive correlation with CPUE during autumn (particularly September and October) in most fishing zones, whereas it showed a negative correlation with CPUE during the remaining fishing seasons. Additionally, a clear shift from negative to positive median coefficients of SST was observed with increasing longitude or latitude.Conclusions The GTWR model with dual temporal factors can offer valuable insights for deciphering the formation mechanism of fishing grounds and provide practical guidance for the sustainable management and resource conservation of Pacific Chub Mackerel in the northwest Pacific Ocean. The resource abundance of Pacific Chub Mackerel is closely associated with marine environmental conditions. This study centered on the resource dynamics of Pacific Chub Mackerel in the northwest Pacific Ocean, specifically examining catches from Chinese operations in the fishing ground. By incorporating geographical and temporal dimensions, we investigated the fluctuations relationship between sea surface temperature and the catch per unit effort of Pacific Chub Mackerel. The results demonstrated that when analyzing the effects of marine environmental variables on Pacific Chub Mackerel fishing grounds, spatiotemporal variability should be systematically considered.
Objectives In recreational fisheries, the choices individual anglers make have the potential to influence the success of management strategies, emphasizing the need to understand factors that drive angler behavior. Striped Bass Morone saxatilis are one of the most popular recreationally targeted fish species on the Atlantic coast of North America, particularly in the Northeast, making understanding angler practices and perceptions of the fishery essential for effective management.Methods Using an online nonprobabilistic survey, we surveyed Striped Bass saltwater anglers, investigating perceptions regarding catch-and-release best practices, angling quality, threats to the stocks, the need for management actions, and angler support for contemporary regulations.Results Anglers reported high voluntary release rates in the fishery, a general understanding of the potential effects angler behaviors can have on the fate of released fish, and awareness of strategies to mitigate negative effects. Perceptions of fishing quality mirrored population assessment data on Striped Bass stocks. Respondents highlighted pressures from the commercial fishery and the loss of juvenile habitats as perceived threats to the population. They expressed strong support for management regulations and various conservation strategies, including adoption of best practices for catch and release and increased scientific research. Despite broad consensus among respondents, attitudes varied with gear preference, with fly anglers demonstrating stronger conservation-oriented views than anglers using conventional tackle.Conclusions Insights gained from this survey reveal some gaps between angler perceptions and scientific evidence but also alignment between management goals and angler beliefs. Collectively, the insights can help shape education and outreach programs, as well as act as important reference points for Striped Bass management and conservation. In a survey of 1,651 Striped Bass anglers fishing along the Atlantic coast of North America, respondents demonstrated general awareness of the fishing practices that most influence postrelease outcomes and support for strong management regulations to promote population recovery.
Objective The Striped Bass Morone saxatilis, native to eastern North America, was brought to the San Francisco Bay on the continent's west coast in the late 19th century. Since then, the abundance of both native and nonnative populations has varied under changing fishing pressure and ecosystem conditions. The species has decreased in abundance in its nonnative range, while abundance in the native range has varied. Therefore, the objective of our study was to compare growth among and within nonnative and native ranges through time.Methods To meet our objective, we used long-term, fishery-independent length-at-age data (scale based) from the nonnative range in California (n = 234,248) and the native Chesapeake Bay in Maryland (n = 36,648), provided by each state's natural resource agency. We first fitted age- and sex-specific generalized additive models and linear regressions to determine the relationship of length at age with time within each range. We used linear models, pairwise comparisons, and von Bertalanffy growth models fitted to pooled data sets and three distinct stock status time periods within each range to determine whether length at age and lifetime growth trajectories differed among and within ranges and whether results were robust to variable stock statuses.Results Striped Bass introduced into California were longer than their native counterparts in the Chesapeake Bay, generally at age 8 and younger for both sexes. Furthermore, within both ranges, the length at age changed through time. At ages up to and including age 7, native Striped Bass length decreased for both sexes, while nonnative fish length increased at age 3, followed by decreases through age 7, throughout the time series. At age 8, nonnative males and native females also exhibited declines in length.Conclusions Like other anadromous fishes, growth differed between native and nonnative ranges, with larger young Striped Bass observed in the nonnative range. Although testing the mechanisms that drive growth differences was beyond our scope of study, we hypothesized that rapid early growth in the nonnative range resulted from optimum estuarine water temperatures combined with ancestral adaptations. Similarly, we did not test the mechanisms driving decreased length at age through time. However, temporal shifts in length at age within the nonnative range were likely driven by elevated natural mortality, continual fishing pressure, and prey shifts, while temporal shifts in the native range were likely driven by increasing temperature, hypoxia, and disease, coupled with fisheries selection and prey shifts. These differences in Striped Bass growth among ranges and over time highlight the complex interplay of ecology, environment, and evolution on fish life history and have important implications for migration and management. Young nonnative Striped Bass in California grew faster (greater length at age) than native Chesapeake Bay fish, and lengths at age 7 and younger have generally decreased through time for both sexes in each range. Results have implications for migration and fisheries management.
Objective The Common Snook Centropomus undecimalis is an important species in Florida's estuaries that is highly targeted in recreational fisheries. Loss of juvenile habitat is thought to have contributed substantially to population declines. Further impacts to juvenile Common Snook may further reduce populations or delay recovery. Nonnative Pike Killifish Belonesox belizanus have been linked to decreases in small-bodied native fishes in Florida, raising concerns about their potential impacts on early juvenile Common Snook. This study assessed the impacts of Pike Killifish on growth, abundance, and weight at length of early juvenile Common Snook through field enclosures, field sampling, and modeling completed during 2012 and 2013.Methods Field enclosures were used to assess potential impacts of Pike Killifish on daily growth of early juvenile Common Snook. Standardized field sampling was used to compare the abundance and weight at length of early juvenile Common Snook from locations with and without co-occurring Pike Killifish. Theoretical impacts on production of late-stage juvenile Common Snook were assessed with a population model.Results The enclosure study showed no significant differences in the daily growth of early juvenile Common Snook with and without Pike Killifish present. Abundances of early juvenile Common Snook from field locations with and without co-occurring Pike Killifish were not significantly different. Weight at length for Common Snook at locations with co-occurring Pike Killifish was only lower for the smallest early juveniles compared to those at locations without Pike Killifish. Theoretical modeling showed that minimal increases in natural mortality or decreases in growth of early juvenile Common Snook had small impacts on late-stage juvenile production, while large increases in predation, greater growth reduction, or a combination of the two resulted in larger reductions in late-stage juveniles.Conclusions Pike Killifish appear to have little to no impact on the growth, abundance, or weight at length of early juvenile Common Snook. Models demonstrated that predation by Pike Killifish combined with large reductions in growth of early juvenile Common Snook could significantly reduce the number of early juvenile Common Snook that become late-stage juveniles. Common Snook are important recreational fishing targets and top predators in Florida estuaries. We investigated whether nonnative Pike Killifish may be causing declines in juvenile Common Snook abundance via predation and resource competition. However, we found little to no impact of Pike Killifish on the growth, abundance, and weight at length of co-occurring juvenile Common Snook.
