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The notion that closely related species resemble each other in ecological niche space (i.e., phylogenetic dependence) has been a long-standing, contentious paradigm in evolutionary biology, the incidence of which is important for predicting the ecosystem-level effects of species loss. Despite being examined across a multitude of terrestrial taxa, many aspects of niche conservatism have yet to be explored in marine species, especially for characteristics related to resource use and trophic behavior (Eltonian niche characteristics, ENCs). We combined ENCs derived from stable isotope ratios at assemblage- and species-levels with phylogenetic comparative methods, to test the hypotheses that benthic marine fishes (1) exhibit similar assemblage-wide ENCs regardless of geographic location and (2) display phylogenetically dependent ENCs at the species level. We used a 12-species sub-set of the monophyletic group Rajidae sampled from three independent assemblages (Central California, Gulf of Alaska, and Northwest Atlantic), which span two ocean basins. Assemblage-level ENCs implied low trophic diversity and high evenness, suggesting that Rajidae assemblages may exhibit a well-defined trophic role, a trend consistent regardless of geographic location. At the species level, we found evidence for phylogenetic dependence of ENCs relating to trophic diversity (i.e., isotopic niche width; SEAc). Whether individuals can be considered functional equivalents across assemblages is hard to ascertain because we did not detect a significant phylogenetic signal for ENCs relating to trophic function (e.g., trophic position). Thus, additional, complimentary approaches are required to further examine the phylogenetic dependence of species functionality. Our approach illustrates the potential of stable isotope-derived niche characteristics to provide insight on macroecological processes occurring across evolutionary time, which could help predict how assemblages may respond to the effects of species loss.

Winter flounder Pseudopleuronectes americanus (Walbaum 1792) are a coastal flatfish species of economic and cultural importance that have dwindled to <15, % of their historic abundance in the southern New England/Mid‐Atlantic region of the United States, with evidence indicating near‐extirpation of certain local populations. This species exhibits intricate behaviors in spawning and migration that contribute to population complexity and resilience. These behaviors encompass full or partial philopatry to natal estuaries, the generation of multiple pulses of larval delivery, and partial migration. The patterns of genetic diversity within and among estuaries and cohorts presented here carry important implications in understanding the susceptibility to demographic shocks, even if the full extent of genetic diversity within and among winter flounder stocks on the US East Coast remains unresolved. Our findings reveal connectivity between estuaries in Long Island, New York, suggesting the potential for genetic rescue of depleted subpopulations. Family reconstruction and relatedness analysis indicate that split cohorts and migration contingents are not the result of genetically distinct lineages. We found no evidence for genetic structure separating these groups, and in some instances, we were able to detect closely related individuals that belonged to different migratory contingents or cohorts. Characterizing the spatial and behavioral organization of this species at the population level is crucial for comprehending its potential for recovery, not only in terms of biomass but also in reinstating the complex population structure that supports resilience. The search for generality in winter flounder spawning and migration behavior remains elusive, but perhaps the lack of generalities within this species is what has allowed it to persist in the face of decades of environmental and anthropogenic stressors. [ABSTRACT FROM AUTHOR]

The southern New England--mid-Atlantic (SNE-MA) stock of winter flounder (Pseudopleuronectes americanus) collapsed in the 1990s without discernable recovery to date. Owing to the lack of recovery, consideration of population subcomponents, which are currently ignored in fisheries stock structure definitions, may be necessary for rebuilding. We used the otolith chemistry tracer manganese-calcium ratios (Mn/Ca) to estimate inshore- versus ocean-nursery contributions of 77.3%/22.7% in SNE-MA, 15.7%/84.3% in the Gulf of Maine (GOM), and 60.0%/40.0% in Georges Bank (GB). In addition, we used strontium- calcium ratios (Sr/Ca) to estimate migratory- and resident-contingent membership of nursery-classified fish. Across all stocks, 30.2% of fish were classified as bay residents, 25.2% as bay migrants, 25.8% as ocean residents, and 18.8% as ocean migrants. Finally, model selection indicated that both nursery-specific and contingent-specific growth models were more appropriate than a common model. Nursery-specific models exhibited increasing deviations in length with age. Contingent-specific model reflected moderate differences at the youngest ages but convergence at older ages. These findings are informative for the population structure and migration ecology of winter flounder; however, simulation is required to determine whether partial migration and substock structure are necessary inputs for sustainable fisheries management. Le stock de plie rouge (Pseudopleuronectes americanus) du sud de la Nouvelle-Angleterre et du Massachusetts (SNE-MA) s'est effondre dans les annees 1990 et ne montre aucun signe de retablissement a ce jour. En raison de cette absence de retablissement, il pourrait etre necessaire, pour reconstituer ce stock, de tenir compte de sous-composantes des populations qui ne sont actuellement pas incluses dans les definitions de la structure du stock utilisees pour la gestion de la peche. Nous avons utilise le rapport Mn/Ca, un traceur de la chimie des otolites, pour estimer des contributions des aires de croissance cotieres et oceaniques de 77,3 % / 22,7 % dans le SNE-MA, 15,7 % / 84,3 % dans le stock du golfe du Maine (GOM) et de 60,0% / 40,0 % dans celui des banc de Georges (GB). Nous avons aussi utilise le rapport Sr/Ca pour estimer la constitution des contingents migrateurs et residents de poissons selon leurs aires de croissance etablies. Pour tous les stocks pris collectivement, 30,2 % des poissons ont ete classes comme residents de baies, 25,2 % comme migrants de baies, 25,8 % comme residents oceaniques et 18,8 % comme migrants oceaniques. Enfin, la selection de modeles indique que tant les modeles de croissance qui precisent l'aire de croissance que ceux qui precisent le contingent conviennent mieux qu'un modele commun. Les modeles precisant l'aire de croissance montrent une augmentation des ecarts de la longueur avec l'age. Les modeles precisant le contingent refletent des differences moderees pour les plus jeunes ages, mais une convergence pour les ages plus avances. Si ces constatations fournissent de l'information sur la structure des populations et l'ecologie de la migration de la plie rouge, des simulations sont toutefois necessaires pour determiner si la migration partielle et la structure des sous-stocks sont des intrants necessaires pour une gestion durable de la peche. [Traduit par la Redaction], Introduction Successful management of commercial fisheries requires an understanding of the population unit of management focus (stock), the degree of connectivity among neighboring stocks, and relative productivity between stocks. Spatial [...]

Winter flounder (Pseudopleuronectes americanus) have declined to less than 11% of their historical abundance in offshore areas and have experienced severe declines and inbreeding in coastal subpopulations. Understanding metapopulation structure and disparate migratory behavior is vital to understanding the species' dynamics. We used acoustic telemetry to evaluate migratory types, homing behavior, and spawning behavior in adult winter flounder (n = 72) in Mattituck Creek, New York. Telemetry results showed that 17% of the tagged individuals displayed resident behavior and remained in the creek year- round despite mean summer temperatures reaching 28[degrees]C. Alternatively, the migratory group (~83%) started to leave the system when the mean water temperature reached 12[degrees]C. A dominant driver of migration was not indicated; instead, migration out of or into the creek appeared complex and related to date, temperature, lunar cycle, photoperiod, and year. Approximate spawning was estimated to occur as early as November and continued through April based on aggregative behaviors of adults and backcalculations of dates using young-of-the-year otoliths. Our results support the emerging view that winter flounder's dynamics reflect local life history and population diversity, which are currently unaccounted for in management. L'abondance des plies rouges (Pseudopleuronectes americanus) a chute a moins de 11 % de sa valeur historique dans les zones extracotieres et l'espece a subi des baisses et une endogamie importantes dans les sous-populations cotieres. La comprehension de la structure de la metapopulation et des comportements migratoires disparates est d'importance vitale pour la comprehension de la dynamique de l'espece dans la region. Nous avons utilise la telemetrie acoustique pour evaluer les types migratoires, le retour et le comportement de frai chez des plies rouges (n = 72)adultes dans lacrique Mattituck (Etatde New York). Les resultats de telemetrie montrent que 17 % des specimens etiquetes presentaient un comportement resident et demeuraient dans la crique toute l'annee malgre des temperatures estivales moyennes atteignant 28[degrees]C. En comparaison, le groupe migrateur (~83 %) commenqait a quitter le reseau quand la temperature moyenne de l'eau atteignait 12[degrees]C. Un moteur dominant de la migration n'est pas ressorti; la migration hors de la crique ou vers celle-ci semble complexe et reliee a la date, la temperature, le cycle lunaire, la photoperiode et l'annee. Il est estime que le frai commence des novembre pour se poursuivre jusqu'a avril, a la lumiere de comportements de regroupement d'adultes et du retrocalcul des dates base sur les otolites. Nos resultats appuient l'opinion emergente selon laquelle la dynamique des plies rouges reflete la diversite locale des cycles biologiques et de la population, un aspect dont la gestion actuelle ne tient pas compte. [Traduit par la Redaction], Introduction Large-scale movements by individuals occur across almost all taxa (Dingle and Drake 2007). The prevalence of migration across taxa indicates that it is a key life history component, particularly [...]

Anthropogenic warming is altering species abundance, distribution, physiology, and more. How changes observed at the species level alter emergent community properties is an active and urgent area of research. Trait‐based ecology and regime shift theory provide complementary ways to understand climate change impacts on communities, but these two bodies of work are only rarely integrated. Lack of integration handicaps our ability to understand community responses to warming, at a time when such understanding is critical. Therefore, we advocate for merging trait‐based ecology with regime shift theory. We propose a general set of principles to guide this merger and apply these principles to research on marine communities in the rapidly warming North Atlantic. In our example, combining trait distribution and regime shift analyses at the community level yields greater insight than either alone. Looking forward, we identify a clear need for expanding quantitative approaches to collecting and merging trait‐based and resilience metrics in order to advance our understanding of climate‐driven community change. [ABSTRACT FROM AUTHOR]

Abstract--Commercial fishermen have argued that localized concentrations of spiny dogfish (Squalus acanthias) in the northeast U.S. shelf large marine ecosystem (NES LME) have impeded their fishing operations when monitoring surveys [...]

Increased commercial importance of spiny dogfish (Squalus acanthias) combined with an often debated, and controversial, ecological impact has warranted an investigation of the relationship among distribution, environment, and prey to better understand the species ecology and inform management. To elucidate mechanisms behind distributional changes, we modeled seasonal occurrence and abundance of neonate, immature, and mature spiny dogfish as functions of abiotic and biotic factors using generalized additive models and Northeast Fisheries Science Center bottom trawl survey data. Significant nonlinear relationships were widespread throughout dogfish stages and seasons. Seasonal occurrence was tightly linked to depth and bottom temperature, with year and Julian day influential for some stages. While these factors also influenced abundance, ecological factors (e.g., squid abundances) significantly contributed to trends for many stages. Potential impacts of climate change were evaluated by forecasting distributions under different temperature scenarios, which revealed higher regional probabilities of occurrence for most stages during a warmer than average year. Our results can be used to better understand the relationship between sampling periods and movement drivers to survey catchability of the population in the Northeast (US) shelf large marine ecosystem. L'importance commerciale croissante de l'aiguillat commun (Squalus acanthias), combinee a un impact ecologique controversy faisant l'objet d'un debat soutenu, a motive l'etude du lien entre repartition, milieu et proies dans le but de mieux comprendre l'ecologie de cette espece et d'en eclairer la gestion. Afin de faire la lumiere sur les mecanismes qui sous-tendent les variations de la repartition, nous avons modelise la presence et l'abondance saisonnieres d'aiguillats communs nouveau-nes, immatures et matures en fonction de facteurs abiotiques et biotiques, a l'aide de modeles additifs generalises et de donnees de leves au chalut de fond du Northeast Fisheries Science Center. Des relations non lineaires significatives etaient repandues pour tous les stades de vie de l'aiguillat et toutes les saisons. La presence saisonniere etait etroitement reliee a la profondeur et la temperature au fond, l'annee et le jour julien exerqant une influence pour certains stades. Si ces facteurs influenqaient egalement l'abondance, des facteurs ecologiques (p. ex. l'abondance de calmars) avaient une incidence significative sur les tendances pour de nombreux stades. Les impacts potentiels des changements climatiques ont ete evalues en predisant les repartitions pour differents scenarios de temperature, ce qui a revele des probabilites regionales accrues de presence pour la plupart des stades durant des annees plus chaudes que la normale. Nos resultats peuvent servir a une meilleure comprehension du lien entre les periodes d'echantillonnage et les facteurs influenqant les deplacements dans revaluation de la capturabilite de la population dans le grand ecosysteme marin de la plate-forme du Nord-Est etats-unien., Introduction The Magnuson-Stevens Fishery Conservation and Management Act of the United States emphasizes the integration of ecosystem considerations into assessment methods (Link et al. 2011) consistent with a move towards [...]

Declines in abundance of commercially valuable groundfish have highlighted the ecological and commercial importance of previously underutilized elasmobranchs in the Northeast (US) shelf large marine ecosystem (NES LME). Seasonal distributions and ontogenetic habitats of one such species, spiny dogfish (Squalus acanthias), were investigated using Northeast Fisheries Science Center (NEFSC) bottom trawl survey data (1963-2009). Neonate, immature, and mature dogfish all selected warmer, more saline, and more southerly locations during spring compared with available locations. During autumn, larger dogfish occupied relatively warmer, shallower, and less saline waters while neonates selected higher salinities. There were strong ontogenetic patterns in habitats occupied. Contrary to expectation, geographic range contracted as abundance increased during autumn. This suggests that niche constraints override density-dependent effects, although detection of relationships within stages was limited by low statistical power. The proportion of mature female survey catch within the Mid-Atlantic Bight was significantly related to temperature, suggesting that environmental conditions surveyed may impact population trends. Collectively, these results highlight critical habitats, suggest mechanisms behind ontogenetic habitat selection, and provide insight into how changing environmental conditions may impact stock assessment. Les baisses d'abondance de poissons de fond a valeur commerciale soulignent l'importance ecologique et commerciale d'elasmobranches auparavant sous-utilises dans le grand ecosysteme marin de la plateforme continentale du nord-est des Etats-Unis (NES LME). Les repartitions saisonnieres et les habitats ontogeniques d'une de ces especes, l'aiguillat commun (Squalus acanthias), ont ete examines a la lumiere de donnees de releves au chalut de fond (1963-2009) du Northeast Fisheries Science Center (NEFSC). Parmi les sites disponibles, les aiguillats nouveau-nes, immatures et matures choisissaient tous des emplacements relativement chauds, salins et meridionaux au printemps. A l'automne, les aiguillats plus grands occupaient des eaux relativement chaudes, moins profondes et moins salines, alors que les nouveau-nes choisissaient des eaux de plus forte salinite. L'occupation des habitats definissait des motifs ontogeniques marques. Contrairement aux attentes, l'aire de repartition geographique diminuait parallelement a l'augmentation de l'abondance a l'automne, ce qui donne a penser que les contraintes touchant a la niche l'emportent sur les effets dependants de la densite, bien que la faible efficacite statistique limite la detection de relations pour des stades donnes. La proportion de femelles matures capturees dans le cadre des releves dans le golfe Medio-atlantique etait significativement reliee a la temperature, donnant a penser que les conditions ambiantes pourraient avoir une incidence sur les tendances des populations. Collectivement, ces resultats font ressortir des habitats essentiels et des mecanismes possibles de selection d'habitats ontogeniques et jettent un eclairage sur l'incidence de l'evolution des conditions ambiantes sur l'evaluation des stocks. [Traduit par la Redaction], Introduction Understanding the habitat preferences of marine fishes is important when describing their spatial distribution and ecology (Perry and Smith 1994; Smith and Page 1996; Shepherd et al. 2002) and [...]

Employing ecological approaches to fisheries management or comprehensive marine spatial planning requires that species assemblage structure be accounted for. Fish and invertebrate spatial distributions from the National Marine Fisheries Service demersal trawl survey conducted in the Georges Bank--Gulf of Maine region were analyzed by bootstrapped principal component analysis ([PCA.sub.Btsp]) and normal PCA ([PCAN.sub.rml]). [PCA.sub.Btsp] produced confidence limits for eigenvalue stopping rules and for eigenvectors to identify significantly correlated species. Stopping rules identified the first six principal components (PCs) as relevant. Initially, summer and fall survey data from 1963 to 2006 were analyzed, but high eigenvector variation led to reductions in the species and time series used. Confidence interval variation was achieved through removal of highly migratory species and restriction of the time series. PC scores were mapped using inverse distance weighted interpolation to reveal multispecies spatial arrangements. Core areas of species groupings and overlapping zones of higher diversity can be delineated and, even under high fishing pressure with large compositional changes, the assemblages maintained robust spatial organization. This spatial organization could be employed to protect appropriate species groups and minimize bycatch. Careful analysis of survey data can help ensure area-based management schemes are consistent with ecological scales. L'utilisation d'approches ecologiques dans la gestion des peches ou la planification globale de l'espace maritime necessite la prise en compte de la structure des assemblages d'especes. Les repartitions spatiales des poissons et invertebres obtenues du leve au chalut de fond du National Marine Fisheries Service effectue dans la region de banc de Georges-golfe du Maine ont ete analysees par analyse en composantes principales avec auto-amorcage ([PCA.sub.Btsp]) et par analyse en composantes principales normal PCA ([PCAN.sub.rml]). La [PCA.sub.Btsp] a produit des limites de confiance pour les regles d'arret des valeurs propres et les vecteurs propres permettant de cerner les especes correlees significativement. Ces regles d'arret ont revele que les six premieres composantes principales (PC) etaient pertinentes. Les donnees estivales et automnales du leve pour la periode de 1963 a 2006 ont d'abord ete analysees, mais la forte variabilite des vecteurs propres a mene a la reduction du nombre d'especes et des series chronologiques utilises. Des variations dans les intervalles de confiance ont ete obtenues en retirant des especes tres migratoires et en restreignant les series chronologiques. Les notes des PC ont ete cartographiees par interpolation par l'inverse de la distance afin de deceler les distributions spatiales multi-especes. Les regions centrales de groupements d'especes et les zones de chevauchement peuvent etre delimitees. L'analyse des donnees de leve peut contribuer a une meilleure concordance des schemas de gestion bases sur la region et des echelles ecologiques. [Traduit par la Redaction], Introduction Anthropogenic activities have been correlated with significant losses in marine biodiversity (Sala and Knowlton 2006). One contributor to this decline is that case-by-case evaluation of anthropogenic impacts in ocean [...]

Abstract--A lack of knowledge of how oceanic habitat is used by juvenile marine migrant Atlantic sturgeon (Acipenser oxyrinchus) is hindering conservation measures directed at restoring severely depleted populations. Identifying the [...]

Abstract: Vertebral samples of little skate (Leucoraja erinacea) and winter skate (Leucoraja ocellata) were collected from Cape Hatteras, USA, to Canadian waters to estimate age, growth, and length at weight [...]

Small pelagics, or forage fish, link lower and higher trophic levels in marine food webs. Recently, attention has been given to the management of forage fish, including anadromous river herring (Alewife Alosa pseudoharengus, blueback herring A. aestivalis) and American shad (A. sapidissima) due to their current depleted status and historically important ecological and economic roles. Little is known about the impact of changes in their biomass on marine food webs and what management practices will promote their recovery. Estimated historical riverine productivity was utilized to evaluate potential ecosystem impacts of the increasing river to ocean connectivity to resemble 19th‐century conditions. The Ecopath with Ecosim modeling framework was used to simulate management strategies, focused on anadromous forage fish, by creating scenarios of fisheries reduction (mixed fishery effort reduction) and river to ocean habitat connectivity (75% of historical connectivity achieved). Sixty‐year simulations covered the entire time series including a 36‐year forecast period to evaluate the ecosystem impacts of management strategies. Results suggest nonlinear relationships and large changes in biomass flows from forage fish to upper trophic levels in the Gulf of Maine ecosystem. Increases in biomass were observed for pelagic sharks, demersal piscivores, and species of conservation concern such as pinnipeds and seabirds, although overall results were strongly influenced by indirect trophic effects. Promoting anadromous forage fish recovery through increased connectivity resulted in the redundancy of marine ecosystem niches that would increase resilience to climate, fisheries, and other perturbations. This study highlights the value of employing ecosystem models for testing management scenarios to contrast different approaches to recover anadromous forage fish towards its former ecological prominence. [ABSTRACT FROM AUTHOR]

The isotopic composition of tooth‐bound collagen has long been used to reconstruct dietary patterns of animals in extant and palaeoecological systems. For sharks that replace teeth rapidly in a conveyor‐like system, stable isotopes of tooth collagen (δ13CTeeth & δ15NTeeth) are poorly understood and lacking in ecological context relative to other non‐lethally sampled tissues. This tissue holds promise, because shark jaws may preserve isotopic chronologies from which to infer individual‐level ecological patterns across a range of temporal resolutions.Carbon and nitrogen stable isotope values were measured and compared between extracted tooth collagen and four other non‐lethally sampled tissues of varying isotopic turnover rates: blood plasma, red blood cells, fin and muscle, from eight species of sharks. Individual‐level isotopic variability of shark tooth collagen was evaluated by profiling teeth of different ages across whole jaws for the shortfin mako shark Isurus oxyrinchus and sandbar shark Carcharhinus plumbeus.Measurements of δ13CTeeth and δ15NTeeth were positively correlated with isotopic values from the four other tissues. Collagen δ13C was consistently 13C‐enriched relative to all other tissues. Patterns for δ15N were slightly less uniform; tooth collagen was generally 15N‐enriched relative to muscle and red blood cells, but congruent with fin and blood plasma (values clustered around a 1:1 relationship).Significant within‐individual variability was observed across whole shortfin mako shark (δ13C range = 1.4‰, δ15N range = 3.6‰) and sandbar shark (δ13C range = 1.2‰–2.4‰, δ15N range = 1.7‰–2.4‰) jaws, which trended with tooth age.We conclude that amino acid composition and associated patterns of isotopic fractionation result in predictable isotopic offsets between tissues. Within‐individual variability of tooth collagen stable isotope values suggests teeth of different ages may serve as ecological chronologies, that could be applied to studies on migration and individual‐level diet variation across diverse time‐scales. Greater understanding of tooth replacement rates, isotopic turnover and associated fractionation of tooth collagen will help refine potential ecological inferences, outlining clear goals for future scientific inquiry. [ABSTRACT FROM AUTHOR]