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Telemetry is increasingly being used to estimate population-level survival rates. However, these estimates may be affected by the detectability of telemetry tags and are reliant on the assumption that telemetry data represent the movements of the tagged fish. Predation on tagged fish has the potential to bias survival estimates, and unlike the issue of detectability, methods to correct for the resulting bias (termed 'predation bias') are not yet developed. In an acoustic telemetry study on inner Bay of Fundy Atlantic salmon (Salmo salar) smolts during 2008 and 2011, unusual tag detection patterns were indicative that some data may have been representative of the movements of predators rather than smolts. To incorporate predation effects into the resulting survival estimates, a suite of 11 summary migration metrics were compared between Atlantic salmon smolts and striped bass (Morone saxatilis). Cluster analyses revealed that 2.4% to 13.6% of tags implanted in smolts exhibited migration patterns more similar to striped bass than to other smolts, which was interpreted here as evidence of predation. Reassigning the fate of these tags as 'depredated-died' reduced estimated survival from 43.5% to 41.1% in 2008 and from 32.6% to 19.0% in 2011 relative to a traditional mark-recapture model, illustrating the effect of predation bias in this case study. L'utilisation de la telemetrie pour estimer les taux de survie a l'echelle de la population est de plus en plus repandue. Ces estimations peuvent toutefois etre influencees par la detectabilite des etiquettes utilisees et reposent sur le principe que les donnees de telemetrie rendent compte des deplacements des poissons marques. La predation de ces derniers pourrait cependant biaiser les estimations des taux de survie et, contrairement au probleme de detectabilite, il n'existe pas encore de methode permettant de corriger le biais qui en resulte (appele <>). Dans une etude de telemetrie acoustique portant sur des saumoneaux de saumon atlantique (Salmo salar) de la haute baie de Fundy, menee en 2008 et 2011, des motifs de detection d'etiquettes inhabituels indiquaient que certaines donnees pouvaient refleter les deplacements de predateurs plutot que ceux des saumoneaux. Afin d'integrer les effets de la predation dans les estimations des taux de survie en decoulant, 11 parametres sommaires associes a la migration de saumoneaux de saumon atlantique et de bars d'Amerique (Morone saxatilis) ont ete compares. Des analyses typologiques ont revele que de 2,4 % a 13,6 % des etiquettes implantees dans des saumoneaux temoignaient d'habitudes migratoires plus semblables a celles de bars d'Amerique qu'a celles d'autres saumoneaux, ce qui a ete interprete comme une preuve de predation. La reaffectation du destin de ces etiquettes a des individus <> s'est traduite par une reduction des taux de survie estimes de 43,5 % a 41,1 % pour 2008, et de 32,6 % a 19,0 % pour 2011, par rapport aux resultats d'un modele de marquage-recapture traditionnel, illustrant ainsi l'effet du biais de predation dans cette etude de cas. [Traduit par la Redaction], Introduction Quantifying the rate and timing of mortality is important for the conservation planning for many fish populations; however, estimating these rates can be difficult given our inability to directly [...]

Acoustic telemetry is a useful tool to monitor the estuarine survival and behaviour of Atlantic salmon postsmolts. Most frequently, survival is reported as the static fraction of tagged postsmolts detected, and while the timing or location of mortality may be reported, covariates of survival or the relationship between migratory behaviour and survival are less often described. In this study, we used acoustic telemetry to follow Atlantic salmon smolts migrating to sea from four rivers in Nova Scotia, Canada. Further, we tested the relationship between migratory behaviour and survival and used mark-recapture models to examine the role of body length and tag-to-body mass as survival covariates. Survival was most heavily impacted in estuarine habitats closest to head-of-tide. Survival was affected by body length at three of four sites. The shape and spatial variability of the body length--survival relationship provided insight on mortality vectors, highlighting the potential roles of predation and osmotic stress. Survival was not influenced by repeated landward-seaward migratory movements; however, there was a significant correlation between residency and survival. La telemetrie acoustique est un outil utile pour la surveillance de la survie et du comportement en estuaire des post-saumoneaux de saumon atlantique. Dans la plupart des cas, le taux de survie signale est la fraction statique de postsaumoneaux marques detectes et, si le moment et le lieu de la mortalite peuvent etre mentionnes, les covariables du taux de survie ou de la relation entre le comportement migratoire et la survie sont moins souvent rapportees. Dans cette l'etude, nous avons fait appel a la telemetrie acoustique pour suivre des saumoneaux de saumon atlantique en migration de la mer vers quatre rivieres de la Nouvelle-Ecosse (Canada). Nous avons en outre verifie le lien entre le comportement migratoire et le taux de survie et utilise des modeles de marquage-recapture pour examiner la longueur du corps et le rapport entre le poids de la marque et celui du corps comme covariables eventuelles du taux de survie. Les impacts sur ce dernier etaient les plus forts dans les habitats estuariens situes les plus pres de la limite de maree. Dans quatre sites, la longueur du corps avait une incidence sur le taux de survie. La forme et la variabilite spatiale de la relation entre la longueur du corps et le taux de survie ont mis en lumiere des vecteurs de mortalite, faisant ressortir un role possible de la predation et du stress osmotique. Si les deplacements migratoires repetes vers la terre ou vers la mer n'avaient pas d'incidence sur le taux de survie, une correlation significative a cependant ete notee entre le temps de residence et le taux de survie. [Traduit par la Redaction], Introduction Atlantic salmon (Salmo salar L.) populations within the southern portion of their North American range have declined dramatically (Parrish et al. 1998; WWF 2001; COSEWIC 2011), due in large [...]

We developed a Bayesian hierarchical model to estimate annual mortality of repeat-spawning Atlantic salmon, Salmo salar, that distinguishes between mortality rates and the confounding effects of consecutive-year and alternate-year repeat-spawning strategies. The model provides annual estimates of two mortality rates: mortality in the first year (Z1), a time period during which salmon are primarily in freshwater (staging, spawning, and overwintering) followed by a brief period at sea, and mortality in the second year (Z2) when salmon are predominantly at sea. When fit to data for the LaHave River (Nova Scotia, Canada) salmon population, Z1 showed an increasing trend throughout the time series, whereas Z2 also increased but in a single, stepwise manner. Once a time series of mortality rates was separated from the other life-history parameters, we were able to demonstrate how they could be used for examining the influence of environmental conditions by comparing the estimated mortality rate time series with the North Atlantic Oscillation Index (NAOI). This comparison uncovered a statistically significant correlation between the NAOI and the survival in the second year after spawning that would not have been evident had the mortality estimation model not been developed. Nous mettons au point un modele hierarchique bayesien afin d'estimer la mortalite annuelle chez le saumon atlantique, Salmo salar, iteropare qui distingue entre les taux de mortalite et les effets confondants des strategies de fraie aux annees consecutives ou aux deux ans. Le modele fournit des estimations annuelles de deux taux de mortalite, la mortalite durant la premiere annee (Z1), une periode de temps pendant laquelle les saumons sont surtout en eau douce (halte migratoire, fraie et hivernage) suivie par une courte periode en mer, et la mortalite durant la seconde annee (Z2) pendant laquelle les saumons sont surtout en mer. Lorsque le modele est ajuste a des donnees provenant de la population de saumons de la riviere LaHave (Nouvelle-Ecosse, Canada), Z1 suit une tendance croissante dans la serie chronologique, alors que Z2 augmente aussi, mais en un seul palier. Une fois qu'une serie chronologique de taux de mortalite est separee des autres variables du cycle biologique, nous avons pu demontrer comment ces taux de mortalite peuvent servir a examiner l'influence des conditions environnementales en comparant la serie chronologique des taux de mortalite et l'indice de l'oscillation nordatlantique (NAOI). Cette comparaison a revele une correlation statistiquement significative entre le NAOI et la survie dans la seconde annee apres la fraie qui n'aurait pas ete evidente sans la mise au point du modele d'estimation de la mortalite. [Traduit par la Redaction], Introduction Widespread declines in Atlantic salmon (Salmo salar) abundance in North America have not abated since the closure of the commercial fisheries (Friedland et al. 2003a; Gibson et al. 2006; [...]

Abstract: We examined relationships between abundance and habitat use in three age classes of juvenile Atlantic salmon (Salmo salar) in the Stewiacke River, Nova Scotia, Canada. Using stream gradient as [...]

Anadromous alewives (Alosa pseudoharengus) are abundant in the Canadian Maritimes, where they support lucrative commercial fisheries. Little is known about their coastal movement, and their potential to interact with anthropogenic structures. Acoustic telemetry can provide detailed information on the spatiotemporal distribution and survival of fishes in coastal areas, using information transmitted from tagged fishes and recorded by moored receivers. However, few acoustic telemetry studies have been performed on clupeids as they are extremely sensitive to handling, and are often compromised by surgical tag implantation. This research assesses the feasibility of a surgical tagging protocol using novel High Residency acoustic tags in alewives, and establishes a baseline of short-term tagging effects. Alewives from the Gaspereau River population were tagged between 2018 (n = 29) and 2019 (n = 96) with non-transmitting models of Vemco/Innovasea V5 HR tags. Tagging effects were evaluated based on recovery rate, reflex impairment, and necropsy-based health assessments. Alewives responded well to tagging, with low mortality (3%) and no observed instances of tag shedding 72 hours post-surgery. The use of sutures to close the incision site had no effect on recovery times. Water temperature and spawning condition had the greatest effect on the behavioural response of fish to tagging. Our findings suggest that, with proper handling and smaller acoustic tags, telemetry studies on alewives are feasible. [ABSTRACT FROM AUTHOR]

To effectively protect at‐risk sharks, resource managers and conservation practitioners must have a good understanding of how fisheries removals contribute to changes in abundance and how regulatory restrictions may impact a population trajectory. This means they need to know the number of animals being removed from a population and whether a given number of removals will lead to population increases or declines. For white shark (Carcharodon carcharias), theoretical quantities like the intrinsic rate of population increase or rebound potential (ability to increase in size following decline) are difficult to conceptualize in terms of real‐world abundance changes, which limits our ability to answer practical management questions. To address this shortfall, we designed a simulation model to evaluate how our understanding of longevity and life history variability of white shark affects our understanding of population trends in the Northwest Atlantic. Then, we quantified the magnitude of removals that could have caused historical population declines, compared these to biologically based reference points, and explored the removal scenarios which would result in population increase. Our results suggest that removals on the order of 100s of juveniles per year could have resulted in population‐level declines in excess of 60% during the 1970s and 1980s. Conservation actions implemented since the 1990s would have needed to be nearly 100% effective at preventing fishing mortality in order for the population to double in abundance over the last 30 years. Total removals from all fleets needed to be exceptionally small to keep them below biological reference points for white shark in the Northwest Atlantic. The population's inherent vulnerability to fishing pressure reaffirms the need for restrictive national and international conservation measures, even under a situation of abundance increase. [ABSTRACT FROM AUTHOR]

Metapopulation structure is typically thought to increase regional species abundance, promote population persistence, and aid in the re-establishment of extirpated populations. However, the underlying theoretical models tended to assume high productivity, making the conservation benefit of metapopulation structure uncertain for endangered species with low productivity. We simulated population assemblages (N = 50) of diadromous fishes under high to low productivity scenarios to explicitly assess how straying (movement from natal to non-natal rivers) contributes to changes in species abundance and extinction risk. The population aggregation exhibited greater total abundance from source–sink dynamics and also exhibited the rescue effect when productivity remained moderately high. However, straying did not ensure persistence of nonviable populations or enable population re-establishment when productivity was low. These results were robust to a wide range of alternate spatial and life-history parameterizations of the simulation model. Relative to a real-world population aggregation of endangered Atlantic salmon (Salmo salar), our results would argue for a shift in remediation priorities to prevent extinction. Although there is strong evolutionary justification for maintaining widespread distributions of endangered diadromous species, the immediate numerical consequences of this approach may hinder recovery. [ABSTRACT FROM AUTHOR]

The production of more than one type of young ones within a single species of marine invertebrate is known as poecilogony. A polychaete poecilogonous is used to investigate potential differences in morphogenesis among offspring.

Quantifying functional relationships between abundance and land use is critical during recovery planning for endangered freshwater and diadromous fishes. However, there is little practical guidance on how much abundance might be expected to change from specific types or magnitudes of land use, making it difficult to identify specific sites for restoration or to prioritize among remediation actions. To address these needs for endangered Atlantic Salmon Salmo salar inhabiting the Southern Upland region of Nova Scotia, Canada, we developed a suite of hierarchical models to evaluate the functional form and magnitude of response of populations to land use at two spatial scales. Juvenile distribution patterns showed a strong longitudinal gradient throughout the stream network, with higher densities occurring in headwaters, which suggests that maintaining connectivity as well as unmodified landscapes in the upper reaches of rivers should be prioritized to aid recovery. Relative to threats, there was no single type of land use that was primarily associated with changes in juvenile abundance. Instead, responses to the combined suite of land‐use types were nonlinear and did not appear dependent on spatial scale. When the proportion of natural forest cover was high, populations appeared to benefit from low levels of anthropogenic land use, declining with increasing human activity only once the average proportion of natural forest cover was low. To use threat relationships in recovery planning, we propose a simple quantitative index based on the extent of development in the vicinity of rivers to identify sites for remediation or protection. To aid future monitoring, we demonstrate why site‐specific electrofishing catchability must be estimated when evaluating population responses to landscape change. [ABSTRACT FROM AUTHOR]

Describing how population-level survival rates are influenced by environmental change becomes necessary during recovery planning to identify threats that should be the focus for future remediation efforts. However, the ways in which data are analyzed have the potential to change our ecological understanding and thus subsequent recommendations for remedial actions to address threats. In regression, distributional assumptions underlying short time series of survival estimates cannot be investigated a priori and data likely contain points that do not follow the general trend (outliers) as well as contain additional variation relative to an assumed distribution (overdispersion). Using juvenile survival data from three endangered Atlantic salmon Salmo salar L. populations in response to hydrological variation, four distributions for the response were compared using lognormal and generalized linear models ( GLM). The influence of outliers as well as overdispersion was investigated by comparing conclusions from robust regressions with these lognormal models and GLMs. The analyses strongly supported the use of a lognormal distribution for survival estimates (i.e., modeling the instantaneous rate of mortality as the response) and would have led to ambiguity in the identification of significant hydrological predictors as well as low overall confidence in the predicted relationships if only GLMs had been considered. However, using robust regression to evaluate the effect of additional variation and outliers in the data relative to regression assumptions resulted in a better understanding of relationships between hydrological variables and survival that could be used for population-specific recovery planning. This manuscript highlights how a systematic analysis that explicitly considers what monitoring data represent and where variation is likely to come from is required in order to draw meaningful conclusions when analyzing changes in survival relative to environmental variation to aid in recovery planning. [ABSTRACT FROM AUTHOR]

The eastern Cape Breton (ECB) designable unit (DU) of Atlantic SalmonSalmo salarcomprises populations in 46 or more rivers in the eastern portion of Cape Breton Island, Nova Scotia, Canada. In 2010, the Committee on the Status of Endangered Wildlife in Canada classified the ECB DU as endangered. In support of recovery planning processes, we developed an integrated, statistical, life history-based model for evaluating the dynamics of populations belonging to this DU. Using maximum likelihood, the model was fitted to recreational fishery catch and effort data, fish counts by divers, intermittent mark–recapture data, and sparse age composition data for two populations in the DU. The model output included estimates of maximum lifetime reproductive rate () and equilibrium population size—parameters that are important for determining extinction risk. Thefor the Middle River population (2.82 spawners/spawner) was double that of the Baddeck River population (1.39 spawners/spawner). Thesevalues would be considered low for Atlantic Salmon populations in general but are higher than those of populations in a neighboring endangered DU to the south. Slightly negative trends in recruitment deviates may indicate declining productivity in the two ECB populations; based on equilibrium analyses, neither population is expected to achieve the proposed recovery targets without an increase in productivity, survival, or both. Atlantic Salmon populations and habitat characteristics in ECB exhibit considerable diversity. Therefore, the dynamics of the Middle River and Baddeck River populations are unlikely to be representative of all populations in the ECB DU. Based on recent trends in recreational fishery catches, these two populations are likely among the healthier populations within the DU. Received July 8, 2014; accepted December 17, 2014 [ABSTRACT FROM AUTHOR]

Typically, juvenile survey data are not used explicitly to determine status, trends, or abundance designations for Atlantic salmon Salmo salar, even though they can be the only source of information for many populations. To determine whether juvenile data can be informative about adult abundance and status in Atlantic salmon, we evaluated the similarities in trends among age-classes for two data-rich populations using a nested log-linear model. We found relatively consistent and significant trends for the age-0, adult and egg time series, but the trends in juvenile density data for older age-classes were less consistent with adult abundance trends. A threshold-based analysis demonstrated that relatively low misclassification rates for adult status relative to a set reference level could be obtained from juvenile density estimates. Together, these results suggest that juvenile density data can be an informative proxy for adult abundance and may be useful as an indicator for large changes in population status relative to reference points. This would make data collection via electrofishing an appropriate monitoring method for fisheries management or conservation programs. However, the validity of the idea that dramatic changes in adult abundance will be mirrored in juvenile data partially depends on the specific age-classes monitored, the survey design, and the timing of density dependence in the population. Using juvenile data as an index would necessitate some prior knowledge of the underlying population dynamics before the method could be applied more generally. [ABSTRACT FROM AUTHOR]

Recovery planning for populations in decline requires a thorough understanding of how life history characteristics, environmental conditions, and human activities interact to determine how abundance changes through time. In a detailed case study of the declining population of Atlantic salmon Salmo salar in the Tobique River, New Brunswick, we demonstrate an equilibrium modeling approach to analyzing the dynamics of the population so as to identify stressors and predict the population-level response to potential recovery actions. Parameter values for the equilibrium analysis were obtained by fitting a life history model to population-specific data, including annual estimates of juvenile density and egg deposition as well as the number and age composition of emigrating smolts. Two unique aspects of the statistical analysis--standardization of the electrofishing data using a generalized linear model and scaling of the juvenile density estimates to total abundance using a catchability coefficient--significantly improved model fits and resulted in parameter estimates that were biologically realistic. The subsequent equilibrium analysis was used to evaluate how population size was expected to change in response to recovery actions focused on fish passage, marine survival, and freshwater production. Recovery actions focused only on freshwater habitat or fish passage were not sufficient to produce an equilibrium population size greater than zero; however, either factor could limit the effectiveness of other recovery actions if not included in the recovery plan. The case study highlights the complex dynamics that can limit population growth, illustrates the need to consider the full life cycle of a species as part of the recovery planning process, and shows that responses to multiple threats may be required to bring about recovery. [ABSTRACT FROM AUTHOR]

We present a method that allows separation of fish mortality caused by handling and capture techniques from that caused by passage through a turbine. Fish that are naturally entrained into the turbine tube are captured with nets deployed in the turbine tailrace for varying lengths of time. The live or dead status of captured fish is modeled as a binomial response that is a function of the duration of net deployment. Within this model, the intercept is an estimate of the mortality of fish that have spent zero time in the net. For species that do not suffer high mortality from other components of the capture process (such as removal from the net), this intercept may be interpreted as an estimate of turbine mortality. If mortality from other components is high, the intercept cannot be interpreted as turbine mortality without correction for mortality from the other sources. We suggest a modification to the model that allows estimation of mortality from these components. We demonstrate the method with data for 12 species of fish captured at the Annapolis Tidal Generating Station, Nova Scotia, Canada. Acute turbine mortality estimates ranged from 0.0% for sea lamprey to 23.4% for American shad . [ABSTRACT FROM AUTHOR]

Provides information on the capture of several rare species of fishes at a hydroelectric generating station, Annapolis Royal, in the Annapolis Basin in Nova Scotia during the fall of 1999. Meek's halfbeak, hyporhampus meeki; Flying Gurnard, dactylopterus volitans; Bluefish, pomatomus saltatrix; Fourbeard rockling, enchelyopus cimbrius.