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File Linking movement and reproductive history of brook trout to assess habitat connectivity in a heterogeneous stream network
1. Defining functional connectivity between habitats in spatially heterogeneous landscapes is a particular challenge for small-bodied aquatic species. Traditional approaches (e.g. mark–recapture studies) preclude an assessment of animal movement over the life cycle (birth to reproduction), and movement of individuals may not represent the degree of gene movement for fecund species. 2. We investigated the degree of habitat connectivity (defined as the exchange of individuals and genes between mainstem and tributary habitats) in a stream brook trout (Salvelinus fontinalis) population using mark–recapture [passive integrated transponder (PIT) tags], stationary PIT-tag antennae and genetic pedigree data collected over 4 years (3425 marked individuals). We hypothesised that: (i) a combination of these data would reveal higher estimates of animal movement over the life cycle (within a generation), relative to more temporally confined approaches, and (ii) movement estimates of individuals within a generation would differ from between-generation movement of genes because of spatial variation in reproductive success associated with high fecundity of this species. 3. Over half of PIT-tagged fish (juveniles and adults) were recaptured within 20 m during periodic sampling, indicating restricted movement. However, continuous monitoring with stationary PIT-tag antennae revealed distinct peaks in trout movements in June and October–November, and sibship data inferred post-emergence movements of young-of-year trout that were too small to be tagged physically. A combination of these methods showed that a moderate portion of individuals (28–33%) moved between mainstem and tributary habitats over their life cycle. 4. Patterns of reproductive success varied spatially and temporally. The importance of tributaries as spawning habitat was discovered by accounting for reproductive history. When individuals born in the mainstem reproduced successfully, over 50% of their surviving offspring were inferred to have been born in tributaries. This high rate of gene movement to tributaries was cryptic, and it would have been missed by estimates based only on movement of individuals. 5. This study highlighted the importance of characterising animal movement over the life cycle for inferring habitat connectivity accurately. Such movements of individuals can contribute to substantial gene movements in a fecund species characterised by high variation in reproductive success.
Located in Science and Data / Brook Trout Related Publications
File text/texmacs Movement Patterns of Brook Trout in a Restored Coastal Stream System in Southern Massachusetts
Populations of anadromous brook trout can be found from northern Canada into New England. It is believed that the extent of anadromy exhibited by coastal brook trout populations decreases with latitude, but the ecology and movements of the more southern populations are less studied. A 33-month acoustic telemetry study of anadromous brook trout (Salvelinus fontinalis) was conducted in a restored coastal stream and adjacent marine system in southeastern Massachusetts. Movement and migration patterns of 54 brook trout were investigated for individual differences and common features. Individuals exhibited a range of movement patterns. Some were more resident and only moved short distances, while others moved great distances covering the entire stretch of the stream (7.25 km) and moving into the marine environment. General Additive Mixed Models revealed that date was the major influence on brook trout movement between habitats and predicted peaks in movement in the spring and fall. Downstream movement peaked in the spring and in the fall, suggesting post-spawning feeding migration. Fish transitioned between habitats more often at new and full moons and when stream temperature was between 8 and 12 °C. Upstream transitions peaked as temperatures declined in winter 2011. Fifty percent of tagged brook trout were detected in the estuary during the study, suggesting that it is an important habitat for the population. In summer 2012, 14 tagged brook trout (20% of active tags) resided near one receiver at the head of the tide, which contained a thermal refugium in the form of a cold-water spring seep. Of the 84 tagged brook trout, 9.5% moved to the marine environment. Warm temperatures in saline Buttermilk Bay in the summer and cold temperatures in winter probably discourage some individuals from entering the marine environment. Compared to more northern coastal populations of brook trout, the Red Brook population appears to be less anadromous.
Located in Science and Data / Brook Trout Related Publications
File Population regulation of brook trout (Salvelinus fontinalis) in Hunt Creek, Michigan: a 50-year study
1. Fisheries models generally are based on the concept that strong density dependence exists in fish populations. Nonetheless, there are few examples of long-term density dependence in fish populations. 2. Using an information theoretical approach (AIC) with regression analyses, we examined the explanatory power of density dependence, flow and water temperature on the per capita rate of change and growth (annual mean total length) for the whole population, adults, 1+ and young-of-the-year (YOY) brook trout (Salvelinus fontinalis) in Hunt Creek, Michigan, USA, between 1951 and 2001. This time series represents one of the longest quantitative population data sets for fishes. 3. Our analysis included four data sets: (i) Pooled (1951–2001), (ii) Fished (1951–65), (iii) Unfished (1966–2001) and (iv) Temperature (1982–2001). 4. Principle component analyses of winter flow data identified a gradient between years with high mean daily winter flows, high daily maximum and minimum flows and frequent high flow events, and years with an opposite set of flow characteristics. Flows were lower during the Fished Period than during the Unfished Period. Winter temperature analyses elucidated a gradient between warm mean, warm minimum and maximum daily stream temperatures and a high number of minimum daily temperatures >6.1 C, and years with the opposite characteristics. Summer temperature analyses contrasted years with warm summer stream temperatures vs years with cool summer stream temperatures. 5. Both YOY and adult densities varied several-fold during the study. Regression analysis did not detect a significant linear or nonlinear stock–recruitment relationship. AIC analysis indicated that density dependence was present in 15 of 16 cases (four population segments · four data sets) for both per capita rate of increase (wi values 0.46–1.00) and growth data (wi values 0.28–0.99). The almost ubiquitous presence of density dependence in both population and growth data is concordant with results from other trout populations and other studies in Michigan.
Located in Science and Data / Brook Trout Related Publications
File Population Response to Habitat Fragmentation in a Stream-Dwelling Brook Trout Population
Fragmentation can strongly influence population persistence and expression of life-history strategies in spatially-structured populations. In this study, we directly estimated size-specific dispersal, growth, and survival of stream-dwelling brook trout in a stream network with connected and naturally-isolated tributaries. We used multiple-generation, individual-based data to develop and parameterize a size-class and location-based population projection model, allowing us to test effects of fragmentation on population dynamics at local (i.e., subpopulation) and system-wide (i.e., metapopulation) scales, and to identify demographic rates which influence the persistence of isolated and fragmented populations. In the naturally-isolated tributary, persistence was associated with higher early juvenile survival (,45% greater), shorter generation time (one-half) and strong selection against large body size compared to the open system, resulting in a stage-distribution skewed towards younger, smaller fish. Simulating barriers to upstream migration into two currently-connected tributary populations caused rapid (2–6 generations) local extinction. These local extinctions in turn increased the likelihood of system-wide extinction, as tributaries could no longer function as population sources. Extinction could be prevented in the open system if sufficient immigrants from downstream areas were available, but the influx of individuals necessary to counteract fragmentation effects was high (7–46% of the total population annually). In the absence of sufficient immigration, a demographic change (higher early survival characteristic of the isolated tributary) was also sufficient to rescue the population from fragmentation, suggesting that the observed differences in size distributions between the naturally-isolated and open system may reflect an evolutionary response to isolation. Combined with strong genetic divergence between the isolated tributary and open system, these results suggest that local adaptation can ‘rescue’ isolated populations, particularly in one-dimensional stream networks where both natural and anthropogenically-mediated isolation is common. However, whether rescue will occur before extinction depends critically on the race between adaptation and reduced survival in response to fragmentation.
Located in Science and Data / Brook Trout Related Publications
File Predicting Brook Trout Occurrence in Stream Reaches throughout their Native Range in the Eastern United States - DeWeber and Wagner 2015
This publication describes a model that was developed to predict Brook Trout population status within individual stream reaches throughout the species' native range in the eastern USA.
Located in Science and Data / Brook Trout Related Publications / Chesapeake Bay Brook Trout Management Strategy-References
File ECMAScript program Predicting Brook Trout Occurrence in Stream Reaches throughout their Native Range in the Eastern United States
The Brook Trout Salvelinus fontinalis is an important species of conservation concern in the eastern USA. We developed a model to predict Brook Trout population status within individual stream reaches throughout the species’ native range in the eastern USA. We utilized hierarchical logistic regression with Bayesian estimation to predict Brook Trout occurrence probability, and we allowed slopes and intercepts to vary among ecological drainage units (EDUs). Model performance was similar for 7,327 training samples and 1,832 validation samples based on the area under the receiver operating curve (»0.78) and Cohen’s kappa statistic (0.44). Predicted water temperature had a strong negative effect on Brook Trout occurrence probability at the stream reach scale and was also negatively associated with the EDU average probability of Brook Trout occurrence (i.e., EDU-specific intercepts). The effect of soil permeability was positive but decreased as EDU mean soil permeability increased. Brook Trout were less likely to occur in stream reaches surrounded by agricultural or developed land cover, and an interaction suggested that agricultural land cover also resulted in an increased sensitivity to water temperature. Our model provides a further understanding of how Brook Trout are shaped by habitat characteristics in the region and yields maps of stream-reach-scale predictions, which together can be used to support ongoing conservation and management efforts. These decision support tools can be used to identify the extent of potentially suitable habitat, estimate historic habitat losses, and prioritize conservation efforts by selecting suitable stream reaches for a given action. Future work could extend the model to account for additional landscape or habitat characteristics, include biotic interactions, or estimate potential Brook Trout responses to climate and land use changes.
Located in Science and Data / Brook Trout Related Publications
File Probabilistic measures of climate change vulnerability, adaptation action benefits, and related uncertainty from maximum temperature metric selection
Predictions of the projected changes in species distribution models and potential adaptation action benefits can help guide conservation actions. There is substantial uncertainty in projecting species distributions into an unknown future, however, which can undermine confidence in predictions or misdirect conservation actions if not properly considered. Recent studies have shown that the selection of alternative climate metrics describing very different climatic aspects (e.g., mean air temperature vs. mean precipitation) can be a substantial source of projection uncertainty. It is unclear, however, how much projection uncertainty might stem from selecting among highly correlated, ecologically similar climate metrics (e.g., maximum temperature in July, maximum 30-day temperature) describing the same climatic aspect (e.g., maximum temperatures) that is known to limit a species’ distribution. It is also unclear how projection uncertainty might propagate into predictions of the potential benefits of adaptation actions that might lessen climate change effects. We provide probabilistic measures of climate change vulnerability, adaptation action benefits, and related uncertainty stemming from the selection of four maximum temperature metrics for brook trout (Salvelinus fontinalis), a cold-water salmonid of conservation concern in the eastern U.S. Projected losses in suitable stream length varied by as much as 20% among alternative maximum temperature metrics for mid-century climate projections, which was similar to variation among three climate models. Similarly, the regional average predicted increase in brook trout occurrence probability under an adaptation action scenario of full riparian forest restoration varied by as much as 0.2 among metrics. Our use of Bayesian inference provides probabilistic measures of vulnerability and adaptation action benefits for individual stream reaches that properly address statistical uncertainty and can help guide conservation actions. Our study demonstrates that even relatively small differences in the definitions of climate metrics can result in very different projections and reveal high uncertainty in predicted climate change effects.
Located in Science and Data / Brook Trout Related Publications
File chemical/x-pdb Quantifying the effect of semi-natural riparian cover on stream temperatures: implications for salmonid habitat management
Previous studies examining the effects of riparian cover on stream temperatures have led to highly variable findings. In an attempt to reduce these uncertainties, this study examines the relationship between stream temperature variability and local climatic conditions over discrete 300-m sections of a watercourse. Seventeen stream sections were chosen within the Slaney catchment on the basis of riparian cover and size. Continuous monitoring over a 2-year period from May 2010 found that riparian cover had a measurable cooling effect on water temperatures at small spatial scales. The magnitude of this effect was dependent on stream size and local climactic conditions.
Located in Science and Data / Brook Trout Related Publications
File Response of fish assemblages to declining acidic deposition in Adirondack Mountain lakes, 1984-2012
Adverse effects of acidic deposition on the chemistry and fish communities were evident in Adirondack Mountain lakes during the 1980s and 1990s. Fish assemblages and water chemistry in 43 Adirondack Long-Term Monitoring (ALTM) lakes were sampled by the Adirondack Lakes Survey Corporation and the New York State Department of Environmental Conservation during three periods (1984-87, 1994-2005, and 2008-12) to document regional impacts and potential biological recovery associated with the 1990 amendments to the 1963 Clean Air Act (CAA). We assessed standardized data from 43 lakes sampled during the three periods to quantify the response of fish-community richness, total fish abundance, and brook trout (Salvelinus fontinalis) abundance to declining acidity that resulted from changes in U.S. airquality management between 1984 and 2012. During the 28-year period, mean acid neutralizing capacity (ANC) increased significantly from 3 to 30 meq/L and mean inorganic monomeric Al concentrations decreased significantly from 2.22 to 0.66 mmol/L, yet mean species richness, all species or total catch per net night (CPNN), and brook trout CPNN did not change significantly in the 43 lakes. Regression analyses indicate that fishery metrics were not directly related to the degree of chemical recovery and that brook trout CPNN may actually have declined with increasing ANC. While the richness of fish communities increased with increasing ANC as anticipated in several Adirondack lakes, observed improvements in water quality associated with the CAA have generally failed to produce detectable shifts in fish assemblages within a large number of ALTM lakes. Additional time may simply be needed for biological recovery to progress, or else more proactive efforts may be necessary to restore natural fish assemblages in Adirondack lakes in which water chemistry is steadily recovering from acidification.
Located in Science and Data / Brook Trout Related Publications
File Restoration of brook trout across their native range using fish toxicants and electrofishing: are we successful ecologically and socially?
PDF of PowerPoint presentation by Matt Kulp, fishery biologist with the Great Smoky Mountains National Park, and coauthors, reviewing historic and contemporary restoration efforts to restore brook trout using toxicants and electrofishing. Matt surveyed state and agency biologists about projects to remove invasive species and replace brook trout. This presentation and associated database describe the outcomes and factors in success and failures.
Located in Science and Data / Brook Trout Related Publications
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