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Adfluvial brook trout Salvelinus fontinalis populations in the Lake Superior basin have suffered declines over the last century due to habitat degradation and exploitation. Natural resources agencies throughout the basin have restored habitat and implemented restrictive angling regulations as tools to protect remnant coaster brook trout populations, but the success of these practices is unknown in some locations. We used electrofishing and passive integrated transponder (PIT) tag movement data from 2008 to 2020 to describe population characteristics, temporal trends, and adfluvial life history of coaster brook trout in Washington Harbor, Isle Royale National Park, Lake Superior after implementation of catch-and-release regulations in 2004. Our results document the presence of an adfluvial coaster brook trout population in Washington Harbor, Isle Royale. Temporal trends indicate that brook trout abundance and distribution in Washington Harbor increased since earlier observations in the late 1990s and early 2000s likely due to enactment of protective regulations, and increased stream flows and water levels observed in recent years in both Washington Creek and Lake Superior, respectively. Annual tag detection of Washington Harbor brook trout in Washington Creek at the antenna arrays varied from 25% in 2009 to 100% in 2011 and 2013, and averaged 60.7% throughout the study. Peak in adfluvial brook trout use of Washington Creek was from August – October with few detections occurring outside of the presumed spawning period. This study provides valuable insight into the population characteristics, movement patterns, and temporal increase in abundance of an adfluvial brook trout population in Lake Superior. [ABSTRACT FROM AUTHOR]

We conducted a large-scale assessment of unconventional oil and gas (UOG) development effects on brook trout ( Salvelinus fontinalis ) distribution. We compiled 2231 brook trout collection records from the Upper Susquehanna River Watershed, USA. We used boosted regression tree (BRT) analysis to predict occurrence probability at the 1:24,000 stream-segment scale as a function of natural and anthropogenic landscape and climatic attributes. We then evaluated the importance of landscape context (i.e., pre-existing natural habitat quality and anthropogenic degradation) in modulating the effects of UOG on brook trout distribution under UOG development scenarios. BRT made use of 5 anthropogenic (28% relative influence) and 7 natural (72% relative influence) variables to model occurrence with a high degree of accuracy [Area Under the Receiver Operating Curve (AUC) = 0.85 and cross-validated AUC = 0.81]. UOG development impacted 11% ( n = 2784) of streams and resulted in a loss of predicted occurrence in 126 (4%). Most streams impacted by UOG had unsuitable underlying natural habitat quality ( n = 1220; 44%). Brook trout were predicted to be absent from an additional 26% ( n = 733) of streams due to pre-existing non-UOG land uses (i.e., agriculture, residential and commercial development, or historic mining). Streams with a predicted and observed (via existing pre- and post-disturbance fish sampling records) loss of occurrence due to UOG tended to have intermediate natural habitat quality and/or intermediate levels of non-UOG stress. Simulated development of permitted but undeveloped UOG wells ( n = 943) resulted in a loss of predicted occurrence in 27 additional streams. Loss of occurrence was strongly dependent upon landscape context, suggesting effects of current and future UOG development are likely most relevant in streams near the probability threshold due to pre-existing habitat degradation. [ABSTRACT FROM AUTHOR]

Ecosystem impacts due to invasive species continue to attract significant conservation effort worldwide. In aquatic ecosystems, physical interventions such as suppression and eradication of non-native species are typically expensive, long-term commitments, with few examples of lasting success in the absence of significant ongoing effort. Control of non-native species is a major conservation and restoration challenge, as a species' demographic resilience and connectivity within networks can limit the ability of suppression or eradication efforts to influence populations. Simulation tools can provide valuable insights for the management of these systems - from evaluation of tradeoffs between time and effort to prediction of relative success rates of alternative strategies in changing environments. In the Pacific Northwest region of the U.S., the eastern brook trout (EBT; Salvelinus fontinalis ) is a non-native invasive species that competes with native fish species across a wide spatial scale due to extensive human-mediated introduction starting in the early 20th century. The goal of this study was to simulate the individual movement and demographics of EBT before, during, and following implementation of control efforts in tributaries within the Pend Oreille River watershed. The ultimate purpose of the model was to inform mitigation decisions through the investigation of alternative management actions in an adaptive management framework. Our results indicate that eradication of EBT is improbable in large systems via electrofishing, but suppression is a viable alternative given sustained management efforts. Changes to scheduling, effort, and length of electrofishing suppression treatments had minimal effects on EBT population recovery times. We reproduced the effects of compensatory responses to control treatments, including increases in juvenile survival and emigration rates, and demonstrated that these mechanisms are likely drivers of recovery following treatment. Our study highlights the many benefits of incorporating spatially explicit, individual-based models into management plans for the control of invasive species. [ABSTRACT FROM AUTHOR]

We provide an assessment of thermal characteristics and climate change vulnerability for brook trout ( Salvelinus fontinalis ) habitats in the upper Shavers Fork sub-watershed, West Virginia. Spatial and temporal (2001–2015) variability in observed summer (6/1–8/31) stream temperatures was quantified in 23 (9 tributary, 14 main-stem) reaches. We developed a mixed effects model to predict site-specific mean daily stream temperature from air temperature and discharge and coupled this model with a hydrologic model to predict future (2016–2100) changes in stream temperature under low (RCP 4.5) and high (RCP 8.5) emissions scenarios. Observed mean daily stream temperature exceeded the 21 °C brook trout physiological threshold in all but one main-stem site, and 3 sites exceeded proposed thermal limits for either 63- and 7-day mean stream temperature. We modeled mean daily stream temperature with a high degree of certainty ( R 2 = 0.93; RMSE = 0.76 °C). Predicted increases in mean daily stream temperature in main-stem and tributary reaches ranged from 0.2 °C (RCP 4.5) to 1.2 °C (RCP 8.5). Between 2091 and 2100, the average number of days with mean daily stream temperature > 21 °C increased within main-stem sites under the RCP 4.5 (0–1.2 days) and 8.5 (0 − 13) scenarios; however, no site is expected to exceed 63- or 7-day thermal limits. During the warmest 10 years, ≥ 5 main-stem sites exceeded the 63- or 7-day thermal tolerance limits under both climate emissions scenarios. Years with the greatest increases in stream temperature were characterized by low mean daily discharge. Main-stem reaches below major tributaries never exceed thermal limits, despite neighboring reaches having among the highest observed and predicted stream temperatures. Persistence of thermal refugia within upper Shavers Fork would enable persistence of metapopulation structure and life history processes. However, this will only be possible if projected increases in discharge are realized and offset expected increases in air temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • No microplastic items were found in water and zooplankton samples. • Low microplastic items were found in sediment, tadpoles, and fish. • Young fish resulted more contaminated by microplastic items. • Shape, color, and chemical type of microplastics were the same in all compartments. • Salvelius fontinalis could be a good bioindicator of microplastic pollution. Microplastic (MP) pollution is a major environmental concern for mountain ecosystem and for high-mountain lakes in particular, which are recognized indicators of global change. In this study, the presence of MPs was assessed in abiotic (water and sediment) and biotic (zooplankton, tadpoles, fish) compartments of two high-mountain lakes (Upper Lake Balma and Lower Lake Balma) in the Cottian Alps (northwest Italy). No MPs were found in water and zooplankton samples, whereas the mean MPs in sediment samples was 1.33 ± 0.67 items/m3 and 1.75 ± 0.62 items/m3 in Lower and Upper Lake Balma, respectively. The mean MPs in tadpoles of Rana temporaria was 0.33 ± 0.58 items/individual and 0.66 ± 0.58 items/individual in Lower and Upper Lake Balma, respectively. The mean number of MPs items found in the gastrointestinal tract (GIT) of fish (Salvelinus fontinalis) was considerably higher in specimens from the Lower (0.45 items/g GIT) than in those from the Upper Lake (0.20 items/g GIT). There was a negative relationship between fish size (weight and age) and MPs abundance in the GIT of fish, indicating that young fish accumulated more MP items probably due to the high prey ingestion rate compared to adults. The same MPs color (blue, white, black), shape (fibers and fragments), and chemical type (polypropylene and polyethylene) were found in the compartments of both lakes. Our findings suggest the use of S. fontinalis as an indicator of MP pollution in high-mountain lakes. Further studies are needed to better understand the sources and the effects of MPs in these remote ecosystems. [ABSTRACT FROM AUTHOR]

• Upland streams of New England frequently experience low pH, high inorganic Al conditions. • Acid-Al conditions are related to season, site buffer conditions and elevation. • Fish diversity and abundance is reduced at sites with high acid-Al. • Salmonid gill Al accumulation is significantly increased at sites with high acid-Al. • Elevated acid-Al impairs osmoregulatory proteins of Atlantic salmon. In spite of overall improvements in air and water quality, biological stress from low pH and high concentrations of inorganic aluminum continue to impact fish and fish habitat in northeastern North America, with independent and interactive effects on individuals, populations and communities. Integrative indicators can therefore be useful in monitoring both impact and recovery across multiple scales. Using coupled water chemistry (pH, conductivity, and base cation and inorganic aluminum concentration), geographic (site elevation and watershed area) and biological (fish diversity, fish abundance, gill aluminum concentration and gill physiology) data, we developed an integrated indicator of acid-aluminum stress across the White and Green mountains in central New England, USA. As has been established in a number of previous studies, preliminary analysis clearly indicated that across all sites, inorganic aluminum concentration was consistently greatest during the spring season. Structural Equation modeling (SEM) revealed that toxic conditions (concurrent low pH and high concentrations of inorganic aluminum) were well summarized with an integrated toxicity score, related to both base cation concentrations and elevation, with sites at higher elevations more likely to experience toxic conditions as well as low base cation concentrations. Fish diversity and abundance generally trended negatively with toxicity score, with fewer cyprinids and sculpins at high toxicity score sites. In spite of considerable variation among individuals, gill aluminum was positively related to toxicity score for both Atlantic salmon and brook trout. Observed elevated gill aluminum levels associated with reduced gill metabolic activity in Atlantic salmon smolts from impacted systems likely result in impaired osmoregulatory function and seawater tolerance. Overall, our results suggest that the integrated toxicity score metric is associated with a syndrome of acute physiological stress, reduced abundance, and low species diversity for sensitive stream fishes in New England, and can likely serve as a reliable indicator of continued impairment or recovery of acid-aluminum vulnerable systems in this ecoregion. [ABSTRACT FROM AUTHOR]

There is mounting evidence that populations of brook trout (Salvelinus fontinalis) inhabiting bays and tributaries along the north shore of Lake Superior exhibit partial migration. In this system some fish originate in tributaries and move into the lake for much of the year, grow large and migrate back into tributaries to spawn, whilst other smaller fish reside in tributaries and grow slowly. This study determined whether the stream dwelling brook trout reach sexual maturity in the stream habitats, a criterion needed to distinguish partial migration from other forms of migration that could maintain divergent forms and life histories of brook trout. Maturational development was determined for fish collected in July and August. Sampling these populations during fall spawning was not permitted due to conservation concerns. Male and females sampled from tributaries displayed δ13C signatures and growth histories characteristic of stream residency. Assessment of maturational development suggested that 33% of females would have been expected to spawn in the fall of that year. Our findings demonstrate that a portion of fish residing in tributaries reach sexual maturity without adopting summer residency in the lake providing evidence for partial migration over other forms of migration. Improved understanding of the variation in migratory behaviour in these brook trout populations will contribute to their conservation and management in the face of lake-wide declines of the migrant fish. [ABSTRACT FROM AUTHOR]

Abstract: A Mid-Atlantic multimetric index provides a quick and cost effective assessment of brook trout streams or potential brook trout streams in the Mid-Atlantic United States. Using five core metrics – three in-stream metrics (riffle/run quality, dissolved oxygen content and water temperature) and two watershed metrics (percent land use in agriculture and distance to the nearest road from the survey site), the index can be calculated in the field by professional natural resource managers or trained volunteers. The index should be used in concert with other assessment tools, including a classification model designed to allow resource managers to quickly screen a given stream reach in order to determine its potential for supporting sustainable populations of brook trout. Used in tandem, the classification model could provide a preliminary assessment of a stream, followed by a secondary assessment using an index rating to further evaluate stream quality and potential. [Copyright &y& Elsevier]

Abstract: Industrial fish production exposes fish to potentially stressful conditions, which in turn may induce infections by opportunistic pathogens. Probiotics appear to be a promising way to prevent opportunistic infections in aquaculture. In this study, we tested the inhibitory potential of endogenous bacterial communities found in the mucus of brook charr (Salvelinus fontinalis) against two major pathogens Flavobacterium columnare and Flavobacterium psychrophilum. Nine bacterial strains were isolated from brook charr skin mucus and tested for potential antagonistic activity. Results from both agar diffusion assays and broth co-culture assays showed the presence of antagonism. We identified seven bacterial strains, collected from unstressed fish, which exerted strong antagonism against F. psychrophilum and/or F. columnare. These strains were mixed and used to treat columnaris disease in an in vivo experiment in which four distinct fish families were tested. This treatment resulted in a decrease of mortality (54–86%) across fish families indicating that candidates from the host microbiota are potentially suitable for probiotic development. This would allow for the efficient (ability to adhere and colonize the host mucus) and durable management (antagonistic effect against pathogens which would be harmless for the host and safe for its environment) of opportunistic diseases in aquaculture. [Copyright &y& Elsevier]

Abstract: Genetic differentiation among brook trout (Salvelinus fontinalis) of different life history forms and populations can result from reproductive isolation imposed by natural or anthropogenically derived barriers to gene flow, behavioral incompatibilities, or differential exposure to environmental cues. We used multi-locus microsatellite genotypes and likelihood and Bayesian-based analyses to characterize the degree of genetic differentiation and evidence of introgression among stream resident brook trout above a natural barrier, and putative stream residents and adfluvial (coaster) brook trout from below the barrier in the Salmon Trout River (STR); the sole tributary along the southern shore of Lake Superior known to be inhabited by a viable remnant population of coaster brook trout. Two genetically differentiated populations were identified, generally associated with individuals inhabiting sections of the STR above and below the falls. No evidence of differentiation was found between a priori classified resident and coaster brook trout from below the falls. Gene flow from individuals above the falls was detected based on evidence of interbreeding between upper river individuals and coasters below the falls. We collected only a relatively small number of individuals that we a priori classified as being stream residents below the falls, and these individuals had a high probability of having ancestry originating from the population above the barrier, which suggests that the stream-resident life history may be exceptionally rare or absent in the lower Salmon Trout River. [Copyright &y& Elsevier]

Abstract: As concerns for losses of migratory species heighten globally, scientists are being challenged to characterize diversity in the migratory behaviors to support scientifically defensible conservation programs. Anecdotal observations of brook trout (Salvelinus fontinalis) inhabiting Lake Superior and its tributaries suggest the occurrence of two forms: a large lake form hypothesized to originate in streams and reside in Lake Superior for significant parts of the year and a small stream form hypothesized to be stream resident. Declines in the lake form are a conservation concern and understanding of the variation in migratory behavior is needed to assist conservation efforts. We used analyses of vertebrae and otoliths to test whether the growth histories of lake and stream caught fish differed as expected for adult and juvenile stages from a migratory population (migration), individuals differing in the age of outmigration to the lake (staggered migration), or a combination of residents and migrants (partial migration). Lake caught fish grew faster and lived longer than stream caught fish and differences in length-at-age were apparent by the end of the first year of life. There was no evidence of individuals abruptly changing growth history in a way that would suggest habitat switches later in life. Growth histories of lake and stream caught brook trout were also similar to those of migrants and residents from other brook trout populations or sub-populations. Our findings support the hypothesis of partial migration as an explanation for the diversity observed in Lake Superior brook trout and demonstrate how analyses of growth histories can help clarify migratory systems in species whose movements are challenging to track. [Copyright &y& Elsevier]

Abstract: Brook trout (Salvelinus fontinalis) are a commercially important coldwater species reared in Wisconsin and the Midwestern United States. Brook trout are raised by private, tribal, state, and federal fish hatchery facilities in Wisconsin. Approximately 10% of private coldwater aquaculture operations are presently raising brook trout of various strains for stocking uses and a limited amount for food markets. Growing brook trout to a larger size, if they can be reared in a shorter time span, may present a potential new sector for the aquaculture market in the Midwestern US. The present study reports hatchery production attributes, i.e., growth, survival, fin condition, feed efficiency, water chemistry requirements and general husbandry of Lake Superior strain (Nipigon) brook trout reared in a recirculating aquaculture system (RAS), operated at an average temperature of 13°C. The recycle system at NADF reared 1379kg of brook trout over a 10-month period from fingerling (9g) to market size (340–454g). The trout grew faster (0.84g/day and 0.64mm/day) in the RAS than fish cultured in traditional flow-through tank culture utilizing ground water at 7.6°C (0.14g/day and 0.35mm/day). Final average weight of RAS fish was 260g, while the flow-through fish averaged 65g. Final tank densities for the RAS averaged 40.4kg/m3 while flow-through tanks averaged 31.2kg/m3. Throughout the project, feed conversions in the RAS ranged from 0.9 to 1.3. Water quality variables such as TAN, nitrite, DO, temperature, TSS, CO2, ph, etc. were within safe limits for brook trout and will be discussed. It does appear from this initial research project that market size brook trout can be raised successfully in a recycle system within a similar time frame as a rainbow trout produced in a Wisconsin typical flow-through facility. [Copyright &y& Elsevier]

Abstract: Brook trout (Salvelinus fontinalis) are found throughout Lake Superior, Lake Nipigon, and their tributaries. Lacustrine and adfluvial life history variants were historically popular with anglers and were called coasters; coaster brook trout populations are now severely reduced and are of conservation concern. Coasters were known to grow larger and mature later than their stream resident counterparts. This study compared movement patterns, age, size, condition, and relative weight of wild coaster and resident brook trout from the Hurricane River, Pictured Rocks National Lakeshore, Michigan. Wild brook trout ≥100 mm from the Hurricane River downstream from Hurricane Falls were tagged with passive integrated transponder tags and monitored for stream-lake movement behavior from May 2003 to November 2007. During 2006 and 2007, brook trout were scale sampled and aged to construct a regression that was then used to calculate the age of all brook trout tagged from 2003 to 2007. Most brook trout movement took place in the fall with October the peak month of emigration with a secondary peak in late spring/early summer and some activity nearly year round. There were no differences found in age structure, size or condition between coasters and residents while in the stream. Our data suggest that a priori growth differences are not determining the expression of coaster outmigration and that stream-lake movements made by coasters, likely driven by habitat requirements, may be highly flexible and facultative. [Copyright &y& Elsevier]

Abstract: Recent advances towards the production of all-female populations of brook trout Salvelinus fontinalis have shown that methyltestosterone treatments applied after first feeding were not efficient in inducing masculinisation in neomales. A process to create all-female populations of brook trout using methyltestosterone was determined from 4 experiments. Different protocols of masculinisation by oral and/or hormonal immersion treatments were tested and the sex ratio of progeny produced from the cross of sex-reversed gynogenetic males with normal females was checked. No sexual dimorphism for growth was recorded, at least until two years of age. Masculinisation trials using oral treatments failed to produce any reversal of sex. Only the application of four weekly immersions beginning one week before hatching, combined with an oral treatment, provided 100% masculinisation. Gynogenetic sex-reversed males crossed with normal females produced 100% females, demonstrating the efficiency of this protocol in reversing the sex of brook trout. This result also highlights an earlier and longer period of sex lability, compared with most other Salmonids, and the need to initiate immersion treatments a long time before the initiation of gonadal differentiation. [Copyright &y& Elsevier]

Abstract: Distributions of species, animals or plants, terrestrial or aquatic, are influenced by numerous factors such as physical and biogeographical gradients. Dominant wind and current directions cause the appearance of gradients in physical conditions whereas biogeographical gradients can be the result of historical events (e.g. glaciations). No spatial modelling technique has been developed to this day that considers the direction of an asymmetric process controlling species distributions along a gradient or network. This paper presents a new method that can model species spatial distributions generated by a hypothesized asymmetric, directional physical process. This method is an eigenfunction-based spatial filtering technique that offers as much flexibility as the Moran''s eigenvector maps (MEM) framework; it is called asymmetric eigenvector maps (AEM) modelling. Information needed to construct eigenfunctions through the AEM framework are the spatial coordinates of the sampling or experimental sites, a connexion diagram linking the sites to one another, prior information about the direction of the hypothesized asymmetric process influencing the response variable(s), and optionally, weights attached to the edges (links). To illustrate how this new method works, AEM is compared to MEM analysis through simulations and in the analysis of an ecological example where a known asymmetric forcing is present. The ecological example reanalyses the dietary habits of brook trout (Salvelinus fontinalis) sampled in 42 lakes of the Mastigouche Reserve, Québec. [Copyright &y& Elsevier]

Abstract: Pathogen-driven selection is believed to be important in the evolution and maintenance of the polymorphism of the major histocompatibility complex (MHC) genes but have been tested for very few vertebrates. In this study, we first investigate by SSCP (single strand conformational polymorphism) the diversity found at the MHC class IIβ gene in a population of brook charr (Salvelinus fontinalis) from the Rupert River (Québec, Canada). Secondly, to explore the survival performances conferred by specific alleles and genotypes, individuals from 23 half- and full-sibling families were infected with Aeromonas salmonicida, the causative agent of furonculosis. From the initial brook charr population, a total of six MHC class IIβ alleles were identified; four complete and two partial coding sequences that include the complete polymorphic β1 domain. One allele, Safo-DAB*0101, was significantly associated with resistance against A. salmonicida. In addition to homozygotes for this allele, its resistance effect was also detected in heterozygotes for two specific genotypes. Other allelic combinations, namely heterozygous genotypes Safo-DAB*0201/*0301 and Safo-DAB*0301/*0401 were significantly associated with increased susceptibility to furonculosis. Given that its frequency was relatively low (0.0873), the negative frequency-dependent selection hypothesis could explain the advantage associated with the allele Safo-DAB*0101 over the other alleles and highlight the importance of this mechanism to sustain variation at the MHC in brook charr. [Copyright &y& Elsevier]

Abstract: Rainbow trout (Oncorhynchus mykiss) display longitudinal and developmental shifts in muscle relaxation rate. This study aimed to determine the role of variations in parvalbumin content in modulating muscle relaxation. Parvalbumin is a low molecular weight protein that buffers myoplasmic Ca2+ and enhances muscle relaxation. In some fish, longitudinal variations in muscle relaxation have been linked to variations in the total amount of parvalbumin present in muscle and in the relative expression of two parvalbumin isoforms. We have demonstrated previously that anterior slow-twitch or red myotomal muscle relaxes more rapidly than that from the posterior for both rainbow and brook trout. Further, younger rainbow trout parr have faster red muscle relaxation rates than older smolts. Here we report similar results for fast-twitch or white muscle. We quantified the parvalbumin expression in red and white muscle from different body positions of rainbow trout parr and smolts and for brook trout (Salvelinus fontinalis) adults. There was a significant shift in total parvalbumin content of muscle: the faster muscle from the anterior myotome contained greater amounts of parvalbumin. For brook trout, longitudinal variation in relaxation rate was also associated with shifts in the relative expression of the two parvalbumin isoforms. The faster muscle of parr contained more parvalbumin. Lastly, trout white muscle tended to have higher levels of parvalbumin and greater levels of the Parv2 (relative to Parv1) isoform as compared to red muscle. Parvalbumin expression correlated with muscle relaxation rate in trout, although there were species-specific differences in the importance of altering total parvalbumin content versus shifts in relative parvalbumin isoform expression. [Copyright &y& Elsevier]

Abstract: The present paper analyses predation patterns, of Percichthys trucha and salmonid fish upon Galaxias maculatus in five lakes of northern Patagonia with differing community and environmental characteristics. Tank experiments were performed to evaluate relative efficiency of native and exotic predators of G. maculatus under treatments with and without cover (aquatic vegetation). Important differences were found between predators with regards to distribution and consumption of G. maculatus. Salmonids are more efficient than P. trucha in consuming G. maculatus in deep environments with scarcely vegetation; in contrast to native species they frequently use the pelagic environment. Although pelagic habitat might have served in the past as a refuge from native predators in the past, G maculatus now experiences intense predation in the pelagic zone by exotic salmonids. It is suggested that the widespread distribution of G. maculatus in Patagonian lakes may have facilitated the success of salmonids throughout Patagonia. [Copyright &y& Elsevier]

Abstract: In fish, the first line of defence against infectious microorganisms is based on non-specific cellular immune mechanisms (innate immunity). In this study, we measured the non-specific immune parameters (natural cytotoxic cells (NCC) activity, lymphoproliferation, percentage of phagocytosis and phagocytic activity) in brook trout (Salvelinus fontinalis) infected by a virulent strain of Aeromonas salmonicida. Eight days post-infection, the mortality of infected fish reached 70%. A transient immunostimulation of the NCC activity was noticed 24h post-infection, but there was no significant difference at 48h. Then, infection of brook trout with A. salmonicida induced a biphasic immune response. At 24h post-infection, lymphoproliferation was drastically depressed but returned to control level at 96h. A slight increase in the percentage of phagocytosis and the phagocytic activity was noticed throughout the experiment. Conversely the cell mortality was significantly higher in infected fish compared to control. The modulation of immunological parameters might reveal important clues on how innate immunity might protect fish from bacterial infections. [Copyright &y& Elsevier]

Furunculosis, caused by the bacterium Aeromonas salmonicida, is a serious pathogen of salmonids including the brook charr (Salvelinus fontinalis). However, within-stock genetic variance for furunculosis resistance and its genetic association with other economically important traits are not known in brook charr. Our objective was a preliminary identification of the heritability of early furunculosis resistance and body weight (WT) in a commercially important Québec strain of brook charr. Survival was expressed quantitatively as survival time (ST; hours) for analysis. Twenty-three half and full sib families of 0+ brook charr in a mixed pedigree were exposed to a concentration of 2.86×105 l-1 infective particles. Heritability estimates within this strain were high for both ST (ha,ST2=0.51±0.03) and WT (ha,WT2=0.57±0.04). Low positive genetic correlation between ST and WT (ra=0.15±0.06) was supported by phenotypic correlation (rp=0.12). Independent or simultaneous pedigreed selection for these traits within this strain might produce significant genetic gain, although indirect selection for tolerance of furunculosis via genetic correlation with body weight is not likely to be successful. [Copyright &y& Elsevier]

Emamectin benzoate 0.2% premix (SLICE™) coated onto pellets and fed to brook trout (Salvelinus fontinalis; 700–900 g) resulted in a 40–60% reduction in the mean number of adult female Salmincola edwardsii, whereas controls exhibited a 20% increase in parasite numbers. In each of two lab-based experiments, ca. 40 trout were tagged and the number of adult female parasites on the gills were counted, then the fish were randomly allocated to one of four tanks (300 l, flow through freshwater, 10–12 °C). The fish in the two tanks were offered medicated feed (nominal dose 50 μg kg−1 bw day−1) for a 7-day period, the other two tanks were fed a control diet. Finally at either 7 (Experiment 1) or 17–31 days (Experiment 2) after the medicated feed treatment, all fish were euthanised and the number of adult female parasites recounted. In Experiment 1, the mean number of parasites fish−1 in the treated group decreased from 118 to 49 (p<0.05), compared to an increase in the control from 109 to 125 (p=0.14). Similarly in Experiment 2, the mean number of parasites fish−1 decreased significantly in the treated group from 56 to 35 (p<0.01), compared to an increase from 67 to 82 in the control (p<0.001). The general health of the fish was improved by the medicated feed in Experiment 1 as indicated by a significant increase in both mean body weight and condition factor compared to the control. [Copyright &y& Elsevier]

A previously parameterized gastric evacuation rate (GER) model of brook trout d S t d t = − ρ L L 1.31 S t , where S t is current stomach mass (g), L is total fish length (cm), t is time (h), and ρ L is the rate parameter constant (g0.5 h−1), was extended to describe the effects of dietary energy density E (kJ g−1), temperature T (°C), feed storage conditions (frozen and non-frozen), and the arrival of an additional meal on GER of total stomach contents. The resulting data revealed a considerable effect of E and T while feed storage conditions and the arrival of an additional meal have no effect on GER of brook trout. The GER tends to increase as the energy contents of the diet were reduced. The relationship between GER and the energy contents of diet was described by a power function of E. The GER increased exponentially as the temperature increases to a maximum value at the optimum temperature (c. 18.9 °C) and then declines rapidly. The optimum temperature model adequately described this temperature dependency of the GER at both low and high temperatures. The estimated parameters of E and T were then added to the GER model of brook trout as d S t d t = − 0.000860 L 1.31 E − 0.41 e 0.08 T 1 − e 1.82 T − 20.6 S t (g h−1). The model was tested to predict the stomach fullness in brook trout fed for three consecutive days. The predicted values were closely in line with the actual values of stomach fullness (r 2 = 0.987). This parameterized model can be used to predict levels of stomach fullness independent of meal size and timing, and should have useful applications in the development of feeding regimes for brook trout. • The effect of dietary energy contents and temperatures on gastric evacuation rates (GER) are included in the GER model for brook trout. • The optimum and upper temperature limits for GER of brook trout are estimated. • The parameterize GER model together with the results from Khan et al. (2016) should prove a useful tool for optimization of feeding regimes for brook trout. • The results of our GER experiments further contribute to the generic knowledge on GE in fish. [ABSTRACT FROM AUTHOR]