The Experts below are selected from a list of 1683 Experts worldwide ranked by ideXlab platform
Ian Bricknell - One of the best experts on this subject based on the ideXlab platform.
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Anti-chemotactic activity in the secretory/excretory products of Lepeophtheirus salmonis
Fish & shellfish immunology, 2020Co-Authors: Jessica Piesz, Sarah E. Barker, Ian BricknellAbstract:Abstract The ectoparasite, Lepeophtheirus salmonis (Kroyer 1837), is effective at avoiding elimination from its host, Atlantic salmon, Salmo salar L., by inhibiting the recruitment of immune cells to the site of attachment. In other ectoparasitic arthropods, numerous factors have been identified that bind or neutralize chemokines preventing their interaction with receptors on the surfaces of immune cells. To determine if L. salmonis is utilizing a similar mechanism of immune modulation, the chemotactic activity of peripheral blood leukocytes (PBL) to leukotriene B4 (LTB4) and the secreted/excreted products (SEPs) of the Sea Louse were investigated in vitro. The results showed that incubation of LTB4 with SEPs reduced leukocyte migration compared to LTB4 immune stimulation alone. Data suggests that one of the mechanisms L. salmonis may be using to regulate immune cell recruitment in Atlantic salmon is by inhibiting or neutralizing the activity of chemokines.
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The Three-spined Stickleback, Gasterosteus aculeatus Linnaeus 1758, plays a minor role as a host of Lepeophtheirus salmonis (Krøyer 1837) in the Gulf of Maine.
Journal of fish diseases, 2019Co-Authors: Michael Pietrak, Alexander J. Jensen, Gayle Barbin Zydlewski, Ian BricknellAbstract:The Sea Louse, Lepeophtheirus salmonis (Kroyer 1837), is a significant parasite of farmed salmon throughout the Northern Hemisphere. Management of on-farm Louse populations can be improved by understanding the role that wild fish play in sustaining and providing refuge for the local population of Sea lice. In this study, 1,064 sticklebacks were captured. Of these animals, 176 individuals were carrying a total of 238 Sea lice, yielding a prevalence and intensity of 16.5% and 1.4 lice per fish, respectively. Detailed examination of the Sea lice on the three-spined sticklebacks captured in Cobscook Bay found two L. salmonis individuals using three-spined sticklebacks as hosts. A 2012 survey of wild fish in Cobscook Bay, Maine, found multiple wild hosts for Caligus elongatus (von Nordmann 1832), including three-spined sticklebacks (Gasterosteus aculeatus L.), but no L. salmonis were found in this earlier study.
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Prevalence, abundance, and distribution of Lepeoptheirus salmonis (Krøyer, 1837) and Caligus elongatus (Nordmann, 1832) on wild Sea trout Salmo trutta L.
ICES Journal of Marine Science, 2008Co-Authors: K. Urquhart, C. C. Pert, R. Kilburn, R. J. Fryer, Ian BricknellAbstract:Urquhart, K., Pert, C. C., Kilburn, R., Fryer, R. J., and Bricknell, I. R. 2008. Prevalence, abundance, and distribution of Lepeoptheirus salmonis (Kroyer, 1837) and Caligus elongatus (Nordmann, 1832) on wild Sea trout Salmo trutta L. - ICES Journal of Marine Science, 65: 171-173.Lepeophtheirus salmonis (Kroyer, 1837) and Caligus elongatus (Nordmann, 1832) were found on 100% and 90%, respectively, of 30 wild Sea trout from the east coast of Scotland. Mean abundances of the same two Sea lice were 7.8 and 7.7, respectively. The distribution of the two species of Sea Louse differed, however, with a greater proportion of L. salmonis in the posterior and anterior dorsal regions, and a greater proportion of C. elongatus in the caudal and posterior ventral regions.
Crawford W. Revie - One of the best experts on this subject based on the ideXlab platform.
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Evaluating the potential for Sea lice to evolve freshwater tolerance as a consequence of freshwater treatments in salmon aquaculture
Aquaculture Environment Interactions, 2019Co-Authors: Maya L. Groner, Mark D. Fast, Emilie Laurin, Marit Stormoen, Javier Sanchez, Crawford W. RevieAbstract:Increasing usage of non-medicinal methods (NMMs) to control Sea Louse infestations on salmon farms has raised questions about whether Sea lice may be able to evolve tolerance of NMMs. Of particular concern is the potential for Sea lice to evolve freshwater tolerance as a result of freshwater treatments. Wild trout and some juvenile salmonids swim into freshwater to control infestations and regain ionic balance after disruption by Sea lice; freshwater tolerance would compromise this potentially adaptive behavior. Here we evaluated the potential for freshwater tolerance to evolve in the Sea Louse Lepeophtheirus salmonis. When exposed to low-salinity water, parasitic stages of Sea lice are able to osmoregulate through the host, while larval planktonic stages are not. Transcriptomic work suggests that Sea lice mount a costly polygenic stress response when exposed to brackish water. The population structure of Sea lice is panmictic in both the Pacific and Atlantic, making it conducive to rapid evolutionary responses. It is unknown how much heritable genetic variation these panmictic populations have for freshwater treatments. While usage of freshwater treatments on wellboats is increasing, it is unclear whether the freshwater itself is a strong selective force; during the freshwater exposure, Sea lice can die from physical disruption during pumping and filtration on the wellboat. Future studies are advised to quantify the heritable variation in freshwater tolerance in Sea Louse populations, characterize mechanisms for freshwater tolerance in planktonic and attached Sea lice, and assess the risk of freshwater tolerance evolution under different management strategies.
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Modelling Sea lice control by lumpfish on Atlantic salmon farms: interactions with mate limitation, temperature and treatment rules.
Diseases of aquatic organisms, 2019Co-Authors: Gregor Mcewan, Maya L. Groner, Allegra A. B. Cohen, Albert K. Imsland, Crawford W. RevieAbstract:Atlantic salmon farming is one of the largest aquaculture sectors in the world. A major impact on farm economics, fish welfare and, potentially, nearby wild salmonid populations, is the Sea Louse ectoparasite Lepeophtheirus salmonis. Sea Louse infestations are most often controlled through application of chemicals, but in most farming regions, Sea lice have evolved resistance to the small set of available chemicals. Therefore, alternative treatment methodologies are becoming more widely used. One increasingly common alternative treatment involves the co-culture of farmed salmon with cleaner fish, which prey on Sea lice. However, despite their wide use, little is understood about the situations in which cleaner fish are most effective. For example, previous work suggests that a low parasite density results in Sea lice finding it difficult to acquire mates, reducing fecundity and population growth. Other work suggests that environmental conditions such as temperature and external Sea Louse pressure have substantial impact on this mate limitation threshold and may even remove the effect entirely. We used an Agent-Based Model (ABM) to simulate cleaner fish on a salmon farm to explore interactions between Sea Louse mating behaviour, cleaner fish feeding rate, temperature and external Sea Louse pressure. We found that Sea Louse mating has a substantial effect on Sea Louse infestations under a variety of environmental conditions. Our results suggest that cleaner fish can control Sea Louse infestations most effectively by maintaining the population below critical density thresholds.
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Tool for predicting Caligus rogercresseyi abundance on salt water salmon farms in Chile
Preventive veterinary medicine, 2018Co-Authors: Sophie St-hilaire, Crawford W. Revie, Thitiwan Patanasatienkul, Anja B. Kristoffersen, Henrik Stryhn, R. Ibarra, A. Tello, Gregor McewanAbstract:Abstract Caligus rogercresseyi is a host-dependent parasite that affects rainbow trout and Atlantic salmon in Chile. Numbers of Sea lice on fish increase over time at relatively predictable rates when the environment is conducive to the parasite’s survival and fish are not undergoing treatment. We developed a tool for the salmon industry in Chile that predicts the abundance of adult Sea lice over time on farms that are relatively isolated. We used data on Sea Louse abundance collected through the SalmonChile INTESAL Sea lice monitoring program to create series of weekly lice counts between lice treatment events on isolated farms. We defined isolated farms as those with no known neighbors within a 10 km Seaway distance and no more than two neighbors within a 20 km Seaway distance. We defined the time between Sea lice treatments as starting the week immediately post treatment and ending the week before a subsequent treatment. Our final dataset of isolated farms consisted of 65 series from 32 farms, between 2009 and 2015. Given an observed abundance at time t = 0, we built a model that predicted 8 consecutive weekly Sea Louse abundance levels, based on the preceding week’s lice prediction. We calibrated the parameters in our model on a randomly selected subset of training data, choosing the parameter combinations that minimized the absolute difference between the predicted and observed Sea Louse abundance values. We validated the parameters on the remaining, unseen, subset of data. We encoded our model and made it available as a Web-accessible applet for producers. We determined a threshold, based on the upper 97.5% predictive interval, as a guideline for producers using the tool. We hypothesize that if farms exceed this threshold, especially if the Sea lice levels are above this threshold 2 and 4 weeks into the model predictions, the Sea Louse population on the farm is likely influenced by sources other than lice within the farm.
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quantifying the influence of salinity and temperature on the population dynamics of a marine ectoparasite
Canadian Journal of Fisheries and Aquatic Sciences, 2016Co-Authors: Maya L. Groner, Erin E. Rees, Gregor Mcewan, G Gettinby, Crawford W. RevieAbstract:Sea lice are common ectoparasites of farmed and wild salmonids and can cause substantial morbidity and mortality in their hosts. While Sea lice infections are common in estuarine areas with variable salinity, the effects of salinity on population dynamics are poorly understood. We used existing literature to parameterize salinity-dependent logistic mortality curves for different life stages of Sea lice. We then used population matrix models to characterize the effects of temperature and salinity on Sea Louse population growth. Our models showed that low salinity decreases survival, while low temperature retards Sea Louse development. In contrast with the linear effects of temperature on Sea Louse development, salinity has a nonlinear effect on Sea Louse survival; values below 20 psu cause mortality, while values above 20 psu have little effect on survival. Simulations showed that Sea Louse population growth can be greatest in zones that are intermediate between estuarine and oceanic. In these cases popula...
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Managing aquatic parasites for reduced drug resistance: lessons from the land.
Journal of the Royal Society Interface, 2016Co-Authors: Gregor Mcewan, Maya L. Groner, Danielle L. Burnett, Mark D. Fast, Crawford W. RevieAbstract:Atlantic salmon farming is one of the largest aquaculture industries in the world. A major problem in salmon farms is the Sea Louse ectoparasite Lepeophtheirus salmonis, which can cause stress, secondary infection and sometimes mortality in the salmon host. Sea lice have substantial impacts on farm economics and potentially nearby wild salmonid populations. The most common method of controlling Sea Louse infestations is application of chemicals. However, most farming regions worldwide have observed resistance to the small set of treatment chemicals that are available. Despite this, there has been little investigation of treatment strategies for managing resistance in aquaculture. In this article, we compare four archetypical treatment strategies inspired by agriculture, where the topic has a rich history of study, and add a fifth strategy common in aquaculture. We use an agent-based model (ABM) to simulate these strategies and their varying applications of chemicals over time and space. We analyse the ABM output to compare how the strategies perform in controlling Louse abundance, number of treatments required and levels of resistance in the Sea Louse population. Our results indicated that among the approaches considered applying chemicals in combination was the most effective over the long term.
James R A Butler - One of the best experts on this subject based on the ideXlab platform.
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wild salmonids and Sea Louse infestations on the west coast of scotland sources of infection and implications for the management of marine salmon farms
Pest Management Science, 2002Co-Authors: James R A ButlerAbstract:The Sea Louse (Lepeophtheirus salmonis Kroyer) is a major health problem for both farmed and wild salmonids. This paper investigates Louse epidemiology and management in the salmonfarming zone of western Scotland. Based on a review of the marine ecology of wild salmon (Salmo salar L) and Sea trout (Salmo trutta L), and catch and farm production statistics, best estimates were made for numbers of wild and farm hosts present in coastal waters in March-June 2000. Applying data for ovigerous female Louse infections and fecundity, the sources and risks of larval transmission to wild salmon and Sea trout were modelled. Farm salmon in the second spring of production were the primary host group (98% of fish), while numbers of wild salmonids (<1%) and escaped farm salmon (2%) were relatively insignificant. Farm salmon produced 97% of Louse eggs at high levels (eight ovigerous lice per fish), and 78% at low levels (one per fish). Wild salmonids produced <1% of eggs under both scenarios, but escaped farm salmon produced 3% and 21%, respectively. All hosts potentially cross-infect one another, but farm salmon are more likely to infect wild and farm smolts, and also other farm salmon. Monitoring of lice on Sea trout in June 1998-2000 by the Association of West Coast Fisheries Trusts corroborated the model's conclusions. Localised epizootics occurred every year and coincided with the presence of ovigerous lice on local farms. In areas of mixed-year class production on farms, epizootics were evident every spring, but occurred every second spring in areas of single-year class production. In 1998-2000 at least 14-40% of Sea trout were infected with potentially lethal infestations of lice. Ovigerous Louse levels of <0.005 per fish were required on farm salmon in the spring of 2000 to produce less eggs than those emitted by wild salmonids. With the industry's continued expansion, and thus increased numbers of farm salmon, a target of zero ovigerous lice will be required on farms to minimise impacts on wild salmonids. Due to the limited long-term efficacy and availability of Louse medicines, management strategies are discussed which will improve control, including single-year class production over large areas, alternate S1-S1/2 smolt inputs, and 11-month production cycles.
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Wild salmonids and Sea Louse infestations on the west coast of Scotland: sources of infection and implications for the management of marine salmon farms†
Pest management science, 2002Co-Authors: James R A ButlerAbstract:The Sea Louse (Lepeophtheirus salmonis Kroyer) is a major health problem for both farmed and wild salmonids. This paper investigates Louse epidemiology and management in the salmonfarming zone of western Scotland. Based on a review of the marine ecology of wild salmon (Salmo salar L) and Sea trout (Salmo trutta L), and catch and farm production statistics, best estimates were made for numbers of wild and farm hosts present in coastal waters in March-June 2000. Applying data for ovigerous female Louse infections and fecundity, the sources and risks of larval transmission to wild salmon and Sea trout were modelled. Farm salmon in the second spring of production were the primary host group (98% of fish), while numbers of wild salmonids (
Cristian Gallardo-escárate - One of the best experts on this subject based on the ideXlab platform.
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Tackling the Molecular Drug Sensitivity in the Sea Louse Caligus rogercresseyi Based on mRNA and lncRNA Interactions.
Genes, 2020Co-Authors: Gustavo Núñez-acuña, Valentina Valenzuela-muñoz, Diego Valenzuela-miranda, Constanza Sáez-vera, Gabriel Arriagada, Cristian Gallardo-escárateAbstract:Caligus rogercresseyi, commonly known as Sea Louse, is an ectoparasite copepod that impacts the salmon aquaculture in Chile, causing losses of hundreds of million dollars per year. This pathogen is mainly controlled by immersion baths with delousing drugs, which can lead to resistant traits selection in lice populations. Bioassays are commonly used to assess Louse drug sensitivity, but the current procedures may mask relevant molecular responses. This study aimed to discover novel coding genes and non-coding RNAs that could evidence drug sensitivity at the genomic level. Sea lice samples from populations with contrasting sensitivity to delousing drugs were collected. Bioassays using azamethiphos, cypermethrin, and deltamethrin drugs were conducted to evaluate the sensitivity and to collect samples for RNA-sequencing. Transcriptome sequencing was conducted on samples exposed to each drug to evaluate the presence of coding and non-coding RNAs associated with the response of these compounds. The results revealed specific transcriptome patterns in lice exposed to azamethiphos, deltamethrin, and cypermethrin drugs. Enrichment analyses of Gene Ontology terms showed specific biological processes and molecular functions associated with each delousing drug analyzed. Furthermore, novel long non-coding RNAs (lncRNAs) were identified in C. rogercresseyi and tightly linked to differentially expressed coding genes. A significant correlation between gene transcription patterns and phenotypic effects was found in lice collected from different salmon farms with contrasting drug treatment efficacies. The significant correlation among gene transcription patterns with the historical background of drug sensitivity suggests novel molecular mechanisms of pharmacological resistance in lice populations.
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Catching the complexity of salmon-Louse interactions.
Fish & shellfish immunology, 2019Co-Authors: Cristian Gallardo-escárate, Valentina Valenzuela-muñoz, Diego Valenzuela-miranda, Gustavo Núñez-acuña, Ana Teresa Gonçalves, Crisleri Carrera, Bárbara P. Benavente, Steven B. RobertsAbstract:The study of host-parasite relationships is an integral part of the immunology of aquatic species, where the complexity of both organisms has to be overlayed with the lifecycle stages of the parasite and immunological status of the host. A deep understanding of how the parasite survives in its host and how they display molecular mechanisms to face the immune system can be applied for novel parasite control strategies. This review highlights current knowledge about salmon and Sea Louse, two key aquatic animals for aquaculture reSearch worldwide. With the aim to catch the complexity of the salmon-Louse interactions, molecular information gleaned through genomic studies are presented. The host recognition system and the chemosensory receptors found in Sea lice reveal complex molecular components, that in turn, can be disrupted through specific molecules such as non-coding RNAs.
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First report of the Sea Louse Caligus rogercresseyi found in farmed Atlantic salmon in the Magallanes region, Chile
Aquaculture, 2019Co-Authors: Gabriel Arriagada, Valentina Valenzuela-muñoz, A.m. Arriagada, P. Núñez-acuña, M. Brossard, K. Montecino, Marcela Lara, Alicia Gallardo, Cristian Gallardo-escárateAbstract:Abstract The marine copepodid Caligus rogercresseyi is the causative agent of Caligidosis, the most important parasitic diSease for the Chilean salmon industry. Historically, C. rogercresseyi has been widely distributed in coastal waters of northern Patagonia (40°15′S to 49°16′ S), where close to 90% of salmon farms are located. In 2017, Sea lice were detected in farmed Atlantic salmon in the Magallanes region (south of 49°16′ S), affecting salmon farms for the first time. This study aimed to identify the Sea Louse C. rogercresseyi infecting Atlantic salmon, and also to report measures and activities conducted by the Chilean Fisheries and Aquaculture Service (SERNAPESCA) in conjunction with the Caligidosis Reference Laboratory (University of Concepcion). The main actions were diagnosis and outbreak confirmation, case definition, surveillance, and implementation of control strategies. Here, the identification of C. rogercresseyi was confirmed through morphological and genetic analyses. In total, there were eight farms in the Magallanes region where at least one C. rogercresseyi individual was detected during 2017. Only in three case farms, C. rogercresseyi presented an epidemic behavior, reaching maximum levels of 24.5 adult lice/fish and 14 juvenile lice/fish. SERNAPESCA implemented different measures aimed to improve the sensitivity of the surveillance system, which yielded new case farms. The two farms with higher Sea lice levels were treated with the organophosphate azamethiphos, resulting in a dramatic reduction of both adult and juvenile lice, although fish were re-infected a few weeks later. Further reSearch is needed to determine the causes of this outbreak and evaluate its consequences for the local salmon industry.
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Modulation of Atlantic salmon miRNome response to Sea Louse infestation.
Developmental and comparative immunology, 2017Co-Authors: Valentina Valenzuela-muñoz, Beatriz Novoa, Antonio Figueras, Cristian Gallardo-escárateAbstract:Abstract MicroRNAs are non-coding RNA that plays a crucial role in post-transcriptional regulation and immune system regulation. On other hand, Sea lice are prevalent parasites that affect salmon farming, generating different degrees of immune suppression depending on the salmon and Sea Louse species. Caligus rogercresseyi for example, which affects the salmon industry in Chile, decreases Th1 response, macrophage activation, TLR-mediated response and iron regulation in infected fish. In this study, we explore Atlantic salmon miRNome during infestation by C. rogercresseyi . Using small RNA sequencing, we annotated 1718 miRNAs for skin and head kidney from infected Atlantic salmon. The most abundant families identified were mir-10, mir-21, mir-30, mir-181 and let7. Significant differences were found between tissue, with 1404 annotated miRNA in head kidney and 529 in skin. Differential analysis of transcript expression indicated that at an early stage of infestation miRNA expression was higher in head kidney than in skin tissue, revealing tissue-specific expression patterns. In parallel, miRNA target prediction using 3′UTRs from highly regulated immune-related genes and iron metabolism showed that mir-140-4 and mir-181a-2-5 modulate the expression of TLR22 and Aminolevulinic acid synthase , respectively. This study contributes knowledge about the immune response of Atlantic salmon during infestation with Sea lice.
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Long noncoding RNAs: Unexplored players in the drug response of the Sea Louse Caligus rogercresseyi
Agri Gene, 2017Co-Authors: Diego Valenzuela-miranda, Kayvan Etebari, Sassan Asgari, Cristian Gallardo-escárateAbstract:Long non-coding RNAs (lncRNAs), endogenous RNAs with restricted or null coding potential, are emerging as key regulators of multiple biological processes in several species. Despite the importance of these transcripts, few studies have characterized marine crustacean lncRNAs or the modulation of these in response to chemical exposure. Therefore, the present study mainly focused on identifying lncRNAs in the Sea Louse Caligus rogercresseyi, an ectoparasite of primary concern to the Chilean salmon industry. A bioinformatics pipeline for lncRNAs discovery was designed, revealing 1835 putative lncRNA sequences in the C. rogercresseyi transcriptome. Furthermore, C. rogercresseyi lncRNAs evidenced features classical of lncRNAs, such as lower values of GC content, length, transcription activity, and minimum free energy as compared with coding transcripts. Furthermore, since developed resistance against delousing drugs is a major threat to the management and control of Sea lice, the transcriptional modulation of C. rogercresseyi lncRNAs during exposure to delousing drugs was also evaluated. Unlike coding transcripts, lncRNAs were mainly downregulated after exposure to either deltamethrin or azamethiphos, showing transcription patterns similar to other, better studied non-coding RNAs in arthropods. Finally, a subset of lncRNAs exhibited a strong transcriptional correlation to genes commonly associated with the drug response, such as ABC transporters, cytochrome p450, and glutathione S-transferase, among others. Our findings provide one of the first comprehensive lncRNA characterizations in a crustacean, contributing towards understandings on the regulatory role of lncRNAs during the drug response in Caligus rogercresseyi.
Martin Krkošek - One of the best experts on this subject based on the ideXlab platform.
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Sea-Louse abundance on salmon farms in relation to parasite-control policy and climate change
ICES Journal of Marine Science, 2020Co-Authors: Sean C. Godwin, Martin Krkošek, John D. Reynolds, Andrew W. BatemanAbstract:Abstract The ectoparasitic copepods, Sea lice (Lepeophtheirus salmonis and Caligus spp.), are major pests to salmon aquaculture and can also affect the health and survival of wild salmon. Policies exist to protect wild salmon by delousing farmed fish when Louse abundance exceeds a threshold, but their effectiveness under future climate change is uncertain. We fitted a Bayesian model for Sea-Louse population dynamics and management to timeseries data of Sea lice on farmed salmon in Pacific Canada and analysed the model under scenarios of warmer climates. We found that in high-temperature years, current parasite control policy becomes ineffective as Sea-Louse abundance is expected to increase. We simulated two alternative management scenarios and observed that both would decrease average Louse counts on farms in high-temperature years relative to the current system but relied on more delousing treatments than are currently performed. We also found evidence that non-salmonids can play a role in Louse transmission to farms, as increased farm colonization of Caligus clemensi occurs in April, coincident with wild herring (Clupea pallasii) spawner abundance. Our results highlight the need for careful management of Sea lice on salmon farms in warmer years and the importance of policies designed to account for future environmental change.
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Bias in self-reported parasite data from the salmon farming industry.
Ecological applications : a publication of the Ecological Society of America, 2020Co-Authors: Sean C. Godwin, Martin Krkošek, John D. Reynolds, Andrew W. BatemanAbstract:Many industries are required to monitor themselves in meeting regulatory policies intended to protect the environment. Self-reporting of environmental performance can place the cost of monitoring on companies rather than taxpayers, but there are obvious risks of bias, often addressed through external audits or inspections. Surprisingly, there have been relatively few empirical analyses of bias in industry self-reported data. Here, we test for bias in reporting of environmental compliance data using a unique data set from Canadian salmon farms, where companies monitor the number of parasitic Sea lice on fish in open Sea pens, in order to minimize impacts on wild fish in surrounding waters. We fit a hierarchical population-dynamics model to these Sea-Louse count data using a Bayesian approach. We found that the industry's monthly counts of two Sea-Louse species, Caligus clemensi and Lepeophtheirus salmonis, increased by a factor of 1.95 (95% credible interval: 1.57, 2.42) and 1.18 (1.06, 1.31), respectively, in months when counts were audited by the federal fisheries department. Consequently, industry Sea-Louse counts are less likely to trigger costly but mandated delousing treatments intended to avoid Sea-Louse epidemics in wild juvenile salmon. These results highlight the potential for combining external audits of industry self-reported data with analyses of their reporting to maintain compliance with regulations, achieve intended conservation goals, and build public confidence in the process.
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Migratory hosts can maintain the high-dose/refuge effect in a structured host-parasite system: The case of Sea lice and salmon.
Evolutionary applications, 2020Co-Authors: Andrew W. Bateman, Martin Krkošek, Stephanie J. Peacock, Mark A. LewisAbstract:Migration can reduce parasite burdens in migratory hosts, but it connects populations and can drive diSease dynamics in domestic species. Farmed salmon are infested by Sea Louse parasites, often carried by migratory wild salmonids, resulting in a costly problem for industry and risk to wild populations when farms amplify Louse numbers. Chemical treatment can control lice, but resistance has evolved in many salmon-farming regions. Resistance has, however, been slow to evolve in the north-east Pacific Ocean, where large wild-salmon populations harbour large Sea Louse populations. Using a mathematical model of host-macroparasite dynamics, we explored the roles of domestic, wild oceanic and connective migratory host populations in maintaining treatment susceptibility in associated Sea lice. Our results show that a large wild salmon population, unexposed to direct infestation by lice from farms; high levels of on-farm treatment; and a healthy migratory host population are all critical to slowing or stopping the evolution of treatment resistance. Our results reproduce the "high-dose/refuge effect," from the agricultural literature, with the added requirement of a migratory host population to maintain treatment susceptibility. This work highlights the role that migratory hosts may play in shared wildlife/livestock diSease, where evolution can occur in ecological time.
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Heavy Sea Louse infection is associated with decreased stomach fullness in wild juvenile sockeye salmon
Canadian Journal of Fisheries and Aquatic Sciences, 2018Co-Authors: Sean C. Godwin, Luke A. Rogers, Martin Krkošek, John D. Reynolds, Lawrence M. DillAbstract:Foraging success can be mediated by parasites, but this is poorly understood for marine fish whose aggregations and patchy prey fields create conditions for intense intraspecific competition. We evaluated whether Sea Louse infection is associated with decreased stomach fullness of wild juvenile sockeye salmon (Oncorhynchus nerka) in Johnstone Strait, BC during their marine migration from the Fraser River. Caligus clemensi comprised 98.6% of the pre-adult and adult lice and 86.5% of the copepodites (freshly attached juvenile lice); the rest were Lepeophtheirus salmonis. We found that infection status was an important predictor of relative stomach fullness for juvenile sockeye (wet stomach content weight divided by body weight), as indicated by mixed-effects model selection, and that highly infected fish had 17% ± 8% lower relative stomach fullness than did lightly infected fish. This Louse-associated reduction in relative stomach fullness occurs as the juvenile sockeye migrate through a food-limited enviro...
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Sea-Louse parasites on juvenile wild salmon in the Broughton Archipelago, British Columbia, Canada.
Ecology, 2016Co-Authors: Stephanie J. Peacock, Andrew W. Bateman, Brendan M. Connors, Martin Krkošek, Scott Rogers, Lauren Portner, Zephyr Polk, Coady Webb, Alexandra MortonAbstract:The global expansion of aquaculture has changed the structure of fish populations in coastal environments, with implications for diSease dynamics. In Pacific Canada, farmed salmon act as reservoir hosts for parasites and pathogens, including Sea lice (Lepeophtheirus salmonis and Caligus clemensi) that can transmit to migrating wild salmon. Assessing the impact of salmon farms on wild salmon requires regular monitoring of Sea-Louse infections on both farmed and wild fish. Since 2001, we have collected juvenile pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon annually at three sites in the Broughton Archipelago in British Columbia, Canada, during the annual juvenile salmon migration from fresh water to the open ocean. From sampled fish, we recorded counts of parasitic copepodid-, chalimus-, and motile-stage Sea lice. We report Louse abundances as well as supplementary observations of fish size, development, and health.