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Louis Bernatchez - One of the best experts on this subject based on the ideXlab platform.
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L: Decline of North Atlantic Eels: a fatal synergy
2016Co-Authors: Thierry Wirth, Louis BernatchezAbstract:Panmictic species pose particular problems for conservation because their welfare can be addressed effec-tively only on a global scale. We recently documented by means of microsatellite analysis that the European Eel (Anguilla anguilla) is not panmictic but instead shows genetic isolation by distance. In this study, we extended the analysis to the American Eel (A. rostrata) by applying identical analytical procedures and statistical power. Results obtained for the American Eel were in sharp contrast with those obtained for the European Eel: the null hypothesis of panmixia could not be rejected, and no isolation by distance was detected. This implies that the species must be managed as a single population. Using Bayesian statistics, we also found that the effective population sizes for both species were surprisingly low and that the populations had undergone severe contractions, most probably during the Wisconsinan glaciation. The apparent sensitivity of Eels to climatic changes affecting the strength and position of the Gulf Stream 20 000 years ago is particularly worrying, given the effects of the ongoing global warming on the North Atlantic climate. Moreover, additional short-term stresses such as surging glass Eel prizes, overfishing and lethal parasitic infections negatively affect Eel population size. The fascinating transatlantic migration and life cycle of Atlantic Eels is also their Achilles ’ hEel as these negative short- and long-term effects will probably culminate in a fatal synergy if drastic conservation measures are not implemented to protect these international biological resources
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Current Biology Report RAD Sequencing Highlights Polygenic Discrimination of Habitat Ecotypes in the Panmictic American Eel
2016Co-Authors: Louis BernatchezAbstract:The two primary ways that species respond to heterogeneous environments is through local adaptation and phenotypic plasticity. The American Eel (Anguilla rostrata) presents a paradox; despite inhabiting drastically different environ-ments [1], the species is panmictic [2, 3]. Spawning takes place only in the southern Sargasso Sea in the Atlantic Ocean [1]. Then, the planktonic larvae (leptocephali) disperse to rearing locations from Cuba to Greenland, and juveniles colonize either freshwater or brackish/saltwater habitats, where they spend 3–25 years before returning to the Sargasso Sea to spawn as a panmictic species. Depending on rearing habitat, individuals exhibit drastically different ecotypes [4–6]. I
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ARTICLE Growth, Female Size, and Sex Ratio Variability in American Eel of Different Origins in Both Controlled Conditions and the Wild: Implications for Stocking Programs
2016Co-Authors: Caroline L. Côte, Martin Castonguay, Scott A Pavey, Joshua A. Stacey, Thomas C. Pratt, Louis BernatchezAbstract:Freshwater Eels Anguilla spp. are declining worldwide, and a major challenge is understanding why these panmictic species show contrasting patterns of intraspecific phenotypic variation and recruitment. We present results on studies of the American Eel A. rostrata to understand and discriminate the effects of origin and plasticity on growth and sex determination. We considered two separate growth and one length-at-age data sets. The first growth data set originated from a 34-month rearing experiment starting from the glass Eel life stage to test the effects of origin, salinity, and density on growth and sex determination. The second growth data set originated from a shorter rearing experiment of 18 months starting at the yellow Eel stage (around 3 years old) and compared transplanted individuals in Lake Ontario (LO) with natural migrants to the LO area. The third data set compared transplanted individuals in LO sampled by electrofishing with naturally migrating individuals. Sex ratios were identical for all origins and treatments in the long-term growth experiment (34–35 % females). While male size distribution had little variability, certain female groups had a large variation in growth and presented fast- and slow-growing clusters. On the other hand, both cases of natural migrants to the LO area were consistent with bein
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discussed. © 2009 The Authors
2016Co-Authors: C. L. Côté, M. Castonguay, G. Verreault, Louis BernatchezAbstract:doi:10.1111/j.1095-8649.2009.02291.x, available online at www.interscience.wiley.com Differential effects of origin and salinity rearing conditions on growth of glass Eels of the American Eel Anguilla rostrata: implications for stocking programme
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Genomic footprints of speciation in Atlantic Eels (Anguilla anguilla and A. rostrata)
2016Co-Authors: Magnus W Jacobsen, Louis Bernatchez, Jose Martin Pujolar, Kasper Munch, Yongchao Niu, Ianbo J Jian, Michael M HansenAbstract:The importance of speciation-with-geneflow scenarios is increasingly appreciated. However, the specific processes and the resulting genomic footprints of selection are subject to much discussion. We studied the genomics of speciation between the two panmictic, sympatrically spawning sister species; European (Anguilla anguilla) and American Eel (A. rostrata). Divergence is assumed to have initiated more than 3 Ma, and although low gene flow still occurs, strong postzygotic barriers are present. Restriction-site-associated DNA (RAD) sequencing identified 328 300 SNPs for subse-quent analysis. However, despite the presence of 3757 strongly differentiated SNPs (FST> 0.8), sliding window analyses of FST showed no larger genomic regions (i.e. hundreds of thousands to millions of bases) of elevated differentiation. Overall FST was 0.041, and linkage disequilibrium was virtually absent for SNPs separated by more than 1000 bp. We suggest this to reflect a case of genomic hitchhiking, where multiple regions are under directional selection between the species. However, low but biologically significant gene flow and high effective population sizes leading t
Fabrizio, Mary C. - One of the best experts on this subject based on the ideXlab platform.
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Evaluating recruitment of American Eel, Anguilla rostrata, in the Potomac River (Spring 2021)
W&M ScholarWorks, 2021Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:American Eel (Anguilla rostrata) is a valuable commercial species along the Atlantic coast of North America from New Brunswick to Florida. Landings from Chesapeake Bay typically represent 60% of the annual United States commercial harvest (ASMFC 2012). American Eel is also important to the recreational fishery as it is often used live as bait for Striped Bass (Morone saxatilis) and Cobia (Rachycentron canadum). In 2020, Chesapeake Bay commercial landings of American Eel (218,005 lbs) were 80% of the U.S. landings (personal communication from the National Marine Fisheries Service, Fisheries Statistics Division). Since the 1980s, harvest along the U.S. Atlantic Coast has declined, with similar patterns occurring in the Canadian Maritime Provinces (Meister and Flagg 1997). The American Eel Benchmark Stock Assessment report (ASMFC 2012) established that the American Eel is depleted in U.S. waters; the 2017 stock assessment update (ASMFC 2017) confirmed that this population remains depleted
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2021 Annual Report Estimating Relative Juvenile Abundance of Ecologically Important Finfish in the Virginia Portion of Chesapeake Bay (1 July 2020 – 30 June 2021)
W&M ScholarWorks, 2021Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:The Trawl Survey provides crucial data to state, regional, and national fisheries management agencies, including the Virginia Marine Resources Commission (VMRC), the Atlantic States Marine Fisheries Commission (ASMFC), the Mid‐Atlantic Fisheries Management Council (MAFMC), and the National Marine Fisheries Service (NMFS). The MAFMC recognizes the juvenile trawl survey as one of the key predictors of Summer Flounder recruitment. Annual indices of juvenile abundance have been generated from trawl survey data for species of key recreational and ecological importance in the Virginia portion of Chesapeake Bay. These include Spot, Atlantic Croaker, Weakfish, Summer Flounder, Black Sea Bass, Scup, Striped Bass, White Perch, White Catfish, Channel Catfish, Blue Catfish, Silver Perch, American Eel, and Bay Anchovy. We completed most targeted tows this past year and only missed the upper‐river stations in the James and Rappahannock rivers and a few shallow Bay stations during July and August 2020 due to COVID‐19 safety restrictions. As a result, we could not calculate an index for American Eel in the James and Rappahannock rivers. We are also unable to calculate an index for the 2019 year‐class of Black Sea Bass due to the stay‐at‐home order that included May 2020, which was an important index month for this species. A summary of other species affected by COVID‐19 restrictions is shown in the table below. (...
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Evaluating Recruitment of American Eel, Anguilla rostrata, in the Potomac River (Spring 2020)
W&M ScholarWorks, 2020Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:American Eel (Anguilla rostrata) is a valuable commercial species along the Atlantic coast of North America from New Brunswick to Florida. Landings from Chesapeake Bay typically represent 60% of the annual United States commercial harvest (ASMFC 2012). American Eel is also important to the recreational fishery as it is often used live as bait for Striped Bass (Morone saxatilis) and Cobia (Rachycentron canadum). In 2016, Chesapeake Bay commercial landings of American Eel (728,717 lbs) were 78% of the U.S. landings (personal communication from the National Marine Fisheries Service, Fisheries Statistics Division). Since the 1980s, harvest along the U.S. Atlantic Coast has declined, with similar patterns occurring in the Canadian Maritime Provinces (Meister and Flagg 1997). The American Eel Benchmark Stock Assessment report (ASMFC 2012) established that the American Eel is depleted in U.S. waters; the 2017 stock assessment update (ASMFC 2017) confirmed that this population remains depleted
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Estimating Relative Abundance of Young-of-Year American Eel, Anguilla rostrata, in the Virginia Tributaries of Chesapeake Bay (Spring 2019)
W&M ScholarWorks, 2020Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:American Eel (Anguilla rostrata) is a valuable commercial species along the Atlantic coast of North America from New Brunswick to Florida. In the U.S., harvests have declined, with similar patterns occurring in the Canadian Maritime Provinces (Meister and Flagg 1997). An average of 62% of the annual landings of U.S. commercial harvest since 1993 have come from the Chesapeake Bay (personal communication from the National Marine Fisheries Service, Fisheries Statistics Division, 9 February 2015). In 2013, Virginia commercial landings were approximately 100,298 lbs; since mandatory reporting began in 1993, average annual landings in Virginia have been 193,200 lbs or 19% of the U.S. American Eel harvest (personal communication from the National Marine Fisheries Service, Fisheries Statistics Division, 9 February 2015). A decline in abundance of American Eel has been observed in recent years with conflicting evidence regarding spatial synchrony throughout their range (Richkus and Whalen 1999; Sullivan et al. 2006). Hypotheses for the decline in abundance include shifts in location of the Gulf Stream, pollution, overfishing, parasites, altered oceanic conditions, and barriers to fish passage (Castonguay et al. 1994; Haro et al. 2000; Knights 2003). Additionally, factors such as unfavorable wind-driven currents may affect glass Eel recruitment on the continental shelf and may have a greater impact than fishing mortality or continental climate change (Knights 2003). However, limited knowledge about fundamental biological characteristics of glass Eels has complicated interpretation of juvenile abundance trends (Sullivan et al. 2006). The Atlantic States Marine Fisheries Commission (ASMFC) adopted the Interstate Fishery Management Plan (FMP) for the American Eel in November 1999. The FMP calls for efforts to collect American Eel data through both fishery-dependent and fishery-independent studies in coastal states. Consequently, member jurisdictions agreed to implement an annual survey for young-of-year (YOY or glass) American Eels. The survey is intended to “…characterize trends in annual recruitment of the YOY Eels over time [to produce a] qualitative appraisal of the annual recruitment of American Eel to the U.S. Atlantic Coast” (ASMFC 2000). The development of these surveys began in 2000 with full implementation by 2001. Survey results provide necessary data on coastal recruitment success and further understanding of American Eel population dynamics. A recent American Eel benchmark stock assessment report found that the American Eel stock status is depleted and emphasized the importance of the coast-wide survey as an index of recruitment over the historical coastal range in the U.S. and an early warning of potential range contraction of the species (ASMFC 2012). In 2019, the Virginia Institute of Marine Science continued its spring sampling to estimate relative abundance of YOY American Eels in Virginia tributaries of Chesapeake Bay
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2020 Annual Report Estimating Relative Juvenile Abundance of Ecologically Important Finfish in the Virginia Portion of Chesapeake Bay (1 July 2019 – 30 June 2020)
W&M ScholarWorks, 2020Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:The Trawl Survey provides crucial data to state, regional, and national fisheries management agencies, including the Virginia Marine Resources Commission (VMRC), the Atlantic States Marine Fisheries Commission (ASMFC), the Mid‐Atlantic Fisheries Management Council (MAFMC), and the National Marine Fisheries Service (NMFS). The MAFMC recognizes the juvenile trawl survey as one of the key predictors of Summer Flounder recruitment. Annual indices of juvenile abundance have been generated from trawl survey data for species of key recreational and ecological importance in the Virginia portion of Chesapeake Bay. These include Spot, Atlantic Croaker, Weakfish, Summer Flounder, Black Sea Bass, Scup, Striped Bass, White Perch, White Catfish, Channel Catfish, Blue Catfish, Silver Perch, American Eel, and Bay Anchovy. In March 2020 the Governor of Virginia issued a stay‐at‐home order due to the COVID‐19 pandemic. As a result, we did not sample during April or May. We were able to resume sampling in June 2020 at a reduced capacity and we visited 61 sites (York River and the Chesapeake Bay). Logistical constraints resulting from policies enacted to reduce potential exposure of staff prevented us from completing the full survey. We report results from June 2020 as Appendix Table 3 as these data are not spatially consistent with previous months. We completed 897 tows from July 2019 to March 2020 and collected 318,954 fishes. Bay Anchovy continue to be the most abundant species observed in the survey, accounting for 57% of all fishes collected. Of the target species for which we provide indices of relative abundance, 12 species categories (considering YOY and age 1+ as distinct categories) exhibited below‐average abundance in 2019 – 2020 (American Eel [all three rivers], Blue Catfish YOY [all three rivers], Channel Catfish juveniles and age 1+ [all three rivers], Silver Perch YOY, Spot YOY, Striped Bass YOY, Summer Flounder YOY, Weakfish YOY, White Catfish juveniles and age 1+ [all three rivers], and White Perch YOY (James River). Five species categories exhibited average abundances Bay Anchovy, Black Sea Bass YOY, Scup YOY, White Perch YOY (York and Rappahannock rivers), and White Perch age 1+ (all three rivers). Only age 1+ Blue Catfish exhibited above‐average abundances in 2019‐2020 (all three rivers). The highest index of abundance for Blue Catfish age 1+ in the James River follows the record year of YOY Blue Catfish recruitment that occurred last year
Tuckey, Troy D. - One of the best experts on this subject based on the ideXlab platform.
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Evaluating recruitment of American Eel, Anguilla rostrata, in the Potomac River (Spring 2021)
W&M ScholarWorks, 2021Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:American Eel (Anguilla rostrata) is a valuable commercial species along the Atlantic coast of North America from New Brunswick to Florida. Landings from Chesapeake Bay typically represent 60% of the annual United States commercial harvest (ASMFC 2012). American Eel is also important to the recreational fishery as it is often used live as bait for Striped Bass (Morone saxatilis) and Cobia (Rachycentron canadum). In 2020, Chesapeake Bay commercial landings of American Eel (218,005 lbs) were 80% of the U.S. landings (personal communication from the National Marine Fisheries Service, Fisheries Statistics Division). Since the 1980s, harvest along the U.S. Atlantic Coast has declined, with similar patterns occurring in the Canadian Maritime Provinces (Meister and Flagg 1997). The American Eel Benchmark Stock Assessment report (ASMFC 2012) established that the American Eel is depleted in U.S. waters; the 2017 stock assessment update (ASMFC 2017) confirmed that this population remains depleted
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2021 Annual Report Estimating Relative Juvenile Abundance of Ecologically Important Finfish in the Virginia Portion of Chesapeake Bay (1 July 2020 – 30 June 2021)
W&M ScholarWorks, 2021Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:The Trawl Survey provides crucial data to state, regional, and national fisheries management agencies, including the Virginia Marine Resources Commission (VMRC), the Atlantic States Marine Fisheries Commission (ASMFC), the Mid‐Atlantic Fisheries Management Council (MAFMC), and the National Marine Fisheries Service (NMFS). The MAFMC recognizes the juvenile trawl survey as one of the key predictors of Summer Flounder recruitment. Annual indices of juvenile abundance have been generated from trawl survey data for species of key recreational and ecological importance in the Virginia portion of Chesapeake Bay. These include Spot, Atlantic Croaker, Weakfish, Summer Flounder, Black Sea Bass, Scup, Striped Bass, White Perch, White Catfish, Channel Catfish, Blue Catfish, Silver Perch, American Eel, and Bay Anchovy. We completed most targeted tows this past year and only missed the upper‐river stations in the James and Rappahannock rivers and a few shallow Bay stations during July and August 2020 due to COVID‐19 safety restrictions. As a result, we could not calculate an index for American Eel in the James and Rappahannock rivers. We are also unable to calculate an index for the 2019 year‐class of Black Sea Bass due to the stay‐at‐home order that included May 2020, which was an important index month for this species. A summary of other species affected by COVID‐19 restrictions is shown in the table below. (...
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Evaluating Recruitment of American Eel, Anguilla rostrata, in the Potomac River (Spring 2020)
W&M ScholarWorks, 2020Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:American Eel (Anguilla rostrata) is a valuable commercial species along the Atlantic coast of North America from New Brunswick to Florida. Landings from Chesapeake Bay typically represent 60% of the annual United States commercial harvest (ASMFC 2012). American Eel is also important to the recreational fishery as it is often used live as bait for Striped Bass (Morone saxatilis) and Cobia (Rachycentron canadum). In 2016, Chesapeake Bay commercial landings of American Eel (728,717 lbs) were 78% of the U.S. landings (personal communication from the National Marine Fisheries Service, Fisheries Statistics Division). Since the 1980s, harvest along the U.S. Atlantic Coast has declined, with similar patterns occurring in the Canadian Maritime Provinces (Meister and Flagg 1997). The American Eel Benchmark Stock Assessment report (ASMFC 2012) established that the American Eel is depleted in U.S. waters; the 2017 stock assessment update (ASMFC 2017) confirmed that this population remains depleted
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Estimating Relative Abundance of Young-of-Year American Eel, Anguilla rostrata, in the Virginia Tributaries of Chesapeake Bay (Spring 2019)
W&M ScholarWorks, 2020Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:American Eel (Anguilla rostrata) is a valuable commercial species along the Atlantic coast of North America from New Brunswick to Florida. In the U.S., harvests have declined, with similar patterns occurring in the Canadian Maritime Provinces (Meister and Flagg 1997). An average of 62% of the annual landings of U.S. commercial harvest since 1993 have come from the Chesapeake Bay (personal communication from the National Marine Fisheries Service, Fisheries Statistics Division, 9 February 2015). In 2013, Virginia commercial landings were approximately 100,298 lbs; since mandatory reporting began in 1993, average annual landings in Virginia have been 193,200 lbs or 19% of the U.S. American Eel harvest (personal communication from the National Marine Fisheries Service, Fisheries Statistics Division, 9 February 2015). A decline in abundance of American Eel has been observed in recent years with conflicting evidence regarding spatial synchrony throughout their range (Richkus and Whalen 1999; Sullivan et al. 2006). Hypotheses for the decline in abundance include shifts in location of the Gulf Stream, pollution, overfishing, parasites, altered oceanic conditions, and barriers to fish passage (Castonguay et al. 1994; Haro et al. 2000; Knights 2003). Additionally, factors such as unfavorable wind-driven currents may affect glass Eel recruitment on the continental shelf and may have a greater impact than fishing mortality or continental climate change (Knights 2003). However, limited knowledge about fundamental biological characteristics of glass Eels has complicated interpretation of juvenile abundance trends (Sullivan et al. 2006). The Atlantic States Marine Fisheries Commission (ASMFC) adopted the Interstate Fishery Management Plan (FMP) for the American Eel in November 1999. The FMP calls for efforts to collect American Eel data through both fishery-dependent and fishery-independent studies in coastal states. Consequently, member jurisdictions agreed to implement an annual survey for young-of-year (YOY or glass) American Eels. The survey is intended to “…characterize trends in annual recruitment of the YOY Eels over time [to produce a] qualitative appraisal of the annual recruitment of American Eel to the U.S. Atlantic Coast” (ASMFC 2000). The development of these surveys began in 2000 with full implementation by 2001. Survey results provide necessary data on coastal recruitment success and further understanding of American Eel population dynamics. A recent American Eel benchmark stock assessment report found that the American Eel stock status is depleted and emphasized the importance of the coast-wide survey as an index of recruitment over the historical coastal range in the U.S. and an early warning of potential range contraction of the species (ASMFC 2012). In 2019, the Virginia Institute of Marine Science continued its spring sampling to estimate relative abundance of YOY American Eels in Virginia tributaries of Chesapeake Bay
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2020 Annual Report Estimating Relative Juvenile Abundance of Ecologically Important Finfish in the Virginia Portion of Chesapeake Bay (1 July 2019 – 30 June 2020)
W&M ScholarWorks, 2020Co-Authors: Tuckey, Troy D., Fabrizio, Mary C.Abstract:The Trawl Survey provides crucial data to state, regional, and national fisheries management agencies, including the Virginia Marine Resources Commission (VMRC), the Atlantic States Marine Fisheries Commission (ASMFC), the Mid‐Atlantic Fisheries Management Council (MAFMC), and the National Marine Fisheries Service (NMFS). The MAFMC recognizes the juvenile trawl survey as one of the key predictors of Summer Flounder recruitment. Annual indices of juvenile abundance have been generated from trawl survey data for species of key recreational and ecological importance in the Virginia portion of Chesapeake Bay. These include Spot, Atlantic Croaker, Weakfish, Summer Flounder, Black Sea Bass, Scup, Striped Bass, White Perch, White Catfish, Channel Catfish, Blue Catfish, Silver Perch, American Eel, and Bay Anchovy. In March 2020 the Governor of Virginia issued a stay‐at‐home order due to the COVID‐19 pandemic. As a result, we did not sample during April or May. We were able to resume sampling in June 2020 at a reduced capacity and we visited 61 sites (York River and the Chesapeake Bay). Logistical constraints resulting from policies enacted to reduce potential exposure of staff prevented us from completing the full survey. We report results from June 2020 as Appendix Table 3 as these data are not spatially consistent with previous months. We completed 897 tows from July 2019 to March 2020 and collected 318,954 fishes. Bay Anchovy continue to be the most abundant species observed in the survey, accounting for 57% of all fishes collected. Of the target species for which we provide indices of relative abundance, 12 species categories (considering YOY and age 1+ as distinct categories) exhibited below‐average abundance in 2019 – 2020 (American Eel [all three rivers], Blue Catfish YOY [all three rivers], Channel Catfish juveniles and age 1+ [all three rivers], Silver Perch YOY, Spot YOY, Striped Bass YOY, Summer Flounder YOY, Weakfish YOY, White Catfish juveniles and age 1+ [all three rivers], and White Perch YOY (James River). Five species categories exhibited average abundances Bay Anchovy, Black Sea Bass YOY, Scup YOY, White Perch YOY (York and Rappahannock rivers), and White Perch age 1+ (all three rivers). Only age 1+ Blue Catfish exhibited above‐average abundances in 2019‐2020 (all three rivers). The highest index of abundance for Blue Catfish age 1+ in the James River follows the record year of YOY Blue Catfish recruitment that occurred last year
David H Secor - One of the best experts on this subject based on the ideXlab platform.
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demographic attributes of yellow phase American Eels anguilla rostrata in the hudson river estuary
Canadian Journal of Fisheries and Aquatic Sciences, 2003Co-Authors: Wendy E Morrison, David H SecorAbstract:Management of American Eels (Anguilla rostrata) requires an understanding of how demographic attributes vary within large estuaries. Yellow-phase American Eel length and age structure, growth, dispersal, nematode infestation rates, loss rate (natural mortality and emigration), and production were measured at six sites throughout the tidal portion of the Hudson River. Short-term dispersal was low, with >70% of Eels at all sites captured <1 km from their original tagging area. Length was similar among sites (total length = 45.7 ± 0.3 cm), whereas age was substantially lower for brackish-water sites (8 ± 4 years) than for freshwater sites (17 ± 4 years). Growth was higher for brackish-water sites than for freshwater sites (8.0 cm·year–1 and 3.4 cm·year–1, respectively). From 1997 to 2000, infestation by the exotic nematode Anguillicola crassus increased dramatically in mean intensity as well as prevalence. Annual loss rates measured for the six sites varied between 9% and 24%, with no statistical difference ...
Martin Castonguay - One of the best experts on this subject based on the ideXlab platform.
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ARTICLE Growth, Female Size, and Sex Ratio Variability in American Eel of Different Origins in Both Controlled Conditions and the Wild: Implications for Stocking Programs
2016Co-Authors: Caroline L. Côte, Martin Castonguay, Scott A Pavey, Joshua A. Stacey, Thomas C. Pratt, Louis BernatchezAbstract:Freshwater Eels Anguilla spp. are declining worldwide, and a major challenge is understanding why these panmictic species show contrasting patterns of intraspecific phenotypic variation and recruitment. We present results on studies of the American Eel A. rostrata to understand and discriminate the effects of origin and plasticity on growth and sex determination. We considered two separate growth and one length-at-age data sets. The first growth data set originated from a 34-month rearing experiment starting from the glass Eel life stage to test the effects of origin, salinity, and density on growth and sex determination. The second growth data set originated from a shorter rearing experiment of 18 months starting at the yellow Eel stage (around 3 years old) and compared transplanted individuals in Lake Ontario (LO) with natural migrants to the LO area. The third data set compared transplanted individuals in LO sampled by electrofishing with naturally migrating individuals. Sex ratios were identical for all origins and treatments in the long-term growth experiment (34–35 % females). While male size distribution had little variability, certain female groups had a large variation in growth and presented fast- and slow-growing clusters. On the other hand, both cases of natural migrants to the LO area were consistent with bein
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Als et al. 2011 data file
2016Co-Authors: Thomas D Als, Martin Castonguay, Michael M Hansen, Gregory E Maes, Lasse Riemann, Kim Aarestrup, Peter Munk, Henrik Sparholt, Reinhold Hanel, Louis BernatchezAbstract:Data file with genotype data for 1010 European glass Eel, 271 European Eel larvae from the Sargasso Sea and 117 American Eel larvae from the Sargasso Sea. Individual number: Sample code for each individual Species.ID: AA = European Eel, AR American Eel Transect/region: Transect in the Sargasso Sea or geographical region in Europe or North Africa Station/sample: Specific station or locality posLat: Latitudinal position posLon: Longitudinal position Date: date of sampling Length..mm: Length of Eel larvae Microsatellite data are listed with one allele per column, i.e. two columns per locus. Microsatellite alleles are denoted by lenghts in bp
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rad sequencing highlights polygenic discrimination of habitat ecotypes in the panmictic American Eel
Current Biology, 2015Co-Authors: Scott A Pavey, Martin Castonguay, Jeremy Gaudin, Eric Normandeau, Melanie Dionne, Celine Audet, Louis BernatchezAbstract:Summary The two primary ways that species respond to heterogeneous environments is through local adaptation and phenotypic plasticity. The American Eel ( Anguilla rostrata ) presents a paradox; despite inhabiting drastically different environments [1], the species is panmictic [2, 3]. Spawning takes place only in the southern Sargasso Sea in the Atlantic Ocean [1]. Then, the planktonic larvae (leptocephali) disperse to rearing locations from Cuba to Greenland, and juveniles colonize either freshwater or brackish/saltwater habitats, where they spend 3–25 years before returning to the Sargasso Sea to spawn as a panmictic species. Depending on rearing habitat, individuals exhibit drastically different ecotypes [4–6]. In particular, individuals rearing in freshwater tend to grow slowly and mature older and are more likely to be female in comparison to individuals that rear in brackish/saltwater [4, 6]. The hypothesis that phenotypic plasticity alone can account for all of the differences was not supported by three independent controlled experiments [7–10]. Here, we present a genome-wide association study that demonstrates a polygenic basis that discriminates these habitat-specific ecotypes belonging to the same panmictic population. We found that 331 co-varying loci out of 42,424 initially considered were associated with the divergent ecotypes, allowing a reclassification of 89.6%. These 331 SNPs are associated with 101 genes that represent vascular and morphological development, calcium ion regulation, growth and transcription factors, and olfactory receptors. Our results are consistent with divergent natural selection of phenotypes and/or genotype-dependent habitat choice by individuals that results in these genetic differences between habitats, occurring every generation anew in this panmictic species.
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population genetics of the American Eel anguilla rostrata fst 0 and north atlantic oscillation effects on demographic fluctuations of a panmictic species
Molecular Ecology, 2013Co-Authors: Caroline Cote, Pierrealexandre Gagnaire, Vincent Bourret, Guy Verreault, Martin Castonguay, Louis BernatchezAbstract:We performed population genetic analyses on the American Eel (Anguilla rostrata) with three main objectives. First, we conducted the most comprehensive analysis of neutral genetic population structure to date to revisit the null hypothesis of panmixia in this species. Second, we used this data to provide the first estimates of contemporary effective population size (Ne) and to document temporal variation in effective number of breeders (Nb) in American Eel. Third, we tested for statistical associations between temporal variation in the North Atlantic Oscillation (NAO), the effective number of breeders and two indices of recruit abundance. A total of 2142 Eels from 32 sampling locations were genotyped with 18 microsatellite loci. All measures of differentiation were essentially zero, and no evidence for significant spatial or temporal genetic differentiation was found. The panmixia hypothesis should thus be accepted for this species. Nb estimates varied by a factor of 23 among 12 cohorts, from 473 to 10 999. The effective population size Ne was estimated at 10 532 (95% CI, 9312–11 752). This study also showed that genetically based demographic indices, namely Nb and allelic richness (Ar), can be used as surrogates for the abundance of breeders and recruits, which were both shown to be positively influenced by variation during high (positive) NAO phases. Thus, long-term genetic monitoring of American glass Eels at several sites along the North American Atlantic coast would represent a powerful and efficient complement to census monitoring to track demographic fluctuations and better understand their causes.
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differential effects of origin and salinity rearing conditions on growth of glass Eels of the American Eel anguilla rostrata implications for stocking programmes
Journal of Fish Biology, 2009Co-Authors: Caroline Cote, Guy Verreault, Martin Castonguay, Louis BernatchezAbstract:In this study, growth patterns were monitored in controlled fresh and brackish water (BW) conditions for 7 months during Anguilla rostrata glass Eel and elver stages. Null hypotheses tested were that there is no significant difference in growth between glass Eels (1) collected from two geographic regions typified by different sex ratios, (2) reared in fresh and BW and (3) due to origin × salinity interactions. It was found that young A. rostrata from Mira River (MR, Cape Breton, Nova Scotia, Canada, an area where both males and females occur) grew faster than those from Grande-Riviere-Blanche (Quebec, Canada, an area where population are highly skewed towards females; 99–100%). Anguilla rostrata from both origins also grew faster in BW, although there was a trend for origin × salinity interactions whereby this effect was more pronounced for fish from the MR. The results support the hypothesis that salinity can influence growth patterns, as possibly can quantitative genetic differences between A. rostrata glass Eels from different origins. Possible explanations for these patterns and potential consequences for sex determination and translocation programmes are discussed.