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Environmental DNA (eDNA) monitoring methods have played a significant role in improving fisheries management decisions. Yet, their impact to date has been rather limited in Canada, where eDNA sampling and analyses are only beginning to be used to inform management and conservation decisions, practices, and policies. Studies investigating hurdles to the incorporation of eDNA evidence into fisheries management decisions generally focus on technical challenges (i.e., risks of false-positive and false-negative detections). We set out to identify challenges that eDNA researchers and conservation practitioners must overcome to fully unlock the benefits of eDNA sampling for fish management in the Canadian context. We discuss aspects of the broad and heterogeneous geography, preponderance of regions located far from densely populated areas, complex political landscape, and cultural diversity of Canada that may complicate the design of reliable eDNA monitoring tools or restrict their use if not adequately addressed. To advocate for the wider use of eDNA sampling, we outline a number of action items that would facilitate the broad adoption of eDNA sampling as a monitoring tool at the Canadian scale. [ABSTRACT FROM AUTHOR]

Lampreys, one of the two surviving groups of ancient vertebrates, have become important models for study in diverse fields of biology. Lampreys (of which there are approximately 40 species) are being studied, for example, (a) to control pest sea lamprey in the North American Great Lakes and to restore declining populations of native species elsewhere; (b) in biomedical research, focusing particularly on the regenerative capability of lampreys; and (c) by developmental biologists studying the evolution of key vertebrate characters. Although a lack of genetic resources has hindered research on the mechanisms regulating many aspects of lamprey life history and development, formerly intractable questions are now amenable to investigation following the recent publication of the sea lamprey genome. Here, we provide an overview of the ways in which genomic tools are currently being deployed to tackle diverse research questions and suggest several areas that may benefit from the availability of the sea lamprey genome. [ABSTRACT FROM AUTHOR]

Considerable uncertainty exists in determination of the phylogeny among extant members of the Dreissenidae, especially those inhabiting the Ponto-Caspian basin, as multiple systematic revisions based on morphological characteristics have failed to resolve relationships within this group of bivalves. In this study we use DNA sequence analyses of two mitochondrial gene fragments, 16S rRNA and cytochrome c oxidase subunit I (COI), to determine phylogenetic relationships among Dreissena rostriformis, D. bugensis, D. polymorpha, D. stankovici, Congeria kusceri, and Mytilopsis leucophaeata. Dreissena stankovici was determined to represent a sister taxa to D. polymorpha and both are more closely related to other extant Dreissena species than Congeria or Mytilopsis. Sequence divergence between D. rostriformis and D. bugensis was relatively low (0.3–0.4%), suggesting that these two taxa constitute a single species. However, environmental differences suggest two races of D. rostriformis, a brackish water race (rostriformis) and a freshwater race (bugensis). Spread of bugensis-type individuals into habitats in the Caspian Sea that are occupied by rostriformis-type individuals may create novel hybridization opportunities. Species-specific molecular markers also were developed in this study since significant intraspecific variation in morphological features complicates dreissenid identification. Using two gene fragments (nuclear 28S and 16S), we identified restriction fragment length polymorphisms (RFLPs) that distinguish among D. rostriformis/bugensis, D. polymorpha, and D. stankovici and revealed the presence of a cryptic invader to the Black Sea basin, Mytilopsis leucophaeata. This is the first report of this North American native in southern Europe. [Copyright &y& Elsevier]

The frequency of hybridization between cutthroat ( Onchorhynchus clarki clarki) and rainbow ( O. mykiss irideus) trout from coastal habitats in British Columbia, Canada, was examined in seven populations where the two species are sympatric with no history of rainbow trout stocking and compared with areas where native rainbow trout populations have been supplemented with hatchery fish (three populations). Four nuclear markers were used to identify each species and interspecific hybrids and one mitochondrial marker showed the direction of gene exchange between species. The frequency of hybrids was significantly higher (Fisher exact test, P<0.001) in river systems where hatchery rainbow trout have been introduced (50.6% hybrids) than in populations where the two species naturally co-occur without supplementation (9.9% hybrids). [ABSTRACT FROM AUTHOR]

Sea lamprey undergo programmed genome rearrangement (PGR) in which ∼20% of the genome is jettisoned from somatic cells during embryogenesis. Although the role of PGR in embryonic development has been studied, the role of the germline-specific region (GSR) in gonad development is unknown. We analysed RNA-sequence data from 28 sea lamprey gonads sampled across life-history stages, generated a genome-guided de novo superTranscriptome with annotations, and identified germline-specific genes (GSGs). Overall, we identified 638 GSGs that are enriched for reproductive processes and exhibit 36x greater odds of being expressed in testes than ovaries. Next, while 55% of the GSGs have putative somatic paralogs, the somatic paralogs are not differentially expressed between sexes. Further, putative orthologs of some the male-biased GSGs have known functions in sex determination or differentiation in other vertebrates. We conclude that the GSR of sea lamprey plays an important role in testicular differentiation and potentially sex determination. RNA-sequencing of sea lamprey gonads at different life-history stage identifies germline-specific genes which are highly expressed in males during spermatogenesis. This suggests a link between male-biased germline expression and sex differentiation in the sea lamprey. [ABSTRACT FROM AUTHOR]

Conservation aquaculture provides a means for promoting environmental stewardship, useful both in the context of restoring native species and limiting the production of invasive species. Aquaculture of lampreys is a relatively recent endeavor aimed primarily at producing animals to support the restoration of declining native populations. However, in the Laurentian Great Lakes, where sea lamprey Petromyzon marinus are invasive, the ability to acquire a reliable source of certain life stages would be a significant benefit to those controlling their populations and studying the species. Here, we apply methodologies developed for Pacific lamprey Entosphenus tridentatus restoration to investigate the feasibility of rearing larval sea lamprey under laboratory conditions. In two experiments lasting 3 and 9 months, we tested the effects of different dietary sources and water temperature (ambient and controlled) on the survival and growth of wild-caught larvae. Rearing conditions had no effect on mortality, as larval survival was 100% in both experiments. Growth was significantly affected by water temperature, with the highest average daily growth rates observed at 22 and 15°C (0.14 mm day−1) and lowest at 8°C (0.06 mm day−1). Diets of yeast alone (0.19 and 0.21 g L−1) performed better than those comprising a mixture of yeast and other material when fed 3 times weekly (rice flour, wheat flour, fish meal; 0.19 and 0.32 g L−1). Averaged across the three constant temperatures (8, 15, and 22°C), larvae fed on yeast grew 0.13 mm day−1 and 0.01 g day−1, whereas on yeast + fish meal, they grew 0.09 mm day−1 and 0.01 g day−1. At ambient temperature (4–20°C), larvae fed on yeast grew 0.15 mm day−1 and 0.01 g day−1, whereas those fed on yeast + wheat flour grew 0.13 mm day−1 and 0.008 g day−1 and those fed on yeast + rice flour grew 0.12 mm day−1 and 0.009 g day−1. An experimental duration of 90 days was sufficient to detect significant changes to larval sea lamprey growth stemming from temperature variation. Overall, rearing of sea lamprey in captivity appears feasible at low density (31–32 g m−2 and 17–25 larvae m−2), but uncertainties remain regarding the most appropriate means of providing adequate feed for these fish in high-density conditions. [ABSTRACT FROM AUTHOR]

Lampreys are jawless fishes that diverged 550 million years ago from other vertebrates. Sequencing of the somatic and the germline genomes of the sea lamprey (Petromyzon marinus) in 2013 and 2018, respectively, has helped to improve our understanding of the genes and gene networks that control many aspects of lamprey development. However, little is known about the genetic basis of gonadal differentiation in lampreys, partly due to the prolonged period during which their gonads remain sexually indeterminate. We performed RNAsequencing on gonadal samples from four chestnut lamprey (Ichthyomyzon castaneus) and six northern brook lamprey (I. fossor) to identify differentially expressed genes (DEG's) and pathways associated with transcriptomic differences in: (1) larvae during early gonadal differentiation versus definitive females (i.e., with oocytes in the slow cytoplasmic growth phase); and (2) females versus definitive males undergoing spermatogonial proliferation. We compared the mapping percentages of these transcriptomes to the two available sea lamprey reference genomes and three annotation files (Ensembl and UCSC for the somatic genome and SIMRbase for the germline genome). We found that mapping the RNA-seq reads to the germline genome gave superior results and, using Trinotate, we provided new putative annotations for 8161 genes in the somatic assembly and 880 genes for the germline assembly. We identified >2000 DEG's between stages and sexes, as well as biological pathways associated with each. Interestingly, some of the upregulated genes (e.g., DEG's associated with spermiation) suggest that changes in gene expression can precede morphological changes by several months. In contrast, only 81 DEG's were evident between the chestnut lamprey (that remains sexually immature during an extended post-metamorphic parasitic feeding phase) and the nonparasitic northern brook lamprey (that undergoes sexual maturation near the end of metamorphosis), but few replicates were available for comparable stages and sexes. This work lays the foundation for identifying and confirming the orthology and the function of genes involved in gonadal development in these and other lamprey species across more developmental stages [ABSTRACT FROM AUTHOR]

Modern lampreys (Petromyzontiformes) are one of two lineages of surviving jawless fishes (agnathans), and are thus of critical importance to understanding the evolution of the vertebrates. Although their fossil record is meager, it appears they have remained morphologically conserved for at least 360 million years, but the origin of their multi-stage life history is unclear. Unlike hagfishes, the other extant group of jawless fishes, which exhibit direct development, all modern lampreys possess a complex life cycle which includes a long-lived freshwater larval (or ammocoete) period, followed by a true metamorphosis into a sexually-immature juvenile and then mature adult which differ dramatically in their morphology and ecology from the larva. Because of their basal position, it is critical to understand when the extant lamprey life history evolved, and if such a life history was present in the last common ancestor of agnathans and gnathostomes. Recent discoveries in paleontology, genomic analyses, and developmental biology are providing insights into this problem. The current review synthesizes these findings and concludes that the ancestral lamprey life cycle followed a direct development. We suggest that the larval period was short and relatively limited if present at all, but that the juvenile included modern larval traits; over the course of evolution, differential selection pressures throughout the lifetime produced distinct larval and juvenile/adult periods. Each period required the dramatically different morphologies seen in modern lampreys, ultimately requiring a true metamorphosis to accommodate the large changes in the body plan and to maximize the efficiency of each life period. As a result, modern lamprey life histories are a patchwork of ancestral and derived characters. [ABSTRACT FROM AUTHOR]

Zebra mussel Dreissena polymorpha (Pallas, 1771), an invasive bivalve in North America, was first recorded in Lake Winnipeg in 2013. Quagga mussel D. bugensis (Andrusov, 1897), a second invasive mussel to North America, has yet to be detected in Manitoba waters. The establishment and continued spread of zebra mussels is of concern. Accordingly, we developed two species-specific and one Dreissena-specific qPCR-based environmental DNA (eDNA) assays designed as a single multiplexed reaction able to identify the presence of zebra mussel and infer the presence of quagga mussel in water samples from at-risk and invaded locations. In 2014, samples were collected from four invaded harbours on Lake Winnipeg during the early (May) and late (October) seasons. Zebra mussel eDNA was detected in 0–33.3% of samples per site early in the season, whereas late season sample detection ranged from 42.9 to 100%. In order to confirm that there was no nonspecific amplification of DNA from local biota, samples were also collected from sites where neither adult nor veliger-stage zebra mussels had been previously observed. These sites included three harbours on Lake Winnipeg and six sites within the Manitoban portion of the Red River. No amplification of eDNA was recorded at these sites except for that at a float-plane dock in the Red River upstream of Lake Winnipeg. Zebra mussels were subsequently detected at this location by sampling for transformed attached individuals. Thus, we demonstrate that eDNA is an early indicator of the presence of zebra mussels and is a useful detection tool at the forefront of their recent invasion in Manitoba. This work provides the foundation for the development of a zebra mussel eDNA monitoring program for waterbodies in Manitoba and western Canada. [ABSTRACT FROM AUTHOR]

The article discusses research which examined the outmigration of anadromous River Lamprey or Lampetra ayresii and its occurrence at the John Day Dam in Columbia River basin. Topics discussed include the prolonged freshwater larval stage, conservation concern for lampreys worldwide and efforts to increase the monitoring of outmigrating juvenile lampreys.

Background: During development, humans and other jawed vertebrates (Gnathostomata) express distinct hemoglobin genes, resulting in different hemoglobin tetramers. Embryonic and fetal hemoglobin have higher oxygen affinities than the adult hemoglobin, sustaining the oxygen demand of the developing organism. Little is known about the expression of hemoglobins during development of jawless vertebrates (Agnatha). Results: We identified three hemoglobin switches in the life cycle of the sea lamprey. Three hemoglobin genes are specifically expressed in the embryo, four genes in the filter feeding larva (ammocoete), and nine genes correspond to the adult hemoglobin chains. During the development from the parasitic to the reproductive adult, the composition of hemoglobin changes again, with a massive increase of chain aHb1. A single hemoglobin chain is expressed constitutively in all stages. We further showed the differential expression of other globin genes: Myoglobin 1 is most highly expressed in the reproductive adult, myoglobin 2 expression peaks in the larva. Globin X1 is restricted to the embryo; globin X2 was only found in the reproductive adult. Cytoglobin is expressed at low levels throughout the life cycle. Conclusion: Because the hemoglobins of jawed and jawless vertebrates evolved independently from a common globin ancestor, hemoglobin switching must also have evolved convergently in these taxa. Notably, the ontogeny of sea lamprey hemoglobins essentially recapitulates their phylogeny, with the embryonic hemoglobins emerging first, followed by the evolution of larval and adult hemoglobins. [ABSTRACT FROM AUTHOR]

Successful integrated management of the invasive predatory sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes of North America is owed largely to the long history of beneficial use of two lampricides: 3-trifluoromethyl-4-nitrophenol (TFM) and 2′,5-dichloro-4′-nitrosalicylanilide (niclosamide). Ensuring continued successful sea lamprey control necessitates consideration of possible next-generation lampricides to supplement or replace current lampricides. This review identifies fifteen hallmarks of success for current lampricides to be used as design criteria in a search for next-generation lampricides. A three-stage research approach is outlined. Targeted research using omics, computer modelling, and high-throughput technology to define molecular mechanisms and high probability molecular targets for sea lamprey selective toxic action is crucial to prioritizing chemical candidates. Targeted delivery or identifying synergists to existing or new lampricides can provide increased efficiency and reduced environmental impact. Ultimate development of next-generation lampricides will rely on traditional toxicity testing methodologies to ensure safety and regulatory compliance. [ABSTRACT FROM AUTHOR]

Despite widespread recognition that municipal wastewaters contain natural and synthetic estrogens, which interfere with development and reproduction of fishes in freshwaters worldwide, there are limited data on the extent to which natural populations of fish can recover from exposure to these compounds. We conducted whole-lake additions of an active component of the birth control pill (17α-ethynylestradiol; EE2) that resulted in the collapse of the fathead minnow (Pimephales promelas) population. Here we quantify physiological, population, and genetic characteristics of this population over the 7 years after EE2 additions stopped to determine if complete recovery was possible. By 3 years posttreatment, whole-body vitellogenin concentrations in male fathead minnow had returned to baseline, and testicular abnormalities were absent In the spring of the fourth year, adult size-frequency distribution and abundance had returned to pretreatment levels. Microsatellite analyses clearly showed that postrecovery fish were descendants of the original EE2-treated population. Results from this whole-lake experiment demonstrate that fish can recover from EE2 exposure at the biochemical through population levels, although the timelines to do so are long for multigenerational exposures. These results suggest that wastewater treatment facilities that reduce discharges of estrogens and their mimics can improve the health of resident fish populations in their receiving environments. [ABSTRACT FROM AUTHOR]

Next-generation sequencing data can be mined for highly informative single nucleotide polymorphisms ( SNPs) to develop high-throughput genomic assays for nonmodel organisms. However, choosing a set of SNPs to address a variety of objectives can be difficult because SNPs are often not equally informative. We developed an optimal combination of 96 high-throughput SNP assays from a total of 4439 SNPs identified in a previous study of Pacific lamprey ( Entosphenus tridentatus) and used them to address four disparate objectives: parentage analysis, species identification and characterization of neutral and adaptive variation. Nine of these SNPs are FST outliers, and five of these outliers are localized within genes and significantly associated with geography, run-timing and dwarf life history. Two of the 96 SNPs were diagnostic for two other lamprey species that were morphologically indistinguishable at early larval stages and were sympatric in the Pacific Northwest. The majority (85) of SNPs in the panel were highly informative for parentage analysis, that is, putatively neutral with high minor allele frequency across the species' range. Results from three case studies are presented to demonstrate the broad utility of this panel of SNP markers in this species. As Pacific lamprey populations are undergoing rapid decline, these SNPs provide an important resource to address critical uncertainties associated with the conservation and recovery of this imperiled species. [ABSTRACT FROM AUTHOR]

Lampreys diverged from the jawed vertebrate lineage approximately 500 million years ago. Lampreys undergo sex differentiation much later than most other vertebrates, and ovarian differentiation occurs several years before testicular differentiation. The genetic basis of lamprey sex differentiation is of particular interest both because of the phylogenetic importance of lampreys and because of their unusual pattern of sex differentiation. As well, differences between parasitic and non-parasitic lampreys may first become evident at ovarian differentiation. However, nothing is known about the genetic basis of ovarian differentiation in lampreys. This study examined potential differences in gene expression before, during, and after ovarian differentiation in parasitic chestnut lamprey Ichthyomyzon castaneus and non-parasitic northern brook lamprey Ichthyomyzon fossor . Eight target genes (17β-hydroxysteroid dehydrogenase, germ cell-less, estrogen receptor β, insulin-like growth factor 1 receptor, daz-associated protein 1, cytochrome c oxidase subunit III, Wilms’ tumour suppressor protein 1, and dehydrocholesterol reductase 7) were examined. Northern brook lamprey displayed higher expression of cytochrome c oxidase subunit III, whereas chestnut lamprey displayed higher expression of insulin-like growth factor 1 receptor; these genes may be involved in apoptosis and oocyte growth, respectively. Presumptive male larvae had higher expression of Wilms’ tumour suppressor protein 1, which may be involved in the undifferentiated gonad and/or later testicular development. Differentiated females had higher expression of 17β hydroxysteroid dehydrogenase and daz-associated protein 1, which may be involved in female development. This study is the first to identify genes that may be involved in ovarian differentiation and fecundity in lampreys. [ABSTRACT FROM AUTHOR]

The parasitic sea lamprey (Petromyzon marinus) has caused extensive losses to commercial fish stocks of the upper Great Lakes of North America. Methods of controlling the sea lamprey include trapping, barriers to prevent migration, and use of a chemical lampricide (3-trifluoromethyl-4-nitrophenol) to kill the filter-feeding larvae. Concerns about the non-specificity of these methods have prompted continued development of species-specific methods to control lampreys outside their native range. In this study, we considered the utility of RNA interference to develop a sea lamprey-specific lampricide. Injection of six different short interfering, double-stranded RNAs (siRNAs) into lamprey embryos first confirmed that the siRNAs could reduce the targeted transcript levels by more than 50%. Two size classes of lamprey larvae were then fed the siRNAs complexed with liposomes, and three of the siRNAs (targeting elongation factor 1α, calmodulin, and α-actinin) reduced transcript levels 2.5, 3.6, and 5.0–fold, respectively, within the lamprey midsections. This is not only the first demonstration of RNAi in lampreys, but it is also the first example of delivery of siRNAs to a non-mammalian vertebrate through feeding formulations. One of the siRNA treatments also caused increased mortality of the larvae following a single feeding of siRNAs, which suggests that prolonged or multiple feedings of siRNAs could be used to kill filter-feeding larvae within streams, following development of a slow-release formulation. The genes targeted in this study are highly conserved across many species, and only serve as a proof-of-concept demonstration that siRNAs can be used in lampreys. Given that RNA interference is a sequence-specific phenomenon, it should be possible to design siRNAs that selectively target gene sequences that are unique to sea lampreys, and thus develop a technology to control these pests without adversely affecting non-target species. [ABSTRACT FROM AUTHOR]

Sea lampreys, , are invasive to the Laurentian Great Lakes where they have decimated native fishes. Great Lakes sea lampreys have been subjected to control measures for several decades, and the drive to control them has led to major advances in understanding their biology and in informing management. In contrast, anadromous sea and Pacific () lampreys have co-evolved with their oceanic prey. Both of these anadromous lampreys are in decline, and a limited amount of information on their biology has stymied conservation. The tendency has been to make biological inferences about anadromous lampreys based on the Great Lakes sea lamprey without justifiable evidence. We identify areas in which key information is missing for the juvenile (parasitic feeding) phase and adult freshwater spawning migrations, and compare and contrast information for these lampreys. Our comparisons reveal major differences, some intriguing similarities, and key unknowns that will require empirical testing. [ABSTRACT FROM AUTHOR]

Invasive sea lamprey (Petromyzon marinus Linnaeus, 1758) are currently managed by the Great Lakes Fishery Commission in an effort to reduce pest populations below levels that cause ecological damage. One technique to improve stream population assessments could be molecular surveillance in the form of environmental DNA (eDNA) monitoring. We developed and validated four probe-based quantitative polymerase chain reaction (qPCR) assays, then used two probes (cytb, nd1) to determine whether eDNA concentration was correlated with adult and larval sea lamprey density in the lab. We found a strong positive correlation between adult sea lamprey densities of 2, 20, and 200 individuals/2000L and eDNA concentrations in tanks using both assays (cytb, nd1). For larval laboratory tank density trials, eDNA concentrations were generally near our limit of quantification and there was no significant difference in copy numbers detected between larval sea lamprey densities of 1, 5, and 25 individuals/28L. Therefore, we examined detection probability rather than concentration with laboratory tank densities. We observed a trend of increasing detection probabilities with increased larval sea lamprey density that approached significance suggesting that when DNA copy numbers are low, detection rates may be more informative in predicting varying densities of larval sea lamprey. The ability to assess sea lamprey densities from a water sample could be a powerful tool to improve traditional assessment and stream ranking techniques. Further refinement of this method in the field may make eDNA surveillance of sea lamprey a reliable part of stream assessments. Rapid eDNA analysis from many streams may help focus traditional assessment efforts, thereby improving the efficiency of invasive sea lamprey control efforts. [ABSTRACT FROM AUTHOR]

Partial anadromy is common within salmonid populations, where resident and anadromous individuals interbreed and overlap in habitat use during portions of life. Deviation to this definition occurs within the Husky Lakes drainage basin (HLDB), Northwest Territories, where freshwater resident, semi-anadromous, and brackish-water resident lake trout ( Salvelinus namaycush) life history types are documented. In this study, microsatellite DNA variation was assayed to evaluate genetic structuring among life history types from the HLDB and adjacent lower Mackenzie River system. Significant differentiation was resolved among most locations and life histories (global FST = 0.192). Brackish-water residents were differentiated from all locations and life histories, including sympatric semi-anadromous individuals, providing evidence for genetically fixed strategies. Also, this provides the first evidence of breeding partial migration in salmonids using brackish-water environments, where brackish-water residents and semi-anadromous migrants interact during the nonbreeding season, but the latter migrate elsewhere to spawn. Alternatively, the lack of genetic differentiation between semi-anadromous and Sitidgi Lake residents suggests conditional mating tactics may also influence partial anadromy. This work provides novel insights into partial anadromy in Arctic salmonids and expands our knowledge of biodiversity in this region. [ABSTRACT FROM AUTHOR]

The Pacific LampreyEntosphenus tridentatus, an anadromous fish native to the northern Pacific Ocean and bordering freshwater habitats, has recently experienced steep declines in abundance and range contractions along the West Coast of North America. During the early 1990s, Native American tribes recognized the declining numbers of lamprey and championed their importance. In 2012, 26 entities signed a conservation agreement to coordinate and implement restoration and research for Pacific Lamprey. Regional plans have identified numerous threats, monitoring needs, and strategies to conserve and restore Pacific Lamprey during their freshwater life stages. Prime among these are needs to improve lamprey passage, restore freshwater habitats, educate stakeholders, and implement lamprey-specific research and management protocols. Key unknowns include range-wide trends in status, population dynamics, population delineation, limiting factors, and marine influences. We synthesize these key unknowns, with a focus on the freshwater life stages of lamprey in the Columbia River basin. [ABSTRACT FROM AUTHOR]

Capelin ( Mallotus villosus (Müller, 1776)), a focal forage fish in the north Atlantic, spawn on both beach and demersal (deep-water) sites throughout their circumpolar distribution. Although these habitats rarely occur in close proximity, demersal spawning sites within 4 km of beach spawning sites (subtidal) have recently been discovered in two coastal embayments in Newfoundland, Canada. The physical environment differs considerably between beach and subtidal spawning sites, creating the potential for local adaptation and genetic divergence of capelin from the two habitats, but this has never been investigated on a fine spatial scale. We use eight microsatellite loci to test for genetic divergence between capelin spawning at beach and subtidal sites within these two coastal regions in Newfoundland. We found no genetic differentiation between fish spawning at beach and subtidal sites or between the two regions. The results from this fine-scale study are in agreement with the lack of habitat-based structure reported in other studies examining beach and demersal sites separated by a larger geographic area. We suggest that instead of showing site fidelity and local adaptation, the facultative use of alternate spawning habitats may be a more successful strategy in an unpredictable environment. [ABSTRACT FROM AUTHOR]

Unlike most anadromous fishes that have evolved strict homing behaviour, Pacific lamprey ( Entosphenus tridentatus) seem to lack philopatry as evidenced by minimal population structure across the species range. Yet unexplained findings of within-region population genetic heterogeneity coupled with the morphological and behavioural diversity described for the species suggest that adaptive genetic variation underlying fitness traits may be responsible. We employed restriction site-associated DNA sequencing to genotype 4439 quality filtered single nucleotide polymorphism ( SNP) loci for 518 individuals collected across a broad geographical area including British Columbia, Washington, Oregon and California. A subset of putatively neutral markers ( N = 4068) identified a significant amount of variation among three broad populations: northern British Columbia, Columbia River/southern coast and 'dwarf' adults ( FCT = 0.02, P ≪ 0.001). Additionally, 162 SNPs were identified as adaptive through outlier tests, and inclusion of these markers revealed a signal of adaptive variation related to geography and life history. The majority of the 162 adaptive SNPs were not independent and formed four groups of linked loci. Analyses with matsam software found that 42 of these outlier SNPs were significantly associated with geography, run timing and dwarf life history, and 27 of these 42 SNPs aligned with known genes or highly conserved genomic regions using the genome browser available for sea lamprey. This study provides both neutral and adaptive context for observed genetic divergence among collections and thus reconciles previous findings of population genetic heterogeneity within a species that displays extensive gene flow. [ABSTRACT FROM AUTHOR]

Most species with lengthy migrations display some degree of natal homing; some (e.g. migratory birds and anadromous salmonids) show spectacular feats of homing. However, studies of the sea lamprey ( Petromyzon marinus) indicate that this anadromous species locates spawning habitat based on pheromonal cues from larvae rather than through philopatry. Previous genetic studies in the anadromous Pacific lamprey ( Entosphenus tridentatus) have both supported and rejected the hypothesis of natal homing. To resolve this, we used nine microsatellite loci to examine the population structure in 965 Pacific lamprey from 20 locations from central British Columbia to southern California and supplemented this analysis with mitochondrial DNA restriction fragment length polymorphism analysis on a subset of 530 lamprey. Microsatellite analysis revealed (i) relatively low but often statistically significant genetic differentiation among locations (97% pairwise FST values were <0.04 but 73.7% were significant); and (ii) weak but significant isolation by distance ( r2 = 0.0565, P = 0.0450) but no geographic clustering of samples. The few moderate FST values involved comparisons with sites that were geographically distant or far upstream. The mtDNA analysis-although providing less resolution among sites (only 4.7% FST values were significant)-was broadly consistent with the microsatellite results: (i) the southernmost site and some sites tributary to the Salish Sea were genetically distinct; and (ii) southern sites showed higher haplotype and private haplotype richness. These results are inconsistent with philopatry, suggesting that anadromous lampreys are unusual among species with long migrations, but suggest that limited dispersal at sea precludes panmixia in this species. [ABSTRACT FROM AUTHOR]

Parapatric freshwater and anadromous parasitic lampreys (Petromyzontiformes) from southwestern Vancouver Island, British Columbia, have been described as distinct taxa (Vancouver lamprey ( (Beamish, 1982)) and Pacific lamprey ( (Richardson, 1836)), respectively), using morphology, life history, and physiology. We tested for genetic differentiation at microsatellite DNA loci between these taxa and similar freshwater parasitic lampreys from two other lakes. The number of alleles and expected heterozygosity averaged 3.8 and 0.50, respectively, across loci and populations, and anadromous populations were more variable than freshwater populations. Population subdivision was moderate ( FST = 0.096, P < 0.001) and 3% of the total variation was found between taxa and 1.7% was found among populations within taxa (both P < 0.001). Parapatric freshwater and anadromous parasitic lampreys separated by a maximum of 40 km were more distinct (mean FST = 0.042) than were anadromous populations located 800 km from one another (mean FST = 0.012). Localities within lakes with parasitic freshwater lampreys, however, showed little differentiation ( FST = 0.0-0.08). Our data support recognizing E. macrostomus and E. tridentatus as distinct species, but similar levels of differentiation between these taxa and other freshwater parasitic lampreys suggest a species complex where the taxonomy remains unclear. [ABSTRACT FROM AUTHOR]

Using different classes of genetic markers can provide insight into the role of selection, as well as a broader context for identifying population differentiation. We used nine microsatellite loci and polymorphisms at eight gene loci (major histocompatibility complex (MHC) classes I and II, growth hormones 1 and 2, transferrin, and immunoglobin heavy-chain) to determine population structure in six coastal populations (Vancouver Island, VI) and five interior populations (Fraser River, FR) of Chinook salmon (Oncorhynchus tshawytscha) in British Columbia, Canada. FST and G′ST values for specific VI gene loci were significantly higher than those for the FR and VI microsatellite loci or the FR gene loci. Pairwise microsatellite FST values were correlated with geographic distance across regions, but not using the gene locus marker data. Neighbor-joining cluster analyses showed one VI population as particularly divergent based on the gene locus data, while the VI and FR microsatellite locus and the FR gene locus analyses yielded no anomalous population divergence. The VI MHC class II marker FST values were exceptionally high, indicative of probable directional selection acting on MHC class II. Our results are consistent with local adaptation in Chinook salmon, but the nature of the local adaptation likely differs among regions. [ABSTRACT FROM AUTHOR]