Journal of Fish Biology

Previous studies have estimated the size, mass, and population of hypothetical unknown animals in a large, oligotrophic freshwater loch in Scotland based on biomass and other observational considerations. The eel hypothesis proposes that the anthrozoological phenomenon at Loch Ness can be explained in part by observations of large specimens of European eel (Anguilla anguilla), as these animals are most compatible with morphological, behavioural, and environmental considerations. The present study expands upon the eel hypothesis and related literature by estimating the probability of observing eels at least as large as have been proposed, using catch data from Loch Ness and other freshwater bodies in Europe. Skew normal and generalized extreme value distributions were fitted to eel body length distributions in order to estimate cumulative distribution functions from which probabilities were obtained. The chances of finding a large eel in Loch Ness are around 1 in 50, 000 for a 1-meter specimen, which is reasonable given the lochs fish stock and suggests some sightings of smaller unknown animals may be accounted for by large eels. However, the probability of finding a specimen upwards of 6 meters is essentially zero, therefore eels probably do not account for sightings of larger animals. The existence of exceedingly large eels in the loch is not likely based on purely statistical considerations.

Evolution of morphological traits is hypothesized to act on an extended time scale, yet studies have suggested that these changes are possible within a few generations. Trophic polymorphism enabled through niche adaptations and ecological opportunity is one phenomenon that facilitate occurrence of rapid adaptive variation, common in many northern freshwater fish species. One such species is Arctic charr, which is known for its extensive variation in morphology and the occurrence of morphs. However, the speed at which such morphological variation arises is poorly studied despite the importance for understanding the onset of evolution. The aim of this study was to elucidate this process in a gradient of eight lakes that was stocked with Arctic charr in the period from 1910 to 1917 from Lake Tinnsjoen, Norway. We used morphological measurements to test for differences in traits between populations and Haldane and Darwins evolutionary rates to estimate divergence rates in traits. We also tested for correlation between putative genetic and morphological divergence. In addition, we contrasted the morphological divergence with that expected under neutral genetic expectations, using 12 microsatellite markers, to analyze whether and which morphological differences that is following early genetic divergence. A significant genetic differentiation was found between the source population and five of the translocated populations with corresponding differences in morphological traits for four of the populations. Population genetic structuring indicated six different genetic clusters. The translocated populations also exhibited trait divergence estimated with both Haldane and Darwins rates. Differences in morphological traits showed a significant correlation with genetic divergence, and the morphological differences were most likely affected by differences in lake parameters such as maximum depth, lake size and fish community. We conclude that intraspecific morphological and genetic divergence can form on short evolutionary time scales with important implications for conservation and management practices.

Freshwater ecosystems have been severely fragmented by artificial in-stream structures designed to manage water for human use. Significant efforts have been made to reconnect freshwater systems for fish movement, through the design and installation of dedicated fish passage structures (fishways) and by incorporating fish-sensitive design features into conventional infrastructure (e.g. culverts). Key to the success of these structures is making sure that the water velocities within them do not exceed the swimming capacities of the local fish species. Swimming performance data is scarce for Australian fish, which have a reduced swimming capacity when compared to many North American and European species. To help close this knowledge gap and assist fisheries management and civil engineering, we report the swimming performance capacities of twenty-one small-bodied fish and juveniles (< 10 cm) of large bodied species native to Australia as measured by critical swimming speed (Ucrit) and burst swimming speed (Usprint) in a recirculating flume. This data is complemented by endurance swim trials in a 12-meter hydraulic flume channel, and by measures of flume traverse success. Building on the utility of this dataset, we used a panel of morphological, behavioural and ecological traits to first assess their relative contributions to the observed swimming performance data, and second, to determine if they could be used to predict swimming performance capacity - a useful tool to assist in the management of species of conservation concern where access to swimming performance data may be limited. We found that body length combined with depth station (benthic, pelagic or surface) explained most of the interspecific variation in observed swimming performance data, followed by body shape and tail shape. These three traits were the most effective at predicting swimming performance in a model/unknown fish. This data will assist civil engineers and fisheries managers in Australia to mitigate the impact of in-stream structures on local fish populations.

Populations of Atlantic salmon continue to suffer marked declines in abundance due to stressors acting in both their freshwater and marine habitats. It is therefore an imperative to identify populations in need of increased conservation intervention, with the aim of preserving as much as possible the genetic diversity present within the species. Previous microsatellite-based analyses have shown the chalk rivers of southern England and northern France to hold genetically distinct populations of salmon. However, these salmon populations have never been investigated in the same study. Using a suite of 93 single nucleotide polymorphism loci and samples from 42 British Isles and French rivers, we demonstrate the French and English chalk salmon to be closely related and distinct from salmon inhabiting non-chalk rivers. The identification of a small number of significant FST outliers suggests that this distinction is driven by local adaptation. We propose that the chalk and non-chalk salmon be designated as two distinct Evolutionarily Significant Units that each contain multiple Management Units. The chalk river salmon, especially those from southern England, are identified as making a significant contribution to the overall diversity of the species within the English Channel region. As a consequence, we propose that the salmon populations of the chalk streams may meet the criteria for recognition as a distinct subspecies of salmon, Salmo salar calcariensis. Taken together, the results presented here highlight the urgent need for enhanced conservation and protection for the Atlantic salmon populations inhabiting the chalk rivers of southern England and northern France.

Non-native species are a leading threat to fish biodiversity. They pose risks to native populations through human-mediated introductions resulting in hybridization events, which could result in demographic or genetic swamping. Catostomus fishes in the Upper Colorado River Basin are an example of this. Extensive hybridization occurs between non-native white suckers (C. commersonii ) and native flannelmouth and bluehead suckers (C. latipinnis and C. discobolus). This system provides a suitable model for using genomic analyses to test the efficacy of an intervention to reduce the abundance of non-native species and production of hybrid offspring. This study implemented a Resistance Board Weir (RBW) as a fish barrier across Roubideau Creek, a tributary of the Gunnison River in Colorado (USA), to restrict non-native sucker participation in spawning events. Conducted over four years, the study gathered genomic data from larval fish samples, pre- and post-implementation of the RBW. We used genomic data to determine the efficacy of a RBW at limiting non-native and hybridized sucker larval production. We found no significant effect of the weir on the proportion of white sucker ancestry in larval fish across the four years of the study, which included three years of weir usage when access was successfully controlled for variable amounts of time. Overall, this work provides insight into the efficacy of a resistance board weir as a management tool for non-native suckers, and highlights interannual variability. This work contributes valuable information for policy and fisheries management in Colorado.

ContextLates calcarifer is a widespread Indo-Pacific fish that is important in aquaculture, recreational and commercial fisheries. Genetic divergences from different data sources and sampling schemes have been reported. AimsTo conduct phylogenetic and population genetic analyses from a geographically and phylogenetically representative data set to identify hierarchical divisions within L. calcarifer. We further test the evolutionary significance of genetic units in terms of signatures of adaptation. MethodsUsing a whole-genome sequence data set of 61 fish including an outgroup, we conducted phylogenetic and population genetic analyes. We also generated measures of Fst, nucleotide diversity ({pi}) and Tajimas D (D). Key ResultsWe identify three main lineages of L. calcarifer corresponding to the Indian subcontinent, Southeast Asia and Australasia. Subdivision within each of the three main lineages is also identified and characterized. Adaptively significant differences are indicated within and between the three main lineages. ConclusionsL. calcarifer exhibits genetic divergences at different levels that originate before and during the Pleistocene. These divergences are associated with adaptive divergence but unclear phenotypic changes. ImplicationsThis study highlights the need for comprehensive sampling and integrative study of genotypes and phenotypes across the range of L. calcarifer.

Sustainable fisheries require reliable species identification and understanding of the underlying genetic hierarchies within the targeted species. Three Sebastes species are commonly found in the northeastern Atlantic: Sebastes mentella (beaked redfish), Sebastes norvegicus (golden redfish), and Sebastes viviparus (Norway redfish). These species are morphologically similar and have largely overlapping distribution ranges. Besides, three cryptic species for S. norvegicus and three depth-defined ecotypes for S. mentella have been suggested. Genetic knowledge and methods are needed to identify and monitor these species and to look at their geographic distribution. Here, a total of 99 specimens of S. mentella, S. viviparus as well as S. norvegicus A and B were sequenced in pools and aligned against a reference genome from a sister species, S. fasciatus (Acadian redfish). The measured divergence between all pairs, including the cryptic species pair S. norvegicus A and B, was high (mean FST = 0.33-0.61) and encompassing throughout genomes. Several shared megabase-scale regions of elevated divergence were observed, likely representing regions of reduced recombination. Moreover, 2914 fish collected across the northeastern Atlantic were analysed with a discriminatory SNP panel of high resolution (mean FST= 0.60-0.91), revealed few possible hybrids, and supported further sub-structuring within mentella and S. norvegicus B. The latter was split into two groups, one of which was the previously recognized giant morph and confirmed here for the first time in Norway. Sebastes mentella had two to three groups, likely representing previously identified depth-related ecotypes. Our study shows high genetic distinctiveness between acknowledged northeast-Atlantic Sebastes species, and between the cryptic species S. norvegicus A and B. Previously identified, fast-growing giant seems to be closely related to S. norvegicus B. Only few SNP markers are necessary for accurate species determination, facilitating further studies and widely applicable monitoring.

Changes in growth, survival, maturation and health in Atlantic salmon post-smolts were observed under moderate and more extreme heat-wave conditions for the west coast of Scotland. A Scottish Atlantic salmon breeding programme population of 518 salmon of age 13-14 months, was observed for 4 weeks in summer, in tanks with ambient water temperature or [~] 4 degrees and [~] 8 degrees above ambient temperature. Data were recorded for the fish before and after the challenge. All fish were genotyped using a custom SNP (single nucleotide polymorphism) array (8,978 SNP genotypes after quality control). Temperature-dependant genotype-by-environment interactions and the potential for selective breeding to improve resilience were investigated. Statistical analyses revealed significant differences between thermal environments for body weight, average daily weight gain, and survival, while higher temperature induced earlier maturation, and an increase of gill health scores. QPCR (quantitative polymerase chain reaction) analyses revealed the presence of Aeromonas hydrophila, a pathogen typically more prevalent in warmer climates. Using genomic relationships and animal mixed models, body weight and average daily weight gain provided moderate heritabilities, while between-tank genetic correlations were close to 1, indicating no significant re-ranking of genotypes between the different thermal environments. These findings suggest that even short-term exposure to heat stress may be sufficient to negatively impact survival and gill health, and induce earlier maturation. However, observations took place within a commercial farm where having replicates for each thermal environment was not possible, hence further experiments with larger populations, exposed to more prolonged heat stress are needed.

Phenotypic variation is common along environmental gradients, but it is often unknown to what extent it results from genetic differentiation between populations or phenotypic plasticity. We studied populations of a livebearing fish that have colonized streams rich in toxic hydrogen sulfide (H2S). In nature, there is strong phenotypic differentiation between adjacent sulfidic and nonsulfidic populations. In this study, we varied food availability to pregnant mothers from different populations to induce maternal effects, a form of plasticity, and repeatedly measured life-history and behavioral traits throughout the offsprings ontogeny. Genetic differentiation affected most of the traits we measured, as sulfidic offspring tended to be born larger, mature later, have lower burst swimming performance, be more exploratory, and feed less accurately. In contrast, maternal effects impacted few traits and at a smaller magnitude, even though offspring from poorly provisioned mothers tended to be born larger and be more exploratory. Population differences and maternal effects (when both were present) acted synergistically, and there was no evidence for population differences in plasticity. Overall, our study suggests that phenotypic divergence between these populations in nature is primarily caused by genetic differentiation, and that plasticity mediated by maternal effects accentuates--but does not cause--differences between populations.

Documenting species distributions and hybridization patterns is paramount for elucidating biogeography and understanding speciation processes. Here we combined genetic specimen analysis and environmental DNA (eDNA) to investigate the presence of American eel (Anguilla rotrata) and American x European eel (Anguilla anguilla) hybrids in Greenland freshwater. We further tested the use of eDNA to document hybridization by using European eel mtDNA as a proxy for hybrid occurrence. Overall, eDNA analysis detected mainly American eel but also European eel mtDNA. This finding was validated by DNA sequencing, which identified 3 out of 26 captured eels (14.3%) carrying European eel mtDNA. Five eels (19.2%), including all three with European mtDNA, were heterozygous for species-specific nuclear gene variants, supporting a hybrid ancestry. Further, eDNA successfully identified eels in lakes where they were caught by fyke net fishing, extending their confirmed northern range by 40 km, and indicated eel presence >200km further north. The study provides an empirical demonstration of the use of eDNA to document hybrid occurrence and extends the reported northern distribution of eels in Greenland significantly beyond previous observations. Further, the existence of hybrid eels in Greenland may be key for understanding the complex mechanisms of hybridization between American and European eels.

Variation in body pigmentation attracted fish biologists for a while, but high-throughput genomic studies investigating its molecular basis remain limited to few species and associated conservation issues ignored. Using 75,684 SNPs, we explored the genomic basis of pigmentation pattern variation among individuals of the Atlantic and Mediterranean clades of the brown trout (Salmo trutta), a polytypic species in which Atlantic hatchery individuals are commonly used to supplement local wild populations. Using redundancy analyses and genome-wide association studies, a set of 337 independent "colour patterning loci" (CPLs) significantly associated with pigmentation traits such as the number of red and black spots on flanks, or the presence of a black spot on the pre-opercular bone was identified. CPLs map onto 35 out of 40 brown trout linkage groups indicating a polygenic basis to pigmentation patterns. They are mostly located in coding regions (43.4%) of 223 candidate genes, and correspond to GO-terms known to be involved in pigmentation (e.g. calcium and ion-binding, cell adhesion). Annotated candidates include genes with known pigmentation effects (e.g. SOX10, PEML, SLC45A2), but also the Gap-junction {otimes}2 (GJD2) gene already shown differentially expressed in trout skin. Patterns of admixture were found significantly distinct when using either the full SNP data set or the set of CPLs, indicating that pigmentation patterns accessible to practitioners are not a reliable proxy of genome-wide admixture. Consequences for management are discussed.

Optimized laboratory conditions for research models are crucial for the success of scientific projects. This includes the control of the entire life cycle, access to all developmental stages and maintaining stable physiological conditions. Reducing the life cycle of a research model can also enhance the access to biological material and speed up genetic tool development. Thus, we optimized the rearing conditions for the sea anemone Nematostella vectensis, a cnidarian research model to study embryonic and post-metamorphic processes, such as regeneration. We adopted a semi-automated aquaculture system for N. vectensis and developed a dietary protocol optimized for the different life stages. Thereby, we increased spawning efficiencies and post-spawning survival rates, and considerably reduced the overall life cycle down to two months. To further improve the obtention of CRISPR-Cas9 mutants, we optimized the design of sgRNAs leading to full KO animals in F0 polyps using a single sgRNA. Finally, we show that NHEJ-mediated transgene insertion is possible in N. vectensis. In sum our study provides additional resources for the scientific community that uses or will use N. vectensis as a research model. Summary statementOptimized life cycle, in combination with efficient gene-editing approaches facilitates the establishment of genetic tools in N. vectensis, an emerging model for environmental stress response, regeneration, and longevity.

1The tufted ghost crab Ocypode cursor is a widespread and ecologically significant inhabitant of Mediterranean sandy beaches, including those of Israel, where it is a characteristic component of the coastal ecosystem. An opportunistic omnivore, O. cursor feeds on a broad range of marine and terrestrial resources, including carrion, and has been reported elsewhere preying on sea turtle eggs and hatchlings and scavenging large carcasses. However, feeding on stranded adult sea turtles, particularly loggerhead turtles (Caretta caretta), have not previously been documented in the Mediterranean Sea. During a survey assessing ghost crab populations at Zikim Dunes Nature Reserve (southeastern Mediterranean, Israel) in August 2021, we observed five recently stranded C. caretta carcasses encircled by freshly dug O. cursor burrows, located inland from the high tide line. Burrows surrounding the carcasses were predominantly large-sized, suggesting relocation of adult crabs toward carrion situated landward of their typical supratidal zone. Our findings highlight the opportunistic scavenging behavior of O. cursor and underscore their ecological flexibility in exploiting substantial food resources beyond their usual distribution band. These novel observations contribute to understanding ghost crab trophic ecology and their potential interactions with vulnerable marine species in a changing coastal environment.

Marine-phase salmonid aquaculture is a major component of the coastal economies of Northern Europe, North America and Chile and is under threat from numerous challenges to gill health, many of which originate from the phyto- and zooplankton. Associated losses are growing as a proportion of production year on year. A first step towards mitigating losses is to characterize the biological drivers of poor gill health. Numerous planktonic species have been implicated, including toxic and siliceous microalgae, hydrozoans and scyphozoans; however, rigorous longitudinal surveys of planktonic diversity and gill health have been lacking. In the current study, we present and assess an exhaustive identification approach combining both morphological and molecular methods (environmental DNA metabarcoding) approaches in combination with robust statistical models to identify the planktonic drivers of complex gill disease (CGD) and fish mortality. We undertook longitudinal molecular and microscopic evaluation at two marine aquaculture facilities on the west coast of Scotland using daily data collected during the 2021 growing season (March-October). Examining these two different sites, one sheltered and one exposed to the open sea, we identified new, important, and unexpected planktonic drivers (e.g. doliolids and appendicularians) of CGD and mortality and confirmed the significance of some established threats (e.g. hydrozoans and diatoms). We also explored delayed or lagged effects of planktonic abundances on gill health and undertook a comparison of environmental DNA metabarcoding and microscopy in their ability to identify and quantify planktonic species. Our data highlight the diversity of planktonic threats to salmonid aquaculture as well as the importance of using both molecular and morphological approaches to detect those. Despite our study relying on two farm sites only, our results evidence the role of the different planktonic players on salmon gill disease; there is now an urgent need to expand systematic longitudinal molecular and morphological approach across multiple sites and over multiple years. The resultant catalogue of main biological drivers will enable early warning systems, new treatments and, ultimately, a sustainable platform for future salmonid aquaculture in the marine environment.

Captive-breeding programs as well as and catch-and-release are among the most commonly adopted conservation practices in recreational fisheries. However, risks and benefits associated with their implementation are rarely evaluated. In the case of Atlantic Salmon, while previous studies revealed that captive-bred fish show reduced fitness compared to their wild counterparts in nature. Yet, few examined the extent and causes of their reduced reproductive success or directly compared their contribution to enhance genetic diversity to that of wild fish, including mature male parr. Furthermore, only one study specifically measured the reproductive success of caught and released Atlantic salmon in natural settings, and no study to date evaluated if released salmon are able to reproduce when released at temperature above 20{degrees}C which is known to increase post-release mortality. Here, we use high-throughput microsatellite sequencing of 38 loci to accurately assign 2500 offspring to a comprehensive set of possible parents from a supplemented Atlantic salmon population in Quebec, Canada. The resolved molecular pedigree provided informative insight on the reproductive pattern of both captive-bred salmon and caught-and-released salmon. Captive-bred salmon had fewer partners than their wild conspecifics which lead to a significant reduction of reproductive success relative to that of their wild counterparts. Supplementation of captive-bred salmon significantly contributed to increase genetic diversity but mature male parr did so to an even greater extent and significantly inflated the number of alleles found among offspring. Moreover, our results showed that that at least 83% of caught-and-released salmon did successfully reproduced although caught-and-released female salmon have a significantly reduced reproductive success, averaging 73% of the reproductive output of non-caught salmon. Reproductive success of released salmon was not influenced by water temperature over 20{degrees}C which suggests either that the studied population is locally adapted to warm waters or that they behaviorally regulated body temperature by accessing nearby thermal refugia. Our results should help refining managers ability to analyze the risks and benefits associated with captive-breeding and catch-and-release, and thus, optimize conservation practices used for the preservation of Atlantic salmon populations.

Triggerfishes and filefishes exhibit a wide range of fin and body morphologies, inhabit many marine habitats, and feed on a variety of benthic and pelagic organisms. Particular morphologies are predicted to provide functional advantages for swimming behaviors that facilitate life in diverse habitats and feeding guilds. Ecomorphological relationships can, in turn, inform evolutionary patterns of morphological convergence. We quantified morphological diversity of 80 balistoid species using geometric morphometrics and assigned each species a primary habitat and feeding mode. Results revealed strong evidence for evolutionary integration among body and fin shapes as well as widespread convergence of both high and low aspect ratio (AR) dorsal and anal fins, the fins that power steady locomotion in these fishes. Dorsal and anal fins were determined to be moderately to highly asymmetrical in most species. Families exhibited considerable overlap in fin and body shapes, but triggerfishes generally exhibited higher AR and more asymmetrical fins than filefishes. Fin asymmetry was not strongly associated with ecology. Planktivorous and offshore-pelagic species exhibited high AR dorsal and anal fins suitable for high endurance swimming performance, while benthic grazing and structured reef species exhibited convergence on low AR median fins more suitable for facilitating maneuverability.

Melanoides tuberculata (Thiaridae) is an old-world freshwater snail that is and now circumtropical. After being introduced in the 1960s via the aquarium trade, populations of M. tuberculata are thriving in spring systems of Texas (USA). Field surveys and experimental investigations of temperature tolerance suggest M. tuberculata is stenothermal, and thus range expansions outside of aquatic habitats with water temperatures between 18{degrees} and 32{degrees}C should be unlikely. However, in 2012 snails were detected in natural aquatic habitats with seasonal temperatures below the experimentally determined lethal thermal minimum. To test whether genetic and phenotypic variation might be associated with cold-water tolerance and range expansion, we sequenced the 16S ribosomal rRNA gene and measured qualitative conch morphology of 170 snails collected at 26 sites in three central Texas rivers. We also conducted phylogenetic analyses of M. tuberculata collected globally and in Texas to determine potential source populations and estimate the number of invasion events. Our results show snails detected in variable temperature habitats are genetically divergent and morphologically distinct from snails collected in habitats with stable temperatures. These data are consistent with at least three introduction events into Texas of M. tuberculata sensu lato that are characterized by distinct habitat preferences, physiological tolerances, and/or adaptive behaviors.

1Lumpfish (Cyclopterus lumpus) is a transatlantic marine fish displaying large population sizes and a high potential for dispersal and gene-flow. These features are expected to result in weak population structure. Here, we investigated population genetic structure of lumpfish throughout its natural distribution in the North Atlantic using two approaches: I) 4393 genome wide SNPs and 95 individuals from 10 locations, and II) 139 discriminatory SNPs and 1,669 individuals from 40 locations. Both approaches identified extensive population genetic structuring with a major split between the East and West Atlantic and a distinct Baltic Sea population, as well as further differentiation of lumpfish from the English Channel, Iceland, and Greenland. The targeted discriminatory loci displayed [~]2-5 times higher divergence than the genome wide approach, revealing further evidence of local population substructures. Lumpfish from Isfjorden in Svalbard were highly distinct but resembled most fish from Greenland. The Kattegat area in the Baltic transition zone, formed a previously undescribed distinct genetic group. Also, further subdivision was detected within North America, Iceland, West Greenland, Barents Sea, and Norway. Although lumpfish have considerable potential for dispersal and gene-flow, the observed high levels of population structuring throughout the Atlantic suggests that this species displays natal homing and potentially local populations with adaptive differences. This fine-scale population structure calls for consideration when defining management units for lumpfish fishing stocks and in decisions related to sourcing and moving lumpfish for farming and cleaner fish use.

The Laurentian Great Lakes (LGL) formed following the retreat of the Wisconsin glaciation 15-9 ka and provided a vast volume of freshwater habitat for coregonines, which included a diverse endemic complex of ciscoes. However, anthropogenic impacts in the 19th and 20th centuries resulted in declines and losses of ciscoes, leaving only Lake Superior with a relatively intact complex that still dominates its prey fish community. In the 1920s, W. Koelz described six putative cisco species from Lake Superior: Coregonus artedi, C. hoyi, C. kiyi, C. zenithicus, C. reighardi, and C. nigripinnis. Of these, artedi, hoyi and kiyi remain extant and abundant in Lake Superior, zenithicus is considered extirpated throughout the LGL except in Lake Superior, and reighardi and nigripinnis are considered extinct and had been synonymized as zenithicus in Lake Superior. Using an integration of morphological and genetic approaches, we present results reaffirming the presence of artedi, hoyi, and kiyi, and new evidence for the presence of reighardi, a species thought to be extinct. Our analysis did not elucidate the presence of zenithicus and nigripinnis, leaving their status unresolved. The principal morphological characters that discriminate artedi, hoyi, kiyi, and reighardi are related to habitat and trophic (ecological) specialization and foster niche segregation: eye size, gill raker length, and gill raker spacing, the same as those that foster niche segregation in subarctic European whitefishes. The discovery of reighardi is expected to stimulate new interest in the development of conservation and restoration plans for rare and imperiled cisco species in the LGL and other freshwater lakes throughout the Northern Hemisphere, and our integrated morphological and genetic approach can benefit these efforts by providing insights for the evolution, diversity, and ecology of ciscoes.

We describe the antipredator armor of a unique population of threespine stickleback (Gasterosteus aculeatus) from Narrows Pond in western Newfoundland and compare traits for this population to nearby populations from marine and freshwater systems. After standardizing for length, Narrows Pond stickleback are shallower bodied and have shorter dorsal spines than stickleback from the other populations. Also, though the number of armor plates for Narrows Pond stickleback is greater than for typical low-plate morphs, the size of the lateral plates for Narrows Pond stickleback is much smaller. Finally, most (nearly 75% of sampled individuals) Narrows Pond stickleback do not have a pelvic structure (bilateral pelvic plate, ascending process, and ventral spine) and the remaining individuals have greatly reduced pelvic girdle whereas all individuals from the other populations possessed complete pelvic structures.