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Variable resource use and responses to environmental conditions can lead to phenotypic diversity and distinct morphotypes within salmonids, including Arctic char (Salvelinus alpinus). Despite the cultural and economic importance of Arctic char in the Inuvialuit Settlement Region (ISR), limited data exist on the extent and presence of morphological diversity in this region. This is of concern for management given climate change impacts on regional fish populations. The authors investigated morphological diversity in anadromous Arctic char sampled during their summer marine migration-residency period when seasonal harvesting occurs in a coastal mixed-stock fishery. Geometric morphometric analysis was conducted using digital photographs of live Arctic char (n = 103) of which a sub-set was subsequently implanted with acoustic transmitters (n = 90) and released, and their overwintering lakes determined using active acoustic telemetry surveys. Twenty-three morphological landmarks were established and overlaid on digital images, and nine linear measurements of the body and head were recorded. Principle component analysis and K-means clustering based on linear measurements categorised fish into three morphotypes: slender body and slim head (n = 31), small and short head with a small mouth (n = 46) and elongated head shape with large mouth (n = 26). Tagged individuals of the three morphotypes occupied all lakes with no distinction observed. The three Arctic char morphotypes detected in this coastal mixed-stock fishery could represent adaptation to specific feeding-movement behaviours potentially tied to juvenile residency in freshwater systems, efficient exploitation of the marine prey pulse, or are relicts from ancestral types. To the authors' knowledge, this study is the first to identify distinct Arctic char morphotypes occurring in sympatry in the marine environment. Identifying phenotypic diversity will assist management to promote the sustainability of this regional fishery.

Understanding variability in distributions and habitat-use among populations of anadromous salmonids is essential for their sustainable management. Arctic char ( Salvelinus alpinus) is an important cultural and socioeconomic species; however, knowledge of their spatiotemporal habitat-use during the marine phase is limited. Here, a large-scale acoustic telemetry array was used to determine intraspecific variation in Arctic char summer marine habitat-use tied to overwintering lake occurrence in the Amundsen Gulf. Arctic char tagged in the ocean migrated to two main overwintering lakes, corresponding to distinct migration corridors and separate patterns of marine habitat-use, with one individual exhibiting among the longest recorded char marine migration to date (∼330 km). Arctic char that undertook longer migration distances initiated travel in the ocean towards fresh water 11 days earlier than those completing shorter migration distances; mean departure days (±SD) 2 August (±8.1 days) and 13 August (±6.8 days), corresponding to migration distances of 252 and 131 km, respectively. These findings identify that Arctic char from different populations can occupy distinct marine foraging grounds within a region, with consequences for variable interactions with fisheries.

Mobile consumers often match their movements to short-term resource pulses. In the Arctic, seasonal ice breakup facilitates an ephemeral productivity pulse exploited by marine consumers. The migration of anadromous Arctic char (Salvelinus alpinus) to marine waters occurs around the beginning of ice breakup, but the precise timing of movement is equivocal and current evidence is conflicting. To investigate the migratory timing of Arctic char, 34 individuals were tagged with acoustic telemetry transmitters within Tremblay Sound, Nunavut, Canada in two successive years. All tagged fish entered the marine environment before the coastal ice-off date (mean ± SE: 7.56 ± 0.56 days). Further movement metrics revealed that char utilized much of the sound before the ice-off date, with only slightly higher mean home ranges (0.3 km2 larger) and residency indices (by ~ 0.05) during the period following the ice-off date than prior. Such entry and use of marine waters prior to ice breakup may impart energetic benefits to early migrants, maximizing exploitation of the short, anticipated pulse of productivity. The current study provides a unique example of resource tracking that could confer heightened fitness to a marine consumer in the rapidly warming high Arctic.

© 2021 John Wiley & Sons Ltd Understanding fish movement in the Arctic is paramount during the current era of rapidly warming seas, receding sea ice and associated shifting species distributions and fishing effort. We synthesized the literature and identified key knowledge gaps on the movement ecology of Arctic cod (Boreogadus saida) and Polar/Ice cod (Arctogadus glacialis, both Gadidae) in the context of climate change. Standardized web-based English-language literature searches yielded 51 articles directly relevant and 122 indirectly relevant for the movement ecology of these species combined. Most articles were primarily relevant to B. saida (85% of total filtered articles), occurred during open water season (49/38%) with focus on distribution (32/22%), predators (30/22%), seasonal spawning/feeding movements (22/19%), sea ice association (22/26%), climate change (20/15%) and vertical movements (17/19%) with few focused on horizontal dynamics (3/0%; B. saida/A. glacialis, respectively). Disproportionate data resolution has resulted in greater predictive power of movement models for the European (29% of articles) and North American (86%) Arctic regions relative to the logistically challenging Central Arctic Ocean and Russian-Siberian Arctic shelves (both 7%). The movements of circumpolar Arctic gadids are dependent on complex dynamics that include regional currents, the longevity of ice-flows and polynyas, water stratification and coastal hydrology. Dependence on these interactive and often co-dependent processes highlights major pathways and barriers to movement and distribution at higher latitudes. Despite a recent increase in impactful research, there is a critical need for more direct research on circumpolar gadid movements to aid understanding of climate change impacts on Arctic ecosystems and fisheries.

© 2019 British Ecological Society Interactions between animals structure food webs and regulate ecosystem function and productivity. Quantifying subsurface behavioural interactions among marine organisms is challenging, but technological advances are promoting novel opportunities. Here, we present a framework to estimate when there is a high likelihood that aquatic animal subsurface interactions occur and test for a movement-related behavioural response to those interactions over short temporal scales (days) using a novel multi-sensor biologging package on a large marine predator, the Greenland shark (Somniosus microcephalus). We deployed a recoverable biologging package combining a VEMCO Mobile Transceiver (VMT), accelerometer and a temperature–depth tag to quantitatively assess fine-scale behaviour during detection events, that is when sharks carrying the novel VMT package (animalR, n = 3) detected sharks independently tagged with transmitters in the system (animalT, n = 29). Concurrently, we developed simulations to estimate the distances between animalR and animalT by accounting for their swim speed, the estimated detection efficiency of the VMT and the number of consecutive transmissions recorded. Accelerometer-derived activity indices were then used as a means to test for response to potential interactions when animals are expected to be in close proximity. Based on this approach, the three VMT-equipped Greenland sharks exhibited higher body acceleration and greater depth changes during detections, suggesting a potential behavioural response to the presence of other sharks. A generalized additive model indicated a moderate increasing relationship in activity associated with a greater number of animalT detections. Through the proposed framework, detection events with varying probabilities of interaction likelihoods can be derived and those data isolated and explicitly tested using acceleration data to quantify behavioural interactions. Through inputting known parameters for a species of interest, the framework presented is applicable for all aquatic taxa and can guide future study design.

Inuit are at the forefront of ecosystem change in the Arctic, yet their observations and interpretations are rarely reported in the literature. Climate change impacts are rapidly unfolding in the Arctic and there is a need for monitoring and reporting unique observations. In this short communication, we draw upon observations and experiential knowledge from western Canadian Inuit (Inuvialuit) harvesters combined with a scientific assessment to describe and interpret an unusual account of gelatinous organisms at high densities during summer 2019 in eastern Amundsen Gulf, near Ulukhaktok, Northwest Territories. The gelatinous organisms were identified as primarily appendicularian larvaceans (Oikopleura spp., pelagic tunicates) and their gelatinous “houses”. The organisms were observed within 3–5 km of the marine coast, from ∼1–2 m below the surface and to depths of ∼30 m with an underwater camera. Pelagic tunicates have rarely been documented in the eastern Amundsen Gulf and, to our knowledge, this was the first time these organisms had been noted by the people of Ulukhaktok. The pelagic tunicates clogged subsistence fishing nets and Inuvialuit harvesters were concerned about negative impacts to marine mammals and fishes, which they depend on for food security. These interpretations highlight major knowledge gaps for appendicularians in the Arctic. Video Inuit Ukiuktaktumi nunamingni tautukpaktut nunaktik aalangnujuhianik, taimaa tautukpaktait ilihimaliktait titiraqtauyuitut titiqani. Nunam aallangujuhia tautuktauyuq kayumikhipluni Ukiuktaktun nunanni, taimatun munariyauyukhak titiraqhimayukhat aallangujuhiit. Uvani tittiqaniInuit tautukpaktait ilihimaliktait titiraqhimayut Inuvialuit anguniaqtiinnit attauttimut iliblugit qablunaat tittiratainnutilituritiarumaplugitumayuutigut tamainnut auyanani 2019mi, tahamani Admundson Gulfmi Ulukhaktuum haniani North west Territoriesmi. Tahapkuat uumayut hauniittut imangmi attauttimiitpaktut. Uumayut tahapkuat tautuktauvaktut pingahunikluunniin tallimanitulluunniin kilometresmik ungahiktilanganik tariukmitalvattauk atauhikmikluunniin, malguknikluunniin metresnik ititigiyumi. Ilaani ititqiyami 30 metresmi takunnaqpaktun ajiliurunmun. Tahapkuninga tautuyuittugaluat taja kihimi tautukpaliktait. Ulukhaktuunmiutat taja tautukpaliktait. Tahapkuat uumayut nuvaktut inmate kuvyanut himiutkpiaqpaktut, kuvyallu iqaluguikhutik. Inuit iqalukhiuktullu anguniaqtullu ihumaalugiliktait anguyamingnik niqiqaramik. Tahapkuat ilituriliktavut ilihimatttaingitnaptigit nunaptingni ukiuktaktumi ilitturrinahuaqqaqhaluavut.

Invasive species are expected to experience a unique combination of high genetic drift due to demographic factors while also experiencing strong selective pressures. The paradigm that reduced genetic diversity should limit the evolutionary potential of invasive species, and thus, their potential for range expansion has received little empirical support, possibly due to the choice of genetic markers. Our goal was to test for effects of genetic drift and selection at functional genetic markers as they relate to the invasion success of two paired invasive goby species, one widespread (successful) and one with limited range expansion (less successful). We genotyped fish using two marker types: single nucleotide polymorphisms (SNPs) in known-function, protein-coding genes and microsatellites to contrast the effects of neutral genetic processes. We identified reduced allelic variation in the invaded range for the less successful tubenose goby. SNPs putatively under selection were responsible for the observed differences in population structure between marker types for round goby (successful) but not tubenose goby (less successful). A higher proportion of functional loci experienced divergent selection for round goby, suggesting increased evolutionary potential in invaded ranges may be associated with round goby's greater invasion success. Genes involved in thermal tolerance were divergent for round goby populations but not tubenose goby, consistent with the hypothesis that invasion success for fish in temperate regions is influenced by capacity for thermal tolerance. Our results highlight the need to incorporate functional genetic markers in studies to better assess evolutionary potential for the improved conservation and management of species.

Comparison of highly successful and less successful invasive species can highlight traits that are associated with invasion success, and indicate the associated risk of further establishment or invasion from novel species. We compared variation in δ13C and δ15N, or isotopic niche, in the tissues of matched pairs of highly successful and less successful (respectively) freshwater and marine aquatic invasive species: violet tunicate Botrylloides violaceus and golden star tunicate Botryllus schlosseri from the northwest Atlantic coast; spiny waterflea Bythotrephes longimanus and fishhook waterflea Cercopagis pengoi from the Great Lakes basin; and Pacific oyster Crassostrea gigas and eastern oyster Crassostrea virginica from the northeast Pacific coast. Individual (δ13C and δ15N) and population (Bayesian ellipses of δ13C and δ15N) level comparisons of isotopic niche revealed, in most cases, greater niche breadth in the more successful species of tunicate but the less successful species of waterflea and oyster. Comparison with the literature suggested that a broad dietary niche is less crucial for widespread distribution of aquatic invasive invertebrates than it is for vertebrates (i.e., fishes). Inconsistency in the association between isotopic niche breadth and invasion success could be due to a greater influence of habitat suitability on variation in invertebrate diets. These findings challenge the common assumption that a broader niche promotes invasion success, and thus, have implications for invasive species risk assessment, management, and our understanding of species spread and distribution.

© 2019, Canadian Science Publishing. All rights reserved. Alternative reproductive tactics (ARTs) can generate considerable within-species life history variation but are often overlooked. Here, we use the invasive round goby (Neogobius melanostomus) to address a number of ecological and evolutionary questions about ARTs. Making use of a 12-year, multisite Laurentian Great Lakes data set, we show that the guarder male tactic was twice as common as the sneaker male tactic but that nonreproductive males were the most common morph. The ratio of guarder to sneaker males did not vary spatially despite a wide range of resource densities across sites. Guarders and sneakers spanned similar age ranges, suggesting that the ARTs are nonsequentially expressed. Based on short-term (gut contents) diet analyses, both reproductive tactics consumed fewer types of food and tended to consume fewer items overall when compared with nonreproductive males. Long-term (isotope) diet analyses showed that guarder males fed at a higher trophic level (higher δ15N) and had a broader isotopic niche. Our results show that ARTs are an important aspect of this invasive species’ breeding system and should be accounted for when assessing and managing populations.

© 2017, Springer International Publishing AG Switzerland. Despite a well-developed theoretical basis for the role of genetic diversity in the colonization process, contemporary investigations of genetic diversity in biological invasions have downplayed its importance. Observed reductions in genetic diversity have been argued to have a limited effect on the success of establishment and impact based on empirical studies; however, those studies rarely include assessment of failed or comparatively less-successful biological invasions. We address this gap by comparing genetic diversity at microsatellite loci for taxonomically and geographically paired aquatic invasive species. Our four species pairs contain one highly successful and one less-successful invasive species (Gobies: Neogobius melanostomus, Proterorhinus semilunaris; waterfleas: Bythotrephes longimanus, Cercopagis pengoi; oysters: Crassostrea gigas, Crassostrea virginica; tunicates: Bortylloides violaceous, Botryllus schlosseri). We genotyped 2717 individuals across all species from multiple locations in multiple years and explicitly test whether genetic diversity is lower for less-successful biological invaders within each species pair. We demonstrate that, for gobies and tunicates, reduced allelic diversity is associated with lower success of invasion. We also found that less-successful invasive species tend to have greater divergence among populations. This suggests that intraspecific hybridization may be acting to convert among-population variation to within-population variation for highly successful invasive species and buffering any loss of diversity. While our findings highlight the species-specific nature of the effects of genetic diversity on invasion success, they do support the use of genetic diversity information in the management of current species invasions and in the risk assessment of potential future invaders.

Copyright © 2017 Crown Copyright. Anthropogenic pollution and the introduction of invasive species are two contributing factors to ecosystem degradation. Although Hamilton Harbour (Ontario, Canada), a highly impacted ecosystem, is well-studied, the diet, trophic position, and foraging behaviour of the invasive Round Goby (Neogobius melanostomus) in this area is not well understood. In this study, we compared digestive tract contents, foraging behaviour, and stable isotope values of Round Goby from sites of low and high sediment contamination in Hamilton Harbour. We also assessed prey availability by conducting sediment invertebrate abundance analyses at these sites. Regardless of site, Chironomids, Cladocerans, Copepods and Dreissenids were the most common food items found in Round Goby digestive tracts, and females always had heavier gut contents compared to males. Fish from the high contamination site consumed fewer prey items, had lower gut fullness scores, and fed at a lower trophic level based on lower δ13C and δ15N values. Our results suggest that Round Goby living in highly contaminated areas are feeding less than Round Goby from areas of lower contamination, but that these diet differences do not reflect differences in prey availability. Fish from the high contamination site also typically moved more slowly while foraging. Taken together, these results provide an analysis of the main prey items of Round Goby in Hamilton Harbour, and demonstrate how polluted environments can impact diet, trophic position, and foraging of an introduced fish species.

The trace element requirements of sharks are poorly understood and the dietary intake of metals from prey items in wild sharks has not been measured. In this study whole prey of nursery bound juvenile lemon sharks Negaprion brevirostris, from Bimini, Bahamas were analysed for car- cass total protein, lipids, carbohydrates, ash content, energy, and elemental composition. Metal analysis included 415 prey items from 18 species (fish: Atherinidae, Belonidae, Gerreidae, Haemuli- dae, Lutjanidae, Scaridae, Sphyraenidae; decapod crustaceans: Penaeidae, Portunidae). There were some seasonal and location effects (North Sound versus South Bimini shark nurseries), but overall prey metal concentrations were broadly similar to reports for temperate species. Yellow fin mojarra Gerres cinereus dominate the shark diet, in which electrolytes were similar (Na 10, K 10, Ca 65, and Mg 2 mg g -1 dry weight) but trace metals were higher (Cu 2.4, Zn 96, Fe 63, Mn 0.7 µg g -1 dry weight) than in other prey fish species at Bimini. Swimming crabs (Portunidae) were an important source of dietary Ca, Mg, Cu and Mn for lemon sharks. The calculated daily dietary metal intakes (mg d -1 ) for Cu (0.17), Fe (1.2) and Mn (0.01) of lemon sharks are below previously estimated requirements of other fish. Dietary salt intake (272 mg Na d -1 , 1% dietary salt) is similar to other fishes, but the Ca and Zn intakes are higher. Yellow fin mojarra contained 65% protein, 4% lipid, 23% ash. The average juvenile lemon shark (1.85 kg, 24.84 g daily ration) ate a very lean high protein diet (61.9% protein, 4.6% lipid, 24.9% ash, 8.6% carbohydrate), with a calculated energy intake of 397 kJ d -1 . Overall, the data suggests the gross macronutrient composition of the shark diet is adequate, but some of the trace metals may be limiting in the diet of wild juvenile lemon sharks at Bimini.

© 2015, Springer International Publishing Switzerland. The geographic range of an invasive species is a key determinant of relative impact in the invaded region. Comparison of invasive species that are widespread or rare in invaded ranges can highlight mechanistic traits that determine the risk of impact from invasion. Round Goby (Neogobius melanostomus) is more geographically widespread and abundant than Tubenose Goby (Proterorhinus semilunaris) across invaded ranges of the Laurentian Great Lakes. We used stable isotopes of carbon (δ13C) and nitrogen (δ15N) in liver and muscle to contrast the isotopic niche breadth and niche plasticity of Round Goby and Tubenose Goby near the inflow and outflow of Lake St. Clair and in western Lake Superior. At all sites, Round Goby and Tubenose Goby that matched in size (21–53 mm standard length) had distinct isotopic niches with no overlap, driven by higher δ15N in Round Goby. The variation in isotopic niche, and the mean difference in δ13C and δ15N between muscle and liver, was greater for Round Goby, suggesting both greater seasonal shifts in diet and niche plasticity in this more widely established invader. Round Goby that were significantly larger than Tubenose Goby had broader isotopic niches and greater niche plasticity in the majority of cases and this was associated with isotopic niche overlap with smaller Round Goby and Tubenose Goby. Our findings suggest that a broad and plastic isotopic niche provides scope for wider establishment range in invasive fish species.