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Survival of salmon species (Oncorhynchus spp.) of the Pacific Ocean varies with life stage. As a result, identifying critical periods of mortality that determine brood strength can lead to more [...]

To understand the marine feeding ecology of Arctic lamprey (Lethenteron camtschaticum) in the eastern Bering Sea, visual observations and DNA metabarcoding of gut contents (N = 250) were used to characterize Arctic lamprey diet composition in 2014 and 2015. Differences among individual diets were evaluated by collection year, capture site, and fish size. Hard structures and tissues were observed during visual examinations of gut contents, and 10 ray-finned fish taxa were identified by DNA metabarcoding. The most frequently observed taxa included capelin (Mallotus villosus), Pacific herring (Clupea pallasii), Pacific sand lance (Ammodytes hexapterus), and gadids. Six taxa were reported for the first time as prey for Arctic lamprey. Individual diets differed between collection years, among capture sites, and among size classes; however, both collection year and size class explained only a small portion of diet variability ([R.sup.2] = 0.01 and 0.04, respectively) relative to capture site ([R.sup.2] = 0.49). These study results indicate that Arctic lamprey is a flesh-feeding species and highlight the value of DNA metabarcoding to characterize the diet of a poorly understood lamprey species. Pour comprendre l'ecologie de l'alimentation en mer des lamproies arctiques (Lethenteron camtschaticum) dans la mer de Behring orientale, des observations visuelles et des metacodes-barres d'ADN de contenus stomacaux (N = 250) ont ete utilises pour caracteriser la composition des regimes alimentaires de lamproies arctiques en 2014 et 2015. Les differences de regimes alimentaires entre individus ont ete evaluees en fonction de l'annee de prelevement, du site de capture et de la taille des poissons. Des structures dures et des tissus ont ete observes durant les examens visuels de contenus stomacaux, et 10 taxons de poissons a nageoires a rayons ont ete identifies grace aux metacodes-barres d'ADN. Parmi les taxons les plus frequents figuraient le capelan (Mallotus villosus), le hareng du Pacifique (Clupea pallasii), le lancon gourdeau (Ammodytes hexapterus) et des gadides. Six taxons sont signales pour la premiere fois comme proies de lamproies arctiques. Les regimes alimentaires individuels varient d'une annee de prelevement a l'autre, au sein des sites de capture et au sein des classes de taille; cependant, l'annee de prelevement et la taille n'expliquent qu'une petite partie de la variabilite des regimes alimentaires ([R.sup.2] = 0,01 et 0,04, respectivement) comparativement au site ([R.sup.2] = 0,49). Ces resultats indiquent que la lamproie arctique est une espece mangeuse de chair et soulignent la valeur des metacodes-barres d'ADN pour caracteriser le regime alimentaire d'une espece de lamproies mal comprise. [Traduit par la Redaction], Introduction Characterizing the diets of marine-phase lamprey poses a special challenge to researchers. Diet analysis of fishes has largely relied upon morphological identification of prey remains and (or) undigested hard [...]

Per‐ and polyfluoroalkyl substances (PFAS) and mercury (Hg) are harmful compounds that are widely present in the environment, partly due to spills and atmospheric pollution. The presence of PFAS and Hg in the tissues of animals that are harvested by rural and Indigenous Alaskans is of great concern, yet fish in Arctic Alaska have not previously been assessed for concentrations of PFAS. Fish species of subsistence and recreational importance were collected from nearshore Beaufort and Chukchi Sea, Alaska habitats and assessed for PFAS and total mercury concentrations [THg]. We found multiple PFAS compounds present at low levels (<3 μg/kg) in the muscle tissue of inconnu, broad whitefish, Dolly Varden char, Arctic flounder, saffron cod, humpback whitefish, and least cisco. In addition, [THg] levels in these fish were well below levels triggering local fish consumption guidelines (<170 μg/kg). These initial results indicate no evidence of the Alaska Arctic nearshore fish species examined as an avenue of PFAS or Hg exposure to people who harvest them. However, sources and trends of these contaminants in the Arctic require further investigation. Environ Toxicol Chem 2023;42:2329–2335. © 2023 SETAC [ABSTRACT FROM AUTHOR]

Recent food-web changes in the Laurentian Great Lakes are affecting energy and nutrient allocation to lake whitefish (Coregonus clupeaformis) with potential downstream effects on egg condition and recruitment. We tested whether egg condition was conserved or varied with maternal condition in eight stocks from Lakes Erie, Michigan, and Superior. Egg condition was conserved across stocks based on (i) a lack of correlation between females and eggs for total lipid, DHA, and other essential fatty acids; (ii) higher levels of energy and long-chain polyunsaturated fatty acids (LC-PUFA) in eggs compared with females; and (iii) no among-stock differences for those same variables in eggs. Females from northern Lake Michigan generally made the greatest trade-offs between egg size and fecundity. Highly fecund females provisioned less lipid, but more n-3 LC-PUFA to their eggs. A lack of stock-level patterns in energy and nutrient allocation suggests that trade-offs occur at the level of individual females and that females in poor condition make greater trade-offs among egg size and fecundity, total lipids, and n-3 LC-PUFA than females in good condition. Resume: Des modifications recentes des reseaux trophiques dans les Grands Lacs laurentiens ont une incidence sur l'allocation d'energie et de nutriments chez les grands coregones (Coregonus clupeaformis), incluant des effets en aval potentiels sur l'etat des reufs et le recrutement. Nous avons tente d'etablir si l'etat des reufs etait conserve ou variait selon l'etat d'embonpoint maternel au sein de huit stocks des lacs Erie, Michigan et Superieur. L'etat des reufs etait conserve dans tous les stocks a la lumiere (i) de l'absence de correlation entre les femelles et les reufs sur le plan des lipides totaux, de l'ADH et d'autres acides gras essentiels, (ii) de niveaux plus eleves d'energie et d'acides gras polyinsatures a longue chaine (AGPLC) dans les reufs que chez les femelles et (iii) de l'absence de variation au sein des stocks en ce qui concerne ces memes variables dans les reufs. Les femelles de la partie nord du lac Michigan sont celles qui presentaient les compromis les plus importants entre la taille des reufs et la fecondite. Les femelles tres fecondes transferaient moins de lipides, mais plus d'AGPLC n-3 a leurs reufs. L'absence de tendance en matiere d'allocation d'energie et de nutriments a l'echelle des stocks donne a penser que les compromis s'exercent a l'echelle individuelle chez les femelles et que les femelles en mauvais etat d'embonpoint font de plus grands compromis entre la taille des reufs et la fecondite, les lipides totaux et les AGPLC n-3 que les femelles en bon etat. [Traduit par la Redaction], Introduction Lake whitefish (Coregonus clupeaformis) support important commercial, recreational, and aboriginal subsistence fisheries throughout the Laurentian Great Lakes. From 1995 to 2005, lake whitefish growth and body condition declined precipitously [...]

ABSTRACT. Western mosquitofish (Gambusia affinis) are stocked in Indiana waters for the biological control of mosquitoes. However, this species has the potential to negatively impact native fishes. We examined the [...]

ABSTRACT. The stocking of western mosquitofish (Gambusia affinis) to control mosquitos has been shown to negatively impact native fishes, especially species with similar ecological requirements such as topminnows. As a [...]

ABSTRACT. Western mosquitofish, stocked frequently throughout Indiana, are highly aggressive and often negatively impact native fishes that occupy a similar ecological niche. Because northern starhead topminnows are the most vulnerable [...]

Genetic relationships among lake whitefish (Coregonus clupeaformis) spawning aggregates in Lake Michigan were assessed and used to predict a stock or management unit (MU) model for the resource. We hypothesized that distinct spawning aggregates represented potential MUs and that differences at molecular markers underlie population differentiation. Genetic stock identification using 11 microsatellite loci indicated the presence of six genetic MUs. Resolved MUs corresponded to geographically proximate spawning aggregates clustering into genetic groups. Within MUs, analyses suggested that all but one delineated MU was a stable grouping (i.e., no between-population differences), with the exception being the Hog Island--Traverse Bay grouping. Elk Rapids was the most genetically divergent population within Lake Michigan. However, low [F.sub.st] values suggested that moderate to high levels of gene flow occur or have occurred in the past between MUs. Significant tests of isolation by distance and low pairwise [F.sub.st] values potentially led to conflicting results between traditional analyses and a Bayesian approach. This data set could provide baseline data from which a comprehensive mixed-stock analysis could be performed, allowing for more efficient and effective management of this economically and socially important resource. Nous avons evalue les relations genetiques entre des rassemblements de fraie de grands coregones (Coregonus clupeaformis) au lac Michigan et les avons utilisees pour predire un modele de stocks ou d'unites de gestion (MU) pour cette resource. Nous utilisons l'hypothese selon laquelle, dune part, les rassemblements de fraie distincts representent des MUs potentielles et, d'autre part, des differences au niveau des marqueurs genetiques sous-tendent la differenciation des populations. L'identification des stocks genetiques d'apres 11 locus microsatellites indique la presence de six MUs genetiques. Les MUs identifiees correspondent a des rassemblements de fraie rapproches geographiquement qui se fusionnent en groupes genetiques. Les analyses faites au sein des MUs indiquent que toutes les MU decrites, sauf une, forment des groupes stables (c'est-a-dire sans differences entre les populations), l'exception etant le regroupement Hog Island-- Traverse Bay. La population d'Elk Rapids possede la plus grande divergence genetique au lac Michigan. Cependant, les valeurs faibles de [F.sub.st] laissent croire qu'il y a, ou il y a eu dans le passe, des niveaux moderes a eleves de flux genique entre les MUs. Des tests significatifs d'isolement par la distance et des valeurs faibles de Fst apparies ont conduit a des resultats contradictoires entre les analyses traditionnelles et une approace bayesienne. Cet ensemble de donnees pourrait representer des informations de base a partir desquelles il serait possible de faire une analyse complete des stocks mixtes; cela permettrait une gestion plus concrete et efficace de cette resource qui presente un interet economique et social. [Traduit par la Redaction], Introduction The utility of the stock concept in natural resource management is based on scientific evidence that the overall productivity and evolutionary potential of a species is dependent on maintaining [...]

ABSTRACT. In small inland lakes that support stunted yellow perch Perca flavescens, reduction of fish density by manual removal may be the only feasible approach to increase growth and alter [...]

Capelin Mallotus villosus is a coldwater, marine forage fish that responds quickly to environmental fluctuations; however, little is known about Capelin in Alaskan waters. The objective of the current study was to better understand the distribution and life history of spawning Capelin in northern Norton Sound, Alaska. Surveys were conducted from May through July 2018 to locate and estimate the size of nearshore Capelin aggregations prior to spawning, identify the location and timing of spawning events, characterize spawning habitat, and collect actively spawning fish to examine life history characteristics (e.g., body size, age, fecundity, etc.). Most (85.9%) of the nearshore aggregations were less than 12 m2 in surface area. Spawning Capelin were collected in Norton Sound between June 15 and June 21. At spawning locations, gravel and coarse sand accounted for over 70% of the proportional weight of sediment collected within a beach, and all sediment samples contained Capelin eggs. Spawning males were larger than spawning females in TL (mean ± SD = 148.8 ± 6.7 mm versus 137.0 ± 8.4 mm, respectively) and total weight (21.2 ± 2.9 g versus 13.7 ± 3.0 g), and both sexes were predominately age 3 (age range = 2–4 years). Absolute fecundity was 9,219 ± 4,529 eggs, and the gonadosomatic index was 1.09 ± 0.32% for males and 21.69 ± 8.21% for females. Nearshore aggregation sizes in Norton Sound were smaller than those reported for Newfoundland, but spawning behavior, timing, and water conditions were similar to observations from other Capelin spawning regions (e.g., Greenland), as were size, age, fecundity, and gonadosomatic index estimates. Although the results from the current study update baseline information on spawning Capelin in northern Norton Sound, continued research on their distribution and life history is needed to better understand ecosystem function in the North Pacific Ocean. [ABSTRACT FROM AUTHOR]