Endangered and endemic June sucker (JS, Chasmistes liorus) have been stocked for many years to prevent extinction in Utah Lake, Utah. When unmarked fish appeared in the lake at higher rates than expected from tag loss, we sought to determine if 87 Sr/ 86 Sr and Sr/Ca (signatures) in otoliths, fin rays, and scales could be used to identify whether stocking had created a naturally reproducing population. Signatures from otoliths and fin rays suggested that approximately 38% (12 of 31) of unmarked JS probably came from the Fisheries Experimental Station (FES) hatchery in Logan, Utah, and a minimum of 13% (four of 31) of unmarked JS had signatures that strongly indicated that they were of wild origin. The remaining JS (15 of 31) could not be assigned to any particular location because of signature overlap. While scales were not useful for determining fish provenance, we found a nearly 1:1 relationship between pelvic fin and otolith 87 Sr/ 86 Sr. Thus, fin sections appear to provide a nonlethal structure for laser ablation microchemical analysis to determine origins of unknown origin JS in the future.Résumé : L'empoissonnement du Chasmistes liorus, un poisson endémique en voie de disparition, se poursuit depuis de nombreuses années afin d'en prévenir la disparition dans le lac Utah (Utah, États-Unis). Quand des poissons non marqués ont commencé à apparaître dans ce lac à des fréquences plus grandes que ce que la perte d'étiquettes permet de prévoir, nous avons tenté de déterminer si les rapports 87 Sr/ 86 Sr et Sr/Ca (signatures) dans les otolites, les rayons de nageoire et les écailles pouvaient être utilisés pour établir si l'empoissonnement avait produit une population issue de la reproduction naturelle. Les signatures d'otolites et de rayons semblent indiquer qu'environ 38 % (12 sur 31) des C. liorus non marqués proviennent probablement de l'écloserie de la Fisheries Experimental Station (FES) à Logan (Utah) et au moins 13 % (quatre sur 31) des C. liorus non marqués ont des signatures indiquant fortement qu'ils seraient issus de la reproduction à l'état sauvage. Les autres C. liorus (15 sur 31) ne peuvent être affectés à un endroit précis en raison de la superposition de signatures. Si les écailles ne se sont pas avérées utiles pour déterminer la provenance des poissons, nous avons noté un rapport avoisinant 1:1 des valeurs de 87 Sr/ 86 Sr des nageoires pelviennes et des otolites. Les sections de nageoire semblent donc constituer une structure se prêtant à l'analyse microchimique non létale par ablation laser pour la détermination des origines de C. liorus d'origine inconnue. [Traduit par la Rédaction]

The dynamics of stream and floodplain connectivity are a growing consideration for restoration projects. Restoration of a tributary stream to Utah Lake was undertaken in 2008 with the intent of increasing available spawning and nursery habitat for the endangered June Sucker Chasmistes liorus. Restoration efforts provided an opportunity to evaluate relationships between fish assemblages and variables related to the physiochemical environment, vegetation, and habitat connectivity at floodplain ponds. Fish were collected with beach seines and habitat variables were measured each month at 12 floodplain ponds during March 2010 to March 2011. Total catch was predominated by nonnative species: Green Sunfish Lepomis cyanellus, Western Mosquitofish Gambusia affinis, Black Bullhead Ameiurus melas, Fathead Minnow Pimephales promelas, and Bluegill Lepomis macrochirus. Both indirect and direct gradient analyses indicated a significant correlation between fish assemblages and site connectivity. The percentage and type of macrophyte cover (e.g., emergent, submergent) also played a significant role in structuring fish assemblages. Species richness was generally higher at sites with intermediate to high connectivity than at sites with lower connectivity. Sites with lower connectivity were predominated by Green Sunfish, Mosquitofish, and Fathead Minnow. June Suckers were collected from sites with intermediate values of connectivity and vegetation. Observed patterns suggested connectivity structured initial fish assemblages and macrophyte colonization dynamics; subsequent interactions between local habitat (i.e., percent vegetation) and biotic factors (e.g., competition, predation, etc.) provided site‐specific interactions and structure. The results of this study indicate connectivity dynamics should be an important consideration in stream and floodplain restoration efforts.