Building a Better June Sucker: Characterization of Mouth Shape in the Captive Brood Stock

June sucker, Chasmistes liorus, is an endangered lake sucker endemic to Utah Lake, Utah, USA. Over the last two decades, captive-raised June suckers have been stocked into Utah Lake to augment the wild population. However, it has become apparent that the fish stocked from captive stock may not always represent the typical June sucker morphology. To determine the utility of current captive brood lots to produce June sucker phenotypes, we characterized shape of the lip lobes on the lower jaw of each brood lot. We obtained offspring from within-lot crosses and characterized shape of the lower lips using geometric morphometrics. We compared shape of brood lots to reference samples of June sucker and reference samples of the co-occurring sister species, Utah sucker (Catostomus ardens). Mean shape of the lower lips among brood lots varies from typical June sucker morphology to shapes typical of Utah sucker. Three brood lots had mean shape scores somewhat similar to the reference June sucker mean, and five brood lots had mean shape scores more similar to the reference Utah sucker mean. All other brood lots were intermediate representing hybrid phenotypes. Utilization of all brood lots on a roughly equal basis for augmentation in Utah Lake will likely result in the loss of typical June sucker morphology in the lake within a few decades. We recommend use of brood lots that exhibit June sucker morphology and discontinuance of use of brood lots that represent Utah sucker morphology. In addition, selection on lower lip shape in captive brood lots may be required to recreate June sucker phenotypes from captive brood stock.

Classification of hatchery and wild fish using natural geochemical signatures in otoliths, fin rays, and scales of an endangered catostomid

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 87Sr/86Sr 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 87Sr/86Sr. Thus, fin sections appear to provide a nonlethal structure for laser ablation microchemical analysis to determine origins of unknown origin JS in the future.