June Sucker Stocking Evaluation

June sucker Chasmistes liorus is an endangered species endemic to Utah Lake, Utah. The lake historically supported 13 native fish species, but due to human interactions it now supports a suite of non-native species and only two natives, June sucker and Utah sucker Catostomus ardens. Historically, June sucker were numerous throughout the lake but numbers declined in the latter 1990s to as low as 300 wild individuals with little or no recruitment in the population (USFWS 1999). The decline was attributed to many factors including overharvest, habitat degradation, and predation and competition by non-native species. Due to habitat alterations in the Provo River, most age-0 fish do not successfully transition from larvae to juveniles and those that do are susceptible to predation by non-native fish (Modde and Muirhead 1994, Belk et al. 2001). More than 350,000 individuals longer than 200 mm have been stocked into the lake with a goal of stocking 2.8 million fish (USFWS and URMCC 1998). Monitoring of June sucker includes the use of trap nets, trammel nets, commercial seines, and trawls in the lake proper and a combination of spotlighting and weir operations during the spawning run in the Provo River (USFWS 1999, UDWR 2011). Although hundreds of adult June suckers are captured in the river during spawning each year, juvenile suckers are rarely encountered in the river or in extensive efforts in the lake proper (UDWR 2011). The lack of encounters with juvenile June sucker post-stocking has resulted in little information on their survival.

To obtain post-release survival estimates for captive reared June sucker Marsh & Associates is conducting a series of intensive acoustic telemetry studies. Each discrete segment of the study will provide short-term (60 days) survival rates as well as post-stocking dispersal patterns. Each study segment includes a stocking of ten acoustic tagged fish within a group stocking of at least 500 June sucker. All June sucker released as part of each group will have a 134.2 kHz PIT tag inserted into the abdominal cavity prior to release. This will ensure that additional data will be provided on post-stocking survival through PIT scanning or future capture. PIT scanning and capture data currently available to estimate post-stocking survival will be supplemented by actively scanning for PIT tags from deceased June sucker in locations where potential predators to June sucker congregate (e.g., Bird Island). In addition to these activities, Marsh & Associates is assisting with PIT tagging and annual monitoring activities for June sucker.