Post-stocking fate of June sucker in Utah Lake 2014 Annual Report

June sucker Chasmistes liorus is an endangered species endemic to Utah Lake, UT. The lake historically
supported 13 native fishes, 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. June sucker was once numerous
throughout the lake, but numbers declined in the late 1990s to as few as 300 wild individuals. Many
factors contributed to its decline including overharvest, habitat degradation, and predation and
competition by non-native species. Repatriation of hatchery produced fish is a primary recovery
strategy for June sucker, but fate of stocked fish is not well known. The purpose of this study is to detail immediate post-stocking survival and dispersal of hatchery reared June sucker in Utah Lake.
In the second year of this nominal three-year study, 20 June sucker were surgically implanted with
acoustic telemetry tags. The acoustic tagged fish along with 1165 PIT tagged fish were released from
the shoreline and in open water from boat in two separate stocking events in early and late summer.
Both directional and omnidirectional hydrophones with a receiver were used to actively track fish.
Multiple submersible ultrasonic receivers that continuously scanned for acoustic tags were placed
throughout the study area for passive tracking. Remote PIT scanners were utilized in the lake to scan PIT tagged fish. Survival estimates for each telemetry study were calculated using Kaplan-Meier survival based on the final fate of each acoustic tagged June sucker. Patterns of dispersal were assessed for individual fish by mapping active and passive tracking records in ArcView®.
Kaplan-Meier survival estimates were 0.20 at 8 weeks and 0.00 at the end of the 60 day tracking period for early summer fish. Contact was permanently lost (unknown fate) with six out of ten fish released in late summer, and as a result survival estimates were not calculated. A total of 477 PIT tag contacts representing 263 unique fish were recorded over the four month study period using remote PIT scanners. Average size at stocking since 2007 has been 227 mm, whereas average stocking size of fish scanned in 2014 was 306 mm.
Overall, estimated survival in 2014 was lower than in 2013. The cause of the additional mortality in
2014 was unclear. American white pelican as well as other piscivorous birds are abundant at Utah Lake
and may play a role in post-stocking survival of the fish. In addition, remote PIT scanning suggests that
post-stocking survival is positively related to size at release. With continued efforts these data coupled
with PIT scanning will help to support informed stocking decisions and ultimately ensure the long term
persistence and conservation of the species.

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