Recent mitochondrial DNA research separates Bluehead Sucker in the Bonneville and Snake River basins as genetically dissimilar to the Bluehead Sucker residing in the Colorado River Basin. Ramifications of a taxonomic split could include a petition to be listed under the ESA for the "weaker" species that, in the case of the Bluehead Sucker, would be the populations in the Bonneville and Snake River Basins. In preparation for this petition conservation actions showing progress toward recovery would influence the decision between warranted and not warranted . Current actions being undertaken in the Weber River include reconnecting fragmented sections of the river, improving habitats for all life stages, and the creation of a captive brood. These actions address weaknesses identified for this population through previous research and monitoring. Continued monitoring of the population dynamics of these fragmented portions of this population will allow us to infer the success of these actions going forward. Current monitoring estimates the population of adult fish only through mark recapture surveys. Adding age and growth as a continued metric for this population will allow us to extract additional data such as age at maturity and year class strength while trying to pinpoint environmental factors like water year and flow timing that lead to these successes. The second part of this project will inform the breeding success of the population through young-of-year monitoring. Recruitment has been identified as the main bottleneck to this population. As habitat projects are implemented that create and restore backwater habitats that are crucial to survival of young-of-year monitoring efforts need to be able to show that these habitats are creating a positive impact. Therefore it is crucial to begin monitoring young-of-year numbers to create a baseline to compare future numbers against once habitat projects and supplemental stockings begin. Aditionally this monitoring will inform the endpoint of the brood project ten to fifteen years in the future.

Obtain population metrics through increased monitoring efforts. Objective 1: Obtain Age and Growth Data for all bluehead sucker captured during annual monitoring in Weber River Section 02, 04, and 06 Task 1: Collect pectoral fin rays from all Bluehead sucker sampled during annual monitoring (Biologists and Technicians) Task 2: Mount and section fin rays (technicians) Task 3: Age sections (Biologists). Analyze age and growth data Objective 2: Obtain Young-of-Year Estimates in Weber River Sections 05 and 06 Task 4: Identify Backwater habitats during spring monitoring (Will Be completed in FY 21 during previous FY monitoring) (Biologist and technicians) Task 5: Seine and enumerate Young-of-Year fish in each identified backwater habitat. (Biologist and Technicians) (5 days). Collect 10 to 30 whole individuals of Mountain Sucker / Bluehead Sucker to verify species identification under dissecting microscope from each backwater that has at least 50- 100 of these individuals. (Biologist)

The Utah Wildlife Action Plan lists Inadequate understanding of Ecology and Life History as a level 2 data gap threat. The actions in this project will improve the understanding of the life history within the Weber River Population. This project also addresses the goals of the rangewide conservation agreement for roundtail chub, bluehead sucker and flannelmouth sucker: "Establish and implement qualitative and quantitative long-term population and habitat monitoring programs for roundtail chub, bluehead sucker, and flannelmouth sucker. * Develop and implement monitoring plan for the subject species. * Evaluate conditions of populations using baseline data." - Fish, Colorado River, and Wildlife Council. "Rangewide conservation agreement for roundtail chub Gila robusta, bluehead sucker Catostomus discobolus, and flannelmouth sucker Catostomus latipinnis." Utah Department of Natural Resources, Salt Lake City (2004).

N/A

Age and Growth: Pectoral fin rays will be collected from all Bluehead Sucker captured during annual monitoring efforts. Pectoral fin rays will be severed from the body at the point closest to the body using side-cutting pliers. Fin rays will be stored and dried in coin envelopes with other pertinent data (Total Length, Weight of fish, and a sample number that will be matched with PIT tag number on data sheet). Dry fin rays will be mounted in buehler EpoxiCure resin. Once the resin is cured, resin hardened fin rays will be sectioned using a Buehler Isomet Low Speed saw. Sections will be photographed under a microscope and read by two biologists independently. All aged fish that the biologists concluded different ages for will be read again together to come to a consensus. Age will be plotted against total length and weight to create growth curves. Age groups will be enumerated and compared to historic water values to determine if water level and/or flow timing has an impact on year class strength. Continued monitoring of the age structure of these populations will allow us to infer more in depth metrics than the one time age and growth studies in the past. These metrics include: recruitment variability and age based mortality rates. Young-of-year Monitoring: Likely backwaters will be located during raft electrofishing population estimates in May/June of Calendar Year (Previous Fiscal Year). We will return to and sample identified backwaters via seine from September to November. Fish will be identified to species or species group (YOY Mountain Sucker and Bluehead will likely be grouped as they are hard to differentiate at YOY sizes), measured (TL), and enumerated. A conservative subsample of fish from unidentifiable species groups will be collected and stored in ethanol to be identified under a dissecting microscope. Densities of YOY fish will be recorded and compared year to year as well as with Recruitment indices obtained from continued age and growth work.

Similar tasks on different sections of the Weber river will be completed as the sections are monitored on 3-year rotations. Costs will be similar from year to year. As monitoring is completed from year to year less effort will be required and costs will decrease. The initial baseline data that will be collected now through the next three years will be more intensive. However, the task of finding backwaters to monitor will be removed after the first rotation and fewer adult Bluehead sucker will need to be aged yearly after the initial effort as all adult fish are tagged and growth can be monitored in subsequent captures.

N/A

This project will inform the success of current management efforts for this species (Habitat improvement and connection, as well as brood development and stocking) in this system. Results from this project will direct future management efforts. The initial year of data collection (FY20) has verified success of recent backwater creation habitat project. Specifically Recruitment Variation Indices will be able to be calculated from multiple years of age and growth data. Additionally, survival rates will be calculated for each year class to be able to describe vulnerable age classes which could inform protective actions for these year classes. YOY monitoring in conjunction with the recruitment variation indices will inform the importance of YOY monitoring and whether or not YOY numbers are indicative of strong recruitment.

07/01/2021

06/30/2022

2022

This project, in conjunction with previous projects (WRI 6365 and 6337) collected more than 200 fin ray samples of adult Bluehead Sucker from the three most abundant populations in the weber River. The fin rays were mounted in epoxy and sectioned using a low speed saw. Once sectioned they were imaged using a camera attached to a microscope. The images were then aged by two independent readers. Once they were aged, information was collated to inform a length at age curve (Von-bertalanffy curve) that was used to infer age at sexual maturity (Where growth tapers off), maximum total length, and natural mortality rate. Additionally once age was assigned it could be inferred which year each fish was spawned in allowing us to look back at strong year classes to infer possible events that may signal an increased probability of recruitment to adulthood. Additionally the projects reported on here collected young of year fish abundance estimates by seining backwaters and enumerating the juvenile fish captured at multiple back water habitats along the weber river. Sucker species are difficult to differentiate at young of year sizes (<80mm total Length). As such, a subsample of sucker were collected at each site with sucker present to be taken back and identified under a dissecting microscope. The ratio of sucker species (Bluehead, Mountain, and Utah Sucker) in the identified sub sample could be extrapolated across the suckers enumerated in the larger sample.

This project has greatly improved our knowledge of the age and growth of Bluehead Suckers within the Weber River Drainage. Because of this project, we have been able to determine strong year classes in the three main populations. A disproportionately large number of individuals in sections 5 and 6 (Morgan to echo dam) of the Weber River were spawned in 2012 and 2013, the two years after a very high water event in 2011. Additionally, the strongest year classes in Section 02 (Riverdale and Ogden) were associated with 2017 and 2018, which included a high water year event and the year after. It could be presumed with these correlations that river flows play an important part in creating successful recruiting events for this species. However, the mechanism remains to be seen. Is it spawning habitat availability, or inundation of juvenile rearing habitats? This is something that can be teased out if age and growth work is continued as a monitoring metric with these populations. The high water event in 2017 would yet to be realized by the sampling efforts in sections 05 and 06 since they were sampled most recently in 2020 and 2021 and the minimum age that is most likely to be captured by raft electrofishing is age 3, with age 5 to 6 and older being more likely to be captured due to their coming of spawning age. Likely Spawning age was also determined through this age and growth study. Growth tapers off dramatically for males in years 4 and 5, and females in years 5 and 6, indicating that these ages are when the fish begins to put more energy into reproduction than into growth. The young of year sampling has indicated important backwater habitats for this species and will give us a baseline moving forward when captive produced fish begin being stocked into the weber in coming years. Additionally, Young of year sampling has proved in at least one instance that creation of spawning habitat in conjunction with creation of proximal backwater habitat can provide a boost in spawning success. In the reaches of the Weber located in Ogden a newly created spawning bar was placed upstream of a newly placed backwater habitat. That same year, we monitored that section for both adults and young of year. Approximately 70% of all adults captured in that reach were on the recently created spawning bar and the associated backwater held a significant number of juvenile Bluehead Sucker.

It is my recommendation that age and growth metrics should continue to be a tool used in monitoring all Bluehead Sucker populations within the Weber River. Additionally, the projects being reported on here have given us important information about what has worked in recent years to provide boosts to recruitment. Some, we, as managers do not have the ability to affect (i.e.) good water years. Others like the creation of spawning and rearing habitat, we do have the ability to affect. Also with continued analysis of year class strength through ageing we should be able to identify possible sweet spots in flows which could lead to negotiating possible timed water releases to help with spawning and rearing effectiveness.