SFS Annual Meeting

6/03/2024  |   13:30 - 13:45   |  Freedom Ballroom F

Translocation in a fragmented river increases survival of imperiled fishes Fragmentation restricts access to valuable habitat with severe consequences for populations. Translocations to mitigate the effects of fragmentation are common, but few are rigorously evaluated, particularly for fishes. Over six years, we translocated 1,215 individuals of four imperiled fish species isolated below a barrier on the San Juan River, Utah, USA that restricts access to upstream habitat. We used re-encounter data collected between 2016 and 2022, to inform a spatially-explicit multistate mark-recapture model to estimate survival and transition probabilities of translocated and non-translocated individuals, both below and above the barrier. Individuals of all four species moved large (>200 km) distances upstream following translocation with the maximum upstream encounter distance varying by species. Translocated fish survived at higher rates compared to non-translocated fish below the barrier for three of the four species. Above the barrier, translocated individuals survived at similar rates as non-translocated fish for bluehead sucker (Catostomus discobolus) and flannelmouth sucker (C. latipinnis), while survival rates of translocated endangered Colorado pikeminnow (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus) were higher relative to non-translocated individuals. Transition probabilities from above to below the barrier were generally low for three of the four species but were substantially higher for razorback sucker. Our results suggest translocation to mitigate fragmentation can have demographic benefits for large-river fishes by allowing movements necessary to complete their life history in heterogeneous riverscapes. Given the costs or delays in providing engineered passage solutions or achieving barrier removal, we suggest translocations may provide an alternative conservation strategy in fragmented rivers.

Casey Pennock (Primary Presenter/Author), The Ohio State University, pennock.17@osu.edu;

Brian Healy (Co-Presenter/Co-Author), U.S. Geological Survey, bhealy@usgs.gov;

Matthew Bogaard (Co-Presenter/Co-Author), Washington Department of Fish and Wildlife, Matthew.Bogaard@dfw.wa.gov;

Mark McKinstry (Co-Presenter/Co-Author), US Burearu of Reclamation, mmckinstry@usbr.gov;

Keith Gido (Co-Presenter/Co-Author), Kansas State University, kgido@ksu.edu;

Nate Cathcart (Co-Presenter/Co-Author), Alaska Department of Fish and Game, cncathca@gmail.com;

Brian Hines (Co-Presenter/Co-Author), U.S. Bureau of Reclamation, bhines@usbr.gov;

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6/03/2024  |   13:45 - 14:00   |  Freedom Ballroom F

LONG-TERM CHANGES IN THE ABUNDANCE OF MIGRATORY FRESHWATER FISHES DUE TO HYDROPOWER DAM IN A TROPICAL RIVER The expansion of hydropower dams poses a threat to migratory freshwater fishes. Few long-term studies have monitored their impacts on the abundance of such species in tropical rivers. Here, we investigated temporal changes (2012–2023) in the abundance of six migratory fish species following the beginning of operations of the São Domingos Hydropower Dam (SSD) on the Verde River, a clear-water tributary of the Paraná River, Brazil. The fishes were captured just downstream of the SSD and released into the reservoir annually during the migratory season (October to March). After 12 seasons and 22,625 captured fishes, the abundance of migratory fish at SSD declined by 84% compared to the first year of monitoring. This decline occurred in all six species, particularly in Megaleporinus piavussu (Anostomidae), Prochilodus lineatus (Prochilodontidae), and Salminus brasiliensis (Bryconidae). Additionally, there were significant variations in the total body length of the species among years. Further drastic declines in the abundance of all six species are anticipated with the construction of new hydropower facilities in the Verde River. Continuous monitoring is key to understanding the full scope and magnitude of ecological impacts.

Elaine Corrêa (Primary Presenter/Author), Universidade Federal de Mato Grosso do Sul, elaineccorrea@yahoo.com.br;

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6/03/2024  |   14:00 - 14:15   |  Freedom Ballroom F

Characterizing sub-daily flow variability downstream from hydropower projects Hydropower can help facilitate power grid decarbonization through increased integration of variable renewable sources because it can flexibly respond to energy demands on a short timescale. Operating hydropower dams to respond to real-time energy market conditions can result in rapid and abnormal fluctuations in downstream flow, called hydropeaking. Hydropeaking alters the timing, magnitude, and rate of change of natural flow regimes by rapidly and frequently transitioning between peak and base flow as dictated by market demand. The resulting sub-daily flow variability in downstream reaches strongly affects riverine fishes by increasing stranding risk during dewatering, destabilizing habitat, decreasing production and diversity, and interrupting reproduction, among other impacts. Here, we quantify the intensity and timing of flow regime alterations due to hydropower production in multiple hydrologic regions across the continental United States. Specifically, we characterize and compare flow magnitude, rate of change, and variability using 15-minute flow data from USGS flow gages downstream from selected hydropeaking and run-of-river projects and in reference reaches in unregulated rivers. We also describe seasonal patterns of hydropower-driven flow regime alteration to identify potential impacts to fish during sensitive life history stages. Quantitative approaches that describe flow regime alterations at temporal resolutions (sub-daily) and extents (seasonally) relevant to fish ecology can inform stakeholder decision-making processes to assess or mitigate the potential ecological impacts of flexible hydropower production on downstream fish communities.

Bryan Bozeman (Primary Presenter/Author), Oak Ridge National Laboratory, bozemanbb@ornl.gov;

Carly Hansen (Co-Presenter/Co-Author), Oak Ridge National Laboratory, hansench@ornl.gov;

Paul Matson (Co-Presenter/Co-Author), Oak Ridge National Laboratory, matsonpg@ornl.gov;

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6/03/2024  |   14:15 - 14:30   |  Freedom Ballroom F

Alteration of flow and fish assemblages downstream of surface water reservoirs Streams and their biota are largely impacted by human activities that alter stream hydrology, such as damming and abstraction. Water supply reservoirs alter the flow of a river by storing water and diverting it for human consumption; however, there is a lack of information about how water supply reservoirs alter downstream river flow and subsequent impacts on fish assemblages. Our objectives were to 1) quantify flow alteration downstream of water supply reservoirs, 2) determine how flow alteration impacts fish assemblages. Stream flow data and fish occurrence and abundance were collected at water supply reservoirs (n=6), undammed stream reaches with similar watershed sizes (n=6), and impoundments without water withdrawals (n=3). We analyzed differences in various hydrologic metrics (e.g., 7-day max, low pulse count) between water supply reservoirs, undammed stream reaches, and impoundments without water withdrawals. We also assessed fish-discharge relationships and how those relationships are altered below water supply reservoirs compared to undammed streams and impoundments without water withdrawals. Fish responses were assessed using assemblage data (e.g., non-metric multidimensional scaling) and metrics based on species’ traits (e.g., habitat preference, thermal tolerance). Understanding changes in flow downstream of water supply reservoirs and impacts on fish assemblages will help guide water allocation management toward minimizing impacts on stream ecosystems.

Anna Baynes (Primary Presenter/Author), University of Massachusetts Amherst , abaynes@umass.edu;

Todd Richards (Co-Presenter/Co-Author), Massachusetts Division of Fisheries and Wildlife , todd.richards@state.ma.us;

Allison Roy (Co-Presenter/Co-Author), U.S. Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts Amherst, aroy@eco.umass.edu;

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6/03/2024  |   14:30 - 14:45   |  Freedom Ballroom F

Longfin smelt population modeling in the San Francisco Estuary Freshwater flow is a key control of fish population dynamics. The alteration of river flow regimes arising from water management and climate change is altering environmental conditions and associated fish population dynamics. The San Francisco Bay-Delta experiences seasonal and interannual fluctuations in hydrology, and is host to several endangered and threatened fish species. In particular, this region is at the southern range boundary of the longfin smelt (Spirinchus thaleichthys), a threatened endemic fish. We investigated longfin smelt - ecology relationships over the past five decades, at both intra-annual and interannual scales, determined whether flow-ecology relationships have changed in magnitude or sign through time, and determined which factors are driving fluctuations in the importance of this relationship. By employing breakpoint analysis, MARSS (multivariate autoregressive state-space) models, and dynamic linear models with publicly available datasets, we found consistent breakpoints in environmental variables related to region-wide shifts in conditions, such as drought. Further, MARSS models indicated a unique distribution of populations associated with sampling gear type and habitat. Dynamic linear models further elucidate the time-varying pressures longfin smelt face, such as flow alteration and habitat quality. Future research is needed to examine the interactions between habitat quality and food resources on non-stationary longfin smelt populations.

Parsa Saffarinia (Primary Presenter/Author), University of California, Berkeley, parsas@berkeley.edu;

Stephanie Carlson (Co-Presenter/Co-Author), Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, U.S., smcarlson@berkeley.edu;

Albert Ruhi (Co-Presenter/Co-Author), Department of Environmental Science, Policy, and Management, University of California, Berkeley, albert.ruhi@berkeley.edu;

James Hobbs (Co-Presenter/Co-Author), California Department of Fish and Wildlife, James.Hobbs@wildlife.ca.gov;

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6/03/2024  |   14:45 - 15:00   |  Freedom Ballroom F

Rapid evolution undermines intensive suppression of a widely introduced predatory fish Introduced species are a widespread threat to global biodiversity, spurring costly and time-consuming control efforts. Full eradication of non-native species is rarely achieved, which is attributed to the ineffectiveness of targeted measures at low population densities. Yet, organismal adaptation to suppression strategies is rarely considered, even though evolutionary responses have been observed in response to both selective and non-selective anthropogenic mortality. Here, we report rapid evolutionary change in smallmouth bass that undermined a 23-year suppression effort, facilitating an increased population size with young, fast-growing, and early-maturing individuals. Corresponding genetic data from 1,187 archived fish samples reveal a strong genetic basis for these shifts, with pronounced allele frequency changes in genomic regions associated with a tradeoff from K- to r-selected phenotypes. These adaptive responses were likely induced by the estimated doubling of annual mortality and release from density-dependent competition, rather than directional selection imposed by gear selectivity. The Adirondack bass example emphasizes the speed with which evolutionary response can occur under invasive species suppression efforts and calls for a new era of invasive species management that is adaptive and anticipatory of target population evolutionary response.

Liam Zarri (Primary Presenter/Author), Cornell University, zarriliam@gmail.com;

Clifford Kraft (Co-Presenter/Co-Author), Cornell University, cek7@cornell.edu;

Pete McIntyre (Co-Presenter/Co-Author), Cornell University, pbm3@cornell.edu ;

Diana Baetscher (Co-Presenter/Co-Author), Alaska Fisheries Science Center, diana.baetscher@noaa.gov ;

Kurt Jirka (Co-Presenter/Co-Author), Cornell University, kjj23@cornell.edu;

Eileen Randall (Co-Presenter/Co-Author), Cornell University, eab345@cornell.edu ;

Ben Marcy-Quay (Co-Presenter/Co-Author), University of Vermont, bmarcyqu@uvm.edu ;

Carl St. John (Co-Presenter/Co-Author), Cornell University, cas399@cornell.edu ;

Suresh Sethi (Co-Presenter/Co-Author), Cornell University, suresh.sethi@cornell.edu;

Montana Airey (Co-Presenter/Co-Author), Cornell University, ma2276@cornell.edu;

Thomas Detmer (Co-Presenter/Co-Author), Cornell University, td389@cornell.edu;

Alexander Flecker (Co-Presenter/Co-Author), Cornell University, Ithaca, NY, USA, asf3@cornell.edu;

Nina Therkildsen (Co-Presenter/Co-Author), Cornell University, nt246@cornell.edu ;

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