Shortnose Chasmistes brevirostris and Lost River Suckers Deltistes luxatus endemic to the Klamath River Basin on the California–Oregon border have experienced dramatic population declines in parallel with many other Catostomid species. Captive propagation has become a key element of many endangered fish recovery programs, although there is little evidence of their success in restoring or recovering fish populations. We initiated a novel rearing program for Klamath suckers in 2016 with the goal of developing a husbandry strategy that better balances the ecological, genetic, and demographic risks associated with captive propagation. We collected 4,306 wild-spawned Klamath sucker larvae from a major spawning tributary May–June 2016 and reared them at a geothermal facility established through a partnership with a local landowner and aquaculture expert. Mortality during collection was <1%. We reared larvae in glass aquaria for 17–78 d until they reached approximately 30 mm total length, upon which we moved them to round fiberglass tanks for 14–46 d or until reaching approximately 60 mm total length. Overall survival of larvae to ponding for final growout was 71%. Larval tank-rearing survival was 98% for 37 d until an isolated fish health incident affected three aquarium populations, reducing survival to transfer to 75%. Survival after transfer to round fiberglass tanks for 14–46 d was 94%. This study outlines the first successful collection and early life-history husbandry of wild-spawned endangered Klamath suckers that we are aware of.
Captive propagation has become a key component of many endangered fish recovery programs, although there is limited evidence of their success in restoring or recovering fish populations (Jackson et al. 2004). Seventy-percent of recruitment failures among freshwater fish reintroduction efforts are associated with hatchery fish (Cochran-Biederman et al. 2015). Low survival rates upon release are common, particularly in systems with established nonnative predator populations, significant water operations, and other natural and anthropogenic threats (Schooley and Marsh 2007). Repatriation of hatchery-propagated Bonytail Chub Gila elegans began in 1981, yet to date no measurable yield in adult recruitment has been observed (Minckley et al. 2003; Kappenman et al. 2012). Kootenai White Sturgeon Acipenser transmontanus and Pallid Sturgeon Scaphirhynchus albus are likely to become extinct in the wild before hatchery progeny assimilate into the natural spawning population (Ireland et al. 2002). Still, relatively little has been published on how the use of alternative rearing methods affects growth, survival, and prognosis of listed nongame fishes (Tave et al. 2019), particularly Catostomids, upon release (Day et al. 2017).
Shortnose Chasmistes brevirostris and Lost River Suckers Deltistes luxatus, collectively known as Klamath suckers, occur sympatrically in several large, shallow lakes of the Upper Klamath River Basin on the California–Oregon border and are federally listed as endangered (USFWS 1988) pursuant to the U.S. Endangered Species Act (ESA 1973, as amended). Both species were historically abundant and fished by native peoples but suffered catastrophic declines of overall numbers and in the number of viable populations throughout their range. Significant threats to these species include habitat loss and degradation, disrupted migration corridors, impaired water quality, and predation (USFWS 2013, 2019). Ongoing adult monitoring indicates that spawning populations of Shortnose Sucker in Upper Klamath Lake (UKL) have declined by an estimated 75% (Hewitt et al. 2015). Though both species historically spawned at numerous springs and tributaries throughout UKL, spawning is now restricted to a handful of eastside springs and the Williamson River, a major tributary to UKL. Lost River sucker spawning at eastside shoreline springs of UKL has declined by an estimated 55–60% since 2002 (Hewitt et al. 2015). The primary limiting factor for both species appears to be unnaturally high mortality of larval and first-year juveniles resulting in minimal recruitment to the adult population (USFWS 2013). Typically, only a few age-1 and age-2 individuals are encountered each year, and age-3 and age-4 fish are extremely uncommon in the wild. Further, ongoing monitoring indicates most adult Klamath suckers have reached their expected life of up to 50 y for Lost River Sucker and 30 y for Shortnose Sucker (Hewitt et al. 2018).
The U.S. Fish and Wildlife Service (USFWS) developed a new program in 2015, the Klamath Basin Sucker Rearing Program, that employs rearing strategies designed to limit the scope and magnitude of interactions occurring between hatchery and naturally produced fish, as well as address the need to minimize human intervention in the rearing process (Day et al. 2017). This novel program was initiated in 2016 following a programmatic review of captive rearing methodologies for western Catostomids that found most programs were largely unsuccessful at achieving their identified recovery objectives using existing strategies (Day et al. 2017). The program operates under the hypothesis that conditions in UKL are not conducive to the survival and persistence of early life history suckers. Therefore, efforts aimed at propagating and releasing large numbers of larvae would likely be ineffective and may risk further genetic decline (Day et al. 2017; Willoughby and Christie 2018). Instead, wild-origin larval fish are collected in relatively small numbers for captive rearing in a protective environment for approximately 1–2 y, or until they reach a size at which predation risk and reliance on degraded habitat are minimal. Fish are then released back into UKL at strategically chosen locations based on favorable environmental conditions and postrelease monitoring results (Weissenfluh et al. 2016). No direct gamete collections or broodstock are used.
Although new measures and techniques likely reduce potential deleterious effects of captive rearing, the feasibility of collecting and rearing wild suckers for release is unknown, and the assumption of efficacy of this new strategy in relation to intensive culture remains unsupported. To date, no Klamath suckers have successfully been reared in captivity and subsequently released into natural waters (Stone and Jacobs 2015) and in situ rearing experiments yielded only 1–3% survival (USFWS 2014, 2015). For these reasons, we chose to focus our initial methods on development of larval collection and tank rearing. Our objectives were to 1) demonstrate that collection and rearing of early life-history, wild-spawned Klamath suckers is logistically feasible; and 2) quantify survival of larval Klamath suckers in a modified hatchery setting as baseline information for future rearing efforts.
Experimental rearing facility
We constructed an experimental rearing facility at Gone Fishing, a privately owned aquaculture facility located 16 km south of Klamath Falls, Oregon. The north edge of the property sits at an elevation of 1,274 m, and the southern boundary at 1,259 m, such that the site gently slopes downward toward the west edge of the property. Approximately 0.81 ha (2 acres) are leased by USFWS and dedicated to Klamath Basin Sucker Rearing Program. Water is supplied by an existing geothermal well that is permitted to withdraw 3.79 L/min. Water is pumped at 30°C, which is presumed to be sterile and tempered in a head pond to 16–19°C before use. A low-volume evapotranspiration lagoon is used to contain minimal waste on-site. A 4.5 m × 9 m greenhouse served as the main rearing building at the rearing facility housing nine glass aquaria, 76-L capacity with a bottom drain, and eight fiberglass round tanks, 151-L capacity with bottom drain. Water was pumped directly into the tempering head pond from the geothermal source and flow regulated by a 19-mm Chlorinated poly vinyl chloride valve. A 0.3-horsepower submersible sump pump was used to pump water from the tempering head pond into the greenhouse. A Manta waterprobe (Eureka Water Proves, Austin, TX) logged head-pond dissolved oxygen and pH at hourly intervals. Inside the greenhouse, similar valves were used to regulate flow into individual tanks. Water temperature was not regulated and reflected the natural temperature regime of the head pond, which was designed to replicate thermal conditions in UKL. A HOBO tidbit temperature logger (Onset Computer Corporation, Bourne, MA) recorded water temperature at hourly intervals over the course of the experiment. Water temperature was also checked multiple times daily and tank flow was adjusted accordingly so temperatures did not drop below 15°C or exceed 25°C.
Larval collection and husbandry
We collected larval suckers from 3 May 2016 to 30 June 2016 at Modoc Point Road Bridge, to coincide with the outmigration of sucker larvae from the Williamson River to Upper Klamath Lake, using two modified plankton nets 2.5 m in length with 0.3-m-diameter circular openings. Nets were constructed of 500-μm Nitex® mesh and fitted with a removable cup with 500-μm Nitex® mesh windows. To compensate for low flow velocity, we modified one net with poly vinyl chloride hoops to prevent collapse and fixed a foam float to the collection cup to keep the net suspended in the water column. We set nets simultaneously for 4, 20-min intervals starting at 0300 hours and ending after the fourth set was completed. We used D-frame dip nets made of heavy-duty canvas with 500-μm mesh attached to the bottom to sample shoreline vegetation for approximately 20 min each morning after plankton net sampling. After capture, we removed larvae carefully from the plankton nets by holding the cup in a 3.79-L insulated minnow bucket filled with water from the sampling location, unscrewing it from the net, and allowing fish to swim out of the cup volitionally. We transferred fish caught with D-nets by using 38-mm × 38-mm aquarium dip nets.
Upon arrival at the rearing facility, we gradually acclimated larvae to facility water temperatures at a rate not to exceed 1°C every 15 min until reaching within 0.5°C of facility water temperature. We then transferred larvae to aquaria by partially submerging the bucket into the tank and carefully enumerating fish by eye as they swam out under their own power. We stocked approximately 500 fish in each tank, keeping cohorts based on date of collection together as much as possible. Larvae remained in aquaria until they reached approximately 30 mm total length (TL), as determined by subsampling 10 fish, at which point we moved tank cohorts to round fiberglass tanks. Fish remained in round fiberglass tanks until they reached approximately 60 mm mean TL, as determined by subsampling 10 fish, or as soon as a positive species identification could be made, to ensure that nontarget species collected as bycatch were not retained.
Throughout rearing, we fed all fish a diet of live-hatched San Francisco Bay Brand® Artemia to satiation. We administered feedings daily at 0800, 1200, and 1600 hours. Fish also received a variety of prophylactic treatments (3% salt, 25 ppm Vedco® Formalin 37% active solution, and 0.5 or 1 tsp Pennox 343® Oxytetrocycline Hydrochloride) during holding to prevent or treat any potential diseases or parasites fish may have acquired prior to collection. The USFWS California–Nevada Fish Health Center in Anderson, California, designed all treatment protocols. We administered treatments of 3% salt with 25 ppm Formalin and 3% salt with Oxytetrocycline Hydrochloride 4 d/wk in alternate weeks as either a 4-h static bath or flow-through treatment. We visually observed fish at all feedings and once between each feeding (15 min) to ensure satiation was achieved and that no signs of stress were evident (flashing, lethargy, avoidance of food or particular area of tank). This study used descriptive statistics to report the results of bycatch, number of days to length (30 mm to 60 mm TL), and survival upon transfer to round fiberglass tanks and ponds.
A total of 4,322 larval fishes were captured from the Williamson River from 3 May to 30 June 2016, of which 4,306 (99.6%) were Klamath Suckers. The Klamath Tribes also provided 28 Klamath Suckers collected via investigative dip-net sampling in other areas, which we did not include in this analysis. Only 144 sucker larvae (3.3%) were collected by dip-netting with the remaining 4,162 collected using plankton nets. Mortality during collection was <1%. All fish survived transport to the rearing facility and were successfully transferred into aquaria. Plankton nets consistently yielded higher catches of suckers with lower bycatch than dip nets. Three nontarget species totaling 16 specimens (<1% total catch) were collected by dip-netting, including seven Fathead Minnow Pimephales promelas, five Rainbow Trout Oncorhynchus mykiss, and four Sculpin Cottus sp. that were too small to identify to species. No nontarget species were collected with plankton nets. The highest catches of sucker larvae occurred during the week of 10 May, which corresponds with our estimation of the timing of peak larval outmigration based on adult encounters in the Williamson River.
A total of 4,306 Klamath Suckers were reared in aquaria for 17–78 d (mean = 45.01 d, SD ± 14.39 d) until reaching approximately 30 mm TL. 3,228 fish were then transferred to round fiberglass tanks (N = 3,048) or directly to a lined outdoor rearing pond (N = 180) to avoid potential crowding. Overall survival from initial tank stocking to transfer was 75%. Of 3,048 fish transferred to round fiberglass tanks and reared for 14–46 d (mean = 31.39 d, SD ± 8.96 d) or until reaching approximately 60 mm TL, 2,880 (94%) survived. Overall survival of larvae to ponding for final growout was 71%. Larval tank-rearing survival was 98% for 37 d until an isolated fish health incident of unknown origin affected three aquariums, reducing survival to transfer to 75%.
In its first year the Klamath Basin Sucker Rearing Program saw success in raising wild-spawned larval Klamath suckers, demonstrating the ability to contain and raise healthy Klamath sucker larvae in captivity, at least in small-scale applications. Captive propagation is increasingly being relied on for species recovery and extinction prevention, but significant risks without demonstrable benefits remain (Brown and Day 2002). Alternative methods of preventing extinction of listed fishes are needed, particularly for species that have experienced precipitous declines (Marsh et al. 2015). Literature supports the use of less intensive culture techniques, which increase survival of reared fish (Naslund and Johnsson 2014; Cochran-Biederman et al. 2015; Brignon et al. 2018). Large-scale operations that rely on the high fecundity of a few females can reduce natural genetic diversity within a single captive-bred generation (Christie et al. 2013). Offspring produced from a limited broodstock may outcompete naturally produced fish, reducing effective population size (Britten and Brussard 1996). Relaxed natural and sexual selection pressures are compounded by increased domestication selection, which leads to reduced survival in the wild (Evans et al. 2014).
Our data are limited but indicate approximately 30 d are needed for larvae to reach an average of 30 mm TL under stated rearing conditions, which yielded 75% survival. Further investigation of tank stocking densities and splitting frequencies is needed to refine rearing methods for Klamath suckers. The cause of a single fish die-off that affected three larval aquarium tanks is unknown; no behavior cues or water quality parameters were cause for concern and larvae were too small (<15 mm TL) to reliably apply standard diagnostic techniques. We initiated prophylactic fish health treatments for incoming larvae and did not observe any additional die-offs. Fish health issues may be wild-origin and could be severely debilitating to the rearing program, which relies on collecting larvae from compromised habitats. Historical wetland removal forces larval suckers to out-migrate as soon as 1 d after hatching, which may reduce foraging success, condition, and survival (Cooperman and Markle 2003). Poor water quality is prevalent throughout the Klamath Basin, including low dissolved oxygen, high pH, ammonia toxicity, and high water temperatures (Kann and Smith 1999; Martin and Saiki 1999). Lease et al. (2003) identified structural changes in the gills of larval Lost River suckers exposed to elevated pH and ammonia concentrations, which may indicate increased toxin sensitivity. Janik et al. (2018) also report heavy parasite loads from age-0 Klamath suckers.
Notable challenges we encountered were consistent with prior investigations (Schooley and Marsh 2007). Unresolved phylogenetic relationships and morphological identification of Klamath suckers limit the application of established propagation technique (e.g., maintaining broodstock, pedigree analysis, and genetic monitoring), which motivated our shift toward rearing of captured larval suckers regardless of species identification. Given the critical need to address negligible recruitment over the past two decades and rapidly senescing adult Shortnose and Lost River Sucker populations (USFWS 2013), we determined that survival of any larval sucker species through our investigation would be beneficial to understanding early life-history needs of Klamath suckers and the development of a conservation supplementation program. Our year-1 returns were far higher than literature and anecdotal experience led us to expect (Schooley and Marsh 2007; Belk et al. 2011; USFWS 2014, 2015). Earlier efforts to collect and rear larval Klamath suckers were met with extremely limited success resulting in 1–3% survival (USFWS 2014, 2015). We also did not anticipate the need to treat larval fish for diseases such a short time after hatching.
Our limited scale and lack of seasonal repetition precludes making broad conclusions about the future of Klamath sucker husbandry; however, our efforts serve as a baseline for comparison for future culture efforts of this species. We were unable to keep collection cohorts together throughout the rearing process as we had hoped, and are therefore unable to precisely examine number of rearing days as a contributing factor in growth and survival. Future investigations would do well to expand available rearing capacity in order to keep cohorts together and assess growth and survival, and work toward developing the ability to isolate individual Klamath sucker species within the spawning season. Refining methods to minimize tank rearing time and further investigation of prophylactic treatment protocols is necessary to reduce stress and resulting mortality rates. Further refinement of rearing methods and attention to all areas within this program such as growth, condition, physical requirements, and disease-pathology issues are necessary to support an effective rearing program that facilitates successful reintroduction and recovery efforts.
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Reference S1. Hewitt DA, Janney EC, Hayes BS, Harris AC. 2015. Status and trends of adult Lost River (Deltistes luxatus) and shortnose (Chasmistes brevirostris) sucker populations in Upper Klamath Lake, Oregon, 2014. U.S. Geological Survey Open-File Report 2015-1189.
Found at DOI: https://doi.org/10.3996/JFWM-20-059.S1 (1.73 MB PDF).
Reference S2. Hewitt DA, Janney E, Hayes B, Harris A. 2018. Status and trends of adult Lost River (Deltistes luxatus) and shortnose (Chasmistes brevirostris) sucker populations in Upper Klamath Lake, Oregon, 2017. U.S. Geological Survey Open-File Report 2018-1064.
Found at DOI: https://doi.org/10.3996/JFWM-20-059.S2 (885 KB PDF).
Reference S3. Stone R, Jacobs J. 2015. Lost River Sucker culture manual. Anderson, California: U.S. Fish and Wildlife Service, California–Nevada Fish Health Center.
Found at DOI: https://doi.org/10.3996/JFWM-20-059.S3 (1.77 MB PDF); also available at https://www.fws.gov/canvfhc/Reports/Upper%20Klamath/Stone,%20Ron%20and%20J.%20Jacobs,%202015,%20Lost%20River%20Sucker%20Culture%20Manual.pdf.
Reference S4.[USFWS] U.S. Fish and Wildlife Service. 2013. Revised recovery plan for the Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris). Klamath Falls, Oregon: U.S. Fish and Wildlife Service.
Found at DOI: https://doi.org/10.3996/JFWM-20-059.S4 (1.35 MB PDF); also available at https://www.fws.gov/klamathfallsfwo/suckers/sucker_news/FinalRevLRS-SNSRecvPln/FINAL%20Revised%20LRS%20SNS%20Recovery%20Plan.pdf.
Reference S5.[USFWS] U.S. Fish and Wildlife Service. 2014. In situ cage rearing: Upper Klamath Lake and Tule Lake National Wildlife Refuge Sump 1A. Final Report. Klamath Falls, Oregon: U.S. Fish and Wildlife Service.
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Reference S6.[USFWS] U.S. Fish and Wildlife Service. 2015. In situ cage rearing: Upper Klamath Lake and Tule Lake National Wildlife Refuge Sump 1A—Year II. Final Report. Klamath Falls, Oregon: U.S. Fish and Wildlife Service.
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Reference S7.[USFWS] U.S. Fish and Wildlife Service. 2019. Species status assessment for the Endangered Lost River Sucker and Shortnose Sucker. Klamath Falls, Oregon: U.S. Fish and Wildlife Service.
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Reference S8. Weissenfluh D, Day JL, Bottcher J, Tinniswood W, Ophoff J, Gonyaw A. 2016. Identification of potential release sites for endemic Klamath Basin suckers into the Upper Klamath Lake recovery unit. Klamath Falls, Oregon: U.S. Fish and Wildlife Service, Klamath Falls Fish and Wildlife Office.
Found at DOI: https://doi.org/10.3996/JFWM-20-059.S8 (1.53 MB PDF).
We would like to thank B. Phillips, J. Ross, J. Ophoff, A. Gonyaw, E. Spiess, N. Gustafson, and A. Richardson, for collecting larvae and assisting with facility construction. H. Hendrixson of The Nature Conservancy provided boat ramp access and assisted with project design. T. Liskey was instrumental in supporting all aspects of facility construction. J. Linares contributed substantial program support and guidance. S. Foott provided invaluable fish health expertise and assistance. D. Blake, B. Brush, J. Rasmussen, and L. Sada from the Klamath Falls Fish and Wildlife Office provided implementation support. This work would not have been possible without the diligent notetaking and curious experimentation of Kent Russell nearly a decade earlier. This manuscript was greatly improved by input from G. Cappelli. Funding for this work was provided by the U.S. Bureau of Reclamation Interagency Agreement R13PG20201. Lastly, we are immensely grateful to the anonymous reviewers and Associate Editor for their input and insight, which were invaluable in refining this manuscript.
Any use of trade, product, website, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government.
The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the U.S. Fish and Wildlife Service.
Citation: Day JL, Barnes R, Weissenfluh D, Groves JK, Russell K. 2021. Successful collection and captive rearing of wild-spawned larval Klamath suckers. Journal of Fish and Wildlife Management 12(1):216–222; e1944-687X. https://doi.org/10.3996/JFWM-20-059