Assessing causes of mortality for endangered juvenile Lost River suckers (Deltistes luxatus) in mesocosms in Upper Klamath Lake, south-central Oregon, 2016

Unsustainably high mortality within the first 2 years of life prevents endangered Lost River Suckers Deltistes luxatus in Upper Klamath Lake, Oregon, from recruiting to spawning populations. Massive blooms of the cyanobacterium Aphanizomenon flos-aquae and their subsequent death and decay in the lake (bloom-crashes) are associated with high pH, low percent oxygen saturation, high total ammonia concentrations, and spikes in the cyanotoxin microcystin. Poor water quality within the lake is considered the most likely cause of juvenile sucker mortality, but mechanisms causing the high mortality are not known. We introduced PIT-tagged age-1 Lost River suckers into three continuously monitored mesocosms in Upper Klamath Lake to determine the timing of juvenile sucker mortality relative to pH, temperature, and dissolved oxygen. Mortality was inferred from a lack of movement detected on remote PIT tag detection equipment within each mesocosm. Mortality was compared among mesocosms and an indoor tank-held control group. We fitted time-varying Cox hazard models to test hypotheses about short-term and chronic effects of single

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“…Finally, we examined the hypothesis that the range in psat is correlated with the hazard rate (PsatRange model; Hereford et al. ).…”

Section: Methodsmentioning

confidence: 99%

“…In contrast to a previous mesocosm study that lacked comparable water quality data among mesocosm sites (Hereford et al. ), the design of the current study facilitated application of hazard models to test hypotheses about short‐term and chronic effects of single and co‐occurring water quality parameters on fish survival.…”

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confidence: 99%

Mortality of Endangered Juvenile Lost River Suckers Associated with Cyanobacteria Blooms in Mesocosms in Upper Klamath Lake, Oregon

et al. 2020

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“…The presence of Ichthyobodo spp. on wild juvenile Lost River Suckers in the lake has been documented (Burdick et al 2017), and ichthyobodiasis was the identified cause of morbidity for several juvenile Lost River Suckers held in mesocosms in the lake (Hereford et al 2019). Because wild fish are less likely to experience fish‐to‐fish contact, the risk of Ichthyobodo spp.…”

Section: Discussionmentioning

confidence: 99%

Effect of Temperature on Survival of Lost River Suckers with a Natural Infection of Ichthyobodo spp.

et al. 2021

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To compensate for low natural survival of endangered Lost River Suckers Deltistes luxatus, the U.S. Fish and Wildlife Service and the Klamath Tribes have initiated captive rearing programs. We conducted laboratory experiments intended to determine the temperature for optimum growth of juvenile Lost River Suckers; however, due to an unanticipated infection with Ichthyobodo spp., we instead estimated survival in conjunction with temperature and parasite loads. Ichthyobodo spp. are common parasites that infest fish skin and gills; they are known to be present in Upper Klamath Lake and have been found in fish at both the federal and tribal fish‐rearing facilities. All fish held at mean temperatures of 16°C and 19°C survived the entire 65‐d experiment, whereas the median time to death was 27 d at 22°C, 8 d at 24°C, and 7 d at 26°C. Gill samples from all Lost River Suckers tested positive for Ichthyobodo spp. DNA, with a trend toward higher copy numbers in suckers that were held at a mean temperature of 22°C or warmer compared to those held at 19°C or cooler. Fish kept at all temperatures grew slowly. These results suggest that survival of Lost River Suckers with a natural infection of Ichthyobodo spp. was significantly impacted by temperature.

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“…Ichthyobodo is a genus of dinoflagellate protozoans of the skin and gills. Usually, in low numbers, they do not cause clinical signs, or significant mortalities (Martins et al, 2015;Hereford et al, 2019). They have more importance to alevins, juvenile fishes, and even to eggs.…”

Section: Discussionmentioning

confidence: 99%

“…In adults, Ichthyobodo infection is associated with immunosuppression and stress. Higher temperatures accelerate their reproduction; thus, heat stress contributes to both stress and debility, and more Ichthyobodo in water (Woo, 2006;Hereford et al, 2019). There are reports of O. niloticus being more resistant to these ectoparasites and only being infected in the caudal region (Woo, 2006).…”

Section: Discussionmentioning

confidence: 99%

Parasitological diagnosis in food fish produced in a fish farm, in the Zona da Mata, Minas Gerais, southeastern Brazil

Relvas

Balian

Soares

et al. 2020

Rev. Bras. Parasitol. Vet.

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This study identified the parasitic species in juvenile freshwater finfishes during the fattening stage, from a fish farm located in the Zona da Mata (MG), southeastern Brazil, and revealed both macro and microscopical lesions in fish gills. A total of 172 juvenile fishes of different species (Oreochromis niloticus, Ictalurus punctatus, Ctenopharyngodon idella, Cyprinus carpio, Astyanax bimaculatus and Brycon amazonicus) were transported to a laboratory in São Paulo city. The fish were sedated and then euthanized for parasitological analysis. All fish were infected by at least one parasite species. Ten different species of parasites were identified: Apiosoma sp., Epistylis sp., Ichthyobodo sp., trichodinids, Piscinoodinium pillulare, Ichthyophthirius multifiliis, Tetrahymena sp., monogeneans, Centrocestus formosanus metacercariae, and Dermocystidium sp. The best management practices and lack of sanitary control were also discussed.

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Assessing causes of mortality for endangered juvenile Lost River suckers (Deltistes luxatus) in mesocosms in Upper Klamath Lake, south-central Oregon, 2016

Cited by 8 publications

References 31 publications

Mortality of Endangered Juvenile Lost River Suckers Associated with Cyanobacteria Blooms in Mesocosms in Upper Klamath Lake, Oregon

Mortality of Endangered Juvenile Lost River Suckers Associated with Cyanobacteria Blooms in Mesocosms in Upper Klamath Lake, Oregon

Effect of Temperature on Survival of Lost River Suckers with a Natural Infection of Ichthyobodo spp.

Parasitological diagnosis in food fish produced in a fish farm, in the Zona da Mata, Minas Gerais, southeastern Brazil

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