Effects of Ambient Water Quality on the Endangered Lost River Sucker in Upper Klamath Lake, Oregon

Abstract

Populations of the Lost River sucker Deltistes luxatus have declined so precipitously in the Upper Klamath Basin of Oregon and California that this fish was recently listed for federal protection as an endangered species. Although Upper Klamath Lake is a major refuge for this species, fish in the lake occasionally experience mass mortalities during summer and early fall. This field study was implemented to determine if fish mortalities resulted from degraded water quality conditions associated with seasonal blooms of phytoplankton, especially Aphanizomenon flos-aquae. Our results indicated that fish mortality did not always increase as water temperature, pH, and un-ionized ammonia concentration increased in Upper Klamath Lake. Little or no mortality occurred when these water quality variables attained their maximum values. On the other hand, an inverse relation existed between fish mortality and dissolved oxygen concentration. High mortality (Ͼ90%) occurred whenever dissolved oxygen concentrations decreased to 1.05 mg/L, whereas mortality was usually low (Ͻ10%) when dissolved oxygen concentrations equaled or exceeded 1.58 mg/L. Stepwise logistic regression also indicated that the minimum concentration of dissolved oxygen measured was the single most important determinant of fish mortality.

Changes in benthic nutrient sources within a wetland after hydrologic reconnection

“…This is consistent with previously reported ammonia fluxes for the lake [16] and with increasing ammonia concentrations in the water column of the reconnected wetlands between spring and summer [55,56]. Martin and Saiki [61] determined in their fish-cage studies of the Lost River sucker (D. luxatus) that elevated concentrations of un-ionized ammonia might be contributing to the precipitous decline of sucker populations in Upper Klamath Lake, although depletion of dissolved oxygen in the water column (a factor that covaries with ammonia) exerted an even stronger influence on sucker mortality. Benthic flux of ammonia-particularly at elevated pH in the overlying water column-has toxicological implications for endangered fish populations in both lake and wetland environments.…”

Western water and climate change

“…Water quality conditions in the (Upper) Klamath Basin lakes have been a concern with respect to sucker mortality, with the lakes subject to warming and eutrophication with concomitant loss of dissolved oxygen (Kann and Welch 2005). Low levels of dissolved oxygen have been associated with fish mortality (Martin and Saiki 1999).…”

Inter-annual variability in apparent relative production, survival, and growth of juvenile Lost River and shortnose suckers in Upper Klamath Lake, Oregon, 2001–15

“…Low survival during early life stages, limited egg production, and emigration of young fish, may all contribute to the lack of young mature suckers in Upper Klamath Lake populations. Hypothesized causes of low survival include competition with non-native fishes, predation by birds, factors related to poor water quality, cyanotoxins, parasites, dietary deficiencies, and overwinter starvation (Martin and Saiki, 1999;Foott and Stone, 2005;Markle and Dunsmoor, 2007;Burdick, 2013;Kent and others, 2014;Burdick and others, 2015;Evans and others, 2016). Lack of recruitment to the adult Cui-ui (Chasmistes cujus) populations endemic to Pyramid Lake, Nevada, was a result of a lack of connectivity between rearing and spawning habitats that lead to a failure to reproduce (Scoppettone and Rissler, 2012).…”