Dissolved oxygen controls summer habitat of Clear Lake Hitch (Lavinia exilicauda chi), an imperilled potamodromous cyprinid

Abstract

Clear Lake Hitch is an imperilled minnow endemic to Clear Lake, Lake County, California, United States listed as threatened under the California Endangered Species Act (ESA) and a candidate for listing under the United States ESA. It exhibits a potamodromous life cycle whereby adults, which reach up to 6 + years in age and over 350 mm in length, migrate into Clear Lake's ephemeral tributaries briefly during spring to spawn. Conservation and management of Clear Lake Hitch is inhibited, in part, by a lack of information on the lacustrine habitat of nonbreeding individuals within Clear Lake. To address this problem, we sampled Clear Lake Hitch with gill nets in a stratified random sampling design to determine the distribution and habitat associations in early summer 2017 and 2018. We identified abundance‐habitat relationships for juveniles and adults using Bayesian zero‐inflated negative binomial generalised linear mixed modelling. Results indicated that dissolved oxygen concentration was the most important habitat feature measured; juveniles and adults were substantially more abundant in normoxic (≥2 mg/l) than in hypoxic (<2 mg/l) habitat. Both also exhibited weak positive relationships with chlorophyll fluorescence, suggesting relatively productive habitats may support higher numbers of Clear Lake Hitch. Spatially, juveniles were most abundant in nearshore habitats while adults were ubiquitous, indicating an ontogenetic habitat expansion that may be associated with a resource availability‐predation risk trade‐off. Management actions undertaken to improve hypoxia problems in Clear Lake would also improve Clear Lake Hitch habitat.

Prediction of Hypoxia in Eutrophic Polymictic Lakes

“…The reduction of fish habitat due to hypoxia/anoxia is a growing concern (Feyrer et al., 2020; Goldman & Wetzel, 1963). We suggest that the BIW method can be modified to function as an indicator of fish stress resulting from hypoxia.…”

“…For example, mild and severe hypoxia and avoidance for fish have been defined when DO values are lower than 4 mg L −1 and 2 mg L −1 , respectively (Biddanda et al, 2018;Feyrer et al, 2020). The fish tolerance to hypoxia also changes with fish species.…”

“…We calibrated the cumulative energy BIW value to characterize the beginning of the hypoxic period, BIW c1 , for each basin and DO thr (Table 3). For example, mild and severe hypoxia and avoidance for fish have been defined when DO values are lower than 4 mg L −1 and 2 mg L −1 , respectively (Biddanda et al., 2018; Feyrer et al., 2020). The fish tolerance to hypoxia also changes with fish species.…”

Turning up the heat: Long‐term water quality responses to wildfires and climate change in a hypereutrophic lake

“…Clear Lake serves as the primary drinking water source for a population of about 40,000, the majority of which are economically disadvantaged and tribal communities (Lundquist & Smythe, 2010). At full capacity, Clear Lake has a surface area of 177 km 2 , a shoreline length of 160 km, and a total volume of 1.4 × 10 9 m 3 (Feyrer et al, 2020). The Upper Arm comprises about 70% of the lake's surface area and receives approximately 90% of the contributing runoff from the watershed (Rueda et al, 2005).…”