Impacts of lake elevation decline on spawning habitat of a critical, native forage species

Objective

Lake elevation decline is a global phenomenon with pronounced effects in arid regions that changes the characteristics of nearshore habitat area available to lacustrine spawners, potentially impacting recruitment and whole-lake food web dynamics. Our objective was to understand the potential effects of lake elevation decline on spawning habitat for the Tui Chub Siphateles bicolor, a lacustrine spawner and critical component of the native food web in Pyramid Lake, Nevada.

Methods 

We explored the distribution of ripe Tui Chub in nearshore habitat by associating habitat characteristics to ripe Tui Chub CPUE from a custom gill-net configuration, with data analyzed using generalized linear mixed-effects models. We then explored potential spawning habitat availability at all potential lake elevations using an elevation-explicit model of the basin that we developed based on several bathymetric and geospatial data sets and the knowledge of spawner distribution gained in the first component of the study.

Results

Ripe Tui Chub catch was primarily predicted by temperature, reaching a maximum between 14.2°C and 24.8°C found at less than 15 m of depth in Pyramid Lake throughout the summer spawning period. We estimated that with a contemporary decline in lake elevation of 8 m, Pyramid Lake will host the minimum area of spawning habitat based on morphometry alone at a 40% decrease from a theoretical maximum.

Conclusions

A decrease in lake elevation or an increase in lake temperatures—both of which are probable events based on future climate scenarios and estimates of water extraction upstream of Pyramid Lake—is likely to further restrict Tui Chub spawning habitat area. Our results have important implications for ecological water demand in Pyramid Lake and provide managers with information facilitating a science-based approach to managing the fish community.