Fish in the San Francisco Bay are currently under threat from harmful algal blooms known as red tides, which release toxins that can be fatal to aquatic life. Several factors, like high temperatures and low water flow in the Bay-Delta region, can trigger the occurrence of red tides. In August, a red tide coincided with a severe heatwave, exacerbated by three years of drought, resulting in the largest fish kill ever recorded in San Francisco Bay with at least 864 identified sturgeon carcasses.

Andrew Rypel, fish researcher at UC Davis and Director of the Center for Watershed Sciences, proposes that green sturgeon, which face similar difficulties as salmon, could benefit from the implementation of increased migration flows, similar to those used for salmon. In California, dams release pulses of water to help adult salmon migrate from the ocean to the rivers where they spawn. Green sturgeon, like salmon, spend most of their time in the ocean and return to freshwater areas to spawn. However, unlike salmon, green sturgeon go back to the ocean after spawning and can live for a remarkably long time, comparable to human lifespans. 

New work by Scott Colborne et al. 2022, which analyzed 12 years of sturgeon tracking data in the Sacramento River, reveals startling hidden aspects of green sturgeon's lives. One surprising finding is that after arriving in the river as a unified group in the spring, sturgeon separate into two distinct groups after spawning. One group returns to the ocean, while the other group spends the summer in the river before departing in fall. Building on this valuable insight, Andrew Rypel proposes that the implementation of migration pulse flows during the spring and fall would safeguard green sturgeon by preventing their stranding and ensuring their successful return to the ocean.

Learn more about these surprising discoveries in the full article: 

Sturgeon Arose During the Jurassic—Can They Survive the Anthropocene? by Robin Meadows, June 1, 2023.