The Role of Context Dependency in Understanding the Effects of Low Flow Events on Fish

The natural hydrology of streams and rivers has been extensively altered due to dam construction, water diversion, and climate change. An increased frequency of low flow events will affect fish due to shifts in habitat availability, resource availability, and reproductive cues. I reviewed the literature to characterize the approaches taken to assess low flow events and fish, the main effects of low flow events on fish, and the associated mechanistic drivers. Most studies are focused on temperate streams and are comparative in nature. Lowered streamflow is associated with decreased survival, growth, and abundance of fish populations, and shifts in community composition, but there is considerable variation in effects. This variability in effects is likely due to context dependency. I propose three main sources of context dependency that drive variation in fish responses to low flow events: attributes of the low flow event, attributes of the habitat, and attributes of the fish. Awareness of these sources of context dependency can help managers interpret and explain data, predict vulnerability of fish communities, and prioritize appropriate management actions.