The Fish Report
November 9, 2015
Everyone knows that fish need water – but just how much water is often a subject of debate, especially when it comes to fish in California’s highly managed rivers. Many studies and management decisions in the Sacramento-San Joaquin Delta and its tributaries have relied on research that found correlations between water flows and fish populations. Correlation implies a relationship between two things (e.g., when water flows in rivers are high, fish populations tend to increase). However, “correlation does not equal causation,” as the scientific saying goes: just because two factors show similar trends does not necessarily mean that one is directly causing the other. A recent report released by the Delta Independent Science Board (ISB) highlighted the need to better understand the underlying mechanisms behind the relationship between fish and flow, which can inform adaptive management of fish and water in the Delta.