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Delta Smelt Summer 2018

After catching over 800 Delta smelt in 2011 (Figure 1) and near 30 in 2017 (Figure 2), the Summer Townet Survey captured only 3 in 2018 (Figure 3). The pattern is consistent with the spring 20-mm Survey collections

The only option now other than extinction is stocking hatchery smelt in large numbers in their primary summer-fall habitat, the Low Salinity Zone of the Bay-Delta. Release should be near the 2 ppt (3800 EC) location, commonly referred to as X2, which recently has been moving tidally back and forth between Collinsville and Sherman Island in the Sacramento River channel just downstream of the Emmaton gage (Figures 4 and 5). The X2 location has optimum salinity, water temperatures (<70oF), turbidity, and food for Delta smelt.

Figure 1. Summer Townet collections of Delta smelt 2011.

Figure 2. Summer Townet collections of Delta smelt 2017.

Figure 3. Summer Townet collections of Delta smelt 2018.

Figure 4. Water temperature at Emmaton late August 2018. High tide X2 water is 68-69oF.

Figure 5. Salinity (EC) at Emmaton late August 2018. High tide water is near X2 salinity (3800 EC).