Are Delta Smelt Going Extinct?

Recently Dr. Peter Moyle (UC Davis) suggested we “prepare for the extinction of delta smelt”1. Record low summer and fall abundance indices in 2014 following declines over the past decade in the key survey indices have led to major concerns about the future of this endangered species. The first three survey of this winter’s trawl survey brought record lows for January and March (Figure 1). Dr. Moyle and many others are particularly concerned with the March catch of only six adult smelt.

Winter Kodiak Trawl Survey, Delta Smelt Adults

Figure 1. Catch statistics from Winter Kodiak Trawl Survey Jan-Mar 2002-2015. (CDFW data)

Will the record low numbers of Delta Smelt adults be sufficient to bring some recovery when the rains come again as in 2010 and 2011, the last two years with abundant rain and snow before the present drought? As Dr. Moyle pointed out, it is too early to tell. March larval smelt surveys in 2010 and 2011 captured few larvae, as have larval surveys so far this March. This year is different in that the present drought continues whereas the previous drought ended in 2010 and 2011.

Will another year of drought spell disaster for the smelt? That very well may be the case if the State Water Resources Control Board accepts the recent Temporary Urgency Change Petition submitted by the US Bureau of Reclamation and the California Department of Water Resources to change Delta water quality standards. The petition requests relaxation of Delta inflow, outflow and salinity standards, all of which are designed to protect water quality and Delta fish and their habitats, in order to sustain water deliveries to water contractors during the present drought. The changes will undoubtedly lead to higher losses of smelt and further degradation of their freshwater and low-salinity habitat, which could lead to even sharper declines than those apparent during the present and previous droughts. Stay tuned, as we will be keeping close track of events and the Delta Smelt, as well as preparations for their possible extinction.