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Smelt Update – January 2016

The evidence is quite clear from all recent surveys that the Delta and Longfin Smelt populations have indeed crashed,1 and remnants remain vulnerable to Delta exports despite the wet winter to date. The latest survey is the January Kodiak Trawl survey that captured only 7 Delta Smelt (see Figure 1 below). Only 4 have been salvaged at south Delta pumps, compared to 56 last year in January.2 Adult Delta Smelt have been caught in Early Warning Surveys in the central Delta during the past month (Figure 2). The presence of Delta Smelt in south Delta salvage collections and in early warning surveys in the lower San Joaquin River channel in the central Delta indicate a high risk to the remaining population from Delta exports, according to the Smelt Working Group.3

Graph of January Survey Catch

Figure 1. Catch of Delta Smelt in January Kodiak Trawl Survey 2002-2016.4

Graph of Delta Catch

Figure 2. Catch of adult Delta Smelt in Early Warning Survey.5

Similarly, Longfin Smelt are at record low numbers (see latest post6), and larvae are now being collected in small numbers (again record low densities for January surveys) in Suisun Bay and the Delta (Figures 3 and 4). Their presence in the central Delta in the lower San Joaquin River channel indicates that a portion of the population spawned in the central Delta and remain vulnerable to South Delta Exports.

Map of Jan 2016 Catches

Figure 3. Catch density distribution of Longfin Smelt larvae in early January 2016 Smelt Larvae Survey. 7

Map of Jan 2016 Catches Longfin Smelt

Figure 4. Catch density distribution of Longfin Smelt larvae in mid-January 2016 Smelt Larvae Survey.8