Spawning and Rearing of Splittail in a Model Floodplain Wetland

Abstract

The splittail Pogonichthys macrolepidotus, which has been listed as threatened by the U.S. government, does not produce strong year-classes unless it has access to the floodplain habitat of the San Francisco estuary and its tributaries. In this small-scale, single-year study, we tested the hypothesis that managed inundation of a floodplain can be used to support splittail reproduction in dry years, when this habitat type is not readily available. Adult splittails were captured on their 2001 upstream spawning migration and transferred to a 0.1-ha model floodplain wetland. Our results suggest that adults will successfully spawn if they are provided access to floodplain habitat in dry years. In snorkel surveys, progeny showed a significant association with the lower portion of the water column. Young splittails (15-20 mm fork length (FL)) concentrated in edge habitat near an inflow during the day but at night moved into deeper-water habitats, including open water and habitats with submerged vegetation. Larger splittails (28-34 mm FL) used a broad range of habitats both during the day and at night. Juveniles showed significant schooling behavior during the day, then dispersed at night. These observations have potential implications for the design of habitat restoration projects for the splittail, the last remaining representative of its genus.