Status of Splittail in the Sacramento-San Joaquin Estuary

TitleStatus of Splittail in the Sacramento-San Joaquin Estuary
Publication TypeJournal Article
Year of Publication1995
AuthorsMeng, L., & Moyle P. B.
JournalTransactions of the American Fisheries Society
AbstractAnalysis of data from four extensive fish surveys in the Sacramento–San Joaquin estuary indicated that splittail Pogonichthys macrolepidotus, endemic to the Central Valley of California, declined by 62% over a 13-year period. Splittails are now found mostly in the estuary, a fraction of their former range. In a gill-net survey in August 1994, 50% of the splittails taken in the estuary were from the Suisun Bay area, and 50% were just upstream in shallow, well-vegetated areas. Splittails migrate into freshwater to spawn, and river outflow carries juveniles into productive, shallow, low-salinity areas downstream. The high correlation of abundance of young with river outflow (average r 2, 0.60) and a weak stock–recruitment relationship (r 2 = 0.22) indicate that spawning success depends on favorable environmental conditions created by high outflows, such as the number of days that lowland areas remain flooded in the spring. A repeated-measures analysis of variance indicated that splittails prefer shallow, low-salinity habitats. The reductions in splittail abundance and range and the movements and habitat preferences of splittail young and adults correspond to trends and habits of two other species characteristic of the estuary, delta smelt Hypomesus transpacificus and longfin smelt Spirinchus thaleichthys. The largest threats to these three species are changes in water management and increases in water diversions that reduce spawning and rearing areas and other low-salinity habitats in Suisun Bay.