Juvenile delta smelt use of shallow-water and channel habitats in California's Sacramento-San Joaquin Estuary

Juvenile delta smelt, Hypomesus transpacificus, densities were significantly greater in shallow water in Honker Bay and Sherman Lake than in adjacent channels in 1993, indicating that they used shallow areas in bay and flooded island environments as nursery habitats. Densities and lengths were significantly greater on high than low tides in shallow water in Honker Bay, but not in the adjacent channel, suggesting that delta smelt moved tidally between Honker and Grizzly bays. Delta smelt densities did not differ between shallow water and channels in the riverine environments of Montezuma Slough, the lower San Joaquin River, and Cache Slough, presumably because shallow areas were smaller and no embayments existed to retain delta smelt. Delta smelt may be larger in shallow water in Honker Bay and Sherman Lake because 1) fish in shallow water were older and consequently larger or 2) residence time was longer and foraging success was better, resulting in increased growth rates. Availability of shallow habitats to delta smelt increases in high-outflow years when hydrodynamic transport locates the delta smelt population downstream in Suisun, Grizzly, and Honker bays.