In July 1961 the Delta Fish and Wildlife Protection Study began an investigation of the ecology of the Sacramento-San Joaquin estuary in California. Our investigations were designed to answer specific questions raised by water development plans proposed for the estuary, and to provide a background of information that could be used to evaluate these plans.

We have annually prepared a progress report, and more recently published the first volume of our ecological studies; a series of eight papers on fishes of San Pablo and Suisun bays, and of zooplankton and zoobenthos of the Delta and San Pablo and Suisun bays.

This is the second volume of our ecological studies. It consists of 12 individual papers about the distribution, relative abundance, food and spawning habits of fishes in the Sacramento-San Joaquin Delta.