solve the fish protection problem. Tentative plans for protective devices 

 were formulated on the basis of biological work done prior to 1°U£. The 

 efforts of Hatton and Clark indicated an abundance of young salmon and the 

 young of other anadromous fishes entering the Delta seasonally in their 

 seaward migration or originating there from eggs spawned in Delta Channels. 

 It was not difficult to define the problem in fish protection posed by 

 the Delta-Mendota pumping plant. The main questions to be answered were: 

 What can be expected to happen, how much damage will be done, and when 

 will it occur? Existing information gave little assistance in the resolu- 

 tion of these fundamental questions. However, many of the fishery 

 agencies were convinced that some measure of fish protection would 

 have to be provided at the entrance to the pump channel intake. Ideas 

 regarding desirable fish protection centered around three main possi- 

 bilities: 



1. The first and most desirable plan involved construction of 

 the closed channel across or around the Delta with a screen at the head 

 of the canal. This possibility was overruled and the position favoring 

 it was made untenable by the changes in plans of the U. S. Bureau of 

 Reclamation. 



2. A satisfactory screen at the entrance to the pump intake channel 

 and a by-pass originating in the San Joaquin River, passing the screen 

 and ending in Dutch Slough, were to be constructed. The by-pass was to 

 be a channel capable of carrying £00 second feet of San Joaquin River 

 water through the southern part of the Delta. It was to empty into Dutch 

 Slough, which was considered to be outside the influence of the pump draft. 



3. A satisfactory screen was to be constructed as in number 2, but 

 the by-pass, instead of originating in the San Joaquin River, was to begin 

 at the screen and the water volume was to be reduced to 200 cubic feet per 

 second. The by-pass was to course to a point outside the pump draft in- 

 fluence, which was tentatively set at Dutch Slough. 



These plans and certain preliminary engineering specifications were 

 discussed by representatives of the California Division of Fish and Game, 

 the U. S. Fish and Wildlife Service, and the U. S. Bureau of Reclamation 

 during a lengthy conference at Denver, Colorado, in February of 1°1|6. 

 Efforts to bring about realization of the tentative plans for fish pro- 

 tection were unsuccessful mainly because of a lack of sufficiently con- 

 vincing and basic evidence. Consequently, a study of the Delta fisheries 

 problems, recommended in V)hS, was undertaken in August of 19\±6 by the 

 U. S. Fish and Wildlife Service. This report presents the main features 

 of the investigation, which was conducted under the sponsorship and with 

 the financial assistance of the U. S. Bureau of Reclamation. The California 

 Division of Fish and Game cooperated in the study and made valuable con- 

 tributions to present knowledge of Delta fisheries from independent studies 

 which they undertook. 



Dr. James W. Moffett, Chief, Central Valley Investigation, U. S. Fish 

 and Wildlife Service, gave general supervision to the project from its in- 

 ception to its termination. During the preliminary and exploratory work of 



