It is recognized that any or all of the ecological factors men- 

 tioned may affect the well-being of fish in the Delta if the existing 

 environmental balance is disrupted. It was the aim at the outset of 

 the project to determine the importance of each of these factors with 

 regard to the welfare of the fish populations. Although this section 

 of the report will not treat ecological factors as units of the study, 

 it should be stressed that, had the investigation been c arried to com- 

 pletion, rather thorough inquiries into their influences would have 

 been made. Before a real knowledge of the ecology of the Delta waters 

 is gained, these studies will have to be pursued further. 



It should be stated here that all the evidence obtained to date 

 indicates that migrating juvenile fish studies in the Delta are distri- 

 buted in proportion to the amount of water carrying them. Studies on 

 the Sacramento River at Isleton and on Georgiana Slough demonstrated 

 that migrating juvenile salmon were so distributed. It is assumed 

 from this fact that the outflows from the Delta (Sacramento River and 

 Delta-Mendota Canal) will contain fish in numbers proportional to their 

 volume of flow. The same concept applies to inflowing streams, and to 

 the portions of those inflows which would ultimately be pumped. The 

 San Joaquin River, due to its proximity to the Tracy Pumping Plant, 

 assumes unusual importance in this regard, because, at times, the entire 

 flow of this stream and all of its fish will be drawn to the pumps. 



The points t aken up above will be considered in detail under later 

 discussions on king salmon, striped bass, and shad. Other fishes will be 

 mentioned here, but not in relation to population dynamics and project 

 operation. 



The anadromous fishes collected in this study were the king salmon 

 ( Oncorhynchus tschawytscha ), steelhead trout ( Salmo gairdnerii), striped 

 bass ( Roccus saxatalis ), shad ( Alosa sapidissima ), two species of 

 smelt ( Hypomesus olidus and Spirinchus thaleichthys ), and the Pacific 

 lamprey ( Entosphenus tridentatus ) . Other anadromous fishes known to 

 utilize or migrate through the Delta, but not observed in this study 

 are the white sturgeon ( Acipenser transmontanus ) and green sturgeon 

 (Acipenser acutirostris ) . 



The resident fresh-water fishes collected incidental to the study 

 were catfish ( Ictalurus catus and Ameiurus natalis ), largemouth bass 

 ( Micropterus salmoides ), black c rappie ( Pomoxis nigro-maculatus ) , blue- 

 gill ( Lepomis macrochirus ), and warmouth bass ( Chaenobryttus corona - 

 rius ). Cyprinidae noted in the Delta were carp ( Cyprinus carpio ), 

 splittail ( Pogonichthys macrolepidotus ) , squawfish ( Ptycocheilus 

 grandis) , sucker ( Catostomus occidentalis ) , hardhead ( Mylopharodon 

 conocephalus ), Sacramento blackfish ( Orthodon microlepidotus ) , and 

 hitch ( Lavinia exilicauda ) . The fresh-water viviparous perch ( Hystero - 

 carpus traski ) was frequently taken. The three-spined stickleback 



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