METHODS 



Work carried on in 19U6 and 19U7 was preliminary and exploratory in 

 nature. As a result of these preliminary studies, a work program was de- 

 signed, having as its essential features; (a) sampling juvenile popula- 

 tions of fishes by tow-netting from motor launches at stations located in 

 representative parts of the Delta and fished at regular intervals accord- 

 ing to a standard procedurej (b) sampling juvenile populations of fishes 

 with one to six fixed fyke-nets at strategic locations; (c) sampling in- 

 vertebrate faunae and fish eggs by towing plankton nets from motor launches; 

 and (d) collecting data on temperature, turbidity, salinity, flow, and water 

 quality. 



The study of the biology, size, and composition of the fishery re- 

 sources that depend upon or utilize the waters of the Sacramento-San 

 Joaquin Delta, required the development and operation of several types of 

 collecting gear. In the early course of the investigation fyke nets pro- 

 vided the most expedient means of studying movements of the young anadro- 

 mous fishes within the Delta channels. These nets, a trap type of gear, 

 were fished from a fixed position. The nets were half -inch stretched 

 mesh, No. 9 cotton webbing framed on three rings, 5, k, and 3 feet in dia= 

 meter and constructed into a conical trap fifteen feet long. An inner 

 funnel tapering to a ten-inch opening provided the entrance into the trap. 

 Tidal action in the Delta made it necessary to operate the fyke nets from 

 inter-connecting lines either between buoys anchored from the bottom, or 

 between bridge dolphins and piling when these were available. This method 

 permitted the net to fish counter to the direction of the current. Fyke 

 nets were fished daily at several strategic locations for periods of six 

 months to a year (Fig. 2), One net, located in the San Joaquin River, one 

 half mile below the Antioch Bridge, was operated from August, 19U6 to 

 November, 19U9. The information from the fyke-net operations on the time 

 of appearance of the young anadromous fishes in the Delta and the extent 

 of their movements was invaluable, particularly in corroborating the results 

 obtained in tow-net operations. However, the introduction of improved methods 

 of sampling, resulting in more complete information on the fishes in the Delta 

 has precluded the use of the fyke-net data in this report. 



The acquisition of a motor launch in July, 19^7, permitted adoption of 

 more thorough methods of studying the spawning, distribution, and abundance 

 of the early life stages of the fishes within the Delta. Three types of 

 nets were selected for the sampling operations from the launch. A plankton 

 net a half -meter (20 inches) in diameter at the mouth, and constructed of 

 bolting cloth 30 meshes to the inch in the cone was used for collecting 

 eggs and larvae. The tow net, a fifteen foot conical net of half=inch 

 stretched mesh, No. 9 cotton netting, five feet in diameter at the mouth, 

 was used for collecting juvenile fish. The same net with a lining of 

 bobbinett, 8 meshes per inch, was used in collecting post-larval specimens 

 of fish. An adaptation of a trawl net, using half -inch stretched mesh 

 netting, was used periodically for bottom tows 



. 7 



