Smith' described the plankton nets used on the 

 surveys in this region and their history of de- 

 sign and material changes from 1939 to 1969. 

 The standard CalCOFI nets presently used have 

 1/2- and 1-m mouth openings and are made of 

 nylon mesh (see Table 1 for source of net spe- 

 cifications and Fig. 6 for description of mesh 



sizes and assemblies for making plankton tows 

 with either or both nets). The detachable cod 

 end, also of nylon mesh, in which plankton is 

 concentrated during a tow is illustrated and de- 

 scribed in Figure 7 (source of specifications, 

 Table 1). The adapter to couple the cod end to 

 the net is described in the caption of Figure 7. 



^ Smith, P. E. Plankton sampling nets and their data 

 on surveys off California and Baja California since 1939. 

 (Unpublished manuscript.) 



Note: Captions in Figures 4, 6, and 12 emphasize need 

 for swivels in the gear train, usually close to the appa- 

 ratus, to avoid twisting or unlaying wire or lines. 



Figure 6. — Standard CalCOFI nets, 1-m mouth opening, 505-/4 mesh throughout, and 0.5-m mouth opening, 333-/i 

 mesh throughout (see Table 1 for source of specifications). Detachable cod ends are described in Figure 7. Flow- 

 meters (see Table 1 for source of supply) are suspended in the mouth opening (also see Figures 13 and 15) by 

 cloth-covered rubber shock cord. The cord is permanently attached to small metal eyes welded to the mouth rings. 



Attachment to the lugs of the meters are by means of brass snap hooks. The net rings and braces between 

 them are 1-inch I.D. (25.4 mm) galvanized pipe. Large ring is 1 m I.D., small ring is 0.5 m I.D. Nets are tied 

 to the rings with 1/8-inch (4 mm) cotton cord. The three-way bridle is made up of 1/2-inch (12.7 mm) line 

 (hemp, nylon, or diamond-braided polyethylene). Apex of bridle is a 2- or 3-inch I.D. (51 or 76 mm) steel ring 

 of 3/8-inch (9.5 mm) thickness. The apex is 1 m away from the frame when the lines are stretched evenly. 

 (Note: The points of attachment of the bridle to the rings must be no farther apart than shown. If greater than 

 shown, the strain during any tow might bend the pipes to which the rings are welded.) The lead line, usually 

 nylon or hemp, is 3/4- to 1-inch (20-25.5 mm) diameter for easy grasping when pulling nets aboard. (Note: 

 A swivel should be attached between the lead line and the apex of the bridle and another swivel located at the 

 cable clamp — (see Fig. 12). 



If either net is used alone (see Fig. 14) as has been the case in many years of CalCOFI tows with the 1-m net, 

 the same size rings with the same specifications are used with a three-line bridle attached at equal distances on a 

 ring. For the 0.5-m net a lighter lead line may be used, e.g., 1/2 inch (12.7 mm). 



