The Model Gulf III All-Hnetal Plankton Sampler 



The following report of an all-metal, modified 1/2-meter 

 plankton net is a preliminary presentation of the construction plans, 

 operational procedure, and trial results of the Model Gulf III 

 plankton sampler. To date an inadequate number of tows has been 

 made with the net to present tested analysis but preliminary re- 

 sults indicate good possibilitiese 



The towing cable, ^^ wire rope, is attached by means of a shackle 

 and swivel to the upper attachment ring of the sampler, A iiO-pound 

 depressor l/i-S attached to the lower attachment ring by means of a 

 shackle, a swivel, and a 7-foot length of 1" diameter manila line© 

 (See fig, 5.) The 7-foot length permits the depressor to swing free 

 of the after end of the sampler during handling operations. The 1" 

 line is of such size and flexibility as to provide easy handling of 

 the depressor. 



When the current meters have been placed, the two meter dials 

 are zeroed and rags placed in the meters to prevent flow wheels from 

 turning. Just as the sampler is being lowered into the water by 

 means of a davit, the meter rags are removed. The sampler has been 

 lowered into and removed from the water while the ship was underway, 

 at about 6 knots* 



After the towing time has elapsed, the sampler is brought in, 

 the meter rags replaced, and the nosepiece and net removed. The 

 fore meter is removed and meter readings are recorded. The net is 

 hosed down with salt water to wash all plankters into the plankton 

 bucket. After removal of the bucket the entire net is washed with 

 fresh water and scrubbed inside and out with a nylon bristle brush 

 to remove any foreign matter and salt. If this cleaning operation 

 is done thoroughly after each tow, a uniform mesh area is maintained 

 for successive tows. The housing, net, bucket, and current meter 

 are illustrated in figvire 6* 



The depressor developed by John Isaacs is illustrated and dis- 

 cussed in the California Cooperative Sardine Research Program 

 Progress Report, 1950, on page 19« 



