FISHERY BULLETIN: VOL. 71, NO. I 



Individual collector bags of 3/t-inch mesh' were 

 lashed behind the sampler, thereby segregating 

 and retaining the shrimp that entered the sep- 

 arate sampler openings. The dandy lines were 

 attached to the sampler at the four center pad 

 eyes and led freely through shackles at the four 

 corner pad eyes. This method of attachment 

 distributed the pull of the dandy lines across 

 the face of the sampler in the event it hit a heavy 

 object during a tow. Aluminum trawl floats (8- 

 inch diameter) buoyed the sampler upright dur- 

 ing setting and retrieving, whereas water pres- 

 sure maintained this posture while towing. 



During tickler chain (a device used to stim- 

 ulate shrimp off of the seabed and into the trawl) 

 evaluations, the chain was attached directly to 

 the lower dandy lines with cable clamps and 

 shackles. The length of chain was adjusted so 

 it maintained a position 21/2 ft in front of the 

 bottom center of the sampler as determined by 

 scuba diver observations. 



Several mesh sizes' were evaluated using rec- 

 tangular aluminum frames (separator panels) 

 placed over the sampler openings (Figure 1). 

 Aluminum teeth separated the panels on the 

 front of the sampler. Although each frame had 

 mesh of uniform size, the mesh size between 

 frames varied between I14 and 3 inches. Com- 

 parisons of different mesh sizes were facilitated 

 by placing the meshes to be compared on the 

 lateral two columns of vertical openings on the 

 sampler. Two-inch mesh webbing was placed 

 over the center column of the sampler during 

 mesh size comparisons so this column could act 

 as a gross index of relative shrimp abundance 

 on the fishing grounds. The tow direction was 

 reversed after each tow, and the lateral two 

 panels were exchanged on alternate tows to re- 

 duce any difference in catch efficiency by one 

 side of the sampler or the other. 



During fishing trials on shrimp beds off the 

 Washington coast, adequate sample sizes (50- 

 2,000 g of shrimp per collector bag) were ob- 











SIDE VIEW HK^ 



TVPICAL RloeTE I 



8 NEEDED r— 



l'/2 6061 -Te PIPE 



scHED ao 



e" 0IAM6TER ALUMINUM 

 TRAWL FLOATS 



20' OF 1/2 



POLYPROPYLENE 



LINE 



Vi  5' STAINLESS *OLT,j, 

 6 NEEDED !• 



B* DIAMETER ALUMINUM 

 TRAWL FLOAT 



-. ^ 



2^^ 606I-T6 PtFl-U- 



W. lVJ60U-T»^ 



5/s' S061 - T6 ROO ^ 



Figure 1. — Construction specifications for the shrimp 

 sampler and extension. 



tained from tows of 10-min duration without 

 separator panels and 15 min with separator 

 panels. 



The individual collector bags were emptied at 

 the conclusion of each tow and the contents la- 

 beled and frozen. In the laboratory shrimp were 

 thawed and the weight, the carapace length (base 

 of eyestalk to the dorsal posterior margin of the 

 carapace), and sex recorded. 



PRELIMINARY EVALUATIONS 

 OF THE SAMPLER 



' All mesh sizes in this paper are stretched measure. 



' The following mesh and thread sizes and materials 

 were evaluated: 1%-inch mesh, 9 thread, nylon and 

 acetate ; 1 V2-inch mesh, 15 thread, nylon ; 1 % -inch mesh, 

 18 thread, nylon ; 2-inch mesh, 12 thread, nylon ; 2 '/2-inch 

 mesh, 21 thread, nylon; 3-inch mesh, 18 thread, nylon. 



Scientist-divers first appraised the shrimp 

 sampler in Puget Sound as it was being towed 

 on bottom in 8 fm of water at 21/2 knots. On 

 each of eight tows the sampler was reported to 



244 



