FISHERY BULLETIN: VOL. 71, NO. 1 



Table 3. — Shrimp catches with and without a tickler chain attached to the shrimp vertical 



distribution sampler. 



Location 



Date 



Off Grays Harbor, 

 Wash. 



6-23-69 



Off Destruction 

 Island, Wash. 



6-24-69 



8-29-69 



11-13-69 



Total 



26,914 



51,644 



precedes the footrope as the net is being towed 

 on bottom. Even though the tickler chain is 

 accepted and used by most shrimp fishermen 

 under the assumption that it increases catches, 

 very little is known about the effect of this 

 chain on either the quantity of shrimp caught 

 or the vertical distribution of shrimp as they 

 enter the trawl. 



Utilizing the unique features of the shrimp 

 sampler, a brief examination of the effects of 

 tickler chain on shrimp height distribution was 

 undertaken. Unwanted fish and debris were 

 eliminated from the shrimp catches by placing 

 21/2-inch mesh webbing on separator panels over 

 the entire face of the sampler. On alternate tows 

 a length of %-inch tickler chain was placed 

 21/2 ft in front of the bottom of the sampler. 

 All comparative tows were made in the same 

 direction and over the same track line as deter- 

 mined by loran, compass, and depth sounder. 

 Over a 4-month period 22 comparative hauls 

 were made in this manner. 



Table 3 shows the catch of shrimp by weight 

 for these tows. Aggregate catches with the tick- 

 ler chain were nearly twice as great as those 



without the chain. Summation of the total 

 shrimp weights for each sampler height revealed 

 that when the tickler chain was used, a greater 

 proportion of shrimp were taken in the lower 

 sampler openings in contrast to higher distribu- 

 tion without the chain (Table 4). The effects 

 of a tickler chain on the size distribution of 

 shrimp were also examined. The carapace 

 lengths from shrimp in 200-g samples from each 

 sampler opening were measured. These data 

 indicate that at all distances off the bottom, there 



Table 4. — Comparison of shrimp catches at various 

 distances off the bottom in the shrimp vertical distribu- 

 tion sampler with ( + ) or without ( — ) the tickler chain. 

 These data were computed from the 22 tows presented 

 in Table 3. 



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