mild. One solution vas olTorcd by a captain-ovner vho clairaod considpr- 

 able uucces^ wltn hla ti5-foot flat net in which the lead and head lines 

 vjcro similar. One float was attached to tne center of the lead line. 

 The lead lines x^ere attached to the trawl door bracket which was raiced 

 auout 9 incnes above the shoe. United States Fish and Wildlife Service 

 specialists nave described curved doors and more recently doors with 

 wider runners wliich reduce the hazards of bogcing down. 



4.^ ^ . ^^® efficiency of shrliap trawls depends on the extent to which 

 the net is spread. The spreading of the net is controlled larrely by 

 tne attachnent of the various lines to the trawl doors. Carlson (1952) 

 using a 100-foot flat net with doors 9 feet long by 1;0 inches hipil re- 

 ported that the attachn>ent of these lines to pad eyes on the back side 

 of the board, opposite the after or long pair of chains, was found to 

 increase the spread of the boards from 15 feet 3 inches to 53 feet 6 

 inches or by more than IB percent. To obtain maxmura vertical spread 

 of the net and its tending bottom, the pad eyes should be as near the 

 top and bottom of the trawl boards as possible. 



Further Increases in the spread of the net up to 30 percent 

 over the conventional method of operating a shrijnp trawl were mdo 

 luTl; tt ^^ ^^'"^ "^T f ^^""^ ^""^^^ ''''^ ^ experiiTiental winch (Carlson). 



fZti£z.:i:zitTr '''^'"'"' ''°'"' ^^^^^ '°^'^ ^"^ ^^^ ^-^^^-^ 



w>... h.. , ^^°^'^^^^^f»^"tly a «ew type of a flat trawl known as the "I^estcrn 

 Jib has been developed in Frceport, Texas. Experiments have shown that 



ttn.? Vf ^M r^-*? ^^-'"°"* ™°^^^ ^^^ P^l ^^«i^^ ^^^^ the conven- 

 tional 90-loot ilat net and will give more spread. 



^■,-,in r,. . ^^^.I'^y ^ "^^^ ^^^^^ is in the jibs, i.e. the fon.'ard top- 

 side pieces which are hung so that, in use, the strain is with the 

 weobing and the jibs do not pull out of shape. 



.^ ^ ^, Mi^^l-iJ^^aT^.— i/hite shi-iinp are usually available only in 

 P^tn^'^T' '"'t^f Pi»k shriiap are restricted to the hours of darkness. 

 Reseax^ch has not been able to show the pattern of the vertical migration 



?tpn .^f ^•'^•■4 'T""' ^* ^^' ^^^" established that other r,m-ino Crus- 

 tacea are sensitive to sunlight. Some respond to light by „ioving upi 



°h^n T^^ T-7 ^^°'" ^^^ sunlight. The pink P. duorarum and white 

 shrir,ip P. setiferus inove at tiiaes upward from the"i^-b3d. So-called 

 l?fff, T- ^^^''^ I'''''' developed for other fisheries vhere the species 

 ery 8/ ^^^'^^"^^^y* ^"^^ ^^^^ "'^y be of g^-eat value in the shrimp fish- 



_/ A detailed report on this gear is available from the Fisheries 

 Research Board of Canada, Pacific Experimental Station. 



87 



