MEN STILL GO DOWN TO THE SEA 



Since biblical days in Galilee, fishernnen 

 have used about the same gear--nets, hooks, 

 and traps--with few basic changes. Most 

 nnodern innovations within the industry involve 

 auxiliary equipment such as diesel engines, 

 radiotelephones, depth recorders, and navi- 

 gational instruments. The power block and the 

 advent of synthetic lines and webbing were 

 perhaps the most significant breakthroughs in 

 revolutionizing some aspects of fisheries in 

 this generation. The trawl fishery, whichtakes 

 a large percentage of the world catch, however, 

 has changed little during the last two or three 

 generations. 



Electricity Enters the Ocean 



For some years there has been an aura of 

 excitement about using electricity in fishing. 

 Many dollars and many hours have been spent 

 in developing practical applications. In fresh 

 water some of this effort has been successful. 

 In the oceans, however, the salt in the water is 

 a good electrolyte, so we must use considerably 

 more power to be effective, even over short 

 distances, A few breakthroughs have been 

 achieved in nnarine fisheries. One nnenhaden 

 firm used electricity to attract to the mouth 

 of a pump the fish that had been "hardened" in 

 a seine. Also a Scandinavian firm developed an 

 electric shocker for longline hooks. 



Previous annual reports and publications 

 described our efforts to develop a practical 

 electric shrimp trawl. Pulsed current was used 

 to shock shrimp out of the bottonn sediments, 

 where they burrow in daytime, and into the 

 path of the trawl. This gear makes possible 

 daytinne shrimping for brown and pink shrimps; 

 whereas, till now shrimping has been strictly 

 a nighttime endeavor. 



Fishing trials with the electric shrimp trawl 

 and development of practical system com- 

 ponents were connpleted by the scheduled 

 termination date of December 31, 1966. Three 

 George M. Bowers cruises to the major shrimp 

 grounds in the Gulf of Mexico proved that the 

 system was effective for commercial shrimp 

 harvesting. 



After field tests to evaluate and correct 

 deficiencies in the electric shrimp trawl 

 system had been completed, the George M . 

 Bowers was rigged with two standard 40-foot 

 Gulf of Mexico shrimp trawls. The electric 

 shrimp trawl system was installed on the 

 starboard trawl, and a standard 3/8-inch 

 galvanized tickler chain was attached to the 

 port trawl. Except for these modifications, 

 the two trawls were similar; so differences 

 in the amount of shrimp caught in the two nets 



could be attributed largely to the electric 

 system on the starboard trawl. 



Both trawls were dragged simultaneously, 

 day and night. Several 1 -hour drags were made 

 during daylight on each test area. Then, 

 beginning imnnediately after sunset, additional 

 1-hour drags were made in the same area. 

 This day-night procedure was repeated many 

 tinnes. The percentage effectiveness of the 

 electric shrimp trawl system was deternnined 

 by comparing the individual trawl catch rates 

 for the night-time nonelectric trawl and the 

 daytime electric trawl over 24-hour test cycles 

 on each major shrimp ground. 



Fishing trials were made within the major 

 Gulf of Mexico shrimp grounds off Mississippi 

 and Texas for brown shrimp and southern 

 Florida (Tortugas area) for pink shrimp. When 

 average catches (daytime electric trawl/ 

 nighttime nonelectric trawl) were compared, 

 we found that off Mississippi and Texas the 

 daytime electric trawl caught 109 and 95 per- 

 cent of the nighttime nonelectric catch. On the 

 Tortugas shrimp grounds, the catch rate was 

 50 percent. Since the Tortugas shrimp grounds 

 is composed of calcareous sand mixed with 

 shells, whereas the Mississippi and Texas 

 grounds are soft mud, the adhesion-compact- 

 ness characteristics may have been responsi- 

 ble for the reduced catch rate in the Tortugas 

 area. 



Although some unresolved questions remain, 

 the catch rates of the electric trawl demon- 

 strated that the system would be an effective 

 and practical tool in harvesting shrimp in the 

 northern Gulf. We are now applying for a 

 public service patent on the electric trawl 

 system. Several nnanufacturers are interested 

 in reproducing the system or components, and 

 the industry has shown avid interest in the 

 system. Principal aim is to increase catch 

 per unit of effort, thereby allowing for more 

 efficient use of men and equipment. 



Research of the St. Simons Island Station 



The Oregon , operating out of St. Simons 

 Island, Ga., made 10 cruises during the fiscal 

 year. Five of these were directed toward 

 seasonal assessnnent of swordfish, bottomfish, 

 scallops, and offshore shrimp along the south- 

 eastern coast of the United States. Two cruises 

 in the Caribbean Sea in cooperation with the 

 United Nations' Special Fund Caribbean Fish- 

 eries Development Project investigated pri- 

 marily snapper, shrimp, and tuna resources. 

 The remaining three cruises were charters -- 

 two by the Bureau's Biological Laboratory at 

 Brunswick, Ga., and one by Louisiana State 

 University. During the latter cruise a specially 

 installed 35,000-curie cobalt 60 irradiator was 

 used in shrimp preservation studies. 



