April 1951 CCMMERCIAL FISHEl-cIES REVIEW 



SHRIMP 



During tlie second half of I95O the Oregon explored primarily for brown-grooved 

 shrimp (Penaeus aztecus) by following a systematic pattern of exploratory drags in 

 the offshore waters of the north and northwest Gulf of tiexico. Occasional drags 

 were made in depths less than 25 fathoms for purposes of comparison and 16 drags 

 were made at depths greater than 100 fathoms. A total of 162 shrimp-trawl drags 

 were made during the year. Of these, 50 were made with a 100-foot flat trawl in 

 order to estimate the quantities of shrimp obtainable by commercial gear. Hiis flat 

 trawl is a style popular with the fishemien of the Texas coast. An arbitrary figure 

 of 100 pounds of marketable shrimp per hour with a 100-foot flat trawl has been 

 taken as the minimum catch rate of ccmmercial interest. It was found during the 

 course of the work that larger shrimp trawls conventionally rigged did not work 

 well at depths greater than 60 fathoms and the performance of balloon modifications 

 of the shrimp trawl, rigged as on the east coast of Florida, did not work well on 

 the characteristic soft mud bottom of the west Gulf. Conversely, results from the 

 flat trawls on the Florida coast left much to be desired. For deep-water drags and 

 for initial explorations over unknown bottom, a 40-foot flat net without any set- 

 back or undercut has been used successfully. This net, rigged on a bridle to a 

 single cable, is economical because of its small size and simplicity. It has proven 

 satisfactory for comparing the results of the various modifications of the shrimp 

 trawl used on the Oregon. 



Exploratory drags at widely separated intervals were made in from 20 to 100 

 fathoms near the continental shelf from Dry Tortugas to Port Aransas, Texas. Pre- 

 liminary work indicated the need for more detailed explorations near the mouth of 

 the Mississippi River and this was undertaken in the summer and fall. The explor- 

 ations of the Oregon demonstrated the existence in the late summer and fall off the 

 coasts of Alabama, Mississippi, and Louisiana of hitherto unused fishable concen- 

 trations of large brown-grooved shrimp in depths of from 30 to 50 fathoms. 



The best catches were made by the vessel west of the mouth of the Mississippi 

 River in 32 to 34 fathoms and within 20 miles of the coast. On the night of Sep- 

 tember 14, 2,700 pounds of 12- to l6-count (heads-on) shrimp were caught in 11 

 hours with a 100-foot flat trawl. The rate of catch after 9:00 p.m. was approxi- 

 mately 240 pounds per hour. During the August-September operations of the Oregon 

 throughout the 30- to 40-f athom depth range , in the area extending from the 88th 

 'meridian about 50 miles off the coast of Alabama to tne 90th meridian about 50 

 miles off the coast of Alabama to the 90th meridian off the coast of east Louisiana, 

 all drags with the 100-foot flat trawl over suitable bottom produced large unmixed 

 brown-grooved shrimp. The catch rate of fishing at night was better than 100 pounds 

 per hour. From 40 to 50 fathoms the catches were smaller as the depth increased, 

 but the size of the shrimp increased to 6g to 7 count (heads-on) with the increase 

 in depth. These larger shrimp were nearly all females ready to spawn, but they 

 were not found in concentrations of commercial interest beyond the 40-'f athom depth 

 during the period of the vessel's exploration (see Figure 4, p. 6). 



In late November a series of trawl drags were made on a course approximately 

 southeast of Aransas Pass, Texas, at depths of from 9 to 238 fathoms. Work in 

 the snallower water was carried out in cooperation with the M/V Carey of the Texas 

 Game, Fisn and Oyster Commission, 



Work by the Oregon has shown that the brown-grooved shrimp is moderately abun- 

 dant in the extensive areas out to 50 fathoms m the northwest Gulf between 91° and 

 96° W. longi-cude. Tlriis offshore population of brown-grooved shrimp is a very large 



