There is an important ground for brown shrimp, in Hildebrand's 

 words, off Southwest Pass at the mouth of the Mississippi River. However, 

 traveling conditions are for the most part difficult and the returns are 

 small compared with the rich "2U-10" beds so that many fishermen have 

 emigrated with their large trawlers to Port Isabel, New interest was 

 sho^m in the Southwest Pass ground when the fleet became so large in Port 

 Isabel that the catch per boat became less than catches off Southwest 

 Pass. However, not all this bottom is trawlable and much gear has been 

 lost in soft mud and "mud lumps". 



Shaw (I9lij) described mud lumps as domes of fine, tough, 

 structureless clay rising two to ten feet in height usually within a 

 mile or two of the end of the passes of the Mississippi River. Fenneraan 

 (1938) favored the theory that thin layers of highly mobile clay under the 

 pressure of accumulating sediments on the delta are caused to flow later- 

 ally and break through to the surface at favorable points. Whether the 

 mud Ixjmps, as used in the Gulf fishermen's vocabulary, are the same type 

 as the ones studied by Shaw, is not known. Fishermen have used this 

 term to describe trawling conditions 60 to 70 miles from land. Springer 

 (1952) identifies "mud lumps" as soft mud bottom. 



Another bottom type is the very soft mud of the Delta region 

 and offshore in east Texas. Possibly this condition is synonymous with 

 the so-called "suck sand" found off the Colorado River and on Campeche 

 Bank. Often an entire rig is lost when such trawling conditions are 

 encoimtered. 



From Southirest Pass to the submarine canyon, a distance of 

 approximately 20 nautical miles, there is considerable trawling in 

 depths of I4O to $$ fathoms. All other major brown shrimp grounds in 

 the western Gulf of Mexico are in shallovjer water. The Southvest Pass 

 grounds continue westward from the submarine canyon in depths of 12 to 

 29 fathoms to the shell ridge off Big Constance Bayou. In this part of 

 the Southwest Pass groxmds there are obstacles to traveling such as dy- 

 namited wrecks south of Ship Shoal and the extensive area of soft mud 

 south of Trinity Shoal. Some of the soft mud bottom off Trinity Shoal 

 is fished by wrapping the footrope of the trawl until it is a foot or more 

 in diameter. Many places on the Southv/est Pass grounds in former years 

 were seasonally fished for large white shrimp, and it is probably on 

 these grounds that there is the greatest interspecific competition be- 

 tween the adult white and brown shrimp. 



Prior to the summer of 19^3 the vast area from Big Constance 

 Bayou to the Colorado River was not fished for brovm shrimp. It was 

 deemed that there was very little bottom suitable for traveling because 

 of an extensive shell ridge, snapper banks and soft mud, A few bro\m 

 shrimp vjere caught off Freeport in lU to 17 fathoms, and small brown 

 shrimp were caught inshore of the 12-fathom contour. Most of the land- 

 ings of bro\m shrimp at Freeport, Texas, were caught off Pass Cavallo 

 or off Obrogon, Mexico, Active exploration in the area east of the 

 Colorado River was carried out by the shrimping fleet during the summer 



28 



