From Sebroo Bank to about 20 miles below tho Rio Grando, thore 

 is an area tliat is not fishad regularly. The bottom is rouph and thore 

 are locally largo concentrations of shell and sand dollars. Thoae obstacles 

 plna the snapper brinks discourage most fishermen from travrling here. Some 

 tratiling is done at deptlis of 2li, 32-33, and 35 fathoms. 



The next importcuit grovuid, called by Hildobrojid the "2U-10" 

 ground after its most productive portion, extends southward from about 

 20 miles below the Rio Grando to northeast of Sugarloaf Mountain at 

 approximately 23° 15' N. From Sucarloaf Mountaiji southward to Punta 

 Jerea, there are small "pockets" of trawlable ground that should bo in- 

 cluded. There axe an estimated 2,300,000 acres of trawlable bottom in 

 the "2lt-10" ground, Tho fishery is concentrated between 12 and hO fathoms, 

 except in the region of 2l4° 10' N, whore rocks (probably igneous in origin) 

 extend out to 27 fathoms. The depth of the fishery varies seasonally, and 

 the bulk of the xrinter and spring catches ai'e made in depths of 30 to UO 

 fathoi;i3. A nuinber of trawling conditions are encoimtered in tho area. 

 Moot of tho bottom is mud, some of it is soft mud and a small part is 

 shell, (see figure I - 10) 



Bottreen Punta Jerea and Lobos Island the bottom is roclcy. 

 Coral and volccriic necks hinder trawling. The knoim shrimp grounds con- 

 sist of "pockets" of trawlable bottom. Occasionally, a few large catches 

 from this area are unloaded in Port Isabel, 



The next locality of importance is tho Lobos Island ground, 

 •where a small fishery has been developed about 10 miles south of the islcmd, 

 Tho chief pockets of travjlable bottom are in 16-17, 2^-26 and 3U-36 fathoms, 

 and most of tho trawlable bottom, according to the fishermen, is reddish 

 mud. Although this fishing ground has been kno\m to Texas fisherii;on since 

 the days of extensive e:>q3loration along the Mexican coast dxuring 19U7-50, 

 it was not intensively fished until the spring of 1953* Perhaps the 

 heavy run daring 1953 uas, indeed, greater than in previous years as somo 

 fiyhcridon thinlc, and it may well have boon related to the decreased run- 

 off and rainfall on the nurseiy grovmdis in Laguna Tamiahuao 



Between the Lobos Island ground and Obregon, no important brown 

 slirliiip grounds exist, altliough there are pockets of tra^/lable bottoiii at 

 least as far as Alvarado, One of tho largest of these pockets is in 22- 

 35 fathoms east of Alvarado. 



Tho Obregon gi-ound is dolinoatod in figm-a 1-7, It consists 

 of about 800,000 acres of productive bottom. Mud is tho predominant 

 type of bottom and the grounds were found to be surprisingly free of shell 

 during tho investigations conductv^d by Hildebrand in 195l, The limits 

 of this fishei'y are proscribed by sm;xll populations of shrimp on tho 

 neighboring grounds leather than traxjlabla bottoms. Some brown slirimp are 

 caught as far east as Chanpoton, the viost boundai-y of tho pinlc shrimp 

 grounds, but this fishery developed after catches fell on neighboring 

 pink and brown shriiap grounds. The wrest boundary is a shell ridge that 

 run;! offshore from Chiltepoc, At times, a few shriiap are caught in 23- 

 26 fathoms in the area batvieen tho Chiltepec shell ridge and Laguna 

 Carmen. 



31 



