378 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



been cited as a major factor in brown and pink 

 shrimp distribution; white shrimp hkewise are 

 thongiit to distribute themselves accordingly 

 (Hildebrand, 1954; Williams, 1958). Notwith- 

 standing the fact that generations produced by 

 each species may undergo early development on 

 the same inshore nursery grounds, the displace- 

 ment of adult population segments in offshore 

 waters is reasonably discrete. Whereas pink 

 shrimp adults tend to occupy sand-shell bottoms 

 of firm consistency, brown and white shrimp are 

 most often found on much softer bottoms, typ- 

 ically soft clay, mud, or terrigenous silt. Sub- 

 strates inhabited by the latter two species are 

 difficult to differentiate but a second factor, 

 bathymetry, helps to resolve the problem. Con- 

 trasted to their deep-water counterparts, mature 

 white shrimp are ordinarily found only in the 

 nearshore shallows (0-15 fm.), sometimes even in 

 those portions of inshore waters nearest the sea. 

 Whether or not substrate and bathymetry are the 

 major factors governing distribution of littoral 

 Penaeidae on the continental shelf remains 

 problematical. 



White shrimp occur in widely varying quantity 

 at nearly every point on the Gulf's continental 

 shelf. A notable exception is that portion of the 

 shelf lying off southwest Florida (statistical sub- 

 areas 1-4). Commercial concentrations are well 

 defined in humid or semi-humid areas bordered 

 by extensive estuarine complexes. One such area 

 is that lying between Tupilco and Carmen on the 

 east Mexican coast. Here a fairly dense popula- 

 tion of white shrimp, fished in Gulf of Campeche 

 waters by the Mexican fleet, seems to be associated 

 with numerous coastal lagoons, especially the 

 Laguna de Terminos. The most important com- 

 mercial concentrations, however, occur in and off 

 the northern Gulf coast marshes between Apalach- 

 icola and central Texas, with peak population 

 strength being attained in and adjacent to Louisi- 

 ana's vast estuarine complex (table 6). 



Although most white shrimp are taken from 

 20 fathoms or less, the species may occasionally 

 be found at depths up to 45 fathoms (Springer 

 and Bullis, 1952). The 45-fathom contour is 

 therefore taken as the approximate seaward limit 

 of the species range. In addition, the northern 

 Gulf of Mexico stock is arbitrarily subdivided 

 into those units lying east and west of the Missis- 

 sippi River Delta. Commercial statistics of effort 



and production (1956-59) are given in condensed 

 form by months and depths for all coastal areas 

 in appendix tables 1 and 4. Inshore production 

 by specific water body is summarized for the 

 same period in appendix table 5. 

 Eastern Gulf Populations 



Commercial yield. — Over the period 1956-59, 

 white shrimp annually averaged 13 percent by 

 weight of all shrimp taken commercially from 

 offshore waters in the Apalachicola and Pensa- 

 cola-Mississippi River areas. Landings ranged 

 from a low of 1.2 million pounds in 1957 to a 

 high of 2.0 million pounds in 1959. 



Production in the Apalachicola area was rela- 

 tively stable, mildly fluctuating between 0.3 and 

 0.5 million pounds annually. Landings from the 

 Pensacola-Mississippi River area were more erratic, 

 dropping from 1.7 million pounds in 1956 to 0.7 

 million pounds in 1957, and then climbing again 

 to 1.7 miUion pounds in 1959 (fig. 26 A). Seasonal 

 landing patterns for both areas show that each 

 year's white shrimp production peaked approxi- 



COMMERCIAL VrELO (million* of pouni 

 .-APALACHICOLA 

 o-PENSACOLA -MISSISSIPPI RIVER 



':^ •^„««s;',^:$,-^«..-*-... 



Figure 26.— Yield and structure of white shrimp popula- 

 tions off tlie northeastern Gulf coast, 1956-59. 



