White shrimp, continued 



Within Study Area : Postlarval to subadult white shrimp 

 are well established throughout the Texas, Louisiana, 

 and Mississippi estuaries and nearshore Gulf waters, 

 utilizing the nursery habitat generally trom June/July 

 through October/November (Christmas and Etzold 

 1 977) (Table 5.08). For the purposes of Table 5.08, all 

 larval and postlarval stages of white shrimp are consid- 

 ered together as "larvae" (L). 



Life Mode 



Eggs are spawned from spring through fall in offshore 

 waters, where they hatch and develop into larvae 

 (Etzold and Christmas 1977, Klima et al. 1982). Eggs 

 are demersal and larval stages are planktonic. 

 Postlarvae become benthic upon reaching the nursery 

 areas of estuaries, and begin development into the 

 juvenile stage (Perez-Farfante 1 969, Lindnerand Cook 

 1970, McKenzie 1981, Muncy 1984, Williams 1984). 

 As juveniles approach adulthood, they move out of 

 estuaries into coastal waters where they mature and 

 spawn. Both juveniles and adults are demersal in 

 estuarine and coastal waters, and are usually found at 

 depths of <30 m (Perez-Farfante 1969, Lindner and 

 Cook 1970, Etzold and Christmas 1977, McKenzie 

 1981, Muncy 1984, Williams 1984). 



Habitat 



Ty pe: The white shrimp is neritic to estuarine, and 

 pelagic to demersal, depending on the life stage. Eggs 

 and early planktonic larval stages occur in nearshore 

 marine waters. Postlarvae seek estuarine habitats of 

 shallow water with muddy/sand bottoms high in or- 

 ganic detritus, or abundant in marsh grass in oligohaline 

 to euhaline salinities. Juveniles prefer lower salinity 

 waters, and are frequently found in tidal rivers and 

 tributaries throughout their range (Christmas and Etzold 

 1977). Juveniles and sub-adults move into offshore 

 waters during fall and winter. Adults generally inhabit 

 nearshore waters of the Gulf in depths less than 27 m, 

 and are usually more abundant at a depth of 14 m 

 (Perez-Farfante 1 969, Lindner and Cook 1 970, Rent ro 

 and Brusher 1982, Muncy 1984, Williams 1984). 



Substrate : Postlarvae and juveniles inhabit mostly 

 mud or peat bottoms with large quantities of decaying 

 organic matter or vegetative cover (Williams 1955b, 

 Williams 1958). Adults are found on bottoms of soft 

 mud or silt in offshore waters (Perez-Farfante 1969, 

 Lindner and Cook 1 970, Muncy 1 984, Williams 1 984). 

 It has been suggested that white shrimp densities are 

 related to the amount of marsh vegetation available in 

 intertidal estuarine habitats (Turner 1977), but other 

 studies have found abundances to be quite variable in 

 relationship to vegetation (Minello et al. 1990, 

 Zimmerman et al. 1990, Zimmerman pers. comm.). 



Physical/Chemical Characteristics : 

 Temperature: This species is tolerant of temperatures 

 ranging from approximately 7° to 38°C (Williams 1 955b, 

 Joyce 1965, Zein-Eldin and Griffith 1969). Sudden 

 changes in temperature, however, can be detrimental. 

 White shrimp are more tolerant of high temperatures 

 and less tolerant of low temperatures than brown or 

 pink shrimp (Christmas and Etzold 1977). Postlarval 

 white shrimp have been collected in temperatures from 

 12.6° to 30.6°C. Juveniles have been collected in 

 temperatures ranging from 6.5° to 39.0°C, with peaks 

 in abundance between 15° and 33°C (Zein-Eldin and 

 Renaud 1986). Normal growth of juveniles occurs 

 between 15°-16° and 25°-30°C with growth rates de- 

 creasing as temperatures approach > 35°C (Zein-Eldin 

 and Griffith 1 969) or drop below 1 5°C (Christmas and 

 Etzold 1977, St. Amant and Lindner 1966). 



Salinity: White shrimp can be considered euryhaline 

 since most life stages tolerate fairly wide salinity ranges 

 (Gunter 1961, Zein-Eldin and Griffith 1969, Lindner 

 and Cook 1970, Copeland and Bechtel 1974). This 

 species is apparently more tolerant of lower salinities 

 than brown shrimp (Gunter 1 961 ), and does not appear 

 to be affected by sudden salinity drops as the brown 

 shrimp is (Minello et al. 1 990). White shrimp postlarvae 

 have been collected in salinities ranging from 0.4 to 

 37.4% . Juveniles seem to prefer or tolerate lower 

 salinities than do other penaeid species (Williams 

 1955a). They prefer salinities less than 10%o (Zein- 

 Eldin and Renaud 1 986), and have been found several 

 kilometers upstream in rivers and tributaries (Christ- 

 mas and Etzold 1977). Collections of juveniles have 

 occurred in salinities from 0.3%o in Florida to as high as 

 41.3%o in the Laguna Madre of Texas (Gunter 1961, 

 Joyce 1965). Adults are usually found offshore in 

 waters with salinities greater than 27%o (Muncy 1 984). 

 Size appears to be related to salinity tolerance (Will- 

 iams 1955a, Joyce1965). In laboratory studies no 

 growth differences were detected over a salinity range 

 from 2 to 40%o (Zein-Eldin and Griffith 1969). 



Migrations and Movements : White shrimp postlarvae 

 migrate into the estuarine nurseries through passes 

 from May to November, with peaks in June and a 

 second peak in September for the northwest Gulf of 

 Mexico (Baxter and Renfro 1967, Klima et al. 1982). 

 Juveniles migrate farther up the estuary into less saline 

 waterthan brown or pink shrimp (Perez-Farfante 1 969). 

 As shrimp grow and mature they leave the marsh 

 habitat for deeper, higher salinity parts of the estuary 

 prior to their emigration to Gulf waters (Lindner and 

 Cook 1 970). The emigration of juveniles and subadults 

 from estuaries usually occurs in late August and Sep- 

 tember, and appears to be related to the size of the 

 shrimp and the environmental conditions within the 

 estuarine system (Klima et al. 1982). One factor that 



75 



