Grass shrimp, continued 



Table 5.09. Relative abundance of grass shrimp in 

 31 Gulf of Mexico estuaries (from Volume /)■ 



Relative abundance: 



Highly abundant 

 Abundant 

 Common 

 Rare 



® 



o 



blank Not present 



Life stage: 



A - Adults 



S - Spawning 



J - Juveniles 



L - Larvae/postlarvae 



E - Eggs 



Range 



Overall : The range of the grass shrimp is probably 

 discontinuous from Quebec to Nova Scotia, and Maine 

 to Texas (Williams 1984). 



Within Study Area : This is a ubiquitous species, along 

 with its congeners, throughout the estuaries of the Gulf 

 coast from Florida Bay, Florida, to the Laguna Madre, 

 Texas (Table 5.09). It is often replaced in higher 

 salinities by Palaemonetes vulgaris and/or P. interme- 

 dius, and by P. kadiakensis and P. paludosus in fresh 

 water (Hedgepeth 1966). 



Life Mode 



Eggs are carried by the female, and the larvae are 

 planktonic. Juveniles and adults are littoral or estua- 

 rine and benthic, appearing to prefer vegetated areas 

 (Williams 1984). In Georgia salt marshes, juveniles 

 and adults are segregated by habitat (Kneib 1987a). 

 Movements and distribution patterns may be influ- 

 enced by both photoperiod and tidal cycles (Anderson 

 1 985, Kneib 1 987a). Juveniles and adults are omnivo- 

 rous in their feeding habits. 



Habitat 



Type : The grass shrimp occupies habitats ranging 

 from estuarine to riverine (Knowlton and Williams 1970). 

 It is usually found near the water's edge in shallows of 

 bays and creeks, or in marshes, submerged vegetation 

 and oyster reefs (Williams 1984, Anderson 1985). 

 Although most common in shallow waters, it has been 

 collected in waters as deep as 1 7 m. During periods of 

 extreme heat or cold it retreats to deeper channel 

 areas. It is often abundant in turbid waters possibly to 

 avoid predators, but turbidity is not a necessary habitat 

 requirement (Anderson 1985, Killam et al. 1992). It 

 also uses seagrass and other aquatic vegetation as 

 refuge from predation and as foraging areas (Killam et 

 al. 1992). Juveniles are found primarily on vegetated 

 marsh surfaces in the intertidal region, while adults 

 inhabit subtidal areas (Anderson 1985, Kneib 1987a). 



Substrate : Vegetated or oyster shell substrate is pre- 

 ferred (Williams 1984, Anderson 1985). 



Physical/Chemical Characteristics 

 Temperature: The grass shrimp is eurythermal and 

 both juveniles and adults can tolerate from 5° to 38°C, 

 depending on geographic location (Wood 1 967, Christ- 

 mas and Langley 1 973, Anderson 1 985). In laboratory 

 studies an estimated 80% of larvae completed meta- 

 morphosis to postlarval stages at temperatures of 

 20°C to 30°C at salinities ranging from 1 1 to 33% , with 

 optimum development occurring at 20° to 27°C and 1 7 

 to 27% (Sastry and Vargo 1977, McKenney and Neff 

 1 979). Juveniles and adults have optimum survival at 

 temperatures ranging from 18° to 25°C in salinities of 



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