Silver perch, continued 



mostly in estuaries (Lee et al. 1980). They occur in a 

 wide variety of habitats, including backwater areas, 

 tidal tributaries, and over bare bottom areas but show 

 a preference for shallow vegetated seagrass regions 

 (Killam et al. 1992). They also can be found in 

 abundance around other structured habitats such as 

 rocks and seawalls. Adults, although most common in 

 bays and quiet lagoons (De Sylva 1965), can also 

 occur in sandy unvegetated habitats in shallow 

 nearshore waters of the Gulf of Mexico at depths up to 

 1 8 m (Gunter 1 945, Miller 1 964, Killam et al. 1 992). All 

 life stages appear to prefer polyhaline to euhaline 

 salinities (Killam et al. 1 992). Hoese and Moore (1 977) 

 report that the silver perch is more common in higher 

 salinity bays. 



Substrate : Adults are found over mud and sand bot- 

 toms (Robins and Tabb 1965). Juveniles are found 

 along shore zone rivers in ditches, in lower portions of 

 marsh creeks over mud and sand bottoms (Thomas 

 1971), and often over heavy detritus (Hildebrand and 

 Cable 1 930). They usually occur in grass beds (Hoese 

 and Moore 1977, Lee et al. 1980). 



Physical/Chemical Characteristics : 

 Temperature: This is a eurythermal species that is very 

 tolerant of the warm water conditions that are typical of 

 estuaries (Killam et al. 1 992). Ripe individuals or eggs 

 have been collected at 19.4 to 28°C (Johnson 1978). 

 Larvae have been taken in temperatures from 1 6.4° to 

 31.8°C (Jannke 1971). Juveniles are taken in tem- 

 peratures from 4.8° (Thomas 1971) up to 32.5°C 

 (Springer and Woodburn 1960, Wang and Raney 

 1 971 ). Adults have been taken at temperatures from 

 1 0° to 34.5°C (Roessler 1 970, Darovec 1 983). Upper 

 lethal limits determined for fish 20 to 200 mm were 

 LD50 at 34° to 37°C after 3 hours, and LD1 00 at 37° to 

 40°C after 30 minutes (Killam et al. 1992). 



Salinity: The silver perch is a euryhaline species (Killam 

 et al. 1992). Ripe individuals or eggs have been 

 collected at 1 4.3 to 26%o (Johnson 1 978). Larvae have 

 been taken in salinities from <1 to 37.4%o, although 

 most occurred at salinities >10% o (Lippson and Moran 

 1974, Killam et al. 1992). Juveniles are taken in 

 salinities from (Thomas 1971, Wang and Raney 

 1971, Lee etal. 1980) to 35.5%o(Springerand Woodburn 

 1960; Wang and Raney 1971, Wagner 1973). They 

 are most abundant at salinities >20%o (Killam et al. 

 1992). Adults have been found in salinities ranging 

 from to 48%o (Gunter 1945; De Sylva 1965; Wagner 

 1 973, Darovec 1 983), but appear to prefer those parts 

 of the estuary characterized by moderate to high 

 salinities (Killam et al. 1992). 



Movements and Migrations : Adults move to deeper 

 bay waters and offshore in the winter, and return to 



248 



