Spot, continued 



Table 5.36. Relative abundance of spot in 31 Gulf of 



Mexico estuaries (Nelson et al. 1992, VanHoose 



pers. comm.). 



Life stage 



Relative abundance: 



Highly abundant 



® Abundant 



O Common 



V Rare 



blank Not present 



na No data available 



Life stage: 



A - Adults 

 S - Spawning 

 J - Juveniles 

 L - Larvae 

 E - Eggs 



Within Study Area : The spot is found throughout coastal 

 shelf areas of the U.S. Gulf of Mexico from Florida Bay 

 to the Rio Grande River. It is common in both bays and 

 open Gulf areas except at the extremities of its range 

 (Hoese and Moore 1977, Shipp 1986) (Table 5.36). 



Life Mode 



Eggs and early larvae are planktonic and pelagic. 

 Juveniles and adults are demersal in estuarine and 

 coastal waters (Ditty and Shaw 1994). 



Habitat 



Ty pe: The spot utilizes several habitat types through- 

 out its life cycle. Larvae are found in the marine 

 environment, and have been collected in the northern 

 Gulf of Mexico on the continental shelf up to the 40 m 

 isobath, or 130 km offshore. They occur at all depths, 

 but are found primarily in the upper 30 m of the water 

 column (Sogard etal. 1987, Cowan and Shaw 1988). 

 Larvae are transported inshore into estuarine nursery 

 areas where postlarval and juvenile spot are found. 

 Younger juveniles are often found in the shallow head 

 waters of tidal creeks, and sometimes in seagrass 

 beds, while older juveniles move to deeper, more 

 saline areas of estuaries (Wang and Kernehan 1979, 

 Mercer 1 989, Hales and Van Den Avyle 1 989). Adults 

 migrate seasonally between estuarine and coastal 

 waters, with movement offshore occurring in the fall 

 (Hales and Van Den Avyle 1989). 



Substrate : Adults are taken most frequently over mud 

 and sand bottoms in inside waters and offshore waters 

 to at least 132 m (Dawson 1958, Music 1974, Huish 

 and Geaghan 1987). They are also found over mud, 

 sand, and sandy shell bottom. Juveniles are found 

 primarily in nursery areas with mud and detritus bot- 

 toms (Mercer 1989). 



Physical/Chemical Characteristics : 

 Temperature - Eggs and Larvae: Lab-spawned eggs 

 successfully developed at 20°C (Powell and Gordy 

 1 980). In waters in or nearthe Gulf Stream, larvae less 

 than 15 days old have been collected only in water 

 above 1 9.3°C (Warlen and Chester 1 985). Spot below 

 20.0 mm SL have been found below 20°C in Missis- 

 sippi Sound with the majority taken at temperatures 

 from 7° to 15°C (Warren and Sutter 1982). Larvae 

 have been collected at 5° to 1 9.3°C, and juveniles at 4° 

 to 35°C and (Wang and Raney 1971, Wagner 1973, 

 Pineda 1975, Cowan and Shaw 1988, Hales and Van 

 Den Avyle 1989). The upper incipient lethal tempera- 

 ture for post larval and small juvenile spot has been 

 estimated at 35.2°C (Mercer 1989), and the critical 

 thermal maximum for juvenile spot acclimated at 15°C 

 was31.0°C. 



270 



