and early juvenile spotted seatrout. The destruction of 

 this nursery habitat has been blamed for local declines 

 in populations (Tabb 1966). In the Chenier Plain, such 

 grass flats are rare, yet spotted seatrout populations 

 here are not as small as might be expected. A study of 

 the distribution of young spotted seatrout in Barataria 

 Bay indicates that the fish occupy a wide variety of 

 shallow littoral areas and are not concentrated in grass 

 flats. However, in a study of Caminada Pass (one of the 

 tidal inlets of Barataria Bay), postlarval spotted sea- 

 trout were frequently encountered in masses of float- 

 ing ' coffee grounds ' detritus. Such material may offer 

 protective cover for developing young (Sabins and 

 Truesdale 1974). Also, an abrupt decline in abundance 

 of young spotted seatrout in a Texas marsh seemed to 

 be related to the disappearance of beds of widgeongrass 

 {Ruppia maritima). 



Red drum sometimes occur in brackish waters, but 

 they prefer moderate to high salinity. Tagging studies 

 in Texas (Simmons and Breuer 1962) suggest that some 

 ' schools ' of red drum are almost permanent residents 

 in the Gulf proper, while others rarely leave the bays or 

 estuaries. Young red drum tend to seek out sheltered 

 coves and lagoons, where they occupy shallow waters 

 along marsh edges (Sabins 1973, Tarbox 1974, Bass 

 and Avault 1975). Older juveniles and some adults tend 

 to prefer marsh lakes, bayous, and canals during cold 

 months. Large adults seem to concentrate near shell 

 reefs, wrecks, and oil platforms during warm months. 



Little is known about the densities or relative 

 abundance of spotted seatrout or red drum in the 

 Chenier Plain or adjacent areas. Population estimates 

 reported by Herke (1966), Perret et al. (1971) and 

 Perry (1976) are too subject to sampling error to be 

 reliable. 



Spotted seatrout and red drum are typically re- 

 cognized as 'top carnivores ' (Darnell 1958, Day et al. 

 1973, Wagner 1973). Although no detailed analyses of 

 the diet or feeding behavior of either species have been 

 reported for the Chenier Plain, food studies in other 

 areas suggest that they prey on a wide range of fish and 

 crustaceans (Miles 1949, Simmons and Breuer 1962, 

 Tabb 1966, Boothby and Avault 1971, Odum 1971). 

 Many food ' preferences 'attributed to spotted seatrout 

 probably are only indications of changes in the availa- 

 bility of various prey among seasons or locations (Tabb 

 1966). Indeed, Lorio and Schafer (1966) found food 

 preferences of spotted seatrout to be highly correlated 

 with prey availability in a southeastern Louisiana 

 marsh system. 



Because spotted seatrout less than 40 mm (1.6 in) 

 were found to subsist largely on copepods and other 

 zooplankters (Moody 1950), they are perhaps more ap- 

 propriately classed as ' primary carnivores ' as defined 

 by Day et al. (1973). The relative significance of 

 palaemonid shrimp, silversides (Menidia beryllina), and 

 sheepshead minnows {Cypriuodon variegatus) in diets 

 of juvenile spotted seatrout suggests that they feed 

 mainly along littoral zones. 



Although red drum generally feed on the most 

 available animals of ingestible size, three feeding phases 

 have been recognized. Post-larvae and small juveniles 

 (less than 15 mm or 0.6 in) seem to feed primarily on 

 zooplankton; intermediate-sized juveniles (15 to 75 

 mm or 0.6 to 3 in) eat mainly microbenthic animals 

 and small fishes; large juveniles and adults prey on 

 crabs, shrimp, and fishes (Boothby and Avault 1971, 

 Bass and Avault 1975). Red drum appear to feed main- 

 ly on crabs in inland open water habitats, and fishes 

 and shrimps in Gulf waters (Darnell 1958, Simmons 

 and Breuer 1962). 



Spotted seatrout and red drum spawn at different 

 times of the year, but in similar habitats. Spotted sea- 

 trout generally spawn in estuaries from April to Sep- 

 tember near tidal passes, althougli precise sites and 

 habitat conditions are not known for southwestern 

 Louisiana estuaries (Pearson 1929, Hoese 1965, Sabins 

 1973, Tarbox 1974). Some offshore spawning has been 

 reported by Hildebrand and Cable (1934). Recently 

 hatched larvae and early juveniles are typically found 

 near marsh shorelines of lower estuaries from May 

 through August. The rhombic markings of young 

 spotted seatrout enable them to blend well with the 

 mottled patterns created by bottom vegetation and 

 debris (Tabb 1966). By fall and early winter, juveniles 

 have migrated to the upper reaches of estuaries, where 

 they often concentrate in bayous, canals, and along 

 lake shorelines. 



Red drum are believed to spawn in or near the 

 mouths of tidal passes from late August through 

 November (Gunter 1945, Simmons and Breuer 1962, 

 Sabins 1973). The young tend to seek sheltered coves 

 and bayous where they occupy the shallow waters in 

 and along marsh edges (Tarbox 1974, Bass and Avault 

 1975). Like spotted seatrout, older juvenile red drum 

 tend to concentrate in marsh lakes, baycms, and canals 

 during cold months. 



Spotted seatrout adults and large juveniles have 

 been repeatedly observed to move to deeper and more 

 saline areas when salinities drop below 5%;, and tem- 

 peratures drop below 10° C (50° F) (Gunter 1945, 

 Tabb 1966). Overall, the species is known to occur 

 from freshwater to hypersaline conditions, but tends to 

 prefer waters with salinities of 5%o to 20%o (Gunter 

 1945). Normal habitat temperatures range from 8° to 

 35° C (46° to 95° F). 



Although broadly euryhaline, red drum tend to be 

 most frequently encountered (especially older juveniles 

 and adults) at salinities greater than 20%o (Simmons 

 and Breuer 1962). Temperatures of 3° to 33° C (37° to 

 90° F) are tolerated, but, like most other local sciaenids, 

 the red drum is susceptible to sudden cold shocks 

 (Gunter 1945, Simmons and Breuer 1962). 



5.5.7 SOUTHERN FLOUNDER (Paralichtbys 

 lethostigna) 



The southern flounder, common in Gulf coastal 

 waters, is a valuable sport and food fish. This species is 

 commonly found in habitats occupied by spotted sea- 

 trout and redfish. 



258 



