Marum (1979). also working in the white shrimp grounds nearshore of 

 Louisiana, reported zooplankton biomass levels were high as compared to 

 neritic waters of the gulf, and showed that this phenomenon was due to 

 high primary productivity associated with Mississippi River runoff. 

 Based upon characteristic copepod assemblages, the zooplankton community 

 composition in this area was considered typical for the northern Gulf of 

 Mexico. 



A description of the species composition of the demersal 

 macroinvertebrate fauna of soft bottoms of the white shrimp grounds is 

 provided by Defenbaugh (1976) and references therein. Characteristic 

 invertebrates include the epifaunal sea pansy (Renilla muelleri) and the 

 white shrimp. Crustaceans, bivalves and gastropods have been shown to 

 be particularly diverse (Parker 1960; Defenbaugh 1976). 



Benthic mulluscan and crustacean infaunal populations in the white 

 shrimp grounds off Louisiana were recently reported by Farrell (1979). 

 Benthic communities were reported as diverse, with crustaceans (mainly 

 decapods and amphipods), pelecypods, and gastropods being most numerous 

 in his samples. In October 1972 and April 1973, benthic biomass at his 

 offshore control station 17A was between 12 and 15 g/m 2 , whereas during 

 July, October, and January 197^, biomass levels were estimated <5 g/m 2 . 

 In the same general area, Waller (1979) reported infaunal communities at 

 a control station to have been represented by 21 species (mainly 

 polychaetes and crustaceans) having an estimated total biomass of 15.8+ 

 g/m 2 . 



On a biomass basis, the demersal epifauna of the white shrimp 

 grounds is dominated by fishes. For every volume of headed shrimp taken 

 by the white shrimp fishery, an estimated 12 volumes of biomass are 

 discarded and, in general, fish biomass closely parallels discard 

 biomass (Chittenden and McEachran 1976). The demersal epifauna of the 

 white shrimp community is characterized by estuarine-dependent forms as 

 exemplified by the white shrimp. The dominant demersal fishes are 

 mainly representatives of the family Sciaenidae with the Atlantic 

 croaker (Micropo^on undulatus) being the dominant species, representing 

 about 30? of the fishes taken in shrimp trawls (Chittenden and McEachran 

 1976). Based upon shrimp trawl catches, other abundant fishes of the 

 white shrimp community include Atlantic cutlass fish, Trichiurus 

 lepturus , 1H%; silver seatrout, Cvnoscion nothus , 13?; star drum, 

 Stellifer lanceolatus , 10$; sand seatrout, Cvnoscion arenarius , 8$; 

 Atlantic threadfin, Polvdactvlus octonemus , 5%; and sea catfish, AclliS. 

 ££lis_ , 5%. Collectively these 3pecies comprise 85$ of the fishes 

 collected from the white shrimp community in shrimp trawls (Chittenden 

 and McEachran 1976). The dominant pelagic species associated with this 

 community in open waters are probably the Atlantic menhaden (Brevoortia 

 patronus) , mullets ( Mugil spp.) and anchovies (Engraulididae) , all 

 plankton feeders; and the Spanish mackerel ( Scomberomorus maculatus) , a 

 predator. 



36 



