shad and striped mullet do not usually exceed 30.5 

 cm (12 in). In most of Louisiana these species are 

 characteristically euryhaline. They are easUy caught 

 and often used for bait in crab and crayfish traps. 



Gizzard and threadfm shad are widely dis- 

 tributed throughout much of the Mississippi River 

 system and in coastal tributaries, lakes, and estuaries. 

 Shad have strong schooling tendencies and migrate 

 into a wide range of habitats for spawning or feeding. 



In the Chenier Plain area, the two shad species 

 are most abundant in freshwater but are also common 

 in estuaries and bayous with salinities of less than 

 6%o- The striped raullet tends to favor more saline 

 coastal waters, but may sometimes be abundant for 

 relatively long periods of time in freshwater (Reid 

 1956, Herke 1966, Lantz 1970, Crandall et al. 1976, 

 Perry 1976). 



Available data suggest that mullet are more abun- 

 dant than shad in Chenier Plain coastal waters. Standing 

 crops in the Rockefeller Wildlife Refuge were 

 44.4 kg/ha (39.6 lb/a) for striped mullet, 21.4 kg/ha 

 (19.1 lb/a) for gizzard shad, and 12.9 kg/ha (11.5 lb/a) 

 for threadfm shad (Perry 1976). Similar results were 

 obtained for the low-salinity marsh canals near Terre- 

 bone Bay, Louisiana, where striped mullet was the 

 most abundant and gizzard shad the second most abun- 

 dant species (Adkins and Bowman 1976). However, in 

 the freshwater of the Atchafalaya River, standing crops 

 of 130 kg/ha (1 16 lb/a) and 47 kg/ha (42 lb/a) were re- 

 corded for gizzard shad and striped mullet, respectively. 



These three species are most active in the daytime 

 when they do most of their migrating, feeding, and 

 spawning; otherwise, their daOy movements have no 

 particular pattern. Gizzard shad form large schools dur- 

 ing the spring spawning period in the Atchafalaya and 

 lower Mississippi basins. Both shad species tend to mi- 

 grate long distances and occupy diverse habitats. Striped 

 muUet migrate seaward to spawn in the spring, but the 

 young migrate shoreward to use coastal wetlands as 

 nursery grounds. 



Gizzard shad, threadfm shad, and the striped mullet 

 strain tiny plant particles from the water, although zoo- 

 plankton are sometimes consumed in large quantities 

 by juvenile shad. Adults consume primarily algae, 

 vascular plants, planktonic crustaceans, and organic 

 detritus (Reid 1955, Darnell 1958, MUler 1960, Burns 

 1966. Pflieger 1975). Young shad feed more on 

 cladocerans, protozoans, ostracods, and insect larvae 

 and pupae. 



Adult gizzard shad and striped mullet often feed 

 on the top layer of bottom ooze, as indicated by the 

 large amounts of organic detritus, algae, and mud and 

 silt in their digestive tracts (Darnell 1958, Dalquest and 

 Peters 1966). Threadfm shad are either pelagic or lim- 

 netic feeders (Baker and Schmitz 1971). 



Gizzard and threadfm shad spawn primarily from 

 mid-March through June in a variety of habitats from 

 lentic waters of sloughs, ponds, lakes, and bayous to 

 the more lotic waters of large rivers. During the spring 



in the Atchafalaya and lower Mississippi rivers, ripe giz- 

 zard shad migrate upstream in large schools to spawn. 

 Both gizzard shad and threadfm shad typically spawn 

 in large schools near the surface. Eggs are adhesive and 

 demersal and either sink to the bottom or float in the 

 current until they attach (Miller 1960, Burns 1966). 

 Beginning in late March, the larvae occur in large 

 schools in the Mississippi and Atchafalaya drainages 

 and remain abundant through June. Developing juve- 

 niles are most abundant after July. Neither species is 

 known to spawn in waters of greater than 5%o salinity. 



Striped muUet spawn offshore in the Gulf of 

 Mexico, principally from October through February 

 (Arnold and Thompson 1958, Hoese 1965). Complete 

 larval development apparently occurs offshore, as only 

 juveniles are taken in tidal passes and inshore (Perret et 

 al. 1971, Sabins and Truesdale 1974). Young-of the- 

 year begin to invade coastal waters as early as December 

 and by mid-summer juveniles are found throughout 

 coastal habitats. Like many other species spawned in 

 Gulf waters, striped mullet apparently utilize inshore 

 areas as nursery grounds, and make extensive use of 

 coastal marshes. 



Except for introductory plantings of threadfin 

 shad (as forage for sport fish) in reservoirs as far north 

 as Kentucky, there have been few, if any, reported 

 historical changes in the abundance or distribution of 

 the three species. This stability in numbers and distrib- 

 ution is due to the capability of these fishes to thrive in 

 a wide diversity of habitats, especially in southern 

 waters. 



Since each of the three species tends to move about 

 in loose aggregations or in large schools for feeding and 

 migration, they require rather large water systems for 

 their survival. In the Chenier Plain, such a water system 

 would consist of a number of interconnected bayous, 

 canals, estuaries, and tributary rivers. Since these fishes 

 are important forage species, excessive closure or inter- 

 ruption of coastal waterway systems could reduce their 

 populations and thus alter coastal foodchains. 



Since gizzard shad and threadfin shad spawn in 

 waters with a salinity of about 0.5%o, saltwater 

 intrusions could affect their distribution and abund- 

 ance. Threadfin shad are the most sensitive of the 

 three species to low water temperatures. High mortal- 

 ity may occur when temperatures drop to 8°C or lower 

 (Bums 1966, Pflieger 1975). Die-offs of all three species 

 have been known to occur in the Atchafalya Basin 

 because of oxygen deficiency (Bryan et al. 1976). 



5.5.4 LARGEMOUTH BASS (Micropterus salmoides) 

 and BLACK CRAPPIE (Pomoxis nigromacu- 



latus) 



Largemouth bass and black crappie are valuable 

 freshwater sport fishes throughout much of the Missis- 

 sippi River drainage and in some of the coastal waters 

 of the Gulf of Mexico. Largemouth bass are extensively 

 cultivated as a pond fish. 



255 



