Atlantic croaker, continued 



Kernehan 1979). 



Age and Size of Larvae : Larvae upon hatching are 1 .3 

 to 2.0 mm TL (Wang and Kernehan 1 979). Incubation 

 time is 29-32 hours at 23°C and 26-30 hours at 25°C. 

 Fruge and Truesdale (1 978) collected 1 03 larval croaker 

 in coastal waters of Louisiana, ranging in size from 1 .7 

 to 10.5 mm SL. Cowan (1988) determined growth for 

 40-80 day larvae to be approximately 0. 1 9 mm/day. In 

 Texas, young-of-the-year appear from November to 

 January at 1 0-50 mm TL. Larval stage is complete by 

 approximately 1 mm TL when the full complement of 

 spines and soft rays in the dorsal and anal fins are 

 reached (Johnson 1978). 



Juvenile Size of Larvae : Transformation to the juvenile 

 stage occurs at a length of approximately 1 2 mm (Ditty 

 and Shaw 1 994). Juveniles may range in size from 1 1 

 to 140 mm TL (Johnson 1978, White and Chittenden 

 1976). One study from western Louisiana estimates 

 juvenile growth rate at 0.47 mm/day or 1 4.2 mm/month 

 (Arnoldi et al. 1973), while other estimates from the 

 Mississippi Sound area are 3.1 mm/week (Warren 

 1981) and 13.0 mm/month (Warren and Sutter 1982). 



Age and Size of Adults : Maturity in fish sampled from 

 Texas and Louisiana areas was reached after the first 

 year of growth when individuals reached 140 to 170 

 mm TL (White and Chittenden 1 976). Most adults live 

 up to 3 years with some living 4 to 5 years, but rarely 

 longer (Etzold and Christmas 1979, Lassuy 1983). In 

 North Carolina, fish older than 3 years were found 

 offshore, but were rare in estuaries (Ross 1988). The 

 oldest fish recovered there were estimated to be 7 

 years old. The predicted TLs for year classes are: 



1 76.6 mm for age 1 ; 261 .5 mm at age 2; 331 .0 mm at 

 age 3; 388.0 mm at age 4; 434.5 mm at age 5; and 



472.7 mm at age 6 (Ross 1 988). The largest reported 

 specimen was 668 mm TL (Rivas and Roithmayr 

 1 970). Ross (1 988) has derived Van Bertalanffy growth 

 models for this species. 



Food and Feeding 



Trophic mode : Larvae and early juveniles are carni- 

 vores, feeding on zooplankton in the water column 

 (Lassuy 1983). Older juveniles and adults are oppor- 

 tunistic bottom feeding carnivores that prey on poly- 

 chaetes, molluscs, crustaceans, and fish. Juveniles 

 feed by forcefully diving into the substrate, digging as 

 they feed. Adults feed similarly to juveniles, but are 

 capable of taking larger invertebrates and some fishes. 

 Atlantic croaker can, therefore, feed on a secondary or 

 higher trophic level. Feeding is by sight, olfaction, and 

 touch (Mercer 1989). 



Food Items : Young of the year fish are reported to 

 consume polychaete worms, copepods, and mysids, 



while older fish principally feed on crustaceans (sto- 

 matopods, shrimps and crabs), molluscs (gastropods 

 and bivalves), and fish (Levine 1980, Darovec 1983, 

 Sheridan et al. 1984, Mercer 1989). Early juveniles 

 (15-30 mm) feed on zooplankton, switching to benthic 

 mode as they become older and begin consuming 

 infaunal and epifaunal organisms sorted from bottom 

 debris (Mercer 1989). Food items include molluscs 

 (common rangia, Macoma mitchilli, Congeria 

 leucophaeta, Probythinella protera, Texadina 

 sphinctosoma), isopods, amphipods, insects, fish 

 (mostly bay anchovy), and detritus (Levine 1980). 



Biological Interactions 



Predation : Predators of Atlantic croaker are larger 

 piscivorous species such as striped bass, southern 

 flounder, bull shark, blue catfish, yellow bass, spotted 

 seatrout, Atlantic croaker, red drum, sheepshead, blue- 

 fish, and weakfish (Levine 1980, Mercer 1989). 



Factors Influencing Populations : White and Chittenden 

 (1976) show some habitat segregation by life stage, 

 with smaller (<200 mm TL), younger individuals (age 0) 

 occupying the bays and muddy bottoms, while the 

 larger (>200 mm TL), older individuals (age l+) are 

 more localized around oyster reefs. Hoese et al. 

 (1968) noted that faster growing individuals tend to 

 leave Texas bays before the slower growing individu- 

 als, resulting in a bay population of smaller than aver- 

 age sized fish. Warren and Sutter (1983) noted that 

 abundance in Mississippi Sound drops dramatically in 

 July and that these drops may be due to shrimping 

 which begins in June. Shrimping activities may be 

 having an effect on the population of this species. 

 Atlantic croaker comprise an estimated 50% of the fish 

 discarded as bycatch and destroyed during the brown 

 shrimp season, and 18% of those during the white 

 shrimp season (Rogers 1979). The average bycatch 

 from 1 972 to 1 989 was estimated as 7.5 billion croaker 

 (NOAA 1993). This species is considered overex- 

 ploited in the southeastern U.S. 



References 



Allshouse, W.C. 1983. The distribution of immigrating 

 larval and postlarval fishes into the Aransas-Corpus 

 Christi Bay complex. M.S. thesis, Corpus Christi St. 

 Univ., Corpus Christi, TX, 1 18 p. 



Arnoldi, D.C., W.H. Herke, and E.J. Clairain, Jr. 1 973. 

 Estimate of growth rate and length of stay in a marsh 

 nursery of juvenile Atlantic croaker, Micropogon 

 undulatus (Linnaeus), "sandblasted" with fluorescent 

 pigments. Proc. Gulf Caribb. Fish. Inst. 26:158-172. 



280 



