Common snook, continued 



years for females. Volpe (1959) reported a maximum 

 life span of about 7 years. However, Taylor ef al. (1 993) 

 reported that males can live 13 years and attain 925 

 mm TL, and females 1 9 years and 1 , 1 05 mm TL. In the 

 Everglades region, 4 and 5 year old fish comprise 59% 

 of the snook population. The sex ratio is approximately 

 3:1, males to females (Gilmore et al. 1983). 



Food and Feeding 



Trophic Mode : The common snook is an opportunistic 

 carnivore that tends to be piscivorous, with its specific 

 diet varying among habitats (Seaman and Collins 

 1983). The common snook is a visual predator that 

 forages throughout the water column and on the bot- 

 tom, often in narrow passes accompanied by strong 

 currents (Springer and Woodburn 1960, Fore and 

 Schmidt 1973, Seaman and Collins 1983, Manooch 

 1984, NOAM 985). 



Food Items : Larvae are considered stenophagous. 

 They are planktivores preying chiefly on copepods and 

 their eggs and larvae. They also feed on other inver- 

 tebrate eggs, crab zoea, foraminifera, algae, and plant 

 tissue (Harrington and Harrington 1961). In a labora- 

 tory rearing study, larvae began feeding when 2 to 3 

 days old, and accepted rotifers, newly hatched Artemia, 

 and copepod nauplii between 53 and 130 microns in 

 size (Shafland 1977). Late postlarvae also feed on 

 neonatal Gambusia (Gilmore et al. 1983, Shafland 

 1 977). Juveniles become piscivorous at 25 to 30 mm 

 TL with fish constituting a major portion of their diet by 

 56 mm SL (Springer and Woodburn 1960, Shafland 

 and Koehl 1979). Food organisms of juvenile snook 

 include bay anchovy, pinfish, sailfin molly (Poecilia 

 latipinna), western mosquitofish (Gambusia affinis), 

 sheepshead minnow, gobies, silversides, red drum, 

 killifishes, grass shrimp, plant tissue, insects, and other 

 fishes. Smaller specimens have also been reported 

 eating small Crustacea and zooplankton (Springer and 

 Woodburn 1960, Harrington and Harrington 1961, 

 Bryan 1971, Fore and Schmidt 1973, Gilmore et al. 

 1983). Field studies of juvenile snook in Tampa Bay 

 suggest that feeding occurs during daytime hours 

 (McMichael et al. 1 989). Adults consume mostly fish, 

 crabs, and shrimp, but crayfish, and some plant tissue 

 are also utilized (Marshall 1958, Fore and Schmidt 

 1973). Fish constitute the most important component 

 with the following reported from diet studies: menha- 

 den, mojarras, mullet, pinfish and other sparids, an- 

 chovies, pigfish, sailfin and other mollys, western 

 mosquitofish and other Gambusia species (Marshall 

 1 958, Bryan 1 971 , Odum 1 971 ). Crabs found in adult 

 snook stomachs are mostly from the family Portunidae 

 and include blue crab (Callinectes sapidus), C. ornatus, 

 Portunus gibbesii, and P. sayi. Mud crabs (Xanthidae) 

 and hermit crabs (Paguridae) are also part of the 

 common snook's diet (Fore and Schmidt 1973). 



Biological Interactions 



Predation : It is during the larval and juvenile stages that 

 the common snook is vulnerable to predation by other 

 piscivorous species (Seaman and Collins 1983). 



Factors Influencing Populations : Habitat requirements 

 and temperature are probably the most important 

 factors determining the range of snook in U.S. waters 

 (Cooley 1974, Ager et al. 1976, Hoese and Moore 

 1977). The preferred habitats, mangrove and salt 

 marshes, are not extensive in the northwestern Gulf of 

 Mexico which, along with the need for relatively warm 

 temperatures, probably accounts for the relative scar- 

 city of this species. This habitat is similar to that of the 

 tarpon, Megalops atlanticus, which, like the snook, is 

 declining in numbers, giving support to the hypotheses 

 of habitat destruction and/or environmental change as 

 factors in their decline (Marshall 1958, Rivas 1962, 

 Odum 1971, Cooley 1974, Hoese and Moore 1977, 

 Peterson and Gilmore 1991). Interaction with other 

 species include habitat overlapping and parasitism. 

 Possible competition may exist between snook and 

 associated fish such as tarpon, ladyfish, spotted 

 seatrout, silver perch, and bank sea bass (Linton and 

 Rickards 1965). An unidentified nematode has been 

 reported parasitizing the mesentery and stomach wall 

 of snook, but apparently with no ill effects (Marshall 

 1958). Other reported parasites are Philometra 

 centropomi in the nasal mucosa and Prosthenhystera 

 obesa in the gall bladder (Seaman and Collins 1983). 

 Snook have also been identified as a host for 

 Lymphocystisvirus. Larval recruitment and/or juvenile 

 survival may be enhanced by increased upland runoff 

 or marsh flooding (Tilmant et al. 1 989). The presence 

 of juveniles in low salinity areas may be a survival 

 adaptation to exploit areas that are largely free of 

 piscine predators (Fore and Schmidt 1 973). The Texas 

 Parks and Wildlife Department, in cooperation with 

 Texas A&M University and the University of Texas, has 

 been experimenting with hatchery propagation of snook 

 as a means to stock Texas bays (Vega pers. comm.). 

 Studies of hatchery rearing of snook have also been 

 conducted in Florida (Mote 1993). 



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