Gray snapper, continued 



develop rapidly and hatch in about 1 8 hours in ambient 

 seawater (Grimes 1 987). Eggs hatch in the vicinity of 

 offshore reets. 



Age and Size of Larvae : Larval development takes 

 place offshore near spawning sites (Richards et al. 

 1984, Kelly et al. 1986, Powell et al. 1987). Newly 

 hatched larvae absorb their yolk sac within 45 hours 

 (Grimes 1987). Richards and Saksena (1980) gave 

 growth rates of continually fed larvae as 2.7-2.8 mm 

 notocord length (NL) (4 days), 3.0-3.1 mm NL (5 days), 

 3.4 mm NL (7 days), 4.1-4.2 mm NL (9 days), 6.2 mm 

 SL (15 days), 9.6-12.5 mm SL (26 days) and 15.4 mm 

 SL (36 days). The flexion stage occurs at about 4.2 mm 

 SL, and post-flexion at 6.2 mm SL. Larvae are sparsely 

 pigmented. 



Juvenile Size Range : The juvenile stage begins at 12 

 mm SL. They are heavily pigmented and can be 

 identified by a full complement of meristic characters 

 (Richards and Saksena 1 980). Springerand Woodburn 

 (1960) reported mean lengths of Age Class fish for 

 periods of September, November and December 1 957 

 as 33 mm, 42.6 mm and 51.7 mm respectively. The 

 following year they assigned lengths to Age Class 

 fish for October (1 8.2 mm), November (25.3 mm) and 

 December (34 mm). Croker (1962) determined mean 

 fork lengths (FL) using back calculations for age classes 



I through VII as Class I - 81 mm, Class 11-180 mm, 

 Class III - 241 mm, Class IV - 295 mm, Class V - 352 

 mm, Class VI - 431 mm, and Class VII - 456 mm. 

 Different results were obtained in another study, par- 

 ticularly in the later age classes: Class I - 79 mm, Class 



II - 143 mm, Class III - 199 mm, Class IV - 255 mm, 

 Class V - 293 mm, Class VI - 334 mm, Class VII - 381 

 mm, Class VIII - 438 mm, and Class IX - 478 mm 

 (Starck and schroeder 1 971 ). Growth rates of 1 26 + 2 

 mm for the first year and 48-62 mm/year for fish one to 

 fouryears of age have been reported (Rutherford et al. 

 1983). 



Age and Size of Adults : Using sectioned otoliths, 

 Manooch and Matheson (1984) calculated TL for fish 

 up to 19 years of age. Their results were similar to 

 those of Croker (1962). A length of 772 mm was 

 determined for 1 9 year old fish. The oldest specimen 

 they observed was a 775 mm fish, 21 years old. Starck 

 and Schroeder (1 971 ) suggest a maximum weight for 

 the gray snapper at around 8 kg but stated that fish over 

 3.6 kg were rare. Maturity is reached at about 200 mm 

 TL, probably during the third year (Starck and Schroeder 

 1971). In one study, the smallest female observed 

 spawning was 195 mm SL and the smallest ripe male 

 was 185 mm SL (Starck and Schroeder 1971, Hardy 

 1978). Johnson et al. (1994) collected adult gray 

 snapper from Gulf of Mexico commercial and recre- 

 ational fisheries, with a length range of 236 to 764 mm 



TL, and an estimated age range of one to 25 years. 

 Von Bertalanffy growth parameters have been derived 

 for this species (Johnson et al. 1994). 



Food and Feeding 



Trophic Mode : The gray snapper is an opportunistic 

 carnivore at all life stages. 



Food Items : Richards and Saksena (1980) fed zoop- 

 lankton in the 73-110 u.m range in vitro to newly 

 hatched gray snapper larvae. Copepods and amphi- 

 pods are important food items of fish at 10-20 mm 

 (Starck and Schroeder 1971). Juveniles are diurnal 

 feeders that primarily prey on crustaceans, but they 

 also consume fish, molluscs and polychaetes. Very 

 small juveniles (10-20 mm TL) forage primarily on 

 amphipods. Penaeid shrimp dominate the diet of 

 larger juveniles, but a variety of crabs (blue crab, spider 

 crab, mud crabs, and fiddler crabs) are also eaten 

 (Rutherford et al. 1983). Grassbeds appear to be the 

 most important feeding habitat for juveniles and adults 

 (Starck 1971, Harrigan et al. 1989, Hettler 1989). 

 Adults are typically nocturnal predators, consuming 

 fish, shrimp, and crabs. Fish eaten are largely grunts 

 (Haemulon species), but also include killifishes, pipe- 

 fish (Syngnathusspec\es), gulf toadfish (Opsanusbeta), 

 gobies, seahorses (Hippocampus species), and silver 

 jenny (Eucinostomus quia). Algae and marine plants 

 are commonly found, possibly consumed incidentally 

 during routine feeding. Proportions of prey species 

 consumed varies within and among habitats (Rivas 

 1 949, Reid 1 954, Springer and Woodburn 1 960, Tabb 

 and Manning 1 961 , Starck and Davis 1 966, Starck and 

 Schroeder 1 971 , Rutherford et al. 1 983, Harrigan et al. 

 1989, Hettler 1989). 



Biological Interactions 



Predation : Little information on predation of gray snap- 

 per is available, but other carnivorous fishes probably 

 prey on larvae and juveniles. 



Factors Influencing Populations : Abundance and dis- 

 tribution of juveniles appears to be influenced by den- 

 sity and species composition of seagrass (Chester and 

 Thayer 1990). 



231 



