Spotted seatrout, continued 



Age and Size of Larvae : In one laboratory study, larvae 

 grew from a standard length (SL) of 1 .5 mm at hatching 

 to 4.5 mm SL in 15 days at about 25°C (Fable et al. 

 1978). Peebles and Tolley (1988) report growth rates 

 for larval spotted seatrout in south Florida to be ap- 

 proximately 0.4 mm/day. Larval stage sizes range 

 from about 1 .8 to 1 0-1 2 mm TL (Johnson 1 978). 



Juvenile Size Range : Transformation to the juvenile 

 stage occurs at a length of 1 - 1 2 mm (Ditty and Shaw 

 1994). Juveniles range from 10-1 2 to 180-200 mmTL 

 (Johnson 1978). Juvenile growth rates during the fall 

 are about 1 3 to 1 8 mm/month (McMichael and Peters 

 1 989). Along the Gulf coast of Florida, spotted seatrout 

 have been reported to reach 30 1 -337 mm TL at the end 

 of their first year, but growth slows after age I (Murphy 

 and Taylor 1994). Hatchery-reared juveniles have 

 been reported to reach 160 mm TL in 100 days (Van 

 Hoose 1 987). Size at maturity varies among estuaries 

 (Mercer 1984). Spotted seatrout mature between one 

 and three years of age with males tending to mature at 

 smaller sizes than females. 



Age and Size of Adults : Maturity and spawning may 

 first occur at 2 years of age (Pearson 1929), but they 

 can occur at the end of their first year (Lassuy 1983). 

 Males mature as early as theirfirstyearand females by 

 the end of the second year (Klima and Tabb 1959). 

 Some females mature as early as 271 mm SL in Texas, 

 and they are generally all mature by 300 mm SL 

 (Brown-Peterson et al. 1 988). Males are much smaller 

 than females at maturity with all fish 200 mm SL and 

 longer being mature. In a northwest Florida study, 50% 

 of females 200-220 mm FL and 90% of females 220- 

 240 mm FL were mature, all of which were age I 

 (DeVries et al. 1995). Seventy of 73 males, all age I, 

 were found to be mature. There is some variation in 

 growth rate of spotted seatrout throughout its range 

 (Benson 1982), and this variation may be due to 

 ecological rather than genetic factors (Murphy and 

 Taylor 1 994). In Florida, estimated maximum ages are 

 6 to 8 years for females and 5 to 9 years for males 

 (Murphy and Taylor 1994). Adults up to 15 years old 

 have also been reported (Mercer 1984). 



Food and Feeding 



Trophic Mode : The spotted seatrout is an opportunis- 

 tic, visual carnivore that feeds near the surface and in 

 mid-water depths. It feeds mainly in seagrass areas, 

 and relies almost solely on free swimming organisms 

 for food (Darnell 1958, Stewart 1961, Vetter 1977). 



Food Items : The diet of the spotted seatrout changes 

 as it grows and with the seasonal abundance of food 

 items (Pearson 1929, Gunter 1945). Larvae feed 

 primarily on zooplankton, especially copepods, and 

 switch to mostly benthic invertebrates as small juve- 



niles. Juveniles have been found to consume: plank- 

 tonic schizopods, mysids, copepods, isopods, amphi- 

 pods, gastropods, bivalves, caridean and penaeid 

 shrimp, and fish (Stewart 1 961 , Hettler 1 989, McMichael 

 and Peters 1989). Juveniles <30 mm SL consume 

 amphipods, mysids and carideans in equal proportions 

 (Hettler 1989). The single most important food for 

 juveniles >30 mm SL was shrimp. Fish increase in 

 dietary occurrence as juveniles reach 50 mm SL and 

 larger, and can comprise almost 90% of the volume in 

 individuals 105-120 mm SL. Fish species consumed 

 include: bay anchovy, gulf menhaden, shad (Dorosoma 

 sp.), silversides (Menidia sp.), striped mullet, sheeps- 

 head minnow, rainwater killifish (Lucania parva), gulf 

 toadfish (Opsanus beta), inshore lizardfish(Synodus 

 foetens), pipefish (Syngnathus sp.), pinfish, pigfish 

 (Orthopristeschrysopterus), silverjenny (Eucinostomus 

 gula), gray snapper, unidentified snappers (Lutjanus 

 sp.), hardhead silverside (Atherinomorus stipes), 

 goldspotted killifish (Floridichthys carpio), code goby 

 {Gobiosoma robustum), naked goby (G. bosci), clown 

 goby (Microgobiusgulosus), Atlantic croaker, and spot- 

 ted seatrout. Young adults prey on a variety of inver- 

 tebrates and fish, changing almost exclusively to fish 

 as large adults (Gunter 1945, Darnell 1958, Seagle 

 1969, Danker 1979, Levine 1980, Hettler 1989, 

 McMichael and Peters 1989). Some marine vegeta- 

 tion and shell fragments have been noted that were 

 probably picked up while capturing prey (Tabb and 

 Manning 1 961 ). The diets of larger juveniles and adults 

 are skewed to the consumption of shrimp in the warmer 

 months and fish in the cooler months when shrimp are 

 not as available (Pearson 1929, Gunter 1945). Varia- 

 tions in food habits indicates that geographical location 

 and type of estuary influences available prey, and that 

 spotted seatrout stomach contents reflect this avail- 

 ability (Hettler 1989). 



Biological Interactions 



Predation : Known predators of juvenile spotted seatrout 

 include alligator gar (Lepisosteus spatula), striped 

 bass (Morone saxatilis), ladyfish (Elops saurus), tar- 

 pon, bluefish, silver perch, Atlantic croaker, snook, 

 yellow bass (Morone mississippiensis), spotted 

 seatrout, barracuda (Sphyraena barracuda), Spanish 

 mackerel, and king mackerel (Scomberomorus cav- 

 alla) (Miles 1 949, Darnell 1 958, Benson 1 982, Killam et 

 al. 1992). 



Factors Influencing Populations : Species that may 

 possibly compete with spotted seatrout for habitat and 

 food include hardhead cattish, grouper (Mycteroperca 

 sp.), silver perch, red drum, spot, and Atlantic croaker 

 (Killam et al. 1992). Distribution and abundance of 

 juvenile spotted seatrout in Florida Bay appears to be 

 influenced by the biomass, shoot density, and species 

 composition of the seagrass community (Shipp 1986, 



263 



