Tarpon, continued 



ber) was 230 mm, corresponding to a size-specific 

 growth rate of 0.5% SL/day April to September, and 

 0.11 SL/day September to February. The body is 

 opaque at 25.2 mm SL with pigment mostly above the 

 lateral line. Scale formation begins along the lateral 

 line at about 29.7 mm SL (Harrington 1966), and the 

 lateral pores are visible at 51.0 mm SL (Wade 1962). 

 By at least 1 40 mm SL two specialized ray scales cover 

 the uppermost and lowest caudal rays (Jones et al. 

 1978). At 194.1 mm SL, the filamentous ray of the 

 dorsal becomes grooved on the underside, the anal 

 ray has a scaly sheath and the last ray is produced. The 

 caudal fin is scaly (Wade 1962, Jones et al. 1978). 

 Juveniles become darker dorsally with age (Harrington 

 1958). 



Age and Size of Adults : From 1988 through 1993, 

 Crabtree et al. (1995) examined 1,469 juvenile and 

 adult tarpon from south Florida, ranging from 102 to 

 2,045 mm fork length (FL), and estimated their ages 

 based on otoliths. All fish older than ten years were 

 sexually mature. All males were sexually mature by 

 1,175 mm FL, but the smallest mature female was 

 1,285 mm FL (Cyr pers. comm.). Tarpon are long- 

 lived, with ages of males estimated at to 43 years, and 

 females at to 55 years. Growth is rapid until age 1 2, 

 after sexual maturity is attained, then slows consider- 

 ably. For any given age greater than four years, 

 females tend to be larger than males. It has been 

 suggested that tarpon scales are not appropriate for 

 age estimation, as they would indicate a maximum age 

 of only 15 years. A VonBertalanffy growth equation 

 based on otolith age estimates more accurately pre- 

 dicts the known maximum size of tarpon. Ages 

 exceeding 50 years have been reported in captive fish 

 (Killam et al. 1992). Crabtree et al. (1995) examined 

 eighteen captive tarpon with oxytetracycline-marked 

 otoliths, and found growth rates that varied from 95 mm 

 in 20 months, to 235 mm in 21 months. Crabtree et al. 

 (in press) estimated the ages of 87 tarpon from tropical 

 Costa Rican waters, and reported that most were 1 5 to 

 30 years old, with a maximum age of 48 years. The 

 Costa Rican tarpon sampled were significantly smaller 

 than Florida tarpon, and apparently reached maturity 

 at a smaller size. 



Food and Feeding 



Trophic Mode : The tarpon is strictly carnivorous, prey- 

 ing on a wide variety of animal species (Wade 1 962, de 

 Menezes and Paiva 1966, Odum 1971). Feeding 

 begins in Stage II larvae (Mercado and Ciardelli 1 972). 



Food Items : Metamorphic larvae and small juveniles 

 are primarily plankton feeders, preying on copepods 

 (cyclopoid and harpacticoid), mosquito larvae, and 

 detritus (Randall 1 959, Harrington and Harrington 1 960, 

 Harrington and Harrington 1961, Wade 1962, Odum 



1971). Large juveniles (>45 mm SL) begin gradually 

 switching from copepods to small fish such as killi- 

 fishes (Fundulussp.), mosquitofish (Gambusiaaffinis), 

 silversides (Membras martinica and Menidia sp.), and 

 mullet (Mugil sp.), and to caridean shrimp, ostracods, 

 and insects (Simpson 1 954, Harrington and Harrington 

 1 960, Harrington and Harrington 1 961 , Tabb and Man- 

 ning 1961, Hildebrand 1963, Rickards 1968, Odum 

 1 971 ). Adults are strictly carnivorous and feed prima- 

 rily on mid-water prey (Killam et al. 1992). They are 

 predominately piscivorous with fish composing up to 

 95% of their total food volume (Harrington and 

 Harrington 1961). Fish prey includes such species as 

 mullet, marine catfishes (hardhead and gafftopsail), 

 pinfish, sunfish (Lepomis species), sardines, needle- 

 fish, silversides, cutlassfish (Trichiurus lepturus), and 

 anchovies. Shrimp are also an important diet compo- 

 nent. Otherfood items include insects, blue crabs, and 

 ctenophores (Gunter 1945, Miles 1949, Harrington 

 and Harrington 1961, Wade 1962, Hildebrand 1963, 

 Rickards 1968, Odum 1971). 



Biological Interactions 



Predation : Predation of adults is limited to other large 

 predators such as sharks, porpoises, and alligators, 

 while the young fall victim to a variety of fish, including 

 ladyfish (Elopssaurus), spotted seatrout, othertarpon, 

 and to piscivorous birds that include kingfishers, peli- 

 cans, and herons (Randall 1959, Wade 1962, 

 Hildebrand 1963, Rickards 1968, Killam et al. 1992). 



Factors Influencing Populations : Althoughjuvenileand 

 adult tarpon are able to penetrate coastal freshwater 

 habitats, they are sensitive to low temperatures and 

 may be susceptible to fish kills during winter months 

 (Loftus and Kushlan 1987). The development of wet- 

 land areas utilized as nursery habitat by tarpon to 

 provide marketable real estate, highway and bridge 

 construction, etc. may be impacting juvenile survival 

 and recruitment (Randall 1959, Robins 1978). The 

 impoundment of estuarine areas for mosquito control 

 has reduced available habitat for juveniles and may 

 also be affecting recruitment (Cyr 1991, Killam et al. 

 1992). The tarpon is very sensitive to chemicals, and 

 the wide-spread use of pesticides may have a negative 

 impact on this species (Robins 1 978). Possible com- 

 petition may exist between tarpon and such frequently 

 associated species as common snook, spotted seatrout, 

 and ladyfish (Wade 1962, Rickards 1968). Recorded 

 parasites include: isopods (Cymothoa destrum, Nercilia 

 acuminata), remoras (Echeneis naucrates), copepods 

 (Paralebion pearsei), trematodes (Bivescula tarponis), 

 and parasites of the family Hemiuridae (Wade 1962). 



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