Pinfish, continued 



heavy rains reducing salinity to 4%o have been reported 

 to decrease the abundance of juvenile pinfish in a 

 shallow seagrass bed (Cameron 1969b). In addition, 

 Subrahmanyam and Coultas (1980) positively corre- 

 lated salinity and pinfish abundance. Adult pinfish 

 apparently prefer higher salinity waters and stay mostly 

 in the Gulf or close to Gulf passes (Wang and Raney 

 1971). 



Dissolved Oxygen (DO): The oxygen-carrying capac- 

 ity of pinfish blood is related to environmental condi- 

 tions, increasing with lower dissolved oxygen, higher 

 salinities, and increased activity (Cameron 1 970). The 

 incipient lethal level for this species is a DO content of 

 about 1.1 mg/l (Cameron 1969a). 



Migrations and Movements : Larvae begin to move into 

 estuaries from the marine environment when they 

 reach a total length (TL) of 11 mm (Johnson 1978). 

 Juveniles migrate up into the estuaries during spring 

 and summer. Juveniles rarely leave the protected 

 areas of vegetated flats except at night when they 

 move into the nearby sand flats (Stoner 1979). In 

 addition, when water temperatures exceed 32°C in the 

 flats they move to the cooler, deeper waters of chan- 

 nels. Juveniles and adults migrate out of the estuaries 

 in the fall to their spawning grounds in the mostly 

 deeper Gulf waters (Gunter 1945, Perry 1970). Here 

 they aggregate in size groups. Gunter (1 945) reported 

 that some juveniles remain inshore, while Perry (1 970) 

 found a stable adult population remaining offshore in 

 deep (73-91 m) Gulf waters. 



Reproduction 



Mode : This species has separate male and female 

 sexes (gonochoristic). Fertilization is external, by 

 broadcast of milt and roe into the water column (Cody 

 and Bortone 1992). 



Spawning : Spawning location is probably related to 

 water depth and temperature (Johnson 1978). Most 

 studies in the northern Gulf of Mexico indicate that 

 spawning takes place in the fall and winter (Gunter 

 1 945, Reid 1 954, Caldwell 1 957, Christmas and Waller 

 1 973, Sabins and Truesdale 1 974, Kjelson and Johnson 

 1 976, Johnson 1 978, Lee et al. 1 980, Cody and Bortone 

 1992). 



Fecundity : In one study, a 157 mm TL female from 

 Florida collected in November contained an estimated 

 90,000 eggs (Caldwell 1957). In another study, eight 

 pinfish, with standard lengths (SL) ranging from 1 1 1 to 

 152 mm, spawned an estimated 7,700 to 39,200 (av- 

 eraging from 21,600) eggs (Hansen 1970). A pro- 

 tracted spawning period is considered likely for this 

 species based on gonadosomatic indices (Cody and 

 Bortone 1992). 



Growth and Development 



Egg Size and Embryonic Development : The diameter 

 of pinfish eggs is reported to range from 0.90 to 0.93 

 mm (Schimmel 1977) and 0.99 to 1.05 (Cardeilhac 

 1976). 



Age and Size of Larvae : When observed in a laboratory 

 study, larvae hatched after 48 hours when incubated at 

 1 8°C, and were 2.3 mm TL (Cardeilhac 1 976, Johnson 

 1 978). The yolk sac, visible for 24 hours after hatching, 

 was completely absorbed when the larvae reached 2.7 

 mm TL. Larval development is complete when indi- 

 viduals reach 12.0 mm SL (Zieske 1989). Zieske 

 (1989) thoroughly describes pinfish larvae and early 

 juveniles. 



Juvenile Size Range : Juveniles range in size from 15 

 mm TL (12 mm SL) to 100 mm TL or more (Hansen 

 1970, Zieske 1989). 



Age and Size of Adults : The majority of pinfish become 

 sexually mature from 80 to 1 00 mm TL (Hansen 1 970, 

 Johnson 1 978). This usually occurs during the spawn- 

 ing migration or at the offshore spawning grounds 

 (Hansen 1970). Adults average growth increments of 

 80 mm SL after the first year, 50 mm SL after the 

 second, and 45 mm SL after the third (Caldwell 1 957). 

 Most adults are greater than 110 mm TL in size. 



Food and Feeding 



Trophic Mode : Pinfish are voracious predators as 

 juveniles and subadults (Carr and Adams 1 973, Stoner 

 1979). Adults are reported to be omnivorous (Stoner 

 1980). 



Food Items : Juveniles feed primarily on shrimps, mysids, 

 and amphipods (Carr and Adams 1 973, Stoner 1 979, 

 Levine 1980, Schmidt 1993). The diet of adults is 

 similar to juveniles, but has a large component of plant 

 material (Stoner 1980). Weinstein et al. (1982) have 

 reported cellulose digestive activity. Other reported 

 food items are: fish eggs, insect larvae, decapod crabs, 

 bivalve molluscs, and polychaetes (Levine 1980, 

 Schmidt 1993). 



Biological Interactions 



Predation : Pinfish are an important forage item for 

 many fish species (Darcy 1 985). Known piscine preda- 

 tors include alligator gar (Lepisosteus spatula), \ongnose 

 gar (Lepisosteus osseus), ladyfish (Elops saurus), 

 spotted seatrout, red drum, bighead searobin (Prionotus 

 tribulus), southern flounder, and gulf flounder (Gunter 

 1945, Kemp 1949, Darnell 1958, Diener et al. 1974, 

 Muncy 1984, Rozas and Hackney 1984). Pinfish are 

 also preyed on by bottle-nosed dolphin (Tursiops 

 truncatus) (Kemp 1949). 



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