Spanish mackerel, continued 



1 980). In the western Gulf, spring migration apparently 

 occurs as schools move to the north and east along the 

 coast (Wollam 1970, Benson 1982). This movement 

 also terminates in the northern Gulf of Mexico, with 

 abundant numbers off Alabama and Mississippi from 

 April through late fall, and in Texas from March to 

 October with an August peak (Gunter 1945, Springer 

 and Pirson 1 958, Pew 1 966, Franks et al. 1 972, Helser 

 and Malvestuto 1987). Movement in the fall is back 

 southward beginning about September (Gunter 1945, 

 Wollam 1 970, Benson 1 982). The wintering ground for 

 both eastern and western fish is believed to be in the 

 Campeche-Yucatan area (Sutherland and Fable 1 980, 

 Johnson 1 981 ). Fish are caught throughout the year, 

 indicating that some fish move offshore during cold 

 weather and do not migrate (Perret et al. 1971, Moe 

 1972, Christmas and Waller 1973). 



Reproduction 



Mode : This species has separate male and female 

 sexes (gonochoristic). Fertilization is external, by 

 broadcast of milt and roe into the water column (Berrien 

 and Finan 1977). Development is oviparous. 



Spawning : The onset of spawning probably varies with 

 latitude, with fish in the northern part of the range 

 ripening later than those in the southern part (Berrien 

 and Finan 1977). Active and ripening oocytes are 

 present throughout the spring and summer (April 

 through mid-September) in Florida, with spawning 

 probably occurring May through September (Klima 

 1959, Moe 1972, Powell 1975, Berrien and Finan 

 1977, Schmidt et al. 1993). In the western Gulf of 

 Mexico, developing gonads are seen May through 

 September when water temperatures reach 22°C, and 

 spent individuals become increasingly abundant from 

 July to September (Earll 1883, Hoese 1965, Wollam 

 1970, Rice 1979, Finucane and Collins 1986, 

 Lyczkowski-Shultz 1 987). Some spawning may occur 

 in April or October and spawning throughout the year 

 is considered possible in Florida (Finucane and Collins 

 1986). Based on the presence of larval Spanish 

 mackerel in the northern Gulf of Mexico, it can be 

 inferred that spawning occurs April through October, 

 with a peak from August to September (Ditty 1986, 

 Ditty etal. 1988). Spawningcanoccurdayornightwith 

 multiple spawnings possible over a prolonged season 

 (Ryder 1 882, Klima 1 959, Powell 1 975, Benson 1 982, 

 Collette and Nauen 1983, Lyczkowski-Shultz 1987). 

 Spawning takes place in inner shelf waters probably in 

 the vicinity of barrier islands and passes at depths of 1 2 

 to 1 8 m. Spawning also occurs occasionally over the 

 middle and outer shelf, possibly as deep as 200 m 

 (McEachran and Finucane 1978, Benson 1982). 

 Spawning temperatures range from 21 to 31 °C, but are 

 usually in excess of 22°C and seldom below 18°C 

 (Hoese 1965, Benson 1982). Salinities for spawning 



range from 30 to 36.5%, (Hoese 1965, Benson 1982). 

 Peak spawning seems to be during June through 

 August with the eastern and northeastern Gulf of 

 Mexico probably being the most important spawning 

 area (Klima 1 959, Moe 1 972, McEachran and Finucane 

 1978). There is some evidence of spawning near 

 Mississippi Sound (Lukens 1989). 



Fe cund ity: This species is a fractional spawner (Berrien 

 and Finan 1977). Fish in south Florida are sexually 

 mature in their second or third year of life according to 

 otolith annulations counted in one study (Klima 1 959). 

 Another investigator considers these observations to 

 have been overestimated by one year; therefore, fish 

 less than 1 year old may have been mature (Powell 

 1 975). Many class I fish observed had ripe oocytes, but 

 examinations made of these fish during the spawning 

 season suggested eggs were not advanced enough to 

 be spawned that season. Spanish mackerel are prob- 

 ably not fully mature until age class II with the bulk of the 

 spawning population composed of class III and older 

 fish (Powell 1975, Lukens 1989). Fecundity increases 

 with length and weight (Earll 1883, Godcharles and 

 Murphy 1986). Estimates of fecundity are 1.5 million 

 for a 2.7 kg female while a 0.45 kg fish had an estimated 

 300,000 eggs (Earll 1883). Fecundity ranges from 

 100,000 to 2,000,000 eggs for fish ranging 295 to 

 >2,415 g and with fork lengths (FL) of 312 mm to 626 

 mm (Berrien and Finan 1977, Finucane and Collins 

 1986). 



Growth and Development 



Egg Size and Embryonic Development : Development 

 is oviparous. Eggs are buoyant, transparent and 

 smooth with a single oil droplet 0.25 mm in diameter. 

 They are round in shape and 0.91 -1 .1 5 mm in diameter 

 (Earll 1883, Ryder 1882, Benson 1982). The perivi- 

 telline space is approximately 0.1 mm across. Hatch- 

 ing is primarily during summer months and occurs 

 about 25 hours after fertilization at 26°C (McEachran 

 and Finucane 1978, Fritzsche 1978, Godcharles and 

 Murphy 1986). 



Age and Size of Larvae : The larval stage lasts from 

 2.56 to 1 3 mm TL. Larvae are 2.56 mm TL or 2.0 mm 

 standard length (SL) at hatching and attain 2.8 SL 

 within 3 days (Fritzsche 1 978, McEachran and Finucane 

 1978). Other investigators have reported preserved 

 specimens ranging in size from 1.6 to 11.8 mm SL 

 (Richardson and McEachran 1 981 , Lyczkowski-Shultz 

 1 987). The yolk sac is absorbed by 3. 1 8 mm TL on the 

 fourth day (Wollam 1970, Fritzsche 1978). Larval 

 growth rate has been estimated as 1.15 mm/day 

 (DeVries et al. 1990). 



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