Spanish mackerel, continued 



Juvenile Size Range : Juveniles range from 1 3.5 to 225 

 mm TL in size. Eight preopercular spines are present 

 at 1 4 mm TL, and two at 22-25 mm TL (Fritzsche 1 978, 

 Lukens 1989). Females mature at lengths ranging 

 from 250 mm to 450 mm FL, while males can reach 

 maturity anywhere from 209 mm to 336 mm FL. The 

 longest immature fish were a 320 mm FL female and a 

 340 mm FL male. Some age class fish reach sexual 

 maturity, but 100% maturity of a cohort is not reached 

 until at least age class II for males and age class III for 

 females. The majority of spawning fish is probably 

 made up of age class III fish >350 mm FL (Powell 1 975, 

 Helser and Malvestuto 1 987, Lukens 1 989, Schmidt et 

 al. 1993). 



Age and Size of Adults : The average weight range of 

 fish taken by recreational and commercial anglers is 

 0.7-1.8 kg, with most larger fish averaging about 4-5 

 kg. The maximum reported weight is 1 1 kg (Pew 1 966, 

 Meaburn 1978, Benson 1982). Growth rates among 

 adults are rapid until year 5 in females and year 6 in 

 males, and then slow appreciably (Fable et al. 1987). 

 Females reach up to 802 mm FL and grow faster than 

 males which have been recorded up to 723 mm FL 

 (Collette and Ftusso 1978, Fable et al. 1987). Maxi- 

 mum life spans reported for Spanish mackerel have 

 been 1 1 years for females and 7 years for males 

 (Collette and Russo 1978, Fable et al. 1987, Schmidt 

 etal. 1993). However, males have been reported up to 

 10 years in Florida (DeVries pers. comm.). It is be- 

 lieved that females generally live longer than males 

 (Fable et al. 1 987). Von Bertalanffy growth equations 

 have been developed from otolith samples for male 

 and female Spanish mackerel (Helser and Malvestuto 

 1987, Schmidt etal. 1993). 



Food and Feeding 



Trophic mode : The Spanish mackerel is a fast moving 

 surface feeder in pelagic waters, and is primarily pis- 

 civorous (Finucane et al. 1990). 



such as nudibranch larvae, amphipods, penaeid shrimp, 

 and euphausiids. Older juveniles and adults prefer 

 various small fish which can form up to 100% of their 

 diet. Juveniles and small adults (70-420 mm FL) prey 

 chiefly on various anchovies, and also herrings and 

 wrasses. Larger adults (525-675 mm FL) consume 

 other fishes mainly herrings and jacks (Saloman and 

 Naughton 1983, Lukens 1989, Finucane et al. 1990). 

 Spanish mackerel probably become more opportunis- 

 tic as they increase in size with food items varying 

 according to availability. Other animals such as squid, 

 crabs, and shrimp can become important diet compo- 

 nents at this point (Saloman and Naughton 1 983, Pew 

 1966, Rice 1979, Benson 1982). Fish that are preyed 

 on include: sciaenids, alewife, flatfish, menhaden, 

 cutlassfish (Trichiurus lepturus), scaled sardine 

 (Harengula jaguna), Atlantic thread herring 

 (Opisthonema oglinum), Spanish sardine (Sardinela 

 aurita), striped muilet and other mullet, needlefish 

 (Strongylura spp.), jacks (Caranx spp.), lookdown 

 (Selene vomer), inland silverside (Menidia beryllina) 

 and other silversides, striped anchovy (Anchoa 

 hepsetus) and other anchovies, butterfish (Peprilus 

 triacanthus), northern harvestfish (Peprilus paru), spa- 

 defish (Chaetodipterus faber), silver perch, and round 

 scad (Decapturas punctatus) (Earll 1883, Kemp 1949, 

 Breuer 1949, Knapp 1949, Miles 1949, Simmons and 

 Breuer 1964, Pew 1966, Rice 1979, Naughton and 

 Saloman 1981, Lukens 1989, Finucane et al. 1990). 

 Anchovies may be more important in juvenile diets 

 because of their smaller size being more easily swal- 

 lowed by the smaller juvenile mackerel mouth parts 

 (Naughton and Saloman 1981). Important inverte- 

 brate components include various penaeid shrimp 

 (white, pink, and brown shrimp), sealice (Squilla sp.), 

 grass shrimp (Palaemonetes sp.), sand shrimp 

 (Crangon sp.), squid (Loligo sp.), swimming crabs 

 (Portunidae), and mud crabs (Xanthidae) (Kemp 1 949, 

 Miles 1949, Naughton and Saloman 1981, Saloman 

 and Naughton 1983). 



Food Items : The Spanish mackerel is a fast moving 

 voracious predator. They usually feed in loose schools, 

 and feed on schooling prey that occupy the same 

 pelagic habitat, including herrings and sardines 

 (Clupeidae), jacks (Carangidae), anchovies 

 (Engraulidae), and squids (Saloman and Naughton 

 1 983, Shipp 1 986 Lukens 1 989, Finucane et al. 1 990). 

 Shallow continental shelf waters are the favored feed- 

 ing areas, but the mackerel will occasionally forage in 

 the lower, saltier portions of estuaries. Larvae and post 

 larvae are principally piscivorous (Finucane etal. 1990). 

 Larval jacks, herrings, and anchovies occur frequently 

 in larval mackerel stomach contents. Other fish spe- 

 cies consumed by mackerel larvae include: 

 lanternfishes, flatfishes, and puffers. Fish eggs were 

 also found to be a food item as well as invertebrates 



Biological Interactions 



Predation : This species is a major prey item of sharks, 

 including bull shark, dusky shark (C.obscurus), smooth 

 hammerhead (Sphyrna zygaem), porbeagle (Lamna 

 nasas), tiger shark (Galeocerdo cuvierf); and also of 

 dolphins (Tursiops truncatus) (Kemp 1949, Lukens 

 1989). 



Factors Influencing Populations : A potential exists for 

 damage of eggs and larvae present near the water 

 surface by oil pollution (Lukens 1 989). The popularity 

 of this species as a food and game fish may have 

 contributed to a decline in its abundance. 



324 



