dorsal fin is greenish in color and concave, originating slightly in front of the anal fin, which is similarly shaped and equivalent in size.  A series of 7 - 10 (usually 8) finlets lie posterior to both the second dorsal fin and the anal fin (Collette and Nauen 1983). The lateral line curves slightly downward towards the caudal peduncle.  The caudal fin is high and lunate, with a narrow caudal peduncle that has a keel.  The pectoral fins are relatively long and lack scales.  Body color is typically dark blue to blue-green dorsally, silver laterally.  The sides are marked with small, yellow to orange oblong spots above the lateral line.  The pectoral fins are pale yellow with orange-brown edges, while the anal and ventral fins are white (Berrien and Finan 1977ab). 

Synonymy:
Scomber maculates Mitchill, 1815;   Cybium maculatum Cuvier, 1829

Potentially Misidentified Species:
The Spanish mackerel is potentially confused with both the cero,  Scomberomorus regalis, and the king mackerel, S. cavalla.  It is easily distinguished from the king mackerel by its oblong yellowish spots above the lateral line, which does not curve downward at the second dorsal fin as is observed in king mackerel.  The cero is distinguished from the Spanish mackerel by 1 - 2 thin, bronze-colored stripes that run mid-laterally along the body, and by scales on the pectoral fins, a feature absent from both Spanish and king mackerels (Collette and Nauen 1983).

Meristic counts of some key identifying traits:

II.  HABITAT AND DISTRIBUTION 

Regional Occurrence:
In the western Atlantic, Scomberomorus maculatus inhabits coastal waters from the Gulf of Maine to the Yucatan Peninsula (Collette et al. 1978; Godcharles and Murphy 1986).  During the summer months, they are commonly found as far north as Chesapeake Bay, while in fall and winter, they are most common in the waters off central and southern Florida.  Spanish mackerel typically come closer to beaches and enter the lower reaches of estuaries more often than do king mackerel (Godcharles and Murphy 1986). 

Spanish mackerel from as many as 6 geographic areas may mix in the waters off south Florida in the winter months, however, electrophoretic evidence suggests that the Atlantic and Gulf of Mexico populations spawn in the northern parts of their respective ranges, in isolation from other populations (Wollam 1970).  Further, the Gulf population is distinct from Spanish mackerel captured along the eastern U.S. coast (Skow and Chittenden 1981).

IRL Distribution:
Though not considered common within the IRL, adult Spanish mackerel are sometimes observed around inlet areas.  Juveniles may utilize seagrasses as nursery habitat.

III. LIFE HISTORY AND POPULATION BIOLOGY

Age, Size, Lifespan:
Spanish mackerels live approximately 5-8 years (Kilma 1959;  Powell 1975) and may weigh over 12 pounds.  Males reach approximately 50 cm fork length (FL), while females reach 70 cm FL (Johnson et al. 1983; Godcharles and Murphy 1986).  Powell (1975) reported that females grow faster than males, and that fish of the same age tend to be smaller in the Gulf of Mexico than in the South Atlantic.  Schmidt et al. (1993) reported that females live longer and grow larger that males.

Abundance:
Spanish mackerels are not abundant inside the IRL except near inlet mouths; however, they are known to aggregate in large numbers in offshore waters and support a commercial fishery. 

Locomotion:
Though scombrid fishes are known for high performance locomotion, data are limited on the precise mechanisms that enhance their swimming abilities. Thrust is generated with lift-based swimming whereby the narrow caudal peduncle and high, lunate caudal fin produce more than 90% of the thrust, with few significant lateral movements in other areas of the body.   It has been hypothesized that the finlets on the posterior dorsal and ventral surfaces of scombrids aid locomotion, and may, in fact, be accessory locomotor structures that act to deflect water longitudinally to the area of the keels, where flow is then accelerated (Walters 1962).  A study by Nauen and Lauder (2001) supported this hypothesis and showed that finlets do redirect cross-peduncle flow in the horizontal plane.

Reproduction:
Spanish mackerel have an extended spawning season (Powell 1975, Schmidt et al. 1993), with ripe females collected from April through September in Florida.  Larvae are collected from May through September at locations between Cape Canaveral, Florida north to Cape Fear, North Carolina.   Spawning season begins in April in the Carolinas, June in Chesapeake Bay, and August - September in New Jersey and New York (Earll, 1883).  Water temperatures in excess of 25ºC, and salinity between 30 – 36 parts per thousand (ppt) are spawning triggers (Hoese 1907;  Beaumariage 1970).  Larval collection data indicate that spawning occurs at depths of 12-35 meters over the inner continental shelf (McEachran et al 1980). 

Female Spanish mackerel mature in Florida waters by approximately Age 1, when they reach 25 – 35 cm FL.  Males mature at a slightly smaller size (Schmidt et al. 1993).  Fecundity increases with increasing length and weight (Finucane and Collins unpublished in: Godcharles and Murphy 1986), with  females between 35 – 66 cm FL producing between 194,000 to 1.5 million eggs. 

Embryology:
Pelagic eggs measuring  0.9 – 1.3 mm in diameter are round and transparent, containing a single oil droplet.  Hatching occurs approximately 25 hours after fertilization at water temperatures averaging 26ºC (Smith 1907).

Larvae and early juveniles grow 1.9 mm per day for approximately the first 23 days of life.  From 23 - 40 days, growth is accelerated, with young fishes growing as much as 5 mm per day. Thereafter, growth slows to approximately 2.1 mm per day (Schmidt et al. 1993, Peters and Schmidt 1997).   

IV.  PHYSICAL TOLERANCES

Temperature:
Earll (1883) reported that Spanish mackerel are rarely reported from waters cooler than 18ºC.  They are typically collected from waters ranging from 21 - 31 ºC (70 - 88 ºF). Water temperatures in excess of 25ºC triggers spawning in Spanish mackerel (Hoese 1907;  Beaumariage 1970). 

Temperature and salinity are governing factors in the geographic distribution of mackerels, with the northern range of Spanish mackerel extending to the 20ºC isotherm within the 18m depth contour (Munro 1943;  Berrien and Finian 1977a). 

Salinity:
All life history stages of Spanish mackerel typically inhabit waters where salinity fluctuates between 32 – 36 ppt. (Godcharles and Murphy 1986).  Spanish mackerel tend to avoid both freshwater and low salinity waters near river mouths (Earl 1883), though it has been documented that some juveniles inhabit waters where salinity has dropped below 18 ppt (Springer and Woodburn 1960). 

Juveniles are collected from low salinity (12.8 – 19.7 ppt) estuaries as well as from high salinity beaches, suggesting that at least some Spanish mackerel utilize estuaries as nursery grounds (Springer and Woodburn 1960).

V.  COMMUNITY ECOLOGY

Trophic Mode:
Spanish mackerel are schooling pelagic carnivores that feed primarily on estuarine-dependent species such as menhaden (Brevoortia sp.) and anchovies (Anchoa), with squid being the most prevalent invertebrate prey (Godcharles and Murphy 1986).  Juveniles are primarily piscivorous, with anchovies, menhaden, Spanish sardines, and Atlantic thread herring constituting the bulk of the diet.  Less common prey types are mullets (Mugil spp.) and sciaenids. 

Habitats:
Typical habitat for Spanish mackerel includes surface waters of nearshore coastal waters and the lower reaches of tidal estuaries and bays where salinity tends to remain above 10 ppt.  Typical depth distribution ranges from 10 - 35 meters (33 - 115 feet).

Associated Species:
Juvenile king mackerel sometimes mix with schools of Spanish mackerel (Godcharles and Murphy 1986). 

Larvae and juveniles of king mackerel are consumed as prey by species such as the little tunny (Euthynnus alletteratus) and dolphin (Coryphaena hippurus).  Larger king mackerel are sought after by the little tunny, bottlenosed dolphin (Tursiops trucatus) (Cato and Prochaska 1976), and various shark species, including the tiger shark (Galeoverdo cuverie), bull shark (Carcharhinus leucas), and dusky shark (C. obscurus) (Bigelow and Schroeder 1948).

VI. SPECIAL STATUS

Special Status:
None.

Fisheries Importance:

          COMMERCIAL FISHERY:
Florida accounts for 78% of the national commercial harvest of Spanish mackerel annually.  The bulk of the commercial catch in east central Florida is taken between Cape Canaveral and Palm Beach, Florida (Klima 1959;  Powell 1975).  On the West coast of Florida, most of the catch is taken south of Tampa Bay and Ft. Myers.  The statewide commercial catch of Spanish mackerel, Scomberomorus maculatus, between the years 1987 - 2001 was 65.0 million pounds, with a dollar value of over $28.0 million.  Within the 5 county area encompassing the IRL (Volusia, Brevard, Indian River, St. Lucie and Martin Counties) the commercial catch of Scomberomorus maculatus accounts for approximately 57% of the statewide total, with a harvest of 37.1 million pounds, and a value in excess of $16.5 million.   This ranks the Spanish mackerel eighth in commercial value within the IRL, and fourth in pounds harvested.   

Figure 1 below shows the dollar value of the Spanish mackerel fishery to IRL counties by year.  As shown, commercial catch ranged from a low of $642,494 in 1992 to  highs of over $1.3 million in 1988, 1993 and 1995. 

St. Lucie and Martin Counties in the southern portion of the IRL account for the bulk of the commercial harvest, with 45% and 27% of the catch respectively (Figure 2).  After 1992, a significant portion of the harvest (21%) was taken off Brevard County.  From 1987 - 2001, the annual dollar value to St. Lucie County ranged from $244,792 to $750554, averaging $488,167.  In Martin County, the annual dollar amount ranged from $106,247 to $549,314, averaging $300,321; and in Brevard County, the annual dollar amount ranged from $18,823 to $568,467,  averaging $232,685.

Figure 1.  Annual dollar value of the commercial catch of Spanish mackerel to the 5-county
           area of the Indian River Lagoon. 

Figure 2.  Total Spanish mackerel dollar value and percentage by county for the years
              1987 - 2001.
 

Table 1.  Total dollar value of IRL Spanish mackerel, Scomberomorus maculatus between
           1987 - 2001.