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  The King Mackerel, Scoberomorus cavalla.  Illustration by Diana Rome Peebles 1998. Courtesy of Florida Fish
and Wildlife Conservation Commission, Division of Marine Fisheries.

Common Name:
King mackerel;  Sierra

Species Description:
Scomberomorus cavalla, like other scombrid fishes, is elongate, compressed and fusiform.  It grows to approximately
 

0.9 -  1.7 m (3 - 5.6 feet) in length and weighs as much as 45 kg (99 pounds). Body color is typically dark blue to black dorsally, with iridescent areas of blue and green.  The sides are silver to whitish in color.  Young specimens are marked laterally with yellow to yellow-orange spots (Berrien and Finan 1977a), which fade as the animal matures.  Two dorsal fins are present, separated by a deep notch between them.  A series of 7 - 10 finlets (usually 10) lie posterior to the second dorsal fin and to the anal fin on the ventral surface (Collette and Nauen 1983).  The lateral line curves sharply towards the abdomen just below the second dorsal fin.  The caudal peduncle is thin and has a fleshy keel.  The caudal fin is lunate.  The entire body, with the exception of the pectoral fins is scaled.  The mouth is large and set obliquely, with the maxillary reaching to just below the orbit of eye.  The jaw bears 30 triangular teeth on each side (Godcharles and Murphy  1986). 

Synonymy:
Cybium cavalla Cuvier, 1829

Potentially Misidentified Species:
King mackerels are potentially confused with both the cero,  Scomberomorus regalis, and the Spanish mackerel, S. maculatus.  It is easily distinguished from these by its unique lateral line, which curves sharply downward towards the abdomen at the second dorsal fin.  King mackerels also grow significantly larger than either the cero or Spanish mackerel.    

Meristic counts of some key identifying traits:
 

	King Mackerel:	Spanish Mackerel:	Cero:
# Vertebrae:	41-43	52-53	47-49
Dorsal Spines:	12-18	17-19	16-18
Dorsal Rays:	15-18	17-20	16-19
Anal Rays:	16-20	17-20	15-20
Pectoral Fin Rays:	21-23	20-23	20-24
Gill Rakers (lower limb):	6-10	8-13	10-14

II.  HABITAT AND DISTRIBUTION 

Regional Occurrence:
The king mackerel inhabits coastal waters from the Gulf of Maine south to Brazil, including the Gulf of Mexico and the Caribbean (Briggs 1958;  Godcharles and Murphy 1986).  However, the coastal area between Maine and northern Florida is utilized only during the warmest summer months (Collette and Nauen 1983).  Large groups of king mackerels aggregate along the coast of North and South Carolina throughout the spring, summer and fall of the year (Godcharles and Murphy 1986).  In southern and southeastern Florida, king mackerel are found year-round.  Large groups are also observed during summer months in northern areas of the Gulf of Mexico, from Texas through northwestern Florida. 

It has been reported (Williams and Taylor 1978 in Godcharles and Murphy 1986) that  2 distinct populations of king mackerel apparently exist and migrate separately in the Gulf of Mexico and the western Atlantic.  One population, ranges from North Carolina through southeastern Florida, the other ranges from southeastern Florida throughout the northern Gulf of Mexico.  This group returns to southern Florida during winter months.  Tagging data from these populations is additionally supported by genetic analyses which suggest at least 2 distinct populations (Williams and Godcharles 1983).  A third population, which ranges from the Western Gulf of Mexico through Texas and seasonally into Louisiana, has been investigated (DeVries and Grimes 1997).

IRL Distribution:
King mackerel are not typically common inside the IRL or other inland waterways, except near inlets.  However, large groups of king mackerel aggregate in the nearshore and offshore waters off east central Florida from Cape Canaveral, Sebastian, Fort Pierce, and Jupiter Inlets (Godcharles and Murphy 1986). 

III. LIFE HISTORY AND POPULATION BIOLOGY

Age, Size, Lifespan:
Scomberomorus cavalla lives approximately 10 – 11 years.  Growth is variable in this species, with individuals of the same length sometimes differing markedly in age.  In one study (Johnson et al. 1983), fishes of approximately the same length were aged from 1 – 8 years old.  Johnson et al. (1983) reported that females live longer than males and grow faster after the third year.  The oldest female collected was 14 years old and measured 1.4 m (4.6 feet).  The oldest male collected was 12 years old and measured 0.98 m (3.2 feet). 

Abundance:
King mackerels are not abundant inside the IRL, 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 Naeun and Lauder (2001) supported this hypothesis and showed that finlets do redirect cross-peduncle flow in the horizontal plane.

Reproduction:
Male king mackerel mature by 4 years of age after reaching approximately 72 cm (2.4 feet) fork length (FL).  Most females mature by 1 year of age, or upon reaching approximately 14 inches FL (Schmidt et al. 1993).  Fecundity estimates in king mackerel are best correlated with weight (Finucan et al.  unpubl. In:  Godcharles and Murphy 1986), with a 0.68 kg, 47cm (1.5 pounds, 1.5 feet) female producing 69,000 eggs, and a 25.6 kg 1,489 mm (56 pounds, 4.9 feet) female producing 12.2 million eggs (Godcharles and Murphy 1986).

King mackerel spawn in coastal waters off the Gulf of Mexico and South Atlantic (Dwinnell and Futch 1973) and have an extended spawning season (Beaumariage 1973).  Larvae are most commonly collected in surface waters (McEachran et al. 1980) between May and October, peaking in September.  Larvae may be collected from northwestern Florida and Texas, as well as from Palm Beach through Cape Canaveral, Florida, Savannah, GA and Cape fear NC.  North of Cape Canaveral, larvae were generally found along the 200m depth contour of the continental shelf in the vicinity of the Gulf Stream (Wollam 1970;  Burns 1981).  Relatively few larvae are collected from either the eastern Gulf of Mexico south of the Yucatan, or from southeastern Florida (Wollam 1970). 

Embryology:
Vitellogenic eggs are found in king mackerel from May through October, providing further evidence of a protracted spawning season.  Distribution of mean oocyte diameter is bimodal, with the first mode occurring from late May through July.  The second mode occurs from late July through August.  Spent males, and females lacking vitellogenic eggs are observed from early August through December (Beaumariage 1973). 

IV.  PHYSICAL TOLERANCES

Temperature:
Temperature and salinity are believed to be the governing factors in the geographic distribution of mackerels.  The northern range of Scomberomorus cavalla extends approximately to the 20ºC isotherm within the 18m depth contour (Munro 1943;  Berrien and Finian 1977a).  Williams and Taylor (1980) reported that arrival of king mackerel off Florida’s west coast in spring is correlated to changes in water temperature and with the previous year’s air temperature.  Dwinell and Futch (1973) reported that king mackerel larvae in the Gulf of Mexico require temperatures between 26 – 31 ºC for optimum survival and growth;  while those in the south Atlantic require temperatures between 22 – 28 ºC.  

Salinity:
All life history stages of king mackerel typically inhabit waters where salinity fluctuates between 32-36 parts per thousand (ppt).  (Godcharles and Murphy 1986). Dwinell and Futch (1973) reported that king mackerel larvae in the Gulf of Mexico require surface salinities of 27 – 36 ppt for optimum survival and growth; while those in the south Atlantic require a surface salinity of 30 – 37 ppt. 

V.  COMMUNITY ECOLOGY

Trophic Mode:
King mackerels are pelagic carnivores that feed primarily on crustaceans and estuarine-dependent schooling fishes.  Dominant prey types include menhaden (Brevoortia sp.), anchovies (Anchoa sp.)  (Godcharles and Murphy 1986),  Atlantic thread herring (Opisthnema oglinum) and scaled sardines (Harengula jaguana).  King mackerel show a greater preference for invertebrate prey than do Spanish mackerel (Scomberomorus maculatus), a closely related species.  Beaumariage (1973) reported that invertebrate prey, particularly squid and shrimp species could comprise as much as 33% of the diet of king mackerel.  In east central Florida, Spanish sardines (Sardinella aurita), anchovies (Anchoa spp.), mullet (Mugil spp.), flying fish, drum and jacks constitute the major fish species preyed upon, while squid,  nematodes, penaeid shrimp, and isopods are the major invertebrate prey consumed (Godcharles and Murphy 1986).

Habitats:
Scomberomorus cavalla  is primarily found in offshore waters to the edge of the continental shelf.  They sometimes occur nearshore in the vicinity of inlets.

Associated Species:
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 dolphins (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.

Economic Importance:
Commercial and recreational species.

Fisheries Importance: 
          COMMERCIAL FISHERY:
Florida accounts for 40 - 50% of the national commercial harvest of king mackerel annually.  The bulk of the commercial catch in east central Florida is taken between Cape Canaveral and Palm Beach, Florida.  On the West coast of Florida, the catch is centered from Naples to Key West (Beaumariage 1973).  The statewide commercial catch of king mackerel, Scomberomorus cavalla, between the years 1987 - 2001 was 45.2 million pounds, with a dollar value of over $57.3 million.  Within the 5 county area encompassing the IRL (Volusia, Brevard, Indian River, St. Lucie and Martin Counties) the commercial catch of Scomberomorus cavalla accounts for approximately 44% of the statewide total, with a harvest of 19.0 million pounds, and a value in excess of $25.2 million.   This ranks the king mackerel fifth in commercial value within the IRL, and seventh in pounds harvested.   

Figure 1 below shows the dollar value of the king mackerel fishery to IRL counties by year.  As shown, commercial catch ranged from a low of $763,385 in 1993 to  highs of over $2.3 million in 1999.  Low-catch years for this fishery occurred from 1990 - 1996 when the average annual harvest across the entire 5-county area was $1.2 million. 

Indian River and St. Lucie Counties account for the bulk of the commercial harvest, with 38% and 29% of the catch respectively (Figure 2).  From 1987 - 2001, the annual dollar value to Indian River county ranged from $230,000 to $870,000, averaging $491,000.  In St. Lucie county, the annual dollar amount ranged from $330,000 to $1.3 million, averaging $929,000.  This average however, is slightly skewed by the last 3 years of data, from 1999-2001, when the commercial catch jumped to approximately 1 million dollars per year, up from the previous 3 years when the average annual total was $540,000.  Over the same time period, 1999 - 2001, the catch in Indian River County dropped in each of the 3 years, while the catch in Martin County rose in 2 of the 3 years. 

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

 

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

 

Table 1.  Total dollar value of IRL king mackerel, Scomberomrus cavalla between 1987 -
         2001.