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Common Name:
Bluefish

Synonymy:
None

The bluefish is the only living member of the family Pomatomidae, and is closely related to the jacks and pompanos of the family Carangidae.

Potentially Misidentified Species:
None.

Species Description:
Pomatomus saltatrix is an oblong, laterally compressed and streamlined predatory species that reaches 1m (3.3 feet) in total length (TL).  Older juveniles and adult fishes tend to segregate into schools of similarly sized individuals (Olla and Studholme 1971; Wilk 1977).  The head is large and compressed with the mouth set obliquely.  The maxilla extends to the rear of the eye.  The  lower jaw projects from the mouth and has a row of long, unequal teeth on each side.  The tongue, vomer, and palatine bones of the head all have bands of villiform teeth.  Body color is bluish to greenish dorsally, fading to silver ventrally.  The only obvious markings on the body surface occur at the bases of the pectoral fins, which are each blotched with a small dark patch.  Ctenoid scales cover the opercule, cheek, and body, but not the top of the head or a ridge that runs above the cheeks.  Ninety-five scales run along the lateral line.  The spinous portion of the dorsal fin has 8 – 9 spines and is separated by a notch from the soft dorsal fin, which has 24- 25 soft rays.  The anal fin reflects the soft dorsal fin, though it originates somewhat posterior to the dorsal fin, and has 2-3 small spines and 26-28 soft rays.  The pectoral fins are set low on the body, with the pelvic fins set directly inferior to them. (Oliver et al. 1989;  Pottern et al. 1989).  Bluefish can be harmful and are reported to bite when handled.

II.  HABITAT AND DISTRIBUTION 

Regional Occurrence:
The bluefish has a nearly worldwide range in temperate and tropical waters around continental shelves and estuaries.  It is absent only from the northern and central Pacific Ocean.  In the Western Atlantic, it occurs from Nova Scotia south through Brazil, Uruguay and Argentina, including Bermuda, the Gulf of Mexico, the Bahamas, and northern Cuba (Oliver et al. 1989; Pottern et al. 1989).

IRL Distribution:
Bluefish can be seasonally abundant along the coast of Florida (Oliver et al. 1989), especially in late fall and winter when overwintering fish migrate to the east coast of Florida.  During this time, bluefish can be common within the Indian River Lagoon, especially in the vicinity of inlets. 

III. LIFE HISTORY AND POPULATION BIOLOGY

Age, Size, Lifespan:
Pomatomus saltatrix grows to a maximum size of 130 cm TL (4.3 feet) (Randall 1995), and a maximum weight of 14.4 kg (31.7 pounds) (Intl. Game Fish Assoc. 1991).   They live approximately 9 - 11 years.  Males and females grow at approximately the same rates (Richards 1976).

Two distinct stocks of bluefish occur along the Atlantic coast of the U.S.  One stock spawns in late summer in the waters of the continental shelf between Cape Cod and Cape Hatteras, NC.  The other spawns in early spring along the edge of the Gulf Stream between North Carolina and northern Florida.  The stocks are physically distinguished using multivariate morphometric analyses and by differences in growth patterns on the scales.  (Lassiter 1962;  Kendall and Walford 1979).  Yearlings of the spring-spawning group, when compared to the summer-spawning group, were shown to have somewhat larger heads, eyes, pectoral fins and longer maxillae; and relatively shorter dorsal, anal, and ventral fins (Wilk 1977).  There is also a Gulf of Mexico stock that is apparently somewhat less migratory than those that occur along the eastern seaboard.  However, genetic analysis revealed that Gulf of Mexico bluefish mix at least occasionally with those in south Florida such that they can be considered as one stock (Graves et al. 1993).

Abundance:
The bluefish is abundant, especially in fall and winter in Florida waters.  In the Carolinas it is ranked as the #1 gamefish of recreational anglers.  In Florida, anglers often harvest more pounds of bluefish than commercial enterprises. 

Bluefish travel offshore in large schools following schools of baitfishes and other smaller prey species.  Juveniles also school in large numbers, but tend to remain in shallow coastal waters or in estuaries.  They later migrate in fall and winter to join adults offshore for migration to Florida waters. 

Locomotion:
Bluefish passively ventilate their gills when swimming at speeds above 4 – 4.6 body lengths per second.   Below this rate, the gills are ventilated by actively pumping the operculum.

In laboratory studies, Olla et al. (1975) acclimated a captive bluefish population measuring 45 – 55 cm (1.5 – 1.8 feet) at 20ºC, which approximately corresponds to conditions in the Mid-Atlantic bight at the time of summer spawning.  Olla et al. (1975) reported that bluefish under these conditions swam in daylight at a rate of approximately 50cm (1.6 feet) per second. At night, this rate was reduced to 50 cm (0.5 feet) per second. 

Reproduction:
Several geographic races of bluefish are recognized (Lund 1961).  However, based on mtDNA analyses and tagging information, Atlantic coast bluefishes and those that occur in the Gulf of Mexico mix often enough to be considered as a single genetic stock (Graves et al. 1993). 

Pomatomus saltatrix mature sexually during the second year upon reaching approximately 35 - 45 cm (1.15 – 1.48 feet) fork length (FL), with males maturing somewhat earlier than females (Wilk 1977).  Fecundity of 3-4 year old females ranged from 0.6 – 1.4 million eggs (Lippson and Moran 1974). 

The south Atlantic, spring-spawning stock of bluefish reproduces primarily in April and May at the interface of the continental slope and the edge of the Gulf Stream between Cape Hatteras, NC and northern Florida (Wilk 1977).  The mid-Atlantic stock of bluefish spawns in summer from May through September in outer continental shelf waters approximately 50 – 150 km offshore between Cape Cod and Cape Hatteras, NC (Lund and Maltezos 1970; Kendall and Walford 1979). 

Norcross et al. (1974) reported that over 80% of the bluefish eggs they collected were taken more than 55 km offshore.  Spent bluefish in the Middle Atlantic tend to move inshore to Bays and estuaries throughout July and August.

Embryology:
Eggs are buoyant, spherical and measure 0.9 – 1.2 mm in diameter.  The membrane is smooth and transparent, with amber-colored yolk and a single darker colored oil globule measuring approximately 0.3 mm in diameter.  Eggs hatch after 46 – 48 hours into larvae measuring 2.0 – 2.4 mm in total length (TL) (Deuel et al.  1966;  Kendall and Walford 1979).  In newly hatched larvae, the yolk sac comprises over half of body length and melanophores are scattered along the head and back.  Four days after hatching, the yolk is nearly entirely absorbed, the mouth is developed and pigment bands begin to emerge mid-dorsally and mid-ventrally.  Fin rays can be seen when larvae reach approximately 6.0 mm TL, and are fully developed at 13 -14 mm TL.  At this size, larvae resemble adults in overall body form and meristic counts, except that the head appears disproportionately large (Norcross et al. 1974; Lippson and Moran 1974).  Larvae feed on plankton in surface waters until they metamorphose and begin to migrate back to estuaries and other coastal nursery areas.  (Kendall and Walford 1979).   

Larval development takes place on outer continental shelf, generally in the upper 6m of surface waters (Kendall and Walford 1979).  Larvae demonstrate diel vertical migration, concentrating at depths of approximately 4m (13 feet) around midday, and at the surface during the evening hours. 

IV.  PHYSICAL TOLERANCES

Temperature:
Water temperature and photoperiod are major factors that influence movement patterns in bluefish (Olla and Studholme 1971; Wilk 1977).  Spawning in the mid-Atlantic region occurs at temperatures of 17 – 24ºC, while in the south Atlantic region, it occurs at 24 – 26 ºC.  (Norcross et al 1974;  Kendall and Walford 1979).  Bluefish smaller than 250 mm (9.8 inches) TL require temperatures above 10ºC for survival, however larger fishes and adults can withstand short exposure to temperatures as low as 7.5ºC (Lund and Maltezos 1970;  Wilk 1977).  Under laboratory conditions, adult bluefishes survived temperatures up to 30.4ºC (Olla and Studholme 1975).  Loss of equilibrium was observed at a temperature of 35ºC (Olla et al. 1975). 

Olla et al. (1975) examined responses of bluefish to thermal stressors.  At stress temperatures of 12ºC as a thermal minimum, and 30ºC as a thermal maximum, swimming speeds in their aquarium population increased to more than 3 times the acclimation rate, and were maintained.  The schools stopped feeding, and did not separate at night.   These results were interpreted as avoidance behavior, with the schools apparently attempting to swim to more favorable areas.

Like some other large, pelagic species such as tunas, bluefish have the ability to maintain their body temperatures as much as 4ºC above ambient water temperatures.

Salinity:
Bluefish are considered to tolerate moderately euryhaline conditions as both juveniles and as adults.  They are known to enter estuaries where salinity is less than 10 ppt (Lippson and Lippson 1979).   

During spawning, salinity in the mid-Atlantic region is approximately 30 – 32 parts per thousand (ppt).  During the south Atlantic spawning period, salinity is generally 35-38 ppt (Norcross et al 1974;  Kendall and Walford 1979).

Dissolved Oxygen:
As a pelagic, open water species, the bluefish is not well adapted for hypoxic conditions.  Swanson and Sinderman (1979), in the summer of 1976, studied a large mass of hypoxic water that developed off the coast of northern New Jersey.  While small bluefishes that tend to migrate close to the shoreline, and large fishes that tend to remain offshore, appeared in Connecticut and Long Island at the usual time of year, mid-sized fishes were generally absent throughout the summer, thought to have been stopped by the low oxygen conditions and perhaps to have reversed direction, returning to the waters of southern New Jersey and Delaware. 

Other Physical Tolerances:
Though they occur primarily on the continental shelf, the bluefish is able to secrete gases into its swim bladder at the fastest rate known for any fish, thus allowing it to change depth quickly (Bentley and Wiley 1982).

V.  COMMUNITY ECOLOGY

Trophic Mode:
Pomatomus saltatrix are opportunistic, visual, predators whose diet reflects the availability of prey species (Naughton and Saloman 1984).  Larvae prey primarily copepods, cladocerans, and invertebrate eggs (Kendall and Naplin 1981).  Juvenile bluefish prey on small shrimp, anchovies, killifishes, crabs and silversides (Pottern et al. 1989).  Older juveniles and adults prey on schooling fishes, some of which include:  croakers, striped mullet, menhaden, sardines, Atlantic bumper and round scad.  Invertebrate prey includes small portunid crabs, penaeid shrimps, squid and gastropods. 

Kendall and Naplin (1981) reported that the diet of a juvenile bluefish consists of approximately 18% invertebrates, mostly penaeid shrimp and squid;  and 82% vertebrates, primarily pinfish (Lagodon rhomboides) and silversides (Menida spp.).  As juveniles grow, invertebrates become less important in the diet and can be entirely eliminated in favor of small, schooling fishes (Lassiter 1962).   Naughton and Saloman (1984) reported the food habits of bluefishes captured in North and South Carolina showed a distinct preference for other bluefish, as well as for members of the Sciaenidae, Clupeidae, Mugilidae and Engraulidae as preferred prey.

Feeding activity peaks in early morning and continues throughout daylight hours (Lund and Maltezos 1970).  Under laboratory conditions, schools were observed breaking up as prey were pursued, with schools reforming after all prey had been consumed.  Interestingly, Olla et al. (1970) found that prey size motivates feeding in bluefish.  Captive bluefish fed to satiation on small prey immediately resumed feeding when larger prey of the same species were offered. 

Only large predators such as sharks, swordfishes, wahoo, and tunas are known to prey on bluefishes. 

Competitors:
Possible competitors of bluefish include the king mackerel, Spanish mackerel, weakfish, striped bass, bonito and little tunny (Manooch 1984). 

Activity Time:
As visual predators, bluefish are most active during the daylight hours.  Activity increases at daybreak and continues increasing until midday.  Thereafter, activity begins to gradually decline until 1-2 hours after dark when slower night time activity resumes (Lund and Maltezos 1970;  Olla and Studholme 1972). 

Habitats:
Bluefish are a migratory, pelagic species that are dependent on both continental shelf waters and estuaries for spawning and nursery areas respectively.  Adults are found at depths of 2 – 200m (6.6 – 219 feet).  In inshore areas, they tend to be most common along high energy beaches, but can also be common in estuaries and, sometimes, in brackish water areas.  Small fish are common in shallow coastal waters where depths exceed 2m (6.6 feet). 

VI. SPECIAL STATUS

Special Status:
None.

Fisheries Importance:

          COMMERCIAL FISHERY:
The bluefish is an important commercial and recreational species along nearly the entire east coast.  In the southern states, from North Carolina through Florida, the recreational catch can exceed the commercial catch.  The statewide commercial catch of Pomatomus saltatrix between the years 1987 - 2001 was 15.3 million pounds, with a dollar value of over $4.5 million.  Within the 5-county area encompassing the IRL (Volusia, Brevard, Indian River, St. Lucie and Martin Counties) the commercial catch of Pomatomus saltatrix accounts for approximately 58% of the statewide total, with a harvest of 8.9 million pounds, and a value in excess of $2.6 million.   This ranks the bluefish twenty-first in commercial value to IRL counties, and tenth in pounds harvested.   

Figure 1 below shows the dollar value of the bluefish fishery to IRL counties by year.  As shown, commercial catch ranged from a low of $43,077 in 2001 to a high of over $342,328 in 1993.  Of interest is the drastic reduction in the commercial catch following the 1995 banning of gill nets from Florida waters.  This trend is reflective of both the gill net ban and a reduced number of commercial fishers.  Muller (2001) reported that the number of commercial fishers was reduced from 347 in 1984 - 1994 to an average of 127 following the gill net ban. 

Martin and St. Lucie Counties account for the bulk of the commercial harvest, with 38.8% and 31.9% of the catch respectively (Figure 2, Table 3).  From 1987 - 2001, the annual dollar value to Martin County ranged from $151,650 in 1987, dropping to only $6,046 in 2001, with an annual average of $66,727.  In St. Lucie county, the annual dollar amount ranged from a high of $114,217 in 1993 to a low of $3,966 in 1997, with an annual average of $54,832. Of note is the trend in the data that suggests that while the fishery in the Martin County area declined to $3,000 - $6,000 annually after 1999, harvests in St. Lucie County and Brevard County  were much stronger.  

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

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

Table 1.  Total dollar value of IRL bluefish, Pomatomus saltatrix, between 1987 - 2001.